Copyright © 2010-2018 Linux Foundation
Permission is granted to copy, distribute and/or modify this document under the terms of the Creative Commons Attribution-Share Alike 2.0 UK: England & Wales as published by Creative Commons.
For the latest version of the Yocto Project Mega-Manual associated with this Yocto Project release (version 2.3.3), see the Yocto Project Mega-Manual from the Yocto Project documentation page.
This version of the manual is version 2.3.3. For later releases of the Yocto Project (if they exist), go to the Yocto Project documentation page and use the drop-down "Active Releases" button and choose the Yocto Project version for which you want the manual.
For an in-development version of the Yocto Project Mega-Manual, see http://www.yoctoproject.org/docs/latest/mega-manual/mega-manual.html.
Revision History | |
---|---|
Revision 1.8 | April 2015 |
Released with the Yocto Project 1.8 Release. | |
Revision 2.0 | October 2015 |
Released with the Yocto Project 2.0 Release. | |
Revision 2.1 | April 2016 |
Released with the Yocto Project 2.1 Release. | |
Revision 2.2 | October 2016 |
Released with the Yocto Project 2.2 Release. | |
Revision 2.3 | May 2017 |
Released with the Yocto Project 2.3 Release. | |
Revision 2.3.1 | June 2017 |
Released with the Yocto Project 2.3.1 Release. | |
Revision 2.3.2 | September 2017 |
Released with the Yocto Project 2.3.2 Release. | |
Revision 2.3.3 | January 2018 |
Released with the Yocto Project 2.3.3 Release. |
Abstract¶
The Yocto Project Mega-Manual is a concatenation of the published Yocto Project HTML manuals for the given release. The manual exists to help users efficiently search for strings across the entire Yocto Project documentation set.Copyright © 2010-2018 Linux Foundation
Permission is granted to copy, distribute and/or modify this document under the terms of the Creative Commons Attribution-Share Alike 2.0 UK: England & Wales as published by Creative Commons.
For the latest version of the Yocto Project Quick Start associated with this Yocto Project release (version 2.3.3), see the Yocto Project Quick Start from the Yocto Project documentation page.
This version of the manual is version 2.3.3. For later releases of the Yocto Project (if they exist), go to the Yocto Project documentation page and use the drop-down "Active Releases" button and choose the Yocto Project version for which you want the manual.
For an in-development version of the Yocto Project Quick Start, see http://www.yoctoproject.org/docs/latest/yocto-project-qs/yocto-project-qs.html.
Abstract¶
Welcome to the Yocto Project! The Yocto Project is an open-source collaboration project whose focus is developers of embedded Linux systems. Among other things, the Yocto Project uses a build host based on the OpenEmbedded (OE) project, which uses the BitBake tool, to construct complete Linux images. The BitBake and OE components are combined together to form a reference build host, historically known as Poky (Pah-key).
If you do not have a system that runs Linux and you want to give the Yocto Project a test run, you might consider using the Yocto Project Build Appliance. The Build Appliance allows you to build and boot a custom embedded Linux image with the Yocto Project using a non-Linux development system. See the Yocto Project Build Appliance for more information.
This quick start is written so that you can quickly get a build host set up to use the Yocto Project and then build some Linux images. Rather than go into great detail about the Yocto Project and its many capabilities, this quick start provides the minimal information you need to try out the Yocto Project using a supported Linux build host. Reading and using the quick start should result in you having a basic understanding of what the Yocto Project is and how to use some of its core components. You will also have worked through steps to produce two images: one that is suitable for emulation and one that boots on actual hardware. The examples highlight the ease with which you can use the Yocto Project to create images for multiple types of hardware.
For more detailed information on the Yocto Project, you can reference these resources:
Website: The Yocto Project Website provides the latest builds, breaking news, full development documentation, and access to a rich Yocto Project Development Community into which you can tap.
FAQs: Lists commonly asked Yocto Project questions and answers. You can find two FAQs: Yocto Project FAQ on a wiki, and the "FAQ" chapter in the Yocto Project Reference Manual.
Developer Screencast: The Getting Started with the Yocto Project - New Developer Screencast Tutorial provides a 30-minute video created for users unfamiliar with the Yocto Project but familiar with Linux build hosts. While this screencast is somewhat dated, the introductory and fundamental concepts are useful for the beginner.
The Yocto Project through the OpenEmbedded build system provides an open source development environment targeting the ARM, MIPS, PowerPC, and x86 architectures for a variety of platforms including x86-64 and emulated ones. You can use components from the Yocto Project to design, develop, build, debug, simulate, and test the complete software stack using Linux, the X Window System, GTK+ frameworks, and Qt frameworks.
Here are some highlights for the Yocto Project:
Provides a recent Linux kernel along with a set of system commands and libraries suitable for the embedded environment.
Makes available system components such as X11, GTK+, Qt, Clutter, and SDL (among others) so you can create a rich user experience on devices that have display hardware. For devices that do not have a display or where you wish to use alternative UI frameworks, these components need not be installed.
Creates a focused and stable core compatible with the OpenEmbedded project with which you can easily and reliably build and develop.
Fully supports a wide range of hardware and device emulation through the Quick EMUlator (QEMU).
Provides a layer mechanism that allows you to easily extend the system, make customizations, and keep them organized.
You can use the Yocto Project to generate images for many kinds of devices. As mentioned earlier, the Yocto Project supports creation of reference images that you can boot within and emulate using QEMU. The standard example machines target QEMU full-system emulation for 32-bit and 64-bit variants of x86, ARM, MIPS, and PowerPC architectures. Beyond emulation, you can use the layer mechanism to extend support to just about any platform that Linux can run on and that a toolchain can target.
Another Yocto Project feature is the Sato reference User Interface. This optional UI that is based on GTK+ is intended for devices with restricted screen sizes and is included as part of the OpenEmbedded Core layer so that developers can test parts of the software stack.
The following list shows what you need in order to use a Linux-based build host to use the Yocto Project to build images:
Build Host A build host with a minimum of 50 Gbytes of free disk space that is running a supported Linux distribution (i.e. recent releases of Fedora, openSUSE, CentOS, Debian, or Ubuntu).
Build Host Packages Appropriate packages installed on the build host.
The Yocto Project A release of the Yocto Project.
The Yocto Project team verifies each release against recent versions of the most popular Linux distributions that provide stable releases. In general, if you have the current release minus one of the following distributions, you should have no problems.
Ubuntu
Fedora
openSUSE
CentOS
Debian
For a more detailed list of distributions that support the Yocto Project, see the "Supported Linux Distributions" section in the Yocto Project Reference Manual.
The OpenEmbedded build system should be able to run on any modern distribution that has the following versions for Git, tar, and Python.
Git 1.8.3.1 or greater
tar 1.24 or greater
Python 3.4.0 or greater.
If your build host does not meet any of these three listed version requirements, you can take steps to prepare the system so that you can still use the Yocto Project. See the "Required Git, tar, and Python Versions" section in the Yocto Project Reference Manual for information.
Required build host packages vary depending on your build machine and what you want to do with the Yocto Project. For example, if you want to build an image that can run on QEMU in graphical mode (a minimal, basic build requirement), then the build host package requirements are different than if you want to build an image on a headless system or build out the Yocto Project documentation set.
Collectively, the number of required packages is large if you want to be able to cover all cases.
sudo
installed.
The following list shows the required packages needed to build an image that runs on QEMU in graphical mode (e.g. essential plus graphics support). For lists of required packages for other scenarios, see the "Required Packages for the Host Development System" section in the Yocto Project Reference Manual.
Ubuntu and Debian
$ sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib \ build-essential chrpath socat cpio python python3 python3-pip python3-pexpect \ xz-utils debianutils iputils-ping libsdl1.2-dev xterm
Fedora
$ sudo dnf install gawk make wget tar bzip2 gzip python3 unzip perl patch \ diffutils diffstat git cpp gcc gcc-c++ glibc-devel texinfo chrpath \ ccache perl-Data-Dumper perl-Text-ParseWords perl-Thread-Queue perl-bignum socat \ python3-pexpect findutils which file cpio python python3-pip xz SDL-devel xterm
OpenSUSE
$ sudo zypper install python gcc gcc-c++ git chrpath make wget python-xml \ diffstat makeinfo python-curses patch socat python3 python3-curses tar python3-pip \ python3-pexpect xz which libSDL-devel xterm
CentOS
$ sudo yum install -y epel-release $ sudo yum makecache $ sudo yum install gawk make wget tar bzip2 gzip python unzip perl patch \ diffutils diffstat git cpp gcc gcc-c++ glibc-devel texinfo chrpath socat \ perl-Data-Dumper perl-Text-ParseWords perl-Thread-Queue python34-pip xz \ which SDL-devel xterm
Extra Packages for Enterprise Linux
(i.e. epel-release
)
is a collection of packages from Fedora
built on RHEL/CentOS for easy installation
of packages not included in enterprise
Linux by default.
You need to install these packages
separately.
The makecache
command
consumes additional Metadata from
epel-release
.
The last requirement you need to meet before using the
Yocto Project is getting a Yocto Project release.
It is recommended that you get the latest Yocto Project release
by setting up (cloning in
Git terms) a
local copy of the poky
Git repository on
your build host and then checking out the latest release.
Doing so allows you to easily update to newer Yocto Project
releases as well as contribute back to the Yocto Project.
Here is an example from an Ubuntu build host that clones the
poky
repository and then checks out the
latest Yocto Project Release (i.e. 2.3.3):
$ git clone git://git.yoctoproject.org/poky Cloning into 'poky'... remote: Counting objects: 361782, done. remote: Compressing objects: 100% (87100/87100), done. remote: Total 361782 (delta 268619), reused 361439 (delta 268277) Receiving objects: 100% (361782/361782), 131.94 MiB | 6.88 MiB/s, done. Resolving deltas: 100% (268619/268619), done. Checking connectivity... done. $ git checkout pyro
You can also get the Yocto Project Files by downloading Yocto Project releases from the Yocto Project website.
For more information on getting set up with the Yocto Project release, see the "Yocto Project Release" item in the Yocto Project Development Manual.
Now that you have your system requirements in order, you can give Yocto Project a try. You can try out Yocto Project using either the command-line interface or using Toaster, which uses a graphical user interface. If you want to try out the Yocto Project using a GUI, see the Toaster User Manual for information on how to install and set up Toaster.
To use the Yocto Project through the command-line interface, finish this quick start, which presents steps that let you do the following:
Build a qemux86
reference image
and run it in the QEMU emulator.
Easily change configurations so that you can quickly create a second image that you can load onto bootable media and actually boot target hardware. This example uses the MinnowBoard MAX-compatible boards.
Use the following commands to build your image. The OpenEmbedded build system creates an entire Linux distribution, including the toolchain, from source.
By default, the build process searches for source code using a pre-determined order through a set of locations. If you are working behind a firewall and your build host is not set up for proxies, you could encounter problems with the build process when fetching source code (e.g. fetcher failures or Git failures).
If you do not know your proxy settings, consult your local network infrastructure resources and get that information. A good starting point could also be to check your web browser settings. Finally, you can find more information on using the Yocto Project behind a firewall in the Yocto Project Reference Manual FAQ and on the "Working Behind a Network Proxy" wiki page.
Be Sure Your Build Host is Set Up: The steps to build an image in this section depend on your build host being properly set up. Be sure you have worked through the requirements described in the "Setting Up to Use the Yocto Project" section.
Check Out Your Branch:
Be sure you are in the
Source Directory
(e.g. poky
) and then check out
the branch associated with the latest Yocto Project
Release:
$ cd ~/poky $ git checkout -b pyro origin/pyro
Git's checkout
command checks out
the current Yocto Project release into a local branch
whose name matches the release (i.e.
pyro
).
The local branch tracks the upstream branch of the
same name.
Creating your own branch based on the released
branch ensures you are using the latest files for
that release.
Initialize the Build Environment:
Run the
oe-init-build-env
environment setup script to define the OpenEmbedded
build environment on your build host.
$ source oe-init-build-env
Among other things, the script creates the
Build Directory,
which is build
in this case
and is located in the
Source Directory.
After the script runs, your current working directory
is set to the Build Directory.
Later, when the build completes, the Build Directory
contains all the files created during the build.
oe-init-build-env-memres
setup script.
Examine Your Local Configuration File:
When you set up the build environment, a local
configuration file named
local.conf
becomes available in
a conf
subdirectory of the
Build Directory.
Before using BitBake to start the build, you can
look at this file and be sure your general
configurations are how you want them:
To help conserve disk space during builds,
you can add the following statement to your
project's configuration file, which for this
example is
poky/build/conf/local.conf
.
Adding this statement deletes the work
directory used for building a recipe once the
recipe is built.
INHERIT += "rm_work"
By default, the target machine for the build is
qemux86
,
which produces an image that can be used in
the QEMU emulator and is targeted at an
Intel®
32-bit based architecture.
Further on in this example, this default is
easily changed through the
MACHINE
variable so that you can quickly
build an image for a different machine.
Another consideration before you build is the
package manager used when creating the image.
The default local.conf
file selects the RPM package manager.
You can control this configuration by using the
variable.PACKAGE_CLASSES
Selection of the package manager is separate from whether package management is used at runtime in the target image.
For additional package manager selection
information, see the
"package.bbclass
"
section in the Yocto Project Reference Manual.
Start the Build:
Continue with the following command to build an OS image
for the target, which is
core-image-sato
in this example:
$ bitbake core-image-sato
If you experience a build error due to resources
temporarily being unavailable and it appears you
should not be having this issue, it might be due
to the combination of a 4.3+ Linux kernel and
systemd
version 228+
(i.e. see this
link
for information).
To work around this issue, you can try either of the following:
Try the build again.
Modify the "DefaultTasksMax"
systemd
parameter
by uncommenting it and setting it to
"infinity".
You can find this parameter in the
system.conf
file
located in
/etc/systemd
on most systems.
For information on using the
bitbake
command, see the
"BitBake"
section in the Yocto Project Reference Manual, or see the
"BitBake Command"
section in the BitBake User Manual.
For information on other targets, see the
"Images"
chapter in the Yocto Project Reference Manual.
Simulate Your Image Using QEMU: Once this particular image is built, you can start QEMU and run the image:
$ runqemu qemux86
If you want to learn more about running QEMU, see the "Using the Quick EMUlator (QEMU)" chapter in the Yocto Project Development Manual.
Exit QEMU:
Exit QEMU by either clicking on the shutdown icon or by
typing Ctrl-C
in the QEMU
transcript window from which you evoked QEMU.
The following steps show how easy it is to set up to build an
image for a new machine.
These steps build an image for the MinnowBoard MAX, which is
supported by the Yocto Project and the
meta-intel
intel-corei7-64
and intel-core2-32
Board Support Packages
(BSPs).
Create a Local Copy of the
meta-intel
Repository:
Building an image for the MinnowBoard MAX requires the
meta-intel
layer.
Use the git clone
command to create
a local copy of the repository inside your
Source Directory,
which is poky
in this example:
$ cd $HOME/poky $ git clone git://git.yoctoproject.org/meta-intel Cloning into 'meta-intel'... remote: Counting objects: 14039, done. remote: Compressing objects: 100% (4471/4471), done. remote: Total 14039 (delta 8130), reused 13837 (delta 7947) Receiving objects: 100% (14039/14039), 4.27 MiB | 3.98 MiB/s, done. Resolving deltas: 100% (8130/8130), done. Checking connectivity... done.
By default when you clone a Git repository, the
"master" branch is checked out.
Before you build your image that uses the
meta-intel
layer, you must be
sure that both repositories
(meta-intel
and
poky
) are using the same releases.
Consequently, you need to checkout out the
"pyro
" release after
cloning meta-intel
:
$ cd $HOME/poky/meta-intel $ git checkout pyro Branch pyro set up to track remote branch pyro from origin. Switched to a new branch 'pyro'
Configure the Build:
To configure the build, you edit the
bblayers.conf
and
local.conf
files, both of which are
located in the build/conf
directory.
Here is a quick way to make the edits.
The first command uses the
bitbake-layers add-layer
command
to add the meta-intel
layer, which contains the intel-core*
BSPs to the build.
The second command selects the BSP by setting the
MACHINE
variable.
$ cd $HOME/poky/build $ bitbake-layers add-layer "$HOME/poky/meta-intel" $ echo 'MACHINE = "intel-corei7-64"' >> conf/local.conf
If you want a 64-bit build, use the following:
$ echo 'MACHINE = "intel-corei7-64"' >> conf/local.conf
If you want 32-bit images, use the following:
$ echo 'MACHINE = "intel-core2-32"' >> conf/local.conf
Build an Image for MinnowBoard MAX:
The type of image you build depends on your goals.
For example, the previous build created a
core-image-sato
image, which is an
image with Sato support.
It is possible to build many image types for the
MinnowBoard MAX.
Some possibilities are core-image-base
,
which is a console-only image.
Another choice could be a
core-image-full-cmdline
, which is
another console-only image but has more full-features
Linux system functionality installed.
For types of images you can build using the Yocto
Project, see the
"Images"
chapter in the Yocto Project Reference Manual.
Because configuration changes are minimal to set up
for this second build, the OpenEmbedded build system can
re-use files from previous builds as much as possible.
Re-using files means this second build will be much faster
than an initial build.
For this example, the core-image-base
image is built:
$ bitbake core-image-base
If you experience a build error due to resources
temporarily being unavailable and it appears you
should not be having this issue, it might be due
to the combination of a 4.3+ Linux kernel and
systemd
version 228+
(i.e. see this
link
for information).
To work around this issue, you can try either of the following:
Try the build again.
Modify the "DefaultTasksMax"
systemd
parameter
by uncommenting it and setting it to
"infinity".
You can find this parameter in the
system.conf
file
located in
/etc/systemd
on most systems.
Once the build completes, the resulting console-only image is located in the Build Directory here:
tmp/deploy/images/intel-corei7-64/core-image-base-intel-corei7-64.wic
Write the Image:
You can write the image just built to a bootable media
(e.g. a USB key, SATA drive, SD card, etc.) using the
dd
utility:
$ sudo dd if=tmp/deploy/images/intel-corei7-64/core-image-base-intel-corei7-64.wic of=TARGET_DEVICE
In the previous command, the
TARGET_DEVICE
is the device node in
the host machine (e.g. /dev/sdc
, which
is most likely a USB stick, or
/dev/mmcblk0
, which is most likely an
SD card).
Boot the Hardware: With the boot device provisioned, you can insert the media into the MinnowBoard MAX and boot the hardware. The board should automatically detect the media and boot to the bootloader and subsequently the operating system.
If the board does not boot automatically, you can boot it manually from the EFI shell as follows:
Shell> connect -r Shell> map -r Shell> fs0: Shell> bootx64
Shell> bootia32
If you completed all the steps in the previous section then congratulations! What now?
Depending on what you primary interests are with the Yocto Project, you could consider any of the following:
Visit the Yocto Project Web Site: The official Yocto Project web site contains information on the entire project. Visiting this site is a good way to familiarize yourself with the overall project.
Look Through the Yocto Project Development Manual: The Yocto Project Development Manual is a great place to get a feel for how to use the Yocto Project. The manual contains conceptual and procedural information that covers common development models and introduces the Yocto Project open source development environment. The manual also contains several targeted sections that cover specific common tasks such as understanding and creating layers, customizing images, writing new recipes, working with libraries, and configuring and patching the kernel.
Look Through the Yocto Project Software Development Kit (SDK) Developer's Guide: The Yocto Project Software Development Kit (SDK) Developer's Guide describes how to use both the standard SDK and the extensible SDK, which are used primarily for application development. This manual also provides an example workflow that uses the popular Eclipse™ development environment. See the "Workflow using Eclipse™" section.
Learn About Board Support Packages (BSPs): If you want to learn about BSPs, see the Yocto Project Board Support Packages (BSP) Developer's Guide.
Learn About Toaster: Toaster is a web interface to the Yocto Project's OpenEmbedded build system. If you are interested in using this type of interface to create images, see the Toaster User Manual.
Have Available the Yocto Project Reference Manual The Yocto Project Reference Manual, unlike the rest of the Yocto Project manual set, is comprised of material suited for reference rather than procedures. You can get build details, a closer look at how the pieces of the Yocto Project development environment work together, information on various technical details, guidance on migrating to a newer Yocto Project release, reference material on the directory structure, classes, and tasks. The Yocto Project Reference Manual also contains a fairly comprehensive glossary of variables used within the Yocto Project.
Welcome to the Yocto Project Development Manual! This manual provides information on how to use the Yocto Project to develop embedded Linux images and user-space applications that run on targeted devices. The manual provides an overview of image, kernel, and user-space application development using the Yocto Project. Because much of the information in this manual is general, it contains many references to other sources where you can find more detail. For example, you can find detailed information on Git, repositories, and open source in general in many places on the Internet. Another example specific to the Yocto Project is how to quickly set up your host development system and build an image, which you find in the Yocto Project Quick Start.
The Yocto Project Development Manual does, however, provide
guidance and examples on how to change the kernel source code,
reconfigure the kernel, and develop an application using
devtool
.
The following list describes what you can get from this manual:
Information that lets you get set up to develop using the Yocto Project.
Information to help developers who are new to the open source environment and to the distributed revision control system Git, which the Yocto Project uses.
An understanding of common end-to-end development models and tasks.
Information about common development tasks generally used during image development for embedded devices.
Information on using the Yocto Project integration of the QuickEMUlator (QEMU), which lets you simulate running on hardware an image you have built using the OpenEmbedded build system.
Many references to other sources of related information.
This manual will not give you the following:
Step-by-step instructions when those instructions exist in other Yocto Project documentation: For example, the Yocto Project Software Development Kit (SDK) Developer's Guide manual contains detailed instructions on how to install an SDK, which is used to develop applications for target hardware.
Reference material: This type of material resides in an appropriate reference manual. For example, system variables are documented in the Yocto Project Reference Manual.
Detailed public information that is not specific to the Yocto Project: For example, exhaustive information on how to use Git is covered better through the Internet than in this manual.
Because this manual presents overview information for many different topics, supplemental information is recommended for full comprehension. The following list presents other sources of information you might find helpful:
Yocto Project Website: The home page for the Yocto Project provides lots of information on the project as well as links to software and documentation.
Yocto Project Quick Start: This short document lets you get started with the Yocto Project and quickly begin building an image.
Yocto Project Reference Manual: This manual is a reference guide to the OpenEmbedded build system, which is based on BitBake. The build system is sometimes referred to as "Poky".
Yocto Project Software Development Kit (SDK) Developer's Guide: This guide provides information that lets you get going with the standard or extensible SDK. An SDK, with its cross-development toolchains, allows you to develop projects inside or outside of the Yocto Project environment.
Yocto Project Board Support Package (BSP) Developer's Guide: This guide defines the structure for BSP components. Having a commonly understood structure encourages standardization.
Yocto Project Linux Kernel Development Manual: This manual describes how to work with Linux Yocto kernels as well as provides a bit of conceptual information on the construction of the Yocto Linux kernel tree.
Yocto Project Profiling and Tracing Manual: This manual presents a set of common and generally useful tracing and profiling schemes along with their applications (as appropriate) to each tool.
Toaster User Manual: This manual introduces and describes how to set up and use Toaster, which is a web interface to the Yocto Project's OpenEmbedded Build System.
Eclipse IDE Yocto Plug-in: Instructions that demonstrate how an application developer uses the Eclipse Yocto Project Plug-in feature within the Eclipse IDE.
FAQ: A list of commonly asked questions and their answers.
Release Notes: Features, updates and known issues for the current release of the Yocto Project.
Toaster: An Application Programming Interface (API) and web-based interface to the OpenEmbedded build system, which uses BitBake, that reports build information.
Build Appliance: A virtual machine that enables you to build and boot a custom embedded Linux image with the Yocto Project using a non-Linux development system.
Bugzilla: The bug tracking application the Yocto Project uses. If you find problems with the Yocto Project, you should report them using this application.
Yocto Project Mailing Lists: To subscribe to the Yocto Project mailing lists, click on the following URLs and follow the instructions:
http://lists.yoctoproject.org/listinfo/yocto for a Yocto Project Discussions mailing list.
http://lists.yoctoproject.org/listinfo/poky for a Yocto Project Discussions mailing list about the OpenEmbedded build system (Poky).
http://lists.yoctoproject.org/listinfo/yocto-announce for a mailing list to receive official Yocto Project announcements as well as Yocto Project milestones.
http://lists.yoctoproject.org/listinfo
for a listing of all public mailing lists on
lists.yoctoproject.org
.
Internet Relay Chat (IRC):
Two IRC channels on freenode are available
for Yocto Project and Poky discussions: #yocto
and
#poky
, respectively.
OpenEmbedded: The build system used by the Yocto Project. This project is the upstream, generic, embedded distribution from which the Yocto Project derives its build system (Poky) and to which it contributes.
BitBake: The tool used by the OpenEmbedded build system to process project metadata.
BitBake User Manual: A comprehensive guide to the BitBake tool. If you want information on BitBake, see this manual.
Quick EMUlator (QEMU): An open-source machine emulator and virtualizer.
This chapter introduces the Yocto Project and gives you an idea of what you need to get started. You can find enough information to set up your development host and build or use images for hardware supported by the Yocto Project by reading the Yocto Project Quick Start.
The remainder of this chapter summarizes what is in the Yocto Project Quick Start and provides some higher-level concepts you might want to consider.
The Yocto Project is an open-source collaboration project focused on embedded Linux development. The project currently provides a build system that is referred to as the OpenEmbedded build system in the Yocto Project documentation. The Yocto Project provides various ancillary tools for the embedded developer and also features the Sato reference User Interface, which is optimized for stylus-driven, low-resolution screens.
You can use the OpenEmbedded build system, which uses BitBake, to develop complete Linux images and associated user-space applications for architectures based on ARM, MIPS, PowerPC, x86 and x86-64.
While the Yocto Project does not provide a strict testing framework, it does provide or generate for you artifacts that let you perform target-level and emulated testing and debugging. Additionally, if you are an Eclipse™ IDE user, you can install an Eclipse Yocto Plug-in to allow you to develop within that familiar environment.
Here is what you need to use the Yocto Project:
Host System: You should have a reasonably current Linux-based host system. You will have the best results with a recent release of Fedora, openSUSE, Debian, Ubuntu, or CentOS as these releases are frequently tested against the Yocto Project and officially supported. For a list of the distributions under validation and their status, see the "Supported Linux Distributions" section in the Yocto Project Reference Manual and the wiki page at Distribution Support.
You should also have about 50 Gbytes of free disk space for building images.
Packages: The OpenEmbedded build system requires that certain packages exist on your development system (e.g. Python 2.7). See "The Build Host Packages" section in the Yocto Project Quick Start and the "Required Packages for the Host Development System" section in the Yocto Project Reference Manual for the exact package requirements and the installation commands to install them for the supported distributions.
Yocto Project Release:
You need a release of the Yocto Project locally installed on
your development system.
The documentation refers to this set of locally installed files
as the Source Directory.
You create your Source Directory by using
Git to clone a local copy
of the upstream poky
repository,
or by downloading and unpacking a tarball of an official
Yocto Project release.
The preferred method is to create a clone of the repository.
Working from a copy of the upstream repository allows you to contribute back into the Yocto Project or simply work with the latest software on a development branch. Because Git maintains and creates an upstream repository with a complete history of changes and you are working with a local clone of that repository, you have access to all the Yocto Project development branches and tag names used in the upstream repository.
The following transcript shows how to clone the
poky
Git repository into the current
working directory.
The command creates the local repository in a directory
named poky
.
For information on Git used within the Yocto Project, see
the "Git" section.
$ git clone git://git.yoctoproject.org/poky Cloning into 'poky'... remote: Counting objects: 226790, done. remote: Compressing objects: 100% (57465/57465), done. remote: Total 226790 (delta 165212), reused 225887 (delta 164327) Receiving objects: 100% (226790/226790), 100.98 MiB | 263 KiB/s, done. Resolving deltas: 100% (165212/165212), done.
For another example of how to set up your own local Git
repositories, see this
wiki page, which describes how to create local
Git repositories for both
poky
and meta-intel
.
You can also get the Yocto Project Files by downloading Yocto Project releases from the Yocto Project website. From the website, you just click "Downloads" in the navigation pane to the left to display all Yocto Project downloads. Current and archived releases are available for download. Nightly and developmental builds are also maintained at http://autobuilder.yoctoproject.org/pub/nightly/. One final site you can visit for information on Yocto Project releases is the Releases wiki.
Yocto Project Kernel: If you are going to be making modifications to a supported Yocto Project kernel, you need to establish local copies of the source. You can find Git repositories of supported Yocto Project kernels organized under "Yocto Linux Kernel" in the Yocto Project Source Repositories at http://git.yoctoproject.org/cgit.cgi.
This setup can involve creating a bare clone of the Yocto Project kernel and then
copying that cloned repository.
You can create the bare clone and the copy of the bare clone anywhere you like.
For simplicity, it is recommended that you create these structures outside of the
Source Directory, which is usually named poky
.
As an example, the following transcript shows how to create the bare clone
of the linux-yocto-3.19
kernel and then create a copy of
that clone.
clone
command.
Doing so can speed up the process.In the following example, the bare clone is named
linux-yocto-3.19.git
, while the
copy is named my-linux-yocto-3.19-work
:
$ git clone --bare git://git.yoctoproject.org/linux-yocto-3.19 linux-yocto-3.19.git Cloning into bare repository 'linux-yocto-3.19.git'... remote: Counting objects: 3983256, done. remote: Compressing objects: 100% (605006/605006), done. remote: Total 3983256 (delta 3352832), reused 3974503 (delta 3344079) Receiving objects: 100% (3983256/3983256), 843.66 MiB | 1.07 MiB/s, done. Resolving deltas: 100% (3352832/3352832), done. Checking connectivity... done.
Now create a clone of the bare clone just created:
$ git clone linux-yocto-3.19.git my-linux-yocto-3.19-work Cloning into 'my-linux-yocto-3.19-work'... done. Checking out files: 100% (48440/48440), done.
The meta-yocto-kernel-extras
Git Repository:
The meta-yocto-kernel-extras
Git repository contains Metadata needed
only if you are modifying and building the kernel image.
In particular, it contains the kernel BitBake append (.bbappend
)
files that you
edit to point to your locally modified kernel source files and to build the kernel
image.
Pointing to these local files is much more efficient than requiring a download of the
kernel's source files from upstream each time you make changes to the kernel.
You can find the meta-yocto-kernel-extras
Git Repository in the
"Yocto Metadata Layers" area of the Yocto Project Source Repositories at
http://git.yoctoproject.org/cgit.cgi.
It is good practice to create this Git repository inside the Source Directory.
Following is an example that creates the meta-yocto-kernel-extras
Git
repository inside the Source Directory, which is named poky
in this case:
$ cd ~/poky $ git clone git://git.yoctoproject.org/meta-yocto-kernel-extras meta-yocto-kernel-extras Cloning into 'meta-yocto-kernel-extras'... remote: Counting objects: 727, done. remote: Compressing objects: 100% (452/452), done. remote: Total 727 (delta 260), reused 719 (delta 252) Receiving objects: 100% (727/727), 536.36 KiB | 240 KiB/s, done. Resolving deltas: 100% (260/260), done.
Supported Board Support Packages (BSPs): The Yocto Project supports many BSPs, which are maintained in their own layers or in layers designed to contain several BSPs. To get an idea of machine support through BSP layers, you can look at the index of machines for the release.
The Yocto Project uses the following BSP layer naming scheme:
meta-bsp_name
where bsp_name
is the recognized
BSP name.
Here is an example:
meta-raspberrypi
See the "BSP Layers" section in the Yocto Project Board Support Package (BSP) Developer's Guide for more information on BSP Layers.
A useful Git repository released with the Yocto
Project is meta-intel
, which is a
parent layer that contains many supported
BSP Layers.
You can locate the meta-intel
Git
repository in the "Yocto Metadata Layers" area of the Yocto
Project Source Repositories at
http://git.yoctoproject.org/cgit.cgi.
Using
Git to create a local clone of the
upstream repository can be helpful if you are working with
BSPs.
Typically, you set up the meta-intel
Git repository inside the Source Directory.
For example, the following transcript shows the steps to clone
meta-intel
.
meta-intel
branch that matches your
Source Directory
(i.e. poky
) branch.
For example, if you have checked out the "master" branch
of poky
and you are going to use
meta-intel
, be sure to checkout the
"master" branch of meta-intel
.
$ cd ~/poky $ git clone git://git.yoctoproject.org/meta-intel.git Cloning into 'meta-intel'... remote: Counting objects: 11917, done. remote: Compressing objects: 100% (3842/3842), done. remote: Total 11917 (delta 6840), reused 11699 (delta 6622) Receiving objects: 100% (11917/11917), 2.92 MiB | 2.88 MiB/s, done. Resolving deltas: 100% (6840/6840), done. Checking connectivity... done.
The same
wiki page
referenced earlier covers how to set up the
meta-intel
Git repository.
Eclipse Yocto Plug-in: If you are developing applications using the Eclipse Integrated Development Environment (IDE), you will need this plug-in. See the "Using Eclipse" section in the Yocto Project Software Development Kit (SDK) Developer's Guide for more information.
The build process creates an entire Linux distribution, including the toolchain, from source. For more information on this topic, see the "Building Images" section in the Yocto Project Quick Start.
The build process is as follows:
Make sure you have set up the Source Directory described in the previous section.
Initialize the build environment by sourcing a build
environment script (i.e.
oe-init-build-env
or
oe-init-build-env-memres
).
Optionally ensure the conf/local.conf
configuration file,
which is found in the
Build Directory,
is set up how you want it.
This file defines many aspects of the build environment including
the target machine architecture through the
MACHINE
variable,
the packaging format used during the build
(PACKAGE_CLASSES
),
and a centralized tarball download directory through the
DL_DIR
variable.
Build the image using the bitbake
command.
If you want information on BitBake, see the
BitBake User Manual.
Run the image either on the actual hardware or using the QEMU emulator.
bmaptool
¶
An easy way to flash an image to a bootable device is to use
bmaptool
, which is integrated into the
OpenEmbedded build system.
Following, is an example that shows how to flash a Wic image.
bmaptool
to flash any
type of image.
Use these steps to flash an image using
bmaptool
:
bmap-tools
package as mentioned in the note
in the second bullet of step 3 further down, you will need to build
bmaptool
before using it.
Build the tool using the following command:
$ bitbake bmap-tools-native
Add the following to your local.conf
file:
IMAGE_FSTYPES += "wic wic.bmap"
Either have your image ready (pre-built) or take the step build the image:
$ bitbake image
Flash the image to the media by using
bmaptool
depending on your particular
setup:
If you have write access to the media, use this command form:
$ oe-run-native bmaptool copy ./tmp/deploy/images/qemux86-64/core-image-minimal-machine
.wic /dev/sdX
If you do not have write access to the media, use the following commands:
$ sudo bash $ PATH=tmp/sysroots/x86_64-linux/usr/bin/ bmaptool copy ./tmp/deploy/images/qemux86-64/core-image-minimal-machine
.wic /dev/sdX
bmap-tools
package using the
following command and then use the tool
without specifying
PATH
even from the
root account:
$ sudo apt-get install bmap-tools
For help on the bmaptool
command, use either of
the following commands:
$ bmaptool --help $ oe-run-native bmaptool --help
Another option you have to get started is to use pre-built binaries. The Yocto Project provides many types of binaries with each release. See the "Images" chapter in the Yocto Project Reference Manual for descriptions of the types of binaries that ship with a Yocto Project release.
Using a pre-built binary is ideal for developing software
applications to run on your target hardware.
To do this, you need to be able to access the appropriate
cross-toolchain tarball for the architecture on which you are
developing.
If you are using an SDK type image, the image ships with the complete
toolchain native to the architecture (i.e. a toolchain designed to
run on the
SDKMACHINE
).
If you are not using an SDK type image, you need to separately download
and install the stand-alone Yocto Project cross-toolchain tarball.
See the
"Obtaining the SDK"
appendix in the Yocto Project Software Development Kit (SDK)
Developer's Guide for more information on locating and installing
cross-toolchains.
Regardless of the type of image you are using, you need to download the pre-built kernel that you will boot in the QEMU emulator and then download and extract the target root filesystem for your target machine’s architecture. You can get architecture-specific binaries and file systems from machines. You can get installation scripts for stand-alone toolchains from toolchains. Once you have all your files, you set up the environment to emulate the hardware by sourcing an environment setup script. Finally, you start the QEMU emulator. You can find details on all these steps in the Yocto Project Software Development Kit (SDK) Developer's Guide. You can learn more about using QEMU with the Yocto Project in the "Using the Quick EMUlator (QEMU)" section.
Using QEMU to emulate your hardware can result in speed issues
depending on the target and host architecture mix.
For example, using the qemux86
image in the emulator
on an Intel-based 32-bit (x86) host machine is fast because the target and
host architectures match.
On the other hand, using the qemuarm
image on the same Intel-based
host can be slower.
But, you still achieve faithful emulation of ARM-specific issues.
To speed things up, the QEMU images support using distcc
to call a cross-compiler outside the emulated system.
If you used runqemu
to start QEMU, and the
distccd
application is present on the host system, any
BitBake cross-compiling toolchain available from the build system is automatically
used from within QEMU simply by calling distcc
.
You can accomplish this by defining the cross-compiler variable
(e.g. export CC="distcc"
).
Alternatively, if you are using a suitable SDK image or the appropriate
stand-alone toolchain is present,
the toolchain is also automatically used.
QEMU provides a framebuffer interface that makes standard consoles available.
Generally, headless embedded devices have a serial port. If so, you can configure the operating system of the running image to use that port to run a console. The connection uses standard IP networking.
SSH servers exist in some QEMU images.
The core-image-sato
QEMU image has a
Dropbear secure shell (SSH) server that runs with the root
password disabled.
The core-image-full-cmdline
and
core-image-lsb
QEMU images
have OpenSSH instead of Dropbear.
Including these SSH servers allow you to use standard
ssh
and scp
commands.
The core-image-minimal
QEMU image,
however, contains no SSH server.
You can use a provided, user-space NFS server to boot the QEMU session
using a local copy of the root filesystem on the host.
In order to make this connection, you must extract a root filesystem tarball by using the
runqemu-extract-sdk
command.
After running the command, you must then point the runqemu
script to the extracted directory instead of a root filesystem image file.
This chapter helps you understand the Yocto Project as an open source development project. In general, working in an open source environment is very different from working in a closed, proprietary environment. Additionally, the Yocto Project uses specific tools and constructs as part of its development environment. This chapter specifically addresses open source philosophy, using the Yocto Project in a team environment, source repositories, Yocto Project terms, licensing, the open source distributed version control system Git, workflows, bug tracking, and how to submit changes.
Open source philosophy is characterized by software development directed by peer production and collaboration through an active community of developers. Contrast this to the more standard centralized development models used by commercial software companies where a finite set of developers produces a product for sale using a defined set of procedures that ultimately result in an end product whose architecture and source material are closed to the public.
Open source projects conceptually have differing concurrent agendas, approaches, and production. These facets of the development process can come from anyone in the public (community) that has a stake in the software project. The open source environment contains new copyright, licensing, domain, and consumer issues that differ from the more traditional development environment. In an open source environment, the end product, source material, and documentation are all available to the public at no cost.
A benchmark example of an open source project is the Linux kernel, which was initially conceived and created by Finnish computer science student Linus Torvalds in 1991. Conversely, a good example of a non-open source project is the Windows® family of operating systems developed by Microsoft® Corporation.
Wikipedia has a good historical description of the Open Source Philosophy here. You can also find helpful information on how to participate in the Linux Community here.
It might not be immediately clear how you can use the Yocto Project in a team environment, or scale it for a large team of developers. One of the strengths of the Yocto Project is that it is extremely flexible. Thus, you can adapt it to many different use cases and scenarios. However, these characteristics can cause a struggle if you are trying to create a working setup that scales across a large team.
To help with these types of situations, this section presents some of the project's most successful experiences, practices, solutions, and available technologies that work well. Keep in mind, the information here is a starting point. You can build off it and customize it to fit any particular working environment and set of practices.
Systems across a large team should meet the needs of two types of developers: those working on the contents of the operating system image itself and those developing applications. Regardless of the type of developer, their workstations must be both reasonably powerful and run Linux.
For developers who mainly do application level work on top of an existing software stack, the following list shows practices that work best. For information on using a Software Development Kit (SDK), see the Yocto Project Software Development Kit (SDK) Developer's Guide:
Use a pre-built toolchain that contains the software stack itself. Then, develop the application code on top of the stack. This method works well for small numbers of relatively isolated applications.
When possible, use the Yocto Project plug-in for the Eclipse™ IDE and SDK development practices. For more information, see the "Yocto Project Software Development Kit (SDK) Developer's Guide".
Keep your cross-development toolchains
updated.
You can do this through provisioning either as new
toolchain downloads or as updates through a package
update mechanism using opkg
to provide updates to an existing toolchain.
The exact mechanics of how and when to do this are a
question for local policy.
Use multiple toolchains installed locally into different locations to allow development across versions.
For core system development, it is often best to have the build system itself available on the developer workstations so developers can run their own builds and directly rebuild the software stack. You should keep the core system unchanged as much as possible and do your work in layers on top of the core system. Doing so gives you a greater level of portability when upgrading to new versions of the core system or Board Support Packages (BSPs). You can share layers amongst the developers of a particular project and contain the policy configuration that defines the project.
Aside from the previous best practices, there exists a number of tips and tricks that can help speed up core development projects:
Use a Shared State Cache (sstate) among groups of developers who are on a fast network. The best way to share sstate is through a Network File System (NFS) share. The first user to build a given component for the first time contributes that object to the sstate, while subsequent builds from other developers then reuse the object rather than rebuild it themselves.
Although it is possible to use other protocols for the sstate such as HTTP and FTP, you should avoid these. Using HTTP limits the sstate to read-only and FTP provides poor performance.
Have autobuilders contribute to the sstate pool similarly to how the developer workstations contribute. For information, see the "Autobuilders" section.
Build stand-alone tarballs that contain
"missing" system requirements if for some reason
developer workstations do not meet minimum system
requirements such as latest Python versions,
chrpath
, or other tools.
You can install and relocate the tarball exactly as you
would the usual cross-development toolchain so that
all developers can meet minimum version requirements
on most distributions.
Use a small number of shared, high performance systems for testing purposes (e.g. dual, six-core Xeons with 24 Gbytes of RAM and plenty of disk space). Developers can use these systems for wider, more extensive testing while they continue to develop locally using their primary development system.
Enable the PR Service when package feeds need to be incremental with continually increasing PR values. Typically, this situation occurs when you use or publish package feeds and use a shared state. You should enable the PR Service for all users who use the shared state pool. For more information on the PR Service, see the "Working With a PR Service".
Keeping your Metadata and any software you are developing under the control of an SCM system that is compatible with the OpenEmbedded build system is advisable. Of the SCMs BitBake supports, the Yocto Project team strongly recommends using Git. Git is a distributed system that is easy to backup, allows you to work remotely, and then connects back to the infrastructure.
It is relatively easy to set up Git services and create
infrastructure like
http://git.yoctoproject.org,
which is based on server software called
gitolite
with cgit
being used to generate the web interface that lets you view the
repositories.
The gitolite
software identifies users
using SSH keys and allows branch-based
access controls to repositories that you can control as little
or as much as necessary.
Git documentation:
Describes how to install gitolite
on the server.
The gitolite
master index:
All topics for gitolite
.
Interfaces, frontends, and tools: Documentation on how to create interfaces and frontends for Git.
Autobuilders are often the core of a development project. It is here that changes from individual developers are brought together and centrally tested and subsequent decisions about releases can be made. Autobuilders also allow for "continuous integration" style testing of software components and regression identification and tracking.
See "Yocto Project Autobuilder" for more information and links to buildbot. The Yocto Project team has found this implementation works well in this role. A public example of this is the Yocto Project Autobuilders, which we use to test the overall health of the project.
The features of this system are:
Highlights when commits break the build.
Populates an sstate cache from which developers can pull rather than requiring local builds.
Allows commit hook triggers, which trigger builds when commits are made.
Allows triggering of automated image booting and testing under the QuickEMUlator (QEMU).
Supports incremental build testing and from-scratch builds.
Shares output that allows developer testing and historical regression investigation.
Creates output that can be used for releases.
Allows scheduling of builds so that resources can be used efficiently.
The Yocto Project itself uses a hierarchical structure and a
pull model.
Scripts exist to create and send pull requests
(i.e. create-pull-request
and
send-pull-request
).
This model is in line with other open source projects where
maintainers are responsible for specific areas of the project
and a single maintainer handles the final "top-of-tree" merges.
gitolite
software supports both the
push and pull models quite easily.
As with any development environment, it is important to document the policy used as well as any main project guidelines so they are understood by everyone. It is also a good idea to have well structured commit messages, which are usually a part of a project's guidelines. Good commit messages are essential when looking back in time and trying to understand why changes were made.
If you discover that changes are needed to the core layer of the project, it is worth sharing those with the community as soon as possible. Chances are if you have discovered the need for changes, someone else in the community needs them also.
This section summarizes the key recommendations described in the previous sections:
Use Git as the source control system.
Maintain your Metadata in layers that make sense for your situation. See the "Understanding and Creating Layers" section for more information on layers.
Separate the project's Metadata and code by using separate Git repositories. See the "Yocto Project Source Repositories" section for information on these repositories. See the "Getting Set Up" section for information on how to set up local Git repositories for related upstream Yocto Project Git repositories.
Set up the directory for the shared state cache
(SSTATE_DIR
)
where it makes sense.
For example, set up the sstate cache on a system used
by developers in the same organization and share the
same source directories on their machines.
Set up an Autobuilder and have it populate the sstate cache and source directories.
The Yocto Project community encourages you to send patches to the project to fix bugs or add features. If you do submit patches, follow the project commit guidelines for writing good commit messages. See the "How to Submit a Change" section.
Send changes to the core sooner than later as others are likely to run into the same issues. For some guidance on mailing lists to use, see the list in the "How to Submit a Change" section. For a description of the available mailing lists, see the "Mailing Lists" section in the Yocto Project Reference Manual.
The Yocto Project team maintains complete source repositories for all Yocto Project files at http://git.yoctoproject.org/cgit/cgit.cgi. This web-based source code browser is organized into categories by function such as IDE Plugins, Matchbox, Poky, Yocto Linux Kernel, and so forth. From the interface, you can click on any particular item in the "Name" column and see the URL at the bottom of the page that you need to clone a Git repository for that particular item. Having a local Git repository of the Source Directory, which is usually named "poky", allows you to make changes, contribute to the history, and ultimately enhance the Yocto Project's tools, Board Support Packages, and so forth.
For any supported release of Yocto Project, you can also go to the
Yocto Project Website and
select the "Downloads" tab and get a released tarball of the
poky
repository or any supported BSP tarballs.
Unpacking these tarballs gives you a snapshot of the released
files.
The recommended method for setting up the Yocto Project
Source Directory
and the files for supported BSPs
(e.g., meta-intel
) is to use
Git to create a local copy of
the upstream repositories.
Be sure to always work in matching branches for both
the selected BSP repository and the
Source Directory
(i.e. poky
) repository.
For example, if you have checked out the "master" branch
of poky
and you are going to use
meta-intel
, be sure to checkout the
"master" branch of meta-intel
.
In summary, here is where you can get the project files needed for development:
Source Repositories: This area contains IDE Plugins, Matchbox, Poky, Poky Support, Tools, Yocto Linux Kernel, and Yocto Metadata Layers. You can create local copies of Git repositories for each of these areas.
Index of /releases: This is an index of releases such as the Eclipse™ Yocto Plug-in, miscellaneous support, Poky, Pseudo, installers for cross-development toolchains, and all released versions of Yocto Project in the form of images or tarballs. Downloading and extracting these files does not produce a local copy of the Git repository but rather a snapshot of a particular release or image.
"Downloads" page for the Yocto Project Website: Access this page by going to the website and then selecting the "Downloads" tab. This page allows you to download any Yocto Project release or Board Support Package (BSP) in tarball form. The tarballs are similar to those found in the Index of /releases: area.
Following is a list of terms and definitions users new to the Yocto Project development environment might find helpful. While some of these terms are universal, the list includes them just in case:
Append Files: Files that append build information to
a recipe file.
Append files are known as BitBake append files and .bbappend
files.
The OpenEmbedded build system expects every append file to have a corresponding
recipe (.bb
) file.
Furthermore, the append file and corresponding recipe file
must use the same root filename.
The filenames can differ only in the file type suffix used (e.g.
formfactor_0.0.bb
and formfactor_0.0.bbappend
).
Information in append files extends or overrides the information in the similarly-named recipe file. For an example of an append file in use, see the "Using .bbappend Files" section.
BitBake: The task executor and scheduler used by the OpenEmbedded build system to build images. For more information on BitBake, see the BitBake User Manual.
Build Directory:
This term refers to the area used by the OpenEmbedded build
system for builds.
The area is created when you source
the
setup environment script that is found in the Source Directory
(i.e. oe-init-build-env
or
oe-init-build-env-memres
).
The TOPDIR
variable points to the Build Directory.
You have a lot of flexibility when creating the Build
Directory.
Following are some examples that show how to create the
directory.
The examples assume your
Source Directory is
named poky
:
Create the Build Directory inside your
Source Directory and let the name of the Build
Directory default to build
:
$ cd $HOME/poky $ source oe-init-build-env
Create the Build Directory inside your
home directory and specifically name it
test-builds
:
$ cd $HOME $ source poky/oe-init-build-env test-builds
Provide a directory path and
specifically name the Build Directory.
Any intermediate folders in the pathname must
exist.
This next example creates a Build Directory named
YP-18.0.3
in your home directory within the existing
directory mybuilds
:
$cd $HOME $ source $HOME/poky/oe-init-build-env $HOME/mybuilds/YP-18.0.3
TMPDIR
,
which is a temporary directory the build system uses for
its work.
TMPDIR
cannot be under NFS.
Thus, by default, the Build Directory cannot be under NFS.
However, if you need the Build Directory to be under NFS,
you can set this up by setting TMPDIR
in your local.conf
file
to use a local drive.
Doing so effectively separates TMPDIR
from TOPDIR
, which is the Build
Directory.
Classes: Files that provide for logic encapsulation
and inheritance so that commonly used patterns can be defined once and then easily used
in multiple recipes.
For reference information on the Yocto Project classes, see the
"Classes" chapter of the
Yocto Project Reference Manual.
Class files end with the .bbclass
filename extension.
Configuration File:
Configuration information in various .conf
files provides global definitions of variables.
The conf/local.conf
configuration file in
the
Build Directory
contains user-defined variables that affect every build.
The meta-poky/conf/distro/poky.conf
configuration file defines Yocto "distro" configuration
variables used only when building with this policy.
Machine configuration files, which
are located throughout the
Source Directory, define
variables for specific hardware and are only used when building
for that target (e.g. the
machine/beaglebone.conf
configuration
file defines variables for the Texas Instruments ARM Cortex-A8
development board).
Configuration files end with a .conf
filename extension.
Cross-Development Toolchain: In general, a cross-development toolchain is a collection of software development tools and utilities that run on one architecture and allow you to develop software for a different, or targeted, architecture. These toolchains contain cross-compilers, linkers, and debuggers that are specific to the target architecture.
The Yocto Project supports two different cross-development toolchains:
A toolchain only used by and within BitBake when building an image for a target architecture.
A relocatable toolchain used outside of BitBake by developers when developing applications that will run on a targeted device.
Creation of these toolchains is simple and automated. For information on toolchain concepts as they apply to the Yocto Project, see the "Cross-Development Toolchain Generation" section in the Yocto Project Reference Manual. You can also find more information on using the relocatable toolchain in the Yocto Project Software Development Kit (SDK) Developer's Guide.
Image: An image is an artifact of the BitBake build process given a collection of recipes and related Metadata. Images are the binary output that run on specific hardware or QEMU and are used for specific use-cases. For a list of the supported image types that the Yocto Project provides, see the "Images" chapter in the Yocto Project Reference Manual.
Layer: A collection of recipes representing the core, a BSP, or an application stack. For a discussion specifically on BSP Layers, see the "BSP Layers" section in the Yocto Project Board Support Packages (BSP) Developer's Guide.
Metadata:
The files that BitBake parses when building an image.
In general, Metadata includes recipes, classes, and
configuration files.
In the context of the kernel ("kernel Metadata"),
it refers to Metadata in the meta
branches of the kernel source Git repositories.
OE-Core: A core set of Metadata originating
with OpenEmbedded (OE) that is shared between OE and the Yocto Project.
This Metadata is found in the meta
directory of the
Source Directory.
OpenEmbedded Build System: The build system specific to the Yocto Project. The OpenEmbedded build system is based on another project known as "Poky", which uses BitBake as the task executor. Throughout the Yocto Project documentation set, the OpenEmbedded build system is sometimes referred to simply as "the build system". If other build systems, such as a host or target build system are referenced, the documentation clearly states the difference.
Package: In the context of the Yocto Project, this term refers to a recipe's packaged output produced by BitBake (i.e. a "baked recipe"). A package is generally the compiled binaries produced from the recipe's sources. You "bake" something by running it through BitBake.
It is worth noting that the term "package" can, in general, have subtle meanings. For example, the packages referred to in the "The Build Host Packages" section are compiled binaries that, when installed, add functionality to your Linux distribution.
Another point worth noting is that historically within the Yocto Project,
recipes were referred to as packages - thus, the existence of several BitBake
variables that are seemingly mis-named,
(e.g. PR
,
PV
, and
PE
).
Package Groups:
Arbitrary groups of software Recipes.
You use package groups to hold recipes that, when built,
usually accomplish a single task.
For example, a package group could contain the recipes for a
company’s proprietary or value-add software.
Or, the package group could contain the recipes that enable
graphics.
A package group is really just another recipe.
Because package group files are recipes, they end with the
.bb
filename extension.
Poky: The term "poky" can mean several things. In its most general sense, it is an open-source project that was initially developed by OpenedHand. With OpenedHand, poky was developed off of the existing OpenEmbedded build system becoming a commercially supportable build system for embedded Linux. After Intel Corporation acquired OpenedHand, the project poky became the basis for the Yocto Project's build system.
Within the Yocto Project source repositories,
poky
exists as a separate Git
repository you can clone to yield a local copy on your
host system.
Thus, "poky" can refer to the local copy of the Source
Directory used for development within the Yocto
Project.
Finally, "poky" can refer to the default
DISTRO
(i.e. distribution) created when you use the Yocto
Project in conjunction with the
poky
repository to build an image.
Recipe:
A set of instructions for building packages.
A recipe describes where you get source code, which patches
to apply, how to configure the source, how to compile it and so on.
Recipes also describe dependencies for libraries or for other
recipes.
Recipes represent the logical unit of execution, the software
to build, the images to build, and use the
.bb
file extension.
Source Directory:
This term refers to the directory structure created as a result
of creating a local copy of the poky
Git
repository git://git.yoctoproject.org/poky
or expanding a released poky
tarball.
poky
Git repository is the recommended method for setting up
your Source Directory.
Sometimes you might hear the term "poky directory" used to refer to this directory structure.
The Source Directory contains BitBake, Documentation, Metadata and other files that all support the Yocto Project. Consequently, you must have the Source Directory in place on your development system in order to do any development using the Yocto Project.
When you create a local copy of the Git repository, you
can name the repository anything you like.
Throughout much of the documentation, "poky"
is used as the name of the top-level folder of the local copy of
the poky Git repository.
So, for example, cloning the poky
Git
repository results in a local Git repository whose top-level
folder is also named "poky".
While it is not recommended that you use tarball expansion
to set up the Source Directory, if you do, the top-level
directory name of the Source Directory is derived from the
Yocto Project release tarball.
For example, downloading and unpacking
poky-pyro-18.0.3.tar.bz2
results in a
Source Directory whose root folder is named
poky-pyro-18.0.3
.
It is important to understand the differences between the
Source Directory created by unpacking a released tarball as
compared to cloning
git://git.yoctoproject.org/poky
.
When you unpack a tarball, you have an exact copy of the files
based on the time of release - a fixed release point.
Any changes you make to your local files in the Source Directory
are on top of the release and will remain local only.
On the other hand, when you clone the poky
Git repository, you have an active development repository with
access to the upstream repository's branches and tags.
In this case, any local changes you make to the local
Source Directory can be later applied to active development
branches of the upstream poky
Git
repository.
For more information on concepts related to Git repositories, branches, and tags, see the "Repositories, Tags, and Branches" section.
Task:
A unit of execution for BitBake (e.g.
do_compile
,
do_fetch
,
do_patch
,
and so forth).
Upstream: A reference to source code or repositories that are not local to the development system but located in a master area that is controlled by the maintainer of the source code. For example, in order for a developer to work on a particular piece of code, they need to first get a copy of it from an "upstream" source.
Because open source projects are open to the public, they have different licensing structures in place. License evolution for both Open Source and Free Software has an interesting history. If you are interested in this history, you can find basic information here:
In general, the Yocto Project is broadly licensed under the Massachusetts Institute of Technology (MIT) License. MIT licensing permits the reuse of software within proprietary software as long as the license is distributed with that software. MIT is also compatible with the GNU General Public License (GPL). Patches to the Yocto Project follow the upstream licensing scheme. You can find information on the MIT license here. You can find information on the GNU GPL here.
When you build an image using the Yocto Project, the build process uses a
known list of licenses to ensure compliance.
You can find this list in the
Source Directory at
meta/files/common-licenses
.
Once the build completes, the list of all licenses found and used during that build are
kept in the
Build Directory at
tmp/deploy/licenses
.
If a module requires a license that is not in the base list, the build process generates a warning during the build. These tools make it easier for a developer to be certain of the licenses with which their shipped products must comply. However, even with these tools it is still up to the developer to resolve potential licensing issues.
The base list of licenses used by the build process is a combination of the Software Package Data Exchange (SPDX) list and the Open Source Initiative (OSI) projects. SPDX Group is a working group of the Linux Foundation that maintains a specification for a standard format for communicating the components, licenses, and copyrights associated with a software package. OSI is a corporation dedicated to the Open Source Definition and the effort for reviewing and approving licenses that conform to the Open Source Definition (OSD).
You can find a list of the combined SPDX and OSI licenses that the
Yocto Project uses in the
meta/files/common-licenses
directory in your
Source Directory.
For information that can help you maintain compliance with various open source licensing during the lifecycle of a product created using the Yocto Project, see the "Maintaining Open Source License Compliance During Your Product's Lifecycle" section.
The Yocto Project makes extensive use of Git, which is a free, open source distributed version control system. Git supports distributed development, non-linear development, and can handle large projects. It is best that you have some fundamental understanding of how Git tracks projects and how to work with Git if you are going to use the Yocto Project for development. This section provides a quick overview of how Git works and provides you with a summary of some essential Git commands.
For more information on Git, see http://git-scm.com/documentation. If you need to download Git, go to http://git-scm.com/download.
As mentioned earlier in the section "Yocto Project Source Repositories", the Yocto Project maintains source repositories at http://git.yoctoproject.org/cgit.cgi. If you look at this web-interface of the repositories, each item is a separate Git repository.
Git repositories use branching techniques that track content change (not files) within a project (e.g. a new feature or updated documentation). Creating a tree-like structure based on project divergence allows for excellent historical information over the life of a project. This methodology also allows for an environment from which you can do lots of local experimentation on projects as you develop changes or new features.
A Git repository represents all development efforts for a given project.
For example, the Git repository poky
contains all changes
and developments for Poky over the course of its entire life.
That means that all changes that make up all releases are captured.
The repository maintains a complete history of changes.
You can create a local copy of any repository by "cloning" it with the Git
clone
command.
When you clone a Git repository, you end up with an identical copy of the
repository on your development system.
Once you have a local copy of a repository, you can take steps to develop locally.
For examples on how to clone Git repositories, see the
"Getting Set Up" section.
It is important to understand that Git tracks content change and
not files.
Git uses "branches" to organize different development efforts.
For example, the poky
repository has
several branches that include the current
pyro
branch, the
master
branch, and many branches for past
Yocto Project releases.
You can see all the branches by going to
http://git.yoctoproject.org/cgit.cgi/poky/ and
clicking on the
[...]
link beneath the "Branch" heading.
Each of these branches represents a specific area of development.
The master
branch represents the current or most recent
development.
All other branches represent offshoots of the master
branch.
When you create a local copy of a Git repository, the copy has the same set
of branches as the original.
This means you can use Git to create a local working area (also called a branch)
that tracks a specific development branch from the source Git repository.
in other words, you can define your local Git environment to work on any development
branch in the repository.
To help illustrate, here is a set of commands that creates a local copy of the
poky
Git repository and then creates and checks out a local
Git branch that tracks the Yocto Project 2.3.3 Release (Pyro) development:
$ cd ~ $ git clone git://git.yoctoproject.org/poky $ cd poky $ git checkout -b pyro origin/pyro
In this example, the name of the top-level directory of your local Source Directory is "poky" and the name of that local working area (local branch) you just created and checked out is "pyro". The files in your local repository now reflect the same files that are in the "pyro" development branch of the Yocto Project's "poky" upstream repository. It is important to understand that when you create and checkout a local working branch based on a branch name, your local environment matches the "tip" of that development branch at the time you created your local branch, which could be different from the files at the time of a similarly named release. In other words, creating and checking out a local branch based on the "pyro" branch name is not the same as cloning and checking out the "master" branch. Keep reading to see how you create a local snapshot of a Yocto Project Release.
Git uses "tags" to mark specific changes in a repository.
Typically, a tag is used to mark a special point such as the final
change before a project is released.
You can see the tags used with the poky
Git
repository by going to
http://git.yoctoproject.org/cgit.cgi/poky/ and
clicking on the
[...]
link beneath the "Tag" heading.
Some key tags are
dizzy-12.0.0
,
fido-13.0.0
,
jethro-14.0.0
, and
pyro-18.0.3
.
These tags represent Yocto Project releases.
When you create a local copy of the Git repository, you also have access to all the tags. Similar to branches, you can create and checkout a local working Git branch based on a tag name. When you do this, you get a snapshot of the Git repository that reflects the state of the files when the change was made associated with that tag. The most common use is to checkout a working branch that matches a specific Yocto Project release. Here is an example:
$ cd ~ $ git clone git://git.yoctoproject.org/poky $ cd poky $ git checkout -b my-pyro-18.0.3 pyro-18.0.3
In this example, the name of the top-level directory of your local Yocto Project
Files Git repository is poky
.
And, the name of the local branch you have created and checked out is
my-pyro-18.0.3
.
The files in your repository now exactly match the Yocto Project 2.3.3
Release tag (pyro-18.0.3
).
It is important to understand that when you create and checkout a local
working branch based on a tag, your environment matches a specific point
in time and not the entire development branch.
Git has an extensive set of commands that lets you manage changes and perform collaboration over the life of a project. Conveniently though, you can manage with a small set of basic operations and workflows once you understand the basic philosophy behind Git. You do not have to be an expert in Git to be functional. A good place to look for instruction on a minimal set of Git commands is here. If you need to download Git, you can do so here, although any reasonably current Linux distribution should already have an installable package for Git.
If you do not know much about Git, you should educate yourself by visiting the links previously mentioned.
The following list briefly describes some basic Git operations as a way to get started. As with any set of commands, this list (in most cases) simply shows the base command and omits the many arguments they support. See the Git documentation for complete descriptions and strategies on how to use these commands:
git init
: Initializes an empty Git repository.
You cannot use Git commands unless you have a .git
repository.
git clone
:
Creates a local clone of a Git repository.
During collaboration, this command allows you to create a
local Git repository that is on equal footing with a fellow
developer’s Git repository.
git add
: Stages updated file contents
to the index that
Git uses to track changes.
You must stage all files that have changed before you can commit them.
git commit
: Creates a "commit" that documents
the changes you made.
Commits are used for historical purposes, for determining if a maintainer of a project
will allow the change, and for ultimately pushing the change from your local Git repository
into the project’s upstream (or master) repository.
git status
: Reports any modified files that
possibly need to be staged and committed.
git checkout
branch-name
: Changes
your working branch.
This command is analogous to "cd".
git checkout –b
working-branch
: Creates
a working branch on your local machine where you can isolate work.
It is a good idea to use local branches when adding specific features or changes.
This way if you do not like what you have done you can easily get rid of the work.
git branch
: Reports
existing local branches and
tells you the branch in which you are currently working.
git branch -D
branch-name
:
Deletes an existing local branch.
You need to be in a local branch other than the one you are deleting
in order to delete branch-name
.
git pull
: Retrieves information
from an upstream Git
repository and places it in your local Git repository.
You use this command to make sure you are synchronized with the repository
from which you are basing changes (.e.g. the master branch).
git push
:
Sends all your committed local changes to an upstream Git
repository (e.g. a contribution repository).
The maintainer of the project draws from these repositories
when adding changes to the project’s master repository or
other development branch.
git merge
: Combines or adds changes from one
local branch of your repository with another branch.
When you create a local Git repository, the default branch is named "master".
A typical workflow is to create a temporary branch for isolated work, make and commit your
changes, switch to your local master branch, merge the changes from the temporary branch into the
local master branch, and then delete the temporary branch.
git cherry-pick
: Choose and apply specific
commits from one branch into another branch.
There are times when you might not be able to merge all the changes in one branch with
another but need to pick out certain ones.
gitk
: Provides a GUI view of the branches
and changes in your local Git repository.
This command is a good way to graphically see where things have diverged in your
local repository.
git log
: Reports a history of your changes to the
repository.
git diff
: Displays line-by-line differences
between your local working files and the same files in the upstream Git repository that your
branch currently tracks.
This section provides some overview on workflows using Git. In particular, the information covers basic practices that describe roles and actions in a collaborative development environment. Again, if you are familiar with this type of development environment, you might want to just skip this section.
The Yocto Project files are maintained using Git in a "master" branch whose Git history tracks every change and whose structure provides branches for all diverging functionality. Although there is no need to use Git, many open source projects do so. For the Yocto Project, a key individual called the "maintainer" is responsible for the "master" branch of a given Git repository. The "master" branch is the “upstream” repository where the final builds of the project occur. The maintainer is responsible for accepting changes from other developers and for organizing the underlying branch structure to reflect release strategies and so forth.
The project also has an upstream contribution Git repository named
poky-contrib
.
You can see all the branches in this repository using the web interface
of the
Source Repositories organized
within the "Poky Support" area.
These branches temporarily hold changes to the project that have been
submitted or committed by the Yocto Project development team and by
community members who contribute to the project.
The maintainer determines if the changes are qualified to be moved
from the "contrib" branches into the "master" branch of the Git
repository.
Developers (including contributing community members) create and maintain cloned repositories of the upstream "master" branch. These repositories are local to their development platforms and are used to develop changes. When a developer is satisfied with a particular feature or change, they "push" the changes to the appropriate "contrib" repository.
Developers are responsible for keeping their local repository up-to-date with "master". They are also responsible for straightening out any conflicts that might arise within files that are being worked on simultaneously by more than one person. All this work is done locally on the developer’s machines before anything is pushed to a "contrib" area and examined at the maintainer’s level.
A somewhat formal method exists by which developers commit changes and push them into the "contrib" area and subsequently request that the maintainer include them into "master" This process is called “submitting a patch” or "submitting a change." For information on submitting patches and changes, see the "How to Submit a Change" section.
To summarize the environment: a single point of entry exists for changes into the project’s "master" branch of the Git repository, which is controlled by the project’s maintainer. And, a set of developers exist who independently develop, test, and submit changes to "contrib" areas for the maintainer to examine. The maintainer then chooses which changes are going to become a permanent part of the project.
While each development environment is unique, there are some best practices or methods that help development run smoothly. The following list describes some of these practices. For more information about Git workflows, see the workflow topics in the Git Community Book.
Make Small Changes: It is best to keep the changes you commit small as compared to bundling many disparate changes into a single commit. This practice not only keeps things manageable but also allows the maintainer to more easily include or refuse changes.
It is also good practice to leave the repository in a state that allows you to still successfully build your project. In other words, do not commit half of a feature, then add the other half as a separate, later commit. Each commit should take you from one buildable project state to another buildable state.
Use Branches Liberally: It is very easy to create, use, and delete local branches in your working Git repository. You can name these branches anything you like. It is helpful to give them names associated with the particular feature or change on which you are working. Once you are done with a feature or change and have merged it into your local master branch, simply discard the temporary branch.
Merge Changes: The git merge
command allows you to take the
changes from one branch and fold them into another branch.
This process is especially helpful when more than a single developer might be working
on different parts of the same feature.
Merging changes also automatically identifies any collisions or "conflicts"
that might happen as a result of the same lines of code being altered by two different
developers.
Manage Branches: Because branches are easy to use, you should use a system where branches indicate varying levels of code readiness. For example, you can have a "work" branch to develop in, a "test" branch where the code or change is tested, a "stage" branch where changes are ready to be committed, and so forth. As your project develops, you can merge code across the branches to reflect ever-increasing stable states of the development.
Use Push and Pull: The push-pull workflow is based on the
concept of developers "pushing" local commits to a remote repository, which is
usually a contribution repository.
This workflow is also based on developers "pulling" known states of the project down into their
local development repositories.
The workflow easily allows you to pull changes submitted by other developers from the
upstream repository into your work area ensuring that you have the most recent software
on which to develop.
The Yocto Project has two scripts named create-pull-request
and
send-pull-request
that ship with the release to facilitate this
workflow.
You can find these scripts in the scripts
folder of the
Source Directory.
For information on how to use these scripts, see the
"Using Scripts to Push a Change Upstream and Request a Pull" section.
Patch Workflow: This workflow allows you to notify the
maintainer through an email that you have a change (or patch) you would like considered
for the "master" branch of the Git repository.
To send this type of change, you format the patch and then send the email using the Git commands
git format-patch
and git send-email
.
For information on how to use these scripts, see the
"How to Submit a Change"
section.
The Yocto Project uses its own implementation of Bugzilla to track bugs. Implementations of Bugzilla work well for group development because they track bugs and code changes, can be used to communicate changes and problems with developers, can be used to submit and review patches, and can be used to manage quality assurance. The home page for the Yocto Project implementation of Bugzilla is http://bugzilla.yoctoproject.org.
Sometimes it is helpful to submit, investigate, or track a bug against the Yocto Project itself such as when discovering an issue with some component of the build system that acts contrary to the documentation or your expectations. Following is the general procedure for submitting a new bug using the Yocto Project Bugzilla. You can find more information on defect management, bug tracking, and feature request processes all accomplished through the Yocto Project Bugzilla on the wiki page.
Always use the Yocto Project implementation of Bugzilla to submit a bug.
When submitting a new bug, be sure to choose the appropriate Classification, Product, and Component for which the issue was found. Defects for the Yocto Project fall into one of seven classifications: Yocto Project Components, Infrastructure, Build System & Metadata, Documentation, QA/Testing, Runtime and Hardware. Each of these Classifications break down into multiple Products and, in some cases, multiple Components.
Use the bug form to choose the correct Hardware and Architecture for which the bug applies.
Indicate the Yocto Project version you were using when the issue occurred.
Be sure to indicate the Severity of the bug. Severity communicates how the bug impacted your work.
Select the appropriate "Documentation change" item for the bug. Fixing a bug may or may not affect the Yocto Project documentation.
Provide a brief summary of the issue. Try to limit your summary to just a line or two and be sure to capture the essence of the issue.
Provide a detailed description of the issue. You should provide as much detail as you can about the context, behavior, output, and so forth that surrounds the issue. You can even attach supporting files for output from logs by using the "Add an attachment" button.
Be sure to copy the appropriate people in the "CC List" for the bug. See the "How to Submit a Change" section for information about finding out who is responsible for code.
Submit the bug by clicking the "Submit Bug" button.
Contributions to the Yocto Project and OpenEmbedded are very welcome. Because the system is extremely configurable and flexible, we recognize that developers will want to extend, configure or optimize it for their specific uses. You should send patches to the appropriate mailing list so that they can be reviewed and merged by the appropriate maintainer.
The Yocto Project uses a mailing list and patch-based workflow
that is similar to the Linux kernel but contains important
differences.
In general, a mailing list exists through which you can submit
patches.
The specific mailing list you need to use depends on the
location of the code you are changing.
Each component (e.g. layer) should have a
README
file that indicates where to send
the changes and which process to follow.
You can send the patch to the mailing list using whichever approach you feel comfortable with to generate the patch. Once sent, the patch is usually reviewed by the community at large. If somebody has concerns with the patch, they will usually voice their concern over the mailing list. If a patch does not receive any negative reviews, the maintainer of the affected layer typically takes the patch, tests it, and then based on successful testing, merges the patch.
Specific to OpenEmbedded-Core, two commonly used testing trees exist:
"ross/mut" branch:
The "mut" (master-under-test) tree
exists in the poky-contrib
repository
in the
Yocto Project source repositories.
"master-next" branch: This branch is part of the main "poky" repository in the Yocto Project source repositories.
Maintainers use these branches to test submissions prior to merging patches. Thus, you can get an idea of the status of a patch based on whether the patch has been merged into one of these branches.
This system is imperfect and patches can sometimes get lost in the flow. Asking about the status of a patch is reasonable if the patch has been idle for a while with no feedback. The Yocto Project does have plans to use Patchwork to track the status of patches and also to automatically preview patches.
The following sections provide general instructions for both pushing changes upstream and for submitting changes as patches.
The "poky" repository, which is the Yocto Project's reference build environment, is a hybrid repository that contains several individual pieces (e.g. BitBake, OpenEmbedded-Core, meta-yocto, documentation, and so forth) built using the combo-layer tool. The upstream location used for submitting changes varies by component:
Core Metadata:
Send your patch to the
openembedded-core
mailing list. For example, a change to anything under
the meta
or
scripts
directories should be sent
to this mailing list.
BitBake:
For changes to BitBake (i.e. anything under the
bitbake
directory), send your patch
to the
bitbake-devel
mailing list.
"meta-yocto-bsp" and "meta-poky" trees: These trees are part of the "meta-yocto" repository in the Yocto Project source repositories. Use the poky mailing list.
For changes to other layers hosted in the Yocto Project source
repositories (i.e. yoctoproject.org
), tools,
and the Yocto Project documentation, use the
Yocto Project
general mailing list.
For additional recipes that do not fit into the core Metadata, you
should determine which layer the recipe should go into and submit
the change in the manner recommended by the documentation (e.g.
the README
file) supplied with the layer.
If in doubt, please ask on the Yocto general mailing list or on
the openembedded-devel mailing list.
When submitting any change, you can check who you should be notifying. Use either of these methods to find out:
Maintenance File:
Examine the maintainers.inc
file, which is
located in the
Source Directory
at meta-poky/conf/distro/include
, to
see who is responsible for code.
Search by File: Using Git, you can enter the following command to bring up a short list of all commits against a specific file:
git shortlog -- filename
Just provide the name of the file for which you are interested. The information returned is not ordered by history but does include a list of all committers grouped by name. From the list, you can see who is responsible for the bulk of the changes against the file.
For a list of the Yocto Project and related mailing lists, see the "Mailing lists" section in the Yocto Project Reference Manual.
When you send a patch, be sure to include a "Signed-off-by:" line in the same style as required by the Linux kernel. Adding this line signifies that you, the submitter, have agreed to the Developer's Certificate of Origin 1.1 as follows:
Developer's Certificate of Origin 1.1 By making a contribution to this project, I certify that: (a) The contribution was created in whole or in part by me and I have the right to submit it under the open source license indicated in the file; or (b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the same open source license (unless I am permitted to submit under a different license), as indicated in the file; or (c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it. (d) I understand and agree that this project and the contribution are public and that a record of the contribution (including all personal information I submit with it, including my sign-off) is maintained indefinitely and may be redistributed consistent with this project or the open source license(s) involved.
In a collaborative environment, it is necessary to have some sort of standard or method through which you submit changes. Otherwise, things could get quite chaotic. One general practice to follow is to make small, controlled changes. Keeping changes small and isolated aids review, makes merging/rebasing easier and keeps the change history clean should anyone need to refer to it in future.
When you make a commit, you must follow certain standards established by the OpenEmbedded and Yocto Project development teams. For each commit, you must provide a single-line summary of the change and you should almost always provide a more detailed description of what you did (i.e. the body of the commit message). The only exceptions for not providing a detailed description would be if your change is a simple, self-explanatory change that needs no further description beyond the summary. Here are the guidelines for composing a commit message:
Provide a single-line, short summary of the change. This summary is typically viewable in the "shortlist" of changes. Thus, providing something short and descriptive that gives the reader a summary of the change is useful when viewing a list of many commits. You should prefix this short description with the recipe name (if changing a recipe), or else with the short form path to the file being changed.
For the body of the commit message, provide detailed information that describes what you changed, why you made the change, and the approach you used. It might also be helpful if you mention how you tested the change. Provide as much detail as you can in the body of the commit message.
If the change addresses a specific bug or issue that is
associated with a bug-tracking ID, include a reference
to that ID in your detailed description.
For example, the Yocto Project uses a specific convention
for bug references - any commit that addresses a specific
bug should use the following form for the detailed
description.
Be sure to use the actual bug-tracking ID from
Bugzilla for
bug-id
:
Fixes [YOCTO #bug-id
]detailed description of change
You can find more guidance on creating well-formed commit messages at this OpenEmbedded wiki page: http://www.openembedded.org/wiki/Commit_Patch_Message_Guidelines.
The basic flow for pushing a change to an upstream "contrib" Git repository is as follows:
Make your changes in your local Git repository.
Stage your changes by using the git add
command on each file you changed.
Commit the change by using the
git commit
command.
Be sure to provide a commit message that follows the
project’s commit message standards as described earlier.
Push the change to the upstream "contrib" repository by
using the git push
command.
Notify the maintainer that you have pushed a change by making a pull
request.
The Yocto Project provides two scripts that conveniently let you generate and send
pull requests to the Yocto Project.
These scripts are create-pull-request
and
send-pull-request
.
You can find these scripts in the scripts
directory
within the Source Directory.
Using these scripts correctly formats the requests without introducing any whitespace or HTML formatting. The maintainer that receives your patches needs to be able to save and apply them directly from your emails. Using these scripts is the preferred method for sending patches.
For help on using these scripts, simply provide the
-h
argument as follows:
$ poky/scripts/create-pull-request -h $ poky/scripts/send-pull-request -h
You can find general Git information on how to push a change upstream in the Git Community Book.
You can submit patches without using the create-pull-request
and
send-pull-request
scripts described in the previous section.
However, keep in mind, the preferred method is to use the scripts.
Depending on the components changed, you need to submit the email to a specific mailing list. For some guidance on which mailing list to use, see the list in the "How to Submit a Change" section. For a description of the available mailing lists, see the "Mailing Lists" section in the Yocto Project Reference Manual.
Here is the general procedure on how to submit a patch through email without using the scripts:
Make your changes in your local Git repository.
Stage your changes by using the git add
command on each file you changed.
Commit the change by using the
git commit --signoff
command.
Using the --signoff
option identifies you as the person
making the change and also satisfies the Developer's Certificate of
Origin (DCO) shown earlier.
When you form a commit, you must follow certain standards established by the Yocto Project development team. See the earlier section "How to Submit a Change" for Yocto Project commit message standards.
Format the commit into an email message.
To format commits, use the git format-patch
command.
When you provide the command, you must include a revision list or a number of patches
as part of the command.
For example, either of these two commands takes your most
recent single commit and formats it as an email message in
the current directory:
$ git format-patch -1
or
$ git format-patch HEAD~
After the command is run, the current directory contains a
numbered .patch
file for the commit.
If you provide several commits as part of the command,
the git format-patch
command produces a
series of numbered files in the current directory – one for each commit.
If you have more than one patch, you should also use the
--cover
option with the command, which generates a
cover letter as the first "patch" in the series.
You can then edit the cover letter to provide a description for
the series of patches.
For information on the git format-patch
command,
see GIT_FORMAT_PATCH(1)
displayed using the
man git-format-patch
command.
Import the files into your mail client by using the
git send-email
command.
git send-email
, you must have the
the proper Git packages installed.
For Ubuntu, Debian, and Fedora the package is git-email
.The git send-email
command sends email by using a local
or remote Mail Transport Agent (MTA) such as
msmtp
, sendmail
, or through a direct
smtp
configuration in your Git config
file.
If you are submitting patches through email only, it is very important
that you submit them without any whitespace or HTML formatting that
either you or your mailer introduces.
The maintainer that receives your patches needs to be able to save and
apply them directly from your emails.
A good way to verify that what you are sending will be applicable by the
maintainer is to do a dry run and send them to yourself and then
save and apply them as the maintainer would.
The git send-email
command is the preferred method
for sending your patches since there is no risk of compromising whitespace
in the body of the message, which can occur when you use your own mail client.
The command also has several options that let you
specify recipients and perform further editing of the email message.
For information on how to use the git send-email
command,
see GIT-SEND-EMAIL(1)
displayed using
the man git-send-email
command.
Many development models exist for which you can use the Yocto Project. This chapter overviews simple methods that use tools provided by the Yocto Project:
System Development: System Development covers Board Support Package (BSP) development and kernel modification or configuration. For an example on how to create a BSP, see the "Creating a New BSP Layer Using the yocto-bsp Script" section in the Yocto Project Board Support Package (BSP) Developer's Guide. For more complete information on how to work with the kernel, see the Yocto Project Linux Kernel Development Manual.
User Application Development: User Application Development covers development of applications that you intend to run on target hardware. For information on how to set up your host development system for user-space application development, see the Yocto Project Software Development Kit (SDK) Developer's Guide. For a simple example of user-space application development using the Eclipse™ IDE, see the "Developing Applications Using Eclipse™" section.
Temporary Source Code Modification: Direct modification of temporary source code is a convenient development model to quickly iterate and develop towards a solution. Once you implement the solution, you should of course take steps to get the changes upstream and applied in the affected recipes.
Image Development using Toaster: You can use Toaster to build custom operating system images within the build environment. Toaster provides an efficient interface to the OpenEmbedded build that allows you to start builds and examine build statistics.
Using a Development Shell:
You can use a
devshell
to efficiently debug
commands or simply edit packages.
Working inside a development shell is a quick way to set up the
OpenEmbedded build environment to work on parts of a project.
System development involves modification or creation of an image that you want to run on a specific hardware target. Usually, when you want to create an image that runs on embedded hardware, the image does not require the same number of features that a full-fledged Linux distribution provides. Thus, you can create a much smaller image that is designed to use only the features for your particular hardware.
To help you understand how system development works in the Yocto Project, this section covers two types of image development: BSP creation and kernel modification or configuration.
A BSP is a collection of recipes that, when applied during a build, results in an image that you can run on a particular board. Thus, the package when compiled into the new image, supports the operation of the board.
The remainder of this section presents the basic
steps used to create a BSP using the Yocto Project's
BSP Tools.
Although not required for BSP creation, the
meta-intel
repository, which contains
many BSPs supported by the Yocto Project, is part of the example.
For an example that shows how to create a new layer using the tools, see the "Creating a New BSP Layer Using the yocto-bsp Script" section in the Yocto Project Board Support Package (BSP) Developer's Guide.
The following illustration and list summarize the BSP creation general workflow.
Set up your host development system to support development using the Yocto Project: See the "The Linux Distribution" and the "The Build Host Packages" sections both in the Yocto Project Quick Start for requirements.
Establish a local copy of the project files on your system: You need this Source Directory available on your host system. Having these files on your system gives you access to the build process and to the tools you need. For information on how to set up the Source Directory, see the "Getting Set Up" section.
Establish the meta-intel
repository on your system: Having local copies
of these supported BSP layers on your system gives you
access to layers you might be able to build on or modify
to create your BSP.
For information on how to get these files, see the
"Getting Set Up" section.
Create your own BSP layer using the
yocto-bsp
script:
Layers are ideal for
isolating and storing work for a given piece of hardware.
A layer is really just a location or area in which you place
the recipes and configurations for your BSP.
In fact, a BSP is, in itself, a special type of layer.
The simplest way to create a new BSP layer that is compliant with the
Yocto Project is to use the yocto-bsp
script.
For information about that script, see the
"Creating a New BSP Layer Using the yocto-bsp Script"
section in the Yocto Project Board Support (BSP) Developer's Guide.
Another example that illustrates a layer is an application. Suppose you are creating an application that has library or other dependencies in order for it to compile and run. The layer, in this case, would be where all the recipes that define those dependencies are kept. The key point for a layer is that it is an isolated area that contains all the relevant information for the project that the OpenEmbedded build system knows about. For more information on layers, see the "Understanding and Creating Layers" section. For more information on BSP layers, see the "BSP Layers" section in the Yocto Project Board Support Package (BSP) Developer's Guide.
Five BSPs exist that are part of the Yocto Project release:
beaglebone
(ARM),
mpc8315e
(PowerPC),
and edgerouter
(MIPS).
The recipes and configurations for these five BSPs
are located and dispersed within the
Source Directory.
Three core Intel BSPs exist as part of the Yocto
Project release in the
meta-intel
layer:
intel-core2-32
,
which is a BSP optimized for the Core2 family of CPUs
as well as all CPUs prior to the Silvermont core.
intel-corei7-64
,
which is a BSP optimized for Nehalem and later
Core and Xeon CPUs as well as Silvermont and later
Atom CPUs, such as the Baytrail SoCs.
intel-quark
,
which is a BSP optimized for the Intel Galileo
gen1 & gen2 development boards.
When you set up a layer for a new BSP, you should follow a standard layout.
This layout is described in the
"Example Filesystem Layout"
section of the Board Support Package (BSP) Development Guide.
In the standard layout, you will notice a suggested structure for recipes and
configuration information.
You can see the standard layout for a BSP by examining
any supported BSP found in the meta-intel
layer inside
the Source Directory.
Make configuration changes to your new BSP
layer: The standard BSP layer structure organizes the files you need
to edit in conf
and several recipes-*
directories within the BSP layer.
Configuration changes identify where your new layer is on the local system
and identify which kernel you are going to use.
When you run the yocto-bsp
script, you are able to interactively
configure many things for the BSP (e.g. keyboard, touchscreen, and so forth).
Make recipe changes to your new BSP layer: Recipe
changes include altering recipes (.bb
files), removing
recipes you do not use, and adding new recipes or append files
(.bbappend
) that you need to support your hardware.
Prepare for the build: Once you have made all the
changes to your BSP layer, there remains a few things
you need to do for the OpenEmbedded build system in order for it to create your image.
You need to get the build environment ready by sourcing an environment setup script
(i.e. oe-init-build-env
or
oe-init-build-env-memres
)
and you need to be sure two key configuration files are configured appropriately:
the conf/local.conf
and the
conf/bblayers.conf
file.
You must make the OpenEmbedded build system aware of your new layer.
See the
"Enabling Your Layer" section
for information on how to let the build system know about your new layer.
The entire process for building an image is overviewed in the section "Building Images" section of the Yocto Project Quick Start. You might want to reference this information.
Build the image: The OpenEmbedded build system uses the BitBake tool to build images based on the type of image you want to create. You can find more information about BitBake in the BitBake User Manual.
The build process supports several types of images to satisfy different needs. See the "Images" chapter in the Yocto Project Reference Manual for information on supported images.
You can view a video presentation on "Building Custom Embedded Images with Yocto" at Free Electrons. After going to the page, just search for "Embedded". You can also find supplemental information in the Yocto Project Board Support Package (BSP) Developer's Guide. Finally, there is helpful material and links on this wiki page. Although a bit dated, you might find the information on the wiki helpful.
Kernel modification involves changing the Yocto Project kernel, which could involve changing
configuration options as well as adding new kernel recipes.
Configuration changes can be added in the form of configuration fragments, while recipe
modification comes through the kernel's recipes-kernel
area
in a kernel layer you create.
The remainder of this section presents a high-level overview of the Yocto Project kernel architecture and the steps to modify the kernel. You can reference the "Patching the Kernel" section for an example that changes the source code of the kernel. For information on how to configure the kernel, see the "Configuring the Kernel" section. For more information on the kernel and on modifying the kernel, see the Yocto Project Linux Kernel Development Manual.
Traditionally, when one thinks of a patched kernel, they think of a base kernel source tree and a fixed structure that contains kernel patches. The Yocto Project, however, employs mechanisms that, in a sense, result in a kernel source generator. By the end of this section, this analogy will become clearer.
You can find a web interface to the Yocto Project kernel source repositories at http://git.yoctoproject.org. If you look at the interface, you will see to the left a grouping of Git repositories titled "Yocto Linux Kernel." Within this group, you will find several kernels supported by the Yocto Project:
linux-yocto-3.14
- The
stable Yocto Project kernel to use with the Yocto
Project Releases 1.6 and 1.7.
This kernel is based on the Linux 3.14 released kernel.
linux-yocto-3.17
- An
additional, unsupported Yocto Project kernel used with
the Yocto Project Release 1.7.
This kernel is based on the Linux 3.17 released kernel.
linux-yocto-3.19
- The
stable Yocto Project kernel to use with the Yocto
Project Release 1.8.
This kernel is based on the Linux 3.19 released kernel.
linux-yocto-4.1
- The
stable Yocto Project kernel to use with the Yocto
Project Release 2.0.
This kernel is based on the Linux 4.1 released kernel.
linux-yocto-4.4
- The
stable Yocto Project kernel to use with the Yocto
Project Release 2.1.
This kernel is based on the Linux 4.4 released kernel.
linux-yocto-dev
- A
development kernel based on the latest upstream release
candidate available.
For Yocto Project releases 1.7, 1.8, and 2.0,
the LTSI kernel is linux-yocto-3.14
.
For Yocto Project release 2.1, the
LTSI kernel is linux-yocto-4.1
.
The kernels are maintained using the Git revision control system that structures them using the familiar "tree", "branch", and "leaf" scheme. Branches represent diversions from general code to more specific code, while leaves represent the end-points for a complete and unique kernel whose source files, when gathered from the root of the tree to the leaf, accumulate to create the files necessary for a specific piece of hardware and its features. The following figure displays this concept:
Within the figure, the "Kernel.org Branch Point" represents the point in the tree
where a supported base kernel is modified from the Linux kernel.
For example, this could be the branch point for the linux-yocto-3.19
kernel.
Thus, everything further to the right in the structure is based on the
linux-yocto-3.19
kernel.
Branch points to the right in the figure represent where the
linux-yocto-3.19
kernel is modified for specific hardware
or types of kernels, such as real-time kernels.
Each leaf thus represents the end-point for a kernel designed to run on a specific
targeted device.
The overall result is a Git-maintained repository from which all the supported kernel types can be derived for all the supported devices. A big advantage to this scheme is the sharing of common features by keeping them in "larger" branches within the tree. This practice eliminates redundant storage of similar features shared among kernels.
Upstream storage of all the available kernel source code is one thing, while representing and using the code on your host development system is another. Conceptually, you can think of the kernel source repositories as all the source files necessary for all the supported kernels. As a developer, you are just interested in the source files for the kernel on which you are working. And, furthermore, you need them available on your host system.
Kernel source code is available on your host system a couple of different ways. If you are working in the kernel all the time, you probably would want to set up your own local Git repository of the kernel tree. If you just need to make some patches to the kernel, you can access temporary kernel source files that were extracted and used during a build. We will just talk about working with the temporary source code. For more information on how to get kernel source code onto your host system, see the "Yocto Project Kernel" bulleted item earlier in the manual.
What happens during the build?
When you build the kernel on your development system, all files needed for the build
are taken from the source repositories pointed to by the
SRC_URI
variable
and gathered in a temporary work area
where they are subsequently used to create the unique kernel.
Thus, in a sense, the process constructs a local source tree specific to your
kernel to generate the new kernel image - a source generator if you will.
The following figure shows the temporary file structure created on your host system when the build occurs. This Build Directory contains all the source files used during the build.
Again, for additional information on the Yocto Project kernel's architecture and its branching strategy, see the Yocto Project Linux Kernel Development Manual. You can also reference the "Patching the Kernel" section for a detailed example that modifies the kernel.
This illustration and the following list summarizes the kernel modification general workflow.
Set up your host development system to support development using the Yocto Project: See "The Linux Distribution" and "The Build Host Packages" sections both in the Yocto Project Quick Start for requirements.
Establish a local copy of project files on your system: Having the Source Directory on your system gives you access to the build process and tools you need. For information on how to get these files, see the bulleted item "Yocto Project Release" earlier in this manual.
Establish the temporary kernel source files: Temporary kernel source files are kept in the Build Directory created by the OpenEmbedded build system when you run BitBake. If you have never built the kernel in which you are interested, you need to run an initial build to establish local kernel source files.
If you are building an image for the first time, you need to get the build
environment ready by sourcing an environment setup script
(i.e. oe-init-build-env
or
oe-init-build-env-memres
).
You also need to be sure two key configuration files
(local.conf
and bblayers.conf
)
are configured appropriately.
The entire process for building an image is overviewed in the "Building Images" section of the Yocto Project Quick Start. You might want to reference this information. You can find more information on BitBake in the BitBake User Manual.
The build process supports several types of images to satisfy different needs. See the "Images" chapter in the Yocto Project Reference Manual for information on supported images.
Make changes to the kernel source code if applicable: Modifying the kernel does not always mean directly changing source files. However, if you have to do this, you make the changes to the files in the Build Directory.
Make kernel configuration changes if applicable:
If your situation calls for changing the kernel's
configuration, you can use
menuconfig
,
which allows you to interactively develop and test the
configuration changes you are making to the kernel.
Saving changes you make with
menuconfig
updates
the kernel's .config
file.
.config
file, which is
found in the Build Directory at
tmp/sysroots/machine-name
/kernel
.
Doing so, can produce unexpected results when the
OpenEmbedded build system regenerates the configuration
file.
Once you are satisfied with the configuration
changes made using menuconfig
and you have saved them, you can directly compare the
resulting .config
file against an
existing original and gather those changes into a
configuration fragment file
to be referenced from within the kernel's
.bbappend
file.
Additionally, if you are working in a BSP layer
and need to modify the BSP's kernel's configuration,
you can use the
yocto-kernel
script as well as menuconfig
.
The yocto-kernel
script lets
you interactively set up kernel configurations.
Rebuild the kernel image with your changes: Rebuilding the kernel image applies your changes.
Standard and extensible Software Development Kits (SDK) make it easy to develop applications inside or outside of the Yocto Project development environment. Tools exist to help the application developer during any phase of development. For information on how to install and use an SDK, see the Yocto Project Software Development Kit (SDK) Developer's Guide.
A common development workflow consists of modifying project source files that are external to the Yocto Project and then integrating that project's build output into an image built using the OpenEmbedded build system. Given this scenario, development engineers typically want to stick to their familiar project development tools and methods, which allows them to just focus on the project.
Several workflows exist that allow you to develop, build, and test code that is going to be integrated into an image built using the OpenEmbedded build system. This section describes two:
devtool
:
A set of tools to aid in working on the source code built by
the OpenEmbedded build system.
Section
"Using devtool
in Your Workflow"
describes this workflow.
If you want more information that showcases the workflow, click
here
for a presentation by Trevor Woerner that, while somewhat dated,
provides detailed background information and a complete
working tutorial.
Quilt: A powerful tool that allows you to capture source code changes without having a clean source tree. While Quilt is not the preferred workflow of the two, this section includes it for users that are committed to using the tool. See the "Using Quilt in Your Workflow" section for more information.
devtool
in Your Workflow¶
As mentioned earlier, devtool
helps
you easily develop projects whose build output must be part of
an image built using the OpenEmbedded build system.
Three entry points exist that allow you to develop using
devtool
:
devtool add
devtool modify
devtool upgrade
The remainder of this section presents these workflows.
See the
"devtool
Quick Reference"
in the Yocto Project Reference Manual for a
devtool
quick reference.
devtool add
to Add an Application¶
The devtool add
command generates
a new recipe based on existing source code.
This command takes advantage of the
workspace
layer that many devtool
commands
use.
The command is flexible enough to allow you to extract source
code into both the workspace or a separate local Git repository
and to use existing code that does not need to be extracted.
Depending on your particular scenario, the arguments and options
you use with devtool add
form different
combinations.
The following diagram shows common development flows
you would use with the devtool add
command:
Generating the New Recipe:
The top part of the flow shows three scenarios by which
you could use devtool add
to
generate a recipe based on existing source code.
In a shared development environment, it is typical where other developers are responsible for various areas of source code. As a developer, you are probably interested in using that source code as part of your development using the Yocto Project. All you need is access to the code, a recipe, and a controlled area in which to do your work.
Within the diagram, three possible scenarios
feed into the devtool add
workflow:
Left: The left scenario represents a common situation where the source code does not exist locally and needs to be extracted. In this situation, you just let it get extracted to the default workspace - you do not want it in some specific location outside of the workspace. Thus, everything you need will be located in the workspace:
$ devtool add recipe fetchuri
With this command, devtool
creates a recipe and an append file in the
workspace as well as extracts the upstream
source files into a local Git repository also
within the sources
folder.
Middle:
The middle scenario also represents a situation where
the source code does not exist locally.
In this case, the code is again upstream
and needs to be extracted to some
local area - this time outside of the default
workspace.
If required, devtool
always creates
a Git repository locally during the extraction.
Furthermore, the first positional argument
srctree
in this case
identifies where the
devtool add
command
will locate the extracted code outside of the
workspace:
$ devtool add recipe srctree fetchuri
In summary, the source code is pulled from
fetchuri
and extracted
into the location defined by
srctree
as a local
Git repository.
Within workspace, devtool
creates both the recipe and an append file
for the recipe.
Right:
The right scenario represents a situation
where the source tree (srctree) has been
previously prepared outside of the
devtool
workspace.
The following command names the recipe and identifies where the existing source tree is located:
$ devtool add recipe srctree
The command examines the source code and creates a recipe for it placing the recipe into the workspace.
Because the extracted source code already exists,
devtool
does not try to
relocate it into the workspace - just the new
the recipe is placed in the workspace.
Aside from a recipe folder, the command
also creates an append folder and places an initial
*.bbappend
within.
Edit the Recipe:
At this point, you can use devtool edit-recipe
to open up the editor as defined by the
$EDITOR
environment variable
and modify the file:
$ devtool edit-recipe recipe
From within the editor, you can make modifications to the recipe that take affect when you build it later.
Build the Recipe or Rebuild the Image: At this point in the flow, the next step you take depends on what you are going to do with the new code.
If you need to take the build output and eventually
move it to the target hardware, you would use
devtool build
:
$ devtool build recipe
On the other hand, if you want an image to
contain the recipe's packages for immediate deployment
onto a device (e.g. for testing purposes), you can use
the devtool build-image
command:
$ devtool build-image image
Deploy the Build Output:
When you use the devtool build
command to build out your recipe, you probably want to
see if the resulting build output works as expected on target
hardware.
You can deploy your build output to that target hardware by
using the devtool deploy-target
command:
$ devtool deploy-target recipe target
The target
is a live target machine
running as an SSH server.
You can, of course, also deploy the image you build
using the devtool build-image
command
to actual hardware.
However, devtool
does not provide a
specific command that allows you to do this.
Finish Your Work With the Recipe:
The devtool finish
command creates
any patches corresponding to commits in the local
Git repository, moves the new recipe to a more permanent
layer, and then resets the recipe so that the recipe is
built normally rather than from the workspace.
$ devtool finish recipe layer
As mentioned, the devtool finish
command moves the final recipe to its permanent layer.
As a final process of the
devtool finish
command, the state
of the standard layers and the upstream source is
restored so that you can build the recipe from those
areas rather than the workspace.
devtool reset
command to put things back should you decide you
do not want to proceed with your work.
If you do use this command, realize that the source
tree is preserved.
devtool modify
to Modify the Source of an Existing Component¶
The devtool modify
command prepares the
way to work on existing code that already has a recipe in
place.
The command is flexible enough to allow you to extract code,
specify the existing recipe, and keep track of and gather any
patch files from other developers that are
associated with the code.
Depending on your particular scenario, the arguments and options
you use with devtool modify
form different
combinations.
The following diagram shows common development flows
you would use with the devtool modify
command:
Preparing to Modify the Code:
The top part of the flow shows three scenarios by which
you could use devtool modify
to
prepare to work on source files.
Each scenario assumes the following:
The recipe exists in some layer external
to the devtool
workspace.
The source files exist upstream in an un-extracted state or locally in a previously extracted state.
The typical situation is where another developer has created some layer for use with the Yocto Project and their recipe already resides in that layer. Furthermore, their source code is readily available either upstream or locally.
Left:
The left scenario represents a common situation
where the source code does not exist locally
and needs to be extracted.
In this situation, the source is extracted
into the default workspace location.
The recipe, in this scenario, is in its own
layer outside the workspace
(i.e.
meta-
layername
).
The following command identifies the recipe and by default extracts the source files:
$ devtool modify recipe
Once devtool
locates the recipe,
it uses the
SRC_URI
variable to locate the source code and
any local patch files from other developers are
located.
srctree
when using the
devtool modify
command.
With this scenario, however, since no
srctree
argument exists, the
devtool modify
command by default
extracts the source files to a Git structure.
Furthermore, the location for the extracted source is the
default area within the workspace.
The result is that the command sets up both the source
code and an append file within the workspace with the
recipe remaining in its original location.
Middle: The middle scenario represents a situation where the source code also does not exist locally. In this case, the code is again upstream and needs to be extracted to some local area as a Git repository. The recipe, in this scenario, is again in its own layer outside the workspace.
The following command tells
devtool
what recipe with
which to work and, in this case, identifies a local
area for the extracted source files that is outside
of the default workspace:
$ devtool modify recipe srctree
As with all extractions, the command uses
the recipe's SRC_URI
to locate the
source files.
Once the files are located, the command by default
extracts them.
Providing the srctree
argument instructs devtool
where
place the extracted source.
Within workspace, devtool
creates an append file for the recipe.
The recipe remains in its original location but
the source files are extracted to the location you
provided with srctree
.
Right:
The right scenario represents a situation
where the source tree
(srctree
) exists as a
previously extracted Git structure outside of
the devtool
workspace.
In this example, the recipe also exists
elsewhere in its own layer.
The following command tells
devtool
the recipe
with which to work, uses the "-n" option to indicate
source does not need to be extracted, and uses
srctree
to point to the
previously extracted source files:
$ devtool modify -n recipe srctree
Once the command finishes, it creates only an append file for the recipe in the workspace. The recipe and the source code remain in their original locations.
Edit the Source:
Once you have used the devtool modify
command, you are free to make changes to the source
files.
You can use any editor you like to make and save
your source code modifications.
Build the Recipe: Once you have updated the source files, you can build the recipe.
Deploy the Build Output:
When you use the devtool build
command to build out your recipe, you probably want to see
if the resulting build output works as expected on target
hardware.
You can deploy your build output to that target hardware by
using the devtool deploy-target
command:
$ devtool deploy-target recipe target
The target
is a live target machine
running as an SSH server.
You can, of course, also deploy the image you build
using the devtool build-image
command
to actual hardware.
However, devtool
does not provide a
specific command that allows you to do this.
Finish Your Work With the Recipe:
The devtool finish
command creates
any patches corresponding to commits in the local
Git repository, updates the recipe to point to them
(or creates a .bbappend
file to do
so, depending on the specified destination layer), and
then resets the recipe so that the recipe is built normally
rather than from the workspace.
$ devtool finish recipe layer
Because there is no need to move the recipe,
devtool finish
either updates the
original recipe in the original layer or the command
creates a .bbappend
in a different
layer as provided by layer
.
As a final process of the
devtool finish
command, the state
of the standard layers and the upstream source is
restored so that you can build the recipe from those
areas rather than the workspace.
devtool reset
command to put things back should you decide you
do not want to proceed with your work.
If you do use this command, realize that the source
tree is preserved.
devtool upgrade
to Create a Version of the Recipe that Supports a Newer Version of the Software¶
The devtool upgrade
command updates
an existing recipe so that you can build it for an updated
set of source files.
The command is flexible enough to allow you to specify
source code revision and versioning schemes, extract code into
or out of the devtool
workspace, and
work with any source file forms that the fetchers support.
Depending on your particular scenario, the arguments and options
you use with devtool upgrade
form different
combinations.
The following diagram shows a common development flow
you would use with the devtool modify
command:
Initiate the Upgrade:
The top part of the flow shows a typical scenario by which
you could use devtool upgrade
.
The following conditions exist:
The recipe exists in some layer external
to the devtool
workspace.
The source files for the new release
exist adjacent to the same location pointed to by
SRC_URI
in the recipe (e.g. a tarball with the new version
number in the name, or as a different revision in
the upstream Git repository).
A common situation is where third-party software has undergone a revision so that it has been upgraded. The recipe you have access to is likely in your own layer. Thus, you need to upgrade the recipe to use the newer version of the software:
$ devtool upgrade -V version recipe
By default, the devtool upgrade
command
extracts source code into the sources
directory in the workspace.
If you want the code extracted to any other location, you
need to provide the srctree
positional argument with the command as follows:
$ devtool upgrade -V version recipe srctree
Also, in this example, the "-V" option is used to specify
the new version.
If the source files pointed to by the
SRC_URI
statement in the recipe are
in a Git repository, you must provide the "-S" option and
specify a revision for the software.
Once devtool
locates the recipe,
it uses the SRC_URI
variable to locate
the source code and any local patch files from other
developers are located.
The result is that the command sets up the source
code, the new version of the recipe, and an append file
all within the workspace.
Resolve any Conflicts created by the Upgrade:
At this point, there could be some conflicts due to the
software being upgraded to a new version.
This would occur if your recipe specifies some patch files in
SRC_URI
that conflict with changes
made in the new version of the software.
If this is the case, you need to resolve the conflicts
by editing the source and following the normal
git rebase
conflict resolution
process.
Before moving onto the next step, be sure to resolve any such conflicts created through use of a newer or different version of the software.
Build the Recipe:
Once you have your recipe in order, you can build it.
You can either use devtool build
or
bitbake
.
Either method produces build output that is stored
in
TMPDIR
.
Deploy the Build Output:
When you use the devtool build
command or bitbake
to build out your
recipe, you probably want to see if the resulting build
output works as expected on target hardware.
You can deploy your build output to that target hardware by
using the devtool deploy-target
command:
$ devtool deploy-target recipe target
The target
is a live target machine
running as an SSH server.
You can, of course, also deploy the image you build
using the devtool build-image
command
to actual hardware.
However, devtool
does not provide a
specific command that allows you to do this.
Finish Your Work With the Recipe:
The devtool finish
command creates
any patches corresponding to commits in the local
Git repository, moves the new recipe to a more permanent
layer, and then resets the recipe so that the recipe is
built normally rather than from the workspace.
If you specify a destination layer that is the same as
the original source, then the old version of the
recipe and associated files will be removed prior to
adding the new version.
$ devtool finish recipe layer
As a final process of the
devtool finish
command, the state
of the standard layers and the upstream source is
restored so that you can build the recipe from those
areas rather than the workspace.
devtool reset
command to put things back should you decide you
do not want to proceed with your work.
If you do use this command, realize that the source
tree is preserved.
Quilt is a powerful tool that allows you to capture source code changes without having a clean source tree. This section outlines the typical workflow you can use to modify source code, test changes, and then preserve the changes in the form of a patch all using Quilt.
rm_work
enabled,
the workflow described in the
"Using devtool
in Your Workflow"
section is a safer development flow than than the flow that
uses Quilt.
Follow these general steps:
Find the Source Code: Temporary source code used by the OpenEmbedded build system is kept in the Build Directory. See the "Finding Temporary Source Code" section to learn how to locate the directory that has the temporary source code for a particular package.
Change Your Working Directory:
You need to be in the directory that has the temporary source code.
That directory is defined by the
S
variable.
Create a New Patch:
Before modifying source code, you need to create a new patch.
To create a new patch file, use quilt new
as below:
$ quilt new my_changes.patch
Notify Quilt and Add Files: After creating the patch, you need to notify Quilt about the files you plan to edit. You notify Quilt by adding the files to the patch you just created:
$ quilt add file1.c file2.c file3.c
Edit the Files: Make your changes in the source code to the files you added to the patch.
Test Your Changes:
Once you have modified the source code, the easiest way to
your changes is by calling the
do_compile
task as shown in the
following example:
$ bitbake -c compile -f package
The -f
or --force
option forces the specified task to execute.
If you find problems with your code, you can just keep editing and
re-testing iteratively until things work as expected.
do_clean
or
do_cleanall
tasks using BitBake (i.e.
bitbake -c clean package
and
bitbake -c cleanall package
).
Modifications will also disappear if you use the rm_work
feature as described in the
"Building Images"
section of the Yocto Project Quick Start.
Generate the Patch: Once your changes work as expected, you need to use Quilt to generate the final patch that contains all your modifications.
$ quilt refresh
At this point, the my_changes.patch
file has all your edits made
to the file1.c
, file2.c
, and
file3.c
files.
You can find the resulting patch file in the patches/
subdirectory of the source (S
) directory.
Copy the Patch File:
For simplicity, copy the patch file into a directory named files
,
which you can create in the same directory that holds the recipe
(.bb
) file or the
append (.bbappend
) file.
Placing the patch here guarantees that the OpenEmbedded build system will find
the patch.
Next, add the patch into the
SRC_URI
of the recipe.
Here is an example:
SRC_URI += "file://my_changes.patch"
You might find it helpful during development to modify the temporary source code used by recipes to build packages. For example, suppose you are developing a patch and you need to experiment a bit to figure out your solution. After you have initially built the package, you can iteratively tweak the source code, which is located in the Build Directory, and then you can force a re-compile and quickly test your altered code. Once you settle on a solution, you can then preserve your changes in the form of patches. If you are using Quilt for development, see the "Using Quilt in Your Workflow" section for more information.
During a build, the unpacked temporary source code used by recipes
to build packages is available in the Build Directory as
defined by the
S
variable.
Below is the default value for the S
variable as defined in the
meta/conf/bitbake.conf
configuration file in the
Source Directory:
S = "${WORKDIR}/${BP}"
You should be aware that many recipes override the S
variable.
For example, recipes that fetch their source from Git usually set
S
to ${WORKDIR}/git
.
BP
represents the base recipe name, which consists of the name and version:
BP = "${BPN}-${PV}"
The path to the work directory for the recipe
(WORKDIR
)
is defined as follows:
${TMPDIR}/work/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}
The actual directory depends on several things:
As an example, assume a Source Directory top-level folder
named poky
, a default Build Directory at
poky/build
, and a
qemux86-poky-linux
machine target
system.
Furthermore, suppose your recipe is named
foo_1.3.0.bb
.
In this case, the work directory the build system uses to
build the package would be as follows:
poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0
Now that you know where to locate the directory that has the temporary source code, you can use a Quilt as described in section "Using Quilt in Your Workflow" to make your edits, test the changes, and preserve the changes in the form of patches.
Toaster is a web interface to the Yocto Project's OpenEmbedded build system. You can initiate builds using Toaster as well as examine the results and statistics of builds. See the Toaster User Manual for information on how to set up and use Toaster to build images.
When debugging certain commands or even when just editing packages,
devshell
can be a useful tool.
When you invoke devshell
, all tasks up to and
including
do_patch
are run for the specified target.
Then, a new terminal is opened and you are placed in
${
S
}
,
the source directory.
In the new terminal, all the OpenEmbedded build-related environment variables are
still defined so you can use commands such as configure
and
make
.
The commands execute just as if the OpenEmbedded build system were executing them.
Consequently, working this way can be helpful when debugging a build or preparing
software to be used with the OpenEmbedded build system.
Following is an example that uses devshell
on a target named
matchbox-desktop
:
$ bitbake matchbox-desktop -c devshell
This command spawns a terminal with a shell prompt within the OpenEmbedded build environment.
The OE_TERMINAL
variable controls what type of shell is opened.
For spawned terminals, the following occurs:
The PATH
variable includes the
cross-toolchain.
The pkgconfig
variables find the correct
.pc
files.
The configure
command finds the
Yocto Project site files as well as any other necessary files.
Within this environment, you can run configure or compile
commands as if they were being run by
the OpenEmbedded build system itself.
As noted earlier, the working directory also automatically changes to the
Source Directory (S
).
To manually run a specific task using devshell
,
run the corresponding run.*
script in
the
${
WORKDIR
}/temp
directory (e.g.,
run.do_configure.
pid
).
If a task's script does not exist, which would be the case if the task was
skipped by way of the sstate cache, you can create the task by first running
it outside of the devshell
:
$ bitbake -c task
Execution of a task's run.*
script and BitBake's execution of a task are identical.
In other words, running the script re-runs the task
just as it would be run using the
bitbake -c
command.
Any run.*
file that does not
have a .pid
extension is a
symbolic link (symlink) to the most recent version of that
file.
Remember, that the devshell
is a mechanism that allows
you to get into the BitBake task execution environment.
And as such, all commands must be called just as BitBake would call them.
That means you need to provide the appropriate options for
cross-compilation and so forth as applicable.
When you are finished using devshell
, exit the shell
or close the terminal window.
It is worth remembering that when using devshell
you need to use the full compiler name such as arm-poky-linux-gnueabi-gcc
instead of just using gcc
.
The same applies to other applications such as binutils
,
libtool
and so forth.
BitBake sets up environment variables such as CC
to assist applications, such as make
to find the correct tools.
It is also worth noting that devshell
still works over
X11 forwarding and similar situations.
Similar to working within a development shell as described in
the previous section, you can also spawn and work within an
interactive Python development shell.
When debugging certain commands or even when just editing packages,
devpyshell
can be a useful tool.
When you invoke devpyshell
, all tasks up to and
including
do_patch
are run for the specified target.
Then a new terminal is opened.
Additionally, key Python objects and code are available in the same
way they are to BitBake tasks, in particular, the data store 'd'.
So, commands such as the following are useful when exploring the data
store and running functions:
pydevshell> d.getVar("STAGING_DIR", True) '/media/build1/poky/build/tmp/sysroots' pydevshell> d.getVar("STAGING_DIR", False) '${TMPDIR}/sysroots' pydevshell> d.setVar("FOO", "bar") pydevshell> d.getVar("FOO", True) 'bar' pydevshell> d.delVar("FOO") pydevshell> d.getVar("FOO", True) pydevshell> bb.build.exec_func("do_unpack", d) pydevshell>
The commands execute just as if the OpenEmbedded build system were executing them. Consequently, working this way can be helpful when debugging a build or preparing software to be used with the OpenEmbedded build system.
Following is an example that uses devpyshell
on a target named
matchbox-desktop
:
$ bitbake matchbox-desktop -c devpyshell
This command spawns a terminal and places you in an interactive
Python interpreter within the OpenEmbedded build environment.
The OE_TERMINAL
variable controls what type of shell is opened.
When you are finished using devpyshell
, you
can exit the shell either by using Ctrl+d or closing the terminal
window.
This chapter describes fundamental procedures such as creating layers, adding new software packages, extending or customizing images, porting work to new hardware (adding a new machine), and so forth. You will find that the procedures documented here occur often in the development cycle using the Yocto Project.
The OpenEmbedded build system supports organizing Metadata into multiple layers. Layers allow you to isolate different types of customizations from each other. You might find it tempting to keep everything in one layer when working on a single project. However, the more modular your Metadata, the easier it is to cope with future changes.
To illustrate how layers are used to keep things modular, consider
machine customizations.
These types of customizations typically reside in a special layer,
rather than a general layer, called a Board Support Package (BSP)
Layer.
Furthermore, the machine customizations should be isolated from
recipes and Metadata that support a new GUI environment,
for example.
This situation gives you a couple of layers: one for the machine
configurations, and one for the GUI environment.
It is important to understand, however, that the BSP layer can
still make machine-specific additions to recipes within the GUI
environment layer without polluting the GUI layer itself
with those machine-specific changes.
You can accomplish this through a recipe that is a BitBake append
(.bbappend
) file, which is described later
in this section.
The Source Directory
contains both general layers and BSP
layers right out of the box.
You can easily identify layers that ship with a
Yocto Project release in the Source Directory by their
folder names.
Folders that represent layers typically have names that begin with
the string meta-
.
meta-
, but it is a commonly
accepted standard in the Yocto Project community.
For example, when you set up the Source Directory structure,
you will see several layers:
meta
,
meta-skeleton
,
meta-selftest
,
meta-poky
, and
meta-yocto-bsp
.
Each of these folders represents a distinct layer.
As another example, if you set up a local copy of the
meta-intel
Git repository
and then explore the folder of that general layer,
you will discover many Intel-specific BSP layers inside.
For more information on BSP layers, see the
"BSP Layers"
section in the Yocto Project Board Support Package (BSP)
Developer's Guide.
It is very easy to create your own layers to use with the OpenEmbedded build system. The Yocto Project ships with scripts that speed up creating general layers and BSP layers. This section describes the steps you perform by hand to create a layer so that you can better understand them. For information about the layer-creation scripts, see the "Creating a New BSP Layer Using the yocto-bsp Script" section in the Yocto Project Board Support Package (BSP) Developer's Guide and the "Creating a General Layer Using the yocto-layer Script" section further down in this manual.
Follow these general steps to create your layer without the aid of a script:
Check Existing Layers:
Before creating a new layer, you should be sure someone
has not already created a layer containing the Metadata
you need.
You can see the
OpenEmbedded Metadata Index
for a list of layers from the OpenEmbedded community
that can be used in the Yocto Project.
Create a Directory:
Create the directory for your layer.
While not strictly required, prepend the name of the
folder with the string meta-
.
For example:
meta-mylayer meta-GUI_xyz meta-mymachine
Create a Layer Configuration
File:
Inside your new layer folder, you need to create a
conf/layer.conf
file.
It is easiest to take an existing layer configuration
file and copy that to your layer's
conf
directory and then modify the
file as needed.
The
meta-yocto-bsp/conf/layer.conf
file
demonstrates the required syntax:
# We have a conf and classes directory, add to BBPATH BBPATH .= ":${LAYERDIR}" # We have recipes-* directories, add to BBFILES BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \ ${LAYERDIR}/recipes-*/*/*.bbappend" BBFILE_COLLECTIONS += "yoctobsp" BBFILE_PATTERN_yoctobsp = "^${LAYERDIR}/" BBFILE_PRIORITY_yoctobsp = "5" LAYERVERSION_yoctobsp = "3"
Here is an explanation of the example:
The configuration and
classes directory is appended to
BBPATH
.
BBPATH
.
On the other hand, distro layers, such as
meta-poky
, can choose
to enforce their own precedence over
BBPATH
.
For an example of that syntax, see the
layer.conf
file for
the meta-poky
layer.
The recipes for the layers are
appended to
BBFILES
.
The
BBFILE_COLLECTIONS
variable is then appended with the layer name.
The
BBFILE_PATTERN
variable is set to a regular expression and is
used to match files from
BBFILES
into a particular
layer.
In this case,
LAYERDIR
is used to make BBFILE_PATTERN
match within the
layer's path.
The
BBFILE_PRIORITY
variable then assigns a priority to the layer.
Applying priorities is useful in situations
where the same recipe might appear in multiple
layers and allows you to choose the layer
that takes precedence.
The
LAYERVERSION
variable optionally specifies the version of a
layer as a single number.
Note the use of the
LAYERDIR
variable, which expands to the directory of the current
layer.
Through the use of the BBPATH
variable, BitBake locates class files
(.bbclass
),
configuration files, and files that are included
with include
and
require
statements.
For these cases, BitBake uses the first file that
matches the name found in BBPATH
.
This is similar to the way the PATH
variable is used for binaries.
It is recommended, therefore, that you use unique
class and configuration
filenames in your custom layer.
Add Content: Depending
on the type of layer, add the content.
If the layer adds support for a machine, add the machine
configuration in a conf/machine/
file within the layer.
If the layer adds distro policy, add the distro
configuration in a conf/distro/
file within the layer.
If the layer introduces new recipes, put the recipes
you need in recipes-*
subdirectories within the layer.
Optionally Test for Compatibility: If you want permission to use the Yocto Project Compatibility logo with your layer or application that uses your layer, perform the steps to apply for compatibility. See the "Making Sure Your Layer is Compatible With Yocto Project" section for more information.
To create layers that are easier to maintain and that will not impact builds for other machines, you should consider the information in the following sections.
Avoid "overlaying" entire recipes from other layers in your
configuration.
In other words, do not copy an entire recipe into your
layer and then modify it.
Rather, use an append file (.bbappend
)
to override
only those parts of the original recipe you need to modify.
Avoid duplicating include files.
Use append files (.bbappend
)
for each recipe
that uses an include file.
Or, if you are introducing a new recipe that requires
the included file, use the path relative to the original
layer directory to refer to the file.
For example, use
require recipes-core/
package
/
file
.inc
instead of require
file
.inc
.
If you're finding you have to overlay the include file,
it could indicate a deficiency in the include file in
the layer to which it originally belongs.
If this is the case, you should try to address that
deficiency instead of overlaying the include file.
For example, you could address this by getting the
maintainer of the include file to add a variable or
variables to make it easy to override the parts needing
to be overridden.
Proper use of overrides within append files and placement of machine-specific files within your layer can ensure that a build is not using the wrong Metadata and negatively impacting a build for a different machine. Following are some examples:
Modifying Variables to Support
a Different Machine:
Suppose you have a layer named
meta-one
that adds support
for building machine "one".
To do so, you use an append file named
base-files.bbappend
and
create a dependency on "foo" by altering the
DEPENDS
variable:
DEPENDS = "foo"
The dependency is created during any build that
includes the layer
meta-one
.
However, you might not want this dependency
for all machines.
For example, suppose you are building for
machine "two" but your
bblayers.conf
file has the
meta-one
layer included.
During the build, the
base-files
for machine
"two" will also have the dependency on
foo
.
To make sure your changes apply only when
building machine "one", use a machine override
with the DEPENDS
statement:
DEPENDS_one = "foo"
You should follow the same strategy when using
_append
and
_prepend
operations:
DEPENDS_append_one = " foo" DEPENDS_prepend_one = "foo "
As an actual example, here's a line from the recipe for gnutls, which adds dependencies on "argp-standalone" when building with the musl C library:
DEPENDS_append_libc-musl = " argp-standalone"
_append
and _prepend
operations
is recommended as well.
Place Machine-Specific Files
in Machine-Specific Locations:
When you have a base recipe, such as
base-files.bb
, that
contains a
SRC_URI
statement to a file, you can use an append file
to cause the build to use your own version of
the file.
For example, an append file in your layer at
meta-one/recipes-core/base-files/base-files.bbappend
could extend
FILESPATH
using
FILESEXTRAPATHS
as follows:
FILESEXTRAPATHS_prepend := "${THISDIR}/${BPN}:"
The build for machine "one" will pick up your
machine-specific file as long as you have the
file in
meta-one/recipes-core/base-files/base-files/
.
However, if you are building for a different
machine and the
bblayers.conf
file includes
the meta-one
layer and
the location of your machine-specific file is
the first location where that file is found
according to FILESPATH
,
builds for all machines will also use that
machine-specific file.
You can make sure that a machine-specific
file is used for a particular machine by putting
the file in a subdirectory specific to the
machine.
For example, rather than placing the file in
meta-one/recipes-core/base-files/base-files/
as shown above, put it in
meta-one/recipes-core/base-files/base-files/one/
.
Not only does this make sure the file is used
only when building for machine "one", but the
build process locates the file more quickly.
In summary, you need to place all files
referenced from SRC_URI
in a machine-specific subdirectory within the
layer in order to restrict those files to
machine-specific builds.
We also recommend the following:
If you want permission to use the Yocto Project Compatibility logo with your layer or application that uses your layer, perform the steps to apply for compatibility. See the "Making Sure Your Layer is Compatible With Yocto Project" section for more information.
Store custom layers in a Git repository
that uses the
meta-
format.
layer_name
Clone the repository alongside other
meta
directories in the
Source Directory.
Following these recommendations keeps your Source Directory and its configuration entirely inside the Yocto Project's core base.
When you create a layer used with the Yocto Project, it is advantageous to make sure that the layer interacts well with existing Yocto Project layers (i.e. the layer is compatible with the Yocto Project). Ensuring compatibility makes the layer easy to be consumed by others in the Yocto Project community and allows you permission to use the Yocto Project Compatibility logo.
Version 1.0 of the Yocto Project Compatibility Program has been in existence for a number of releases. This version of the program consists of the layer application process that requests permission to use the Yocto Project Compatibility logo for your layer and application. You can find version 1.0 of the form at https://www.yoctoproject.org/webform/yocto-project-compatible-registration. To be granted permission to use the logo, you need to be able to answer "Yes" to the questions or have an acceptable explanation for any questions answered "No".
A second version (2.0) of the Yocto Project Compatibility
Program is currently under development.
Included as part of version 2.0 (and currently available) is
the yocto-compat-layer.py
script.
When run against a layer, this script tests the layer against
tighter constraints based on experiences of how layers have
worked in the real world and where pitfalls have been found.
Part of the 2.0 version of the program that is not currently
available but is in development is an updated compatibility
application form.
This updated form, among other questions, specifically
asks if your layer has passed the test using the
yocto-compat-layer.py
script.
yocto-compat-layer.py
script is
available in OE-Core.
You can use the script to assess the status of your
layers in advance of the 2.0 release of the program.
The remainder of this section presents information on the
version 1.0 registration form and on the
yocto-compat-layer.py
script.
Use the 1.0 version of the form to apply for your layer's compatibility approval. Upon successful application, you can use the Yocto Project Compatibility logo with your layer and the application that uses your layer.
To access the form, use this link: https://www.yoctoproject.org/webform/yocto-project-compatible-registration. Follow the instructions on the form to complete your application.
The application consists of the following sections:
Contact Information: Provide your contact information as the fields require. Along with your information, provide the released versions of the Yocto Project for which your layer is compatible.
Acceptance Criteria: Provide "Yes" or "No" answers for each of the items in the checklist. Space exists at the bottom of the form for any explanations for items for which you answered "No".
Recommendations: Provide answers for the questions regarding Linux kernel use and build success.
yocto-compat-layer.py
Script¶
The yocto-compat-layer.py
script,
which is currently available, provides you a way to
assess how compatible your layer is with the Yocto
Project.
You should run this script prior to using the form to
apply for compatibility as described in the previous
section.
The script divides tests into three areas: COMMON, BSD, and DISTRO. For example, given a distribution layer (DISTRO), the layer must pass both the COMMON and DISTRO related tests. Furthermore, if your layer is a BSP layer, the layer must pass the COMMON and BSP set of tests.
To execute the script, enter the following commands from your build directory:
$ source oe-init-build-env
$ yocto-compat-layer.py your_layer_directory
Be sure to provide the actual directory for your layer as part of the command.
Entering the command causes the script to determine the type of layer and then to execute a set of specific tests against the layer. The following list overviews the test:
common.test_readme
:
Tests if a README
file
exists in the layer and the file is not empty.
common.test_parse
:
Tests to make sure that BitBake can parse the
files without error (i.e.
bitbake -p
).
common.test_show_environment
:
Tests that the global or per-recipe environment
is in order without errors (i.e.
bitbake -e
).
common.test_signatures
:
Tests to be sure that BSP and DISTRO layers do not
come with recipes that change signatures.
bsp.test_bsp_defines_machines
:
Tests if a BSP layer has machine configurations.
bsp.test_bsp_no_set_machine
:
Tests to ensure a BSP layer does not set the
machine when the layer is added.
distro.test_distro_defines_distros
:
Tests if a DISTRO layer has distro configurations.
distro.test_distro_no_set_distro
:
Tests to ensure a DISTRO layer does not set the
distribution when the layer is added.
Before the OpenEmbedded build system can use your new layer,
you need to enable it.
To enable your layer, simply add your layer's path to the
BBLAYERS
variable in your conf/bblayers.conf
file,
which is found in the
Build Directory.
The following example shows how to enable a layer named
meta-mylayer
:
LCONF_VERSION = "6" BBPATH = "${TOPDIR}" BBFILES ?= "" BBLAYERS ?= " \ $HOME/poky/meta \ $HOME/poky/meta-poky \ $HOME/poky/meta-yocto-bsp \ $HOME/poky/meta-mylayer \ "
BitBake parses each conf/layer.conf
file
as specified in the BBLAYERS
variable
within the conf/bblayers.conf
file.
During the processing of each
conf/layer.conf
file, BitBake adds the
recipes, classes and configurations contained within the
particular layer to the source directory.
A recipe that appends Metadata to another recipe is called a
BitBake append file.
A BitBake append file uses the .bbappend
file type suffix, while the corresponding recipe to which
Metadata is being appended uses the .bb
file type suffix.
You can use a .bbappend
file in your
layer to make additions or changes to the content of another
layer's recipe without having to copy the other layer's
recipe into your layer.
Your .bbappend
file resides in your layer,
while the main .bb
recipe file to
which you are appending Metadata resides in a different layer.
Being able to append information to an existing recipe not only avoids duplication, but also automatically applies recipe changes from a different layer into your layer. If you were copying recipes, you would have to manually merge changes as they occur.
When you create an append file, you must use the same root
name as the corresponding recipe file.
For example, the append file
someapp_2.3.3.bbappend
must apply to
someapp_2.3.3.bb
.
This means the original recipe and append file names are
version number-specific.
If the corresponding recipe is renamed to update to a newer
version, you must also rename and possibly update
the corresponding .bbappend
as well.
During the build process, BitBake displays an error on starting
if it detects a .bbappend
file that does
not have a corresponding recipe with a matching name.
See the
BB_DANGLINGAPPENDS_WARNONLY
variable for information on how to handle this error.
As an example, consider the main formfactor recipe and a
corresponding formfactor append file both from the
Source Directory.
Here is the main formfactor recipe, which is named
formfactor_0.0.bb
and located in the
"meta" layer at
meta/recipes-bsp/formfactor
:
SUMMARY = "Device formfactor information" SECTION = "base" LICENSE = "MIT" LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420" PR = "r45" SRC_URI = "file://config file://machconfig" S = "${WORKDIR}" PACKAGE_ARCH = "${MACHINE_ARCH}" INHIBIT_DEFAULT_DEPS = "1" do_install() { # Install file only if it has contents install -d ${D}${sysconfdir}/formfactor/ install -m 0644 ${S}/config ${D}${sysconfdir}/formfactor/ if [ -s "${S}/machconfig" ]; then install -m 0644 ${S}/machconfig ${D}${sysconfdir}/formfactor/ fi }
In the main recipe, note the
SRC_URI
variable, which tells the OpenEmbedded build system where to
find files during the build.
Following is the append file, which is named
formfactor_0.0.bbappend
and is from the
Raspberry Pi BSP Layer named
meta-raspberrypi
.
The file is in the layer at
recipes-bsp/formfactor
:
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
By default, the build system uses the
FILESPATH
variable to locate files.
This append file extends the locations by setting the
FILESEXTRAPATHS
variable.
Setting this variable in the .bbappend
file is the most reliable and recommended method for adding
directories to the search path used by the build system
to find files.
The statement in this example extends the directories to
include
${
THISDIR
}/${
PN
}
,
which resolves to a directory named
formfactor
in the same directory
in which the append file resides (i.e.
meta-raspberrypi/recipes-bsp/formfactor
.
This implies that you must have the supporting directory
structure set up that will contain any files or patches you
will be including from the layer.
Using the immediate expansion assignment operator
:=
is important because of the reference
to THISDIR
.
The trailing colon character is important as it ensures that
items in the list remain colon-separated.
BitBake automatically defines the
THISDIR
variable.
You should never set this variable yourself.
Using "_prepend" as part of the
FILESEXTRAPATHS
ensures your path
will be searched prior to other paths in the final
list.
Also, not all append files add extra files.
Many append files simply exist to add build options
(e.g. systemd
).
For these cases, your append file would not even
use the FILESEXTRAPATHS
statement.
Each layer is assigned a priority value.
Priority values control which layer takes precedence if there
are recipe files with the same name in multiple layers.
For these cases, the recipe file from the layer with a higher
priority number takes precedence.
Priority values also affect the order in which multiple
.bbappend
files for the same recipe are
applied.
You can either specify the priority manually, or allow the
build system to calculate it based on the layer's dependencies.
To specify the layer's priority manually, use the
BBFILE_PRIORITY
variable.
For example:
BBFILE_PRIORITY_mylayer = "1"
It is possible for a recipe with a lower version number
PV
in a layer that has a higher priority to take precedence.
Also, the layer priority does not currently affect the
precedence order of .conf
or .bbclass
files.
Future versions of BitBake might address this.
You can use the BitBake layer management tool to provide a view
into the structure of recipes across a multi-layer project.
Being able to generate output that reports on configured layers
with their paths and priorities and on
.bbappend
files and their applicable
recipes can help to reveal potential problems.
Use the following form when running the layer management tool.
$ bitbake-layerscommand
[arguments
]
The following list describes the available commands:
help:
Displays general help or help on a specified command.
show-layers:
Shows the current configured layers.
show-recipes:
Lists available recipes and the layers that provide them.
show-overlayed:
Lists overlayed recipes.
A recipe is overlayed when a recipe with the same name
exists in another layer that has a higher layer
priority.
show-appends:
Lists .bbappend
files and the
recipe files to which they apply.
show-cross-depends:
Lists dependency relationships between recipes that
cross layer boundaries.
add-layer:
Adds a layer to bblayers.conf
.
remove-layer:
Removes a layer from bblayers.conf
flatten:
Flattens the layer configuration into a separate output
directory.
Flattening your layer configuration builds a "flattened"
directory that contains the contents of all layers,
with any overlayed recipes removed and any
.bbappend
files appended to the
corresponding recipes.
You might have to perform some manual cleanup of the
flattened layer as follows:
Non-recipe files (such as patches) are overwritten. The flatten command shows a warning for these files.
Anything beyond the normal layer
setup has been added to the
layer.conf
file.
Only the lowest priority layer's
layer.conf
is used.
Overridden and appended items from
.bbappend
files need to be
cleaned up.
The contents of each
.bbappend
end up in the
flattened recipe.
However, if there are appended or changed
variable values, you need to tidy these up
yourself.
Consider the following example.
Here, the bitbake-layers
command adds the line
#### bbappended ...
so that
you know where the following lines originate:
... DESCRIPTION = "A useful utility" ... EXTRA_OECONF = "--enable-something" ... #### bbappended from meta-anotherlayer #### DESCRIPTION = "Customized utility" EXTRA_OECONF += "--enable-somethingelse"
Ideally, you would tidy up these utilities as follows:
... DESCRIPTION = "Customized utility" ... EXTRA_OECONF = "--enable-something --enable-somethingelse" ...
The yocto-layer
script simplifies
creating a new general layer.
The default mode of the script's operation is to prompt you for information needed to generate the layer:
The layer priority.
Whether or not to create a sample recipe.
Whether or not to create a sample append file.
Use the yocto-layer create
sub-command
to create a new general layer.
In its simplest form, you can create a layer as follows:
$ yocto-layer create mylayer
The previous example creates a layer named
meta-mylayer
in the current directory.
As the yocto-layer create
command runs,
default values for the prompts appear in brackets.
Pressing enter without supplying anything for the prompts
or pressing enter and providing an invalid response causes the
script to accept the default value.
Once the script completes, the new layer
is created in the current working directory.
The script names the layer by prepending
meta-
to the name you provide.
Minimally, the script creates the following within the layer:
The conf
directory:
This directory contains the layer's configuration file.
The root name for the file is the same as the root name
your provided for the layer (e.g.
).
layer
.conf
The
COPYING.MIT
file:
The copyright and use notice for the software.
The README
file:
A file describing the contents of your new layer.
If you choose to generate a sample recipe file, the script
prompts you for the name for the recipe and then creates it
in
.
The script creates a layer
/recipes-example/example/.bb
file and a
directory, which contains a sample
helloworld.c
source file, along with
a sample patch file.
If you do not provide a recipe name, the script uses
"example".
If you choose to generate a sample append file, the script
prompts you for the name for the file and then creates it
in
.
The script creates a layer
/recipes-example-bbappend/example-bbappend/.bbappend
file and a
directory, which contains a sample patch file.
If you do not provide a recipe name, the script uses
"example".
The script also prompts you for the version of the append file.
The version should match the recipe to which the append file
is associated.
The easiest way to see how the yocto-layer
script works is to experiment with the script.
You can also read the usage information by entering the
following:
$ yocto-layer help
Once you create your general layer, you must add it to your
bblayers.conf
file.
Here is an example where a layer named
meta-mylayer
is added:
BBLAYERS = ?" \ /usr/local/src/yocto/meta \ /usr/local/src/yocto/meta-poky \ /usr/local/src/yocto/meta-yocto-bsp \ /usr/local/src/yocto/meta-mylayer \ "
Adding the layer to this file enables the build system to locate the layer during the build.
You can customize images to satisfy particular requirements. This section describes several methods and provides guidelines for each.
local.conf
¶
Probably the easiest way to customize an image is to add a
package by way of the local.conf
configuration file.
Because it is limited to local use, this method generally only
allows you to add packages and is not as flexible as creating
your own customized image.
When you add packages using local variables this way, you need
to realize that these variable changes are in effect for every
build and consequently affect all images, which might not
be what you require.
To add a package to your image using the local configuration
file, use the
IMAGE_INSTALL
variable with the _append
operator:
IMAGE_INSTALL_append = " strace"
Use of the syntax is important - specifically, the space between
the quote and the package name, which is
strace
in this example.
This space is required since the _append
operator does not add the space.
Furthermore, you must use _append
instead
of the +=
operator if you want to avoid
ordering issues.
The reason for this is because doing so unconditionally appends
to the variable and avoids ordering problems due to the
variable being set in image recipes and
.bbclass
files with operators like
?=
.
Using _append
ensures the operation takes
affect.
As shown in its simplest use,
IMAGE_INSTALL_append
affects all images.
It is possible to extend the syntax so that the variable
applies to a specific image only.
Here is an example:
IMAGE_INSTALL_append_pn-core-image-minimal = " strace"
This example adds strace
to the
core-image-minimal
image only.
You can add packages using a similar approach through the
CORE_IMAGE_EXTRA_INSTALL
variable.
If you use this variable, only
core-image-*
images are affected.
IMAGE_FEATURES
and
EXTRA_IMAGE_FEATURES
¶
Another method for customizing your image is to enable or
disable high-level image features by using the
IMAGE_FEATURES
and EXTRA_IMAGE_FEATURES
variables.
Although the functions for both variables are nearly equivalent,
best practices dictate using IMAGE_FEATURES
from within a recipe and using
EXTRA_IMAGE_FEATURES
from within
your local.conf
file, which is found in the
Build Directory.
To understand how these features work, the best reference is
meta/classes/core-image.bbclass
.
This class lists out the available
IMAGE_FEATURES
of which most map to package groups while some, such as
debug-tweaks
and
read-only-rootfs
, resolve as general
configuration settings.
In summary, the file looks at the contents of the
IMAGE_FEATURES
variable and then maps
or configures the feature accordingly.
Based on this information, the build system automatically
adds the appropriate packages or configurations to the
IMAGE_INSTALL
variable.
Effectively, you are enabling extra features by extending the
class or creating a custom class for use with specialized image
.bb
files.
Use the EXTRA_IMAGE_FEATURES
variable
from within your local configuration file.
Using a separate area from which to enable features with
this variable helps you avoid overwriting the features in the
image recipe that are enabled with
IMAGE_FEATURES
.
The value of EXTRA_IMAGE_FEATURES
is added
to IMAGE_FEATURES
within
meta/conf/bitbake.conf
.
To illustrate how you can use these variables to modify your
image, consider an example that selects the SSH server.
The Yocto Project ships with two SSH servers you can use
with your images: Dropbear and OpenSSH.
Dropbear is a minimal SSH server appropriate for
resource-constrained environments, while OpenSSH is a
well-known standard SSH server implementation.
By default, the core-image-sato
image
is configured to use Dropbear.
The core-image-full-cmdline
and
core-image-lsb
images both
include OpenSSH.
The core-image-minimal
image does not
contain an SSH server.
You can customize your image and change these defaults.
Edit the IMAGE_FEATURES
variable
in your recipe or use the
EXTRA_IMAGE_FEATURES
in your
local.conf
file so that it configures the
image you are working with to include
ssh-server-dropbear
or
ssh-server-openssh
.
You can also customize an image by creating a custom recipe that defines additional software as part of the image. The following example shows the form for the two lines you need:
IMAGE_INSTALL = "packagegroup-core-x11-base package1 package2" inherit core-image
Defining the software using a custom recipe gives you total
control over the contents of the image.
It is important to use the correct names of packages in the
IMAGE_INSTALL
variable.
You must use the OpenEmbedded notation and not the Debian notation for the names
(e.g. glibc-dev
instead of libc6-dev
).
The other method for creating a custom image is to base it on an existing image.
For example, if you want to create an image based on core-image-sato
but add the additional package strace
to the image,
copy the meta/recipes-sato/images/core-image-sato.bb
to a
new .bb
and add the following line to the end of the copy:
IMAGE_INSTALL += "strace"
For complex custom images, the best approach for customizing
an image is to create a custom package group recipe that is
used to build the image or images.
A good example of a package group recipe is
meta/recipes-core/packagegroups/packagegroup-base.bb
.
If you examine that recipe, you see that the
PACKAGES
variable lists the package group packages to produce.
The inherit packagegroup
statement
sets appropriate default values and automatically adds
-dev
, -dbg
, and
-ptest
complementary packages for each
package specified in the PACKAGES
statement.
inherit packages
should be
located near the top of the recipe, certainly before
the PACKAGES
statement.
For each package you specify in PACKAGES
,
you can use
RDEPENDS
and
RRECOMMENDS
entries to provide a list of packages the parent task package
should contain.
You can see examples of these further down in the
packagegroup-base.bb
recipe.
Here is a short, fabricated example showing the same basic pieces:
DESCRIPTION = "My Custom Package Groups" inherit packagegroup PACKAGES = "\ packagegroup-custom-apps \ packagegroup-custom-tools \ " RDEPENDS_packagegroup-custom-apps = "\ dropbear \ portmap \ psplash" RDEPENDS_packagegroup-custom-tools = "\ oprofile \ oprofileui-server \ lttng-tools" RRECOMMENDS_packagegroup-custom-tools = "\ kernel-module-oprofile"
In the previous example, two package group packages are created with their dependencies and their
recommended package dependencies listed: packagegroup-custom-apps
, and
packagegroup-custom-tools
.
To build an image using these package group packages, you need to add
packagegroup-custom-apps
and/or
packagegroup-custom-tools
to
IMAGE_INSTALL
.
For other forms of image dependencies see the other areas of this section.
By default, the configured hostname (i.e.
/etc/hostname
) in an image is the
same as the machine name.
For example, if
MACHINE
equals "qemux86", the configured hostname written to
/etc/hostname
is "qemux86".
You can customize this name by altering the value of the
"hostname" variable in the
base-files
recipe using either
an append file or a configuration file.
Use the following in an append file:
hostname="myhostname"
Use the following in a configuration file:
hostname_pn-base-files = "myhostname"
Changing the default value of the variable "hostname" can be useful in certain situations. For example, suppose you need to do extensive testing on an image and you would like to easily identify the image under test from existing images with typical default hostnames. In this situation, you could change the default hostname to "testme", which results in all the images using the name "testme". Once testing is complete and you do not need to rebuild the image for test any longer, you can easily reset the default hostname.
Another point of interest is that if you unset the variable, the image will have no default hostname in the filesystem. Here is an example that unsets the variable in a configuration file:
hostname_pn-base-files = ""
Having no default hostname in the filesystem is suitable for environments that use dynamic hostnames such as virtual machines.
Recipes (.bb
files) are fundamental components
in the Yocto Project environment.
Each software component built by the OpenEmbedded build system
requires a recipe to define the component.
This section describes how to create, write, and test a new
recipe.
The following figure shows the basic process for creating a new recipe. The remainder of the section provides details for the steps.
You can always write a recipe from scratch. However, three choices exist that can help you quickly get a start on a new recipe:
devtool add
:
A command that assists in creating a recipe and
an environment conducive to development.
recipetool create
:
A command provided by the Yocto Project that automates
creation of a base recipe based on the source
files.
Existing Recipes: Location and modification of an existing recipe that is similar in function to the recipe you need.
devtool add
¶
The devtool add
command uses the same
logic for auto-creating the recipe as
recipetool create
, which is listed
below.
Additionally, however, devtool add
sets up an environment that makes it easy for you to
patch the source and to make changes to the recipe as
is often necessary when adding a recipe to build a new
piece of software to be included in a build.
You can find a complete description of the
devtool add
command in the
"Use devtool add
to Add an Application"
section.
recipetool create
¶
recipetool create
automates creation
of a base recipe given a set of source code files.
As long as you can extract or point to the source files,
the tool will construct a recipe and automatically
configure all pre-build information into the recipe.
For example, suppose you have an application that builds
using Autotools.
Creating the base recipe using
recipetool
results in a recipe
that has the pre-build dependencies, license requirements,
and checksums configured.
To run the tool, you just need to be in your
Build Directory
and have sourced the build environment setup script
(i.e.
oe-init-build-env
or
oe-init-build-env-memres
).
Here is the basic recipetool
syntax:
recipetool -h
or
recipetool create -h
produces the
Python-generated help, which presented differently
than what follows here.
recipetool -h recipetool create [-h] recipetool [-d] [-q] [--color auto | always | never ] create -oOUTFILE
[-m] [-xEXTERNALSRC
]source
-d Enables debug output. -q Outputs only errors (quiet mode). --color Colorizes the output automatically, always, or never. -h Displays Python generated syntax for recipetool. create Causes recipetool to create a base recipe. The create command is further defined with these options: -oOUTFILE
Specifies the full path and filename for the generated recipe. -m Causes the recipe to be machine-specific rather than architecture-specific (default). -xEXTERNALSRC
Fetches and extracts source files fromsource
and places them inEXTERNALSRC
.source
must be a URL. -h Displays Python-generated syntax for create.source
Specifies the source code on which to base the recipe.
Running recipetool create -o
OUTFILE
creates the base recipe and locates it properly in the
layer that contains your source files.
Following are some syntax examples:
Use this syntax to generate a recipe based on source
.
Once generated, the recipe resides in the existing source
code layer:
recipetool create -oOUTFILE
source
Use this syntax to generate a recipe using code that you
extract from source
.
The extracted code is placed in its own layer defined
by EXTERNALSRC
.
recipetool create -oOUTFILE
-xEXTERNALSRC
source
Use this syntax to generate a recipe based on source
.
The options direct recipetool
to
generate debugging information.
Once generated, the recipe resides in the existing source
code layer:
recipetool create -d -oOUTFILE
source
Before writing a recipe from scratch, it is often useful to discover whether someone else has already written one that meets (or comes close to meeting) your needs. The Yocto Project and OpenEmbedded communities maintain many recipes that might be candidates for what you are doing. You can find a good central index of these recipes in the OpenEmbedded metadata index.
Working from an existing recipe or a skeleton recipe is the best way to get started. Here are some points on both methods:
Locate and modify a recipe that is close to what you want to do: This method works when you are familiar with the current recipe space. The method does not work so well for those new to the Yocto Project or writing recipes.
Some risks associated with this method are using a recipe that has areas totally unrelated to what you are trying to accomplish with your recipe, not recognizing areas of the recipe that you might have to add from scratch, and so forth. All these risks stem from unfamiliarity with the existing recipe space.
Use and modify the following
skeleton recipe:
If for some reason you do not want to use
recipetool
and you cannot
find an existing recipe that is close to meeting
your needs, you can use the following structure to
provide the fundamental areas of a new recipe.
DESCRIPTION = "" HOMEPAGE = "" LICENSE = "" SECTION = "" DEPENDS = "" LIC_FILES_CHKSUM = "" SRC_URI = ""
Once you have your base recipe, you should put it in your own layer and name it appropriately. Locating it correctly ensures that the OpenEmbedded build system can find it when you use BitBake to process the recipe.
Storing Your Recipe:
The OpenEmbedded build system locates your recipe
through the layer's conf/layer.conf
file and the
BBFILES
variable.
This variable sets up a path from which the build system can
locate recipes.
Here is the typical use:
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \ ${LAYERDIR}/recipes-*/*/*.bbappend"
Consequently, you need to be sure you locate your new recipe inside your layer such that it can be found.
You can find more information on how layers are structured in the "Understanding and Creating Layers" section.
Naming Your Recipe: When you name your recipe, you need to follow this naming convention:
basename
_version
.bb
Use lower-cased characters and do not include the reserved
suffixes -native
,
-cross
, -initial
,
or -dev
casually (i.e. do not use them
as part of your recipe name unless the string applies).
Here are some examples:
cups_1.7.0.bb gawk_4.0.2.bb irssi_0.8.16-rc1.bb
Understanding recipe file syntax is important for writing recipes. The following list overviews the basic items that make up a BitBake recipe file. For more complete BitBake syntax descriptions, see the "Syntax and Operators" chapter of the BitBake User Manual.
Variable Assignments and Manipulations: Variable assignments allow a value to be assigned to a variable. The assignment can be static text or might include the contents of other variables. In addition to the assignment, appending and prepending operations are also supported.
The following example shows some of the ways you can use variables in recipes:
S = "${WORKDIR}/postfix-${PV}" CFLAGS += "-DNO_ASM" SRC_URI_append = " file://fixup.patch"
Functions:
Functions provide a series of actions to be performed.
You usually use functions to override the default
implementation of a task function or to complement
a default function (i.e. append or prepend to an
existing function).
Standard functions use sh
shell
syntax, although access to OpenEmbedded variables and
internal methods are also available.
The following is an example function from the
sed
recipe:
do_install () { autotools_do_install install -d ${D}${base_bindir} mv ${D}${bindir}/sed ${D}${base_bindir}/sed rmdir ${D}${bindir}/ }
It is also possible to implement new functions that are called between existing tasks as long as the new functions are not replacing or complementing the default functions. You can implement functions in Python instead of shell. Both of these options are not seen in the majority of recipes.
Keywords:
BitBake recipes use only a few keywords.
You use keywords to include common
functions (inherit
), load parts
of a recipe from other files
(include
and
require
) and export variables
to the environment (export
).
The following example shows the use of some of these keywords:
export POSTCONF = "${STAGING_BINDIR}/postconf" inherit autoconf require otherfile.inc
Comments:
Any lines that begin with the hash character
(#
) are treated as comment lines
and are ignored:
# This is a comment
This next list summarizes the most important and most commonly used parts of the recipe syntax. For more information on these parts of the syntax, you can reference the Syntax and Operators chapter in the BitBake User Manual.
Line Continuation: \
-
Use the backward slash (\
)
character to split a statement over multiple lines.
Place the slash character at the end of the line that
is to be continued on the next line:
VAR = "A really long \ line"
Using Variables: ${...}
-
Use the ${
syntax to
access the contents of a variable:
VARNAME
}
SRC_URI = "${SOURCEFORGE_MIRROR}/libpng/zlib-${PV}.tar.gz"
:=
operator instead of
=
when you make the
assignment, but this is not generally needed.
Quote All Assignments: "
-
Use double quotes around the value in all variable
assignments.
value
"
VAR1 = "${OTHERVAR}" VAR2 = "The version is ${PV}"
Conditional Assignment: ?=
-
Conditional assignment is used to assign a value to
a variable, but only when the variable is currently
unset.
Use the question mark followed by the equal sign
(?=
) to make a "soft" assignment
used for conditional assignment.
Typically, "soft" assignments are used in the
local.conf
file for variables
that are allowed to come through from the external
environment.
Here is an example where
VAR1
is set to "New value" if
it is currently empty.
However, if VAR1
has already been
set, it remains unchanged:
VAR1 ?= "New value"
In this next example, VAR1
is left with the value "Original value":
VAR1 = "Original value" VAR1 ?= "New value"
Appending: +=
-
Use the plus character followed by the equals sign
(+=
) to append values to existing
variables.
Here is an example:
SRC_URI += "file://fix-makefile.patch"
Prepending: =+
-
Use the equals sign followed by the plus character
(=+
) to prepend values to existing
variables.
Here is an example:
VAR =+ "Starts"
Appending: _append
-
Use the _append
operator to
append values to existing variables.
This operator does not add any additional space.
Also, the operator is applied after all the
+=
, and
=+
operators have been applied and
after all =
assignments have
occurred.
The following example shows the space being explicitly added to the start to ensure the appended value is not merged with the existing value:
SRC_URI_append = " file://fix-makefile.patch"
You can also use the _append
operator with overrides, which results in the actions
only being performed for the specified target or
machine:
SRC_URI_append_sh4 = " file://fix-makefile.patch"
Prepending: _prepend
-
Use the _prepend
operator to
prepend values to existing variables.
This operator does not add any additional space.
Also, the operator is applied after all the
+=
, and
=+
operators have been applied and
after all =
assignments have
occurred.
The following example shows the space being explicitly added to the end to ensure the prepended value is not merged with the existing value:
CFLAGS_prepend = "-I${S}/myincludes "
You can also use the _prepend
operator with overrides, which results in the actions
only being performed for the specified target or
machine:
CFLAGS_prepend_sh4 = "-I${S}/myincludes "
Overrides: -
You can use overrides to set a value conditionally,
typically based on how the recipe is being built.
For example, to set the
KBRANCH
variable's value to "standard/base" for any target
MACHINE
,
except for qemuarm where it should be set to
"standard/arm-versatile-926ejs", you would do the
following:
KBRANCH = "standard/base" KBRANCH_qemuarm = "standard/arm-versatile-926ejs"
Overrides are also used to separate alternate values
of a variable in other situations.
For example, when setting variables such as
FILES
and
RDEPENDS
that are specific to individual packages produced by
a recipe, you should always use an override that
specifies the name of the package.
Indentation: Use spaces for indentation rather than than tabs. For shell functions, both currently work. However, it is a policy decision of the Yocto Project to use tabs in shell functions. Realize that some layers have a policy to use spaces for all indentation.
Using Python for Complex Operations: ${@
-
For more advanced processing, it is possible to use
Python code during variable assignments (e.g.
search and replacement on a variable).python_code
}
You indicate Python code using the
${@
syntax for the variable assignment:
python_code
}
SRC_URI = "ftp://ftp.info-zip.org/pub/infozip/src/zip${@d.getVar('PV',1).replace('.', '')}.tgz
Shell Function Syntax:
Write shell functions as if you were writing a shell
script when you describe a list of actions to take.
You should ensure that your script works with a generic
sh
and that it does not require
any bash
or other shell-specific
functionality.
The same considerations apply to various system
utilities (e.g. sed
,
grep
, awk
,
and so forth) that you might wish to use.
If in doubt, you should check with multiple
implementations - including those from BusyBox.
Creating a new recipe is usually an iterative process that requires using BitBake to process the recipe multiple times in order to progressively discover and add information to the recipe file.
Assuming you have sourced a build environment setup script (i.e.
oe-init-build-env
or
oe-init-build-env-memres
)
and you are in the
Build Directory,
use BitBake to process your recipe.
All you need to provide is the
of the recipe as described
in the previous section:
basename
$ bitbake basename
During the build, the OpenEmbedded build system creates a
temporary work directory for each recipe
(${
WORKDIR
}
)
where it keeps extracted source files, log files, intermediate
compilation and packaging files, and so forth.
The path to the per-recipe temporary work directory depends on the context in which it is being built. The quickest way to find this path is to have BitBake return it by running the following:
$ bitbake -e basename
| grep ^WORKDIR=
As an example, assume a Source Directory top-level folder named
poky
, a default Build Directory at
poky/build
, and a
qemux86-poky-linux
machine target system.
Furthermore, suppose your recipe is named
foo_1.3.0.bb
.
In this case, the work directory the build system uses to
build the package would be as follows:
poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0
Inside this directory you can find sub-directories such as
image
, packages-split
,
and temp
.
After the build, you can examine these to determine how well
the build went.
temp
directory (e.g.
poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0/temp
).
Log files are named log.taskname
(e.g. log.do_configure
,
log.do_fetch
, and
log.do_compile
).
You can find more information about the build process in the "A Closer Look at the Yocto Project Development Environment" chapter of the Yocto Project Reference Manual.
The first thing your recipe must do is specify how to fetch
the source files.
Fetching is controlled mainly through the
SRC_URI
variable.
Your recipe must have a SRC_URI
variable
that points to where the source is located.
For a graphical representation of source locations, see the
"Sources"
section in the Yocto Project Reference Manual.
The
do_fetch
task uses the prefix of each entry in the
SRC_URI
variable value to determine which
fetcher to use to get your source files.
It is the SRC_URI
variable that triggers
the fetcher.
The
do_patch
task uses the variable after source is fetched to apply
patches.
The OpenEmbedded build system uses
FILESOVERRIDES
for scanning directory locations for local files in
SRC_URI
.
The SRC_URI
variable in your recipe must
define each unique location for your source files.
It is good practice to not hard-code pathnames in an URL used
in SRC_URI
.
Rather than hard-code these paths, use
${
PV
}
,
which causes the fetch process to use the version specified in
the recipe filename.
Specifying the version in this manner means that upgrading the
recipe to a future version is as simple as renaming the recipe
to match the new version.
Here is a simple example from the
meta/recipes-devtools/cdrtools/cdrtools-native_3.01a20.bb
recipe where the source comes from a single tarball.
Notice the use of the
PV
variable:
SRC_URI = "ftp://ftp.berlios.de/pub/cdrecord/alpha/cdrtools-${PV}.tar.bz2"
Files mentioned in SRC_URI
whose names end
in a typical archive extension (e.g. .tar
,
.tar.gz
, .tar.bz2
,
.zip
, and so forth), are automatically
extracted during the
do_unpack
task.
For another example that specifies these types of files, see
the
"Autotooled Package"
section.
Another way of specifying source is from an SCM.
For Git repositories, you must specify
SRCREV
and you should specify
PV
to include the revision with
SRCPV
.
Here is an example from the recipe
meta/recipes-kernel/blktrace/blktrace_git.bb
:
SRCREV = "d6918c8832793b4205ed3bfede78c2f915c23385" PR = "r6" PV = "1.0.5+git${SRCPV}" SRC_URI = "git://git.kernel.dk/blktrace.git \ file://ldflags.patch"
If your SRC_URI
statement includes
URLs pointing to individual files fetched from a remote server
other than a version control system, BitBake attempts to
verify the files against checksums defined in your recipe to
ensure they have not been tampered with or otherwise modified
since the recipe was written.
Two checksums are used:
SRC_URI[md5sum]
and
SRC_URI[sha256sum]
.
If your SRC_URI
variable points to
more than a single URL (excluding SCM URLs), you need to
provide the md5
and
sha256
checksums for each URL.
For these cases, you provide a name for each URL as part of
the SRC_URI
and then reference that name
in the subsequent checksum statements.
Here is an example:
SRC_URI = "${DEBIAN_MIRROR}/main/a/apmd/apmd_3.2.2.orig.tar.gz;name=tarball \ ${DEBIAN_MIRROR}/main/a/apmd/apmd_${PV}.diff.gz;name=patch" SRC_URI[tarball.md5sum] = "b1e6309e8331e0f4e6efd311c2d97fa8" SRC_URI[tarball.sha256sum] = "7f7d9f60b7766b852881d40b8ff91d8e39fccb0d1d913102a5c75a2dbb52332d" SRC_URI[patch.md5sum] = "57e1b689264ea80f78353519eece0c92" SRC_URI[patch.sha256sum] = "7905ff96be93d725544d0040e425c42f9c05580db3c272f11cff75b9aa89d430"
Proper values for md5
and
sha256
checksums might be available
with other signatures on the download page for the upstream
source (e.g. md5
,
sha1
, sha256
,
GPG
, and so forth).
Because the OpenEmbedded build system only deals with
sha256sum
and md5sum
,
you should verify all the signatures you find by hand.
If no SRC_URI
checksums are specified
when you attempt to build the recipe, or you provide an
incorrect checksum, the build will produce an error for each
missing or incorrect checksum.
As part of the error message, the build system provides
the checksum string corresponding to the fetched file.
Once you have the correct checksums, you can copy and paste
them into your recipe and then run the build again to continue.
This final example is a bit more complicated and is from the
meta/recipes-sato/rxvt-unicode/rxvt-unicode_9.20.bb
recipe.
The example's SRC_URI
statement identifies
multiple files as the source files for the recipe: a tarball, a
patch file, a desktop file, and an icon.
SRC_URI = "http://dist.schmorp.de/rxvt-unicode/Attic/rxvt-unicode-${PV}.tar.bz2 \ file://xwc.patch \ file://rxvt.desktop \ file://rxvt.png"
When you specify local files using the
file://
URI protocol, the build system
fetches files from the local machine.
The path is relative to the
FILESPATH
variable and searches specific directories in a certain order:
${
BP
}
,
${
BPN
}
,
and files
.
The directories are assumed to be subdirectories of the
directory in which the recipe or append file resides.
For another example that specifies these types of files, see the
"Single .c File Package (Hello World!)"
section.
The previous example also specifies a patch file.
Patch files are files whose names usually end in
.patch
or .diff
but
can end with compressed suffixes such as
diff.gz
and
patch.bz2
, for example.
The build system automatically applies patches as described
in the
"Patching Code" section.
During the build, the
do_unpack
task unpacks the source with
${
S
}
pointing to where it is unpacked.
If you are fetching your source files from an upstream source
archived tarball and the tarball's internal structure matches
the common convention of a top-level subdirectory named
${
BPN
}-${
PV
}
,
then you do not need to set S
.
However, if SRC_URI
specifies to fetch
source from an archive that does not use this convention,
or from an SCM like Git or Subversion, your recipe needs to
define S
.
If processing your recipe using BitBake successfully unpacks
the source files, you need to be sure that the directory
pointed to by ${S}
matches the structure
of the source.
Sometimes it is necessary to patch code after it has been
fetched.
Any files mentioned in SRC_URI
whose
names end in .patch
or
.diff
or compressed versions of these
suffixes (e.g. diff.gz
are treated as
patches.
The
do_patch
task automatically applies these patches.
The build system should be able to apply patches with the "-p1"
option (i.e. one directory level in the path will be stripped
off).
If your patch needs to have more directory levels stripped off,
specify the number of levels using the "striplevel" option in
the SRC_URI
entry for the patch.
Alternatively, if your patch needs to be applied in a specific
subdirectory that is not specified in the patch file, use the
"patchdir" option in the entry.
As with all local files referenced in
SRC_URI
using file://
, you should place
patch files in a directory next to the recipe either
named the same as the base name of the recipe
(BP
and
BPN
)
or "files".
Your recipe needs to have both the
LICENSE
and
LIC_FILES_CHKSUM
variables:
LICENSE
:
This variable specifies the license for the software.
If you do not know the license under which the software
you are building is distributed, you should go to the
source code and look for that information.
Typical files containing this information include
COPYING
,
LICENSE
, and
README
files.
You could also find the information near the top of
a source file.
For example, given a piece of software licensed under
the GNU General Public License version 2, you would
set LICENSE
as follows:
LICENSE = "GPLv2"
The licenses you specify within
LICENSE
can have any name as long
as you do not use spaces, since spaces are used as
separators between license names.
For standard licenses, use the names of the files in
meta/files/common-licenses/
or the SPDXLICENSEMAP
flag names
defined in meta/conf/licenses.conf
.
LIC_FILES_CHKSUM
:
The OpenEmbedded build system uses this variable to
make sure the license text has not changed.
If it has, the build produces an error and it affords
you the chance to figure it out and correct the problem.
You need to specify all applicable licensing
files for the software.
At the end of the configuration step, the build process
will compare the checksums of the files to be sure
the text has not changed.
Any differences result in an error with the message
containing the current checksum.
For more explanation and examples of how to set the
LIC_FILES_CHKSUM
variable, see the
"Tracking License Changes"
section in the Yocto Project Reference Manual.
To determine the correct checksum string, you
can list the appropriate files in the
LIC_FILES_CHKSUM
variable with
incorrect md5 strings, attempt to build the software,
and then note the resulting error messages that will
report the correct md5 strings.
See the
"Fetching Code"
section for additional information.
Here is an example that assumes the software has a
COPYING
file:
LIC_FILES_CHKSUM = "file://COPYING;md5=xxx"
When you try to build the software, the build system will produce an error and give you the correct string that you can substitute into the recipe file for a subsequent build.
Most software packages have a short list of other packages that they require, which are called dependencies. These dependencies fall into two main categories: build-time dependencies, which are required when the software is built; and runtime dependencies, which are required to be installed on the target in order for the software to run.
Within a recipe, you specify build-time dependencies using the
DEPENDS
variable.
Although nuances exist, items specified in
DEPENDS
should be names of other recipes.
It is important that you specify all build-time dependencies
explicitly.
If you do not, due to the parallel nature of BitBake's
execution, you can end up with a race condition where the
dependency is present for one task of a recipe (e.g.
do_configure
)
and then gone when the next task runs (e.g.
do_compile
).
Another consideration is that configure scripts might
automatically check for optional dependencies and enable
corresponding functionality if those dependencies are found.
This behavior means that to ensure deterministic results and
thus avoid more race conditions, you need to either explicitly
specify these dependencies as well, or tell the configure
script explicitly to disable the functionality.
If you wish to make a recipe that is more generally useful
(e.g. publish the recipe in a layer for others to use),
instead of hard-disabling the functionality, you can use the
PACKAGECONFIG
variable to allow functionality and the corresponding
dependencies to be enabled and disabled easily by other
users of the recipe.
Similar to build-time dependencies, you specify runtime
dependencies through a variable -
RDEPENDS
,
which is package-specific.
All variables that are package-specific need to have the name
of the package added to the end as an override.
Since the main package for a recipe has the same name as the
recipe, and the recipe's name can be found through the
${
PN
}
variable, then you specify the dependencies for the main
package by setting RDEPENDS_${PN}
.
If the package were named ${PN}-tools
,
then you would set RDEPENDS_${PN}-tools
,
and so forth.
Some runtime dependencies will be set automatically at packaging time. These dependencies include any shared library dependencies (i.e. if a package "example" contains "libexample" and another package "mypackage" contains a binary that links to "libexample" then the OpenEmbedded build system will automatically add a runtime dependency to "mypackage" on "example"). See the "Automatically Added Runtime Dependencies" in the Yocto Project Reference Manual for further details.
Most software provides some means of setting build-time configuration options before compilation. Typically, setting these options is accomplished by running a configure script with some options, or by modifying a build configuration file.
pkg-config
now, which is much more
robust.
You can find a list of the *-config
scripts that are disabled list in the
"Binary Configuration Scripts Disabled"
section in the Yocto Project Reference Manual.
A major part of build-time configuration is about checking for
build-time dependencies and possibly enabling optional
functionality as a result.
You need to specify any build-time dependencies for the
software you are building in your recipe's
DEPENDS
value, in terms of other recipes that satisfy those
dependencies.
You can often find build-time or runtime
dependencies described in the software's documentation.
The following list provides configuration items of note based on how your software is built:
Autotools:
If your source files have a
configure.ac
file, then your
software is built using Autotools.
If this is the case, you just need to worry about
modifying the configuration.
When using Autotools, your recipe needs to inherit
the
autotools
class and your recipe does not have to contain a
do_configure
task.
However, you might still want to make some adjustments.
For example, you can set
EXTRA_OECONF
or
PACKAGECONFIG_CONFARGS
to pass any needed configure options that are specific
to the recipe.
CMake:
If your source files have a
CMakeLists.txt
file, then your
software is built using CMake.
If this is the case, you just need to worry about
modifying the configuration.
When you use CMake, your recipe needs to inherit
the
cmake
class and your recipe does not have to contain a
do_configure
task.
You can make some adjustments by setting
EXTRA_OECMAKE
to pass any needed configure options that are specific
to the recipe.
Other:
If your source files do not have a
configure.ac
or
CMakeLists.txt
file, then your
software is built using some method other than Autotools
or CMake.
If this is the case, you normally need to provide a
do_configure
task in your recipe
unless, of course, there is nothing to configure.
Even if your software is not being built by Autotools or CMake, you still might not need to deal with any configuration issues. You need to determine if configuration is even a required step. You might need to modify a Makefile or some configuration file used for the build to specify necessary build options. Or, perhaps you might need to run a provided, custom configure script with the appropriate options.
For the case involving a custom configure
script, you would run
./configure --help
and look for
the options you need to set.
Once configuration succeeds, it is always good practice to
look at the log.do_configure
file to
ensure that the appropriate options have been enabled and no
additional build-time dependencies need to be added to
DEPENDS
.
For example, if the configure script reports that it found
something not mentioned in DEPENDS
, or
that it did not find something that it needed for some
desired optional functionality, then you would need to add
those to DEPENDS
.
Looking at the log might also reveal items being checked for,
enabled, or both that you do not want, or items not being found
that are in DEPENDS
, in which case
you would need to look at passing extra options to the
configure script as needed.
For reference information on configure options specific to the
software you are building, you can consult the output of the
./configure --help
command within
${S}
or consult the software's upstream
documentation.
If your recipe builds an application that needs to
communicate with some device or needs an API into a custom
kernel, you will need to provide appropriate header files.
Under no circumstances should you ever modify the existing
meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc
file.
These headers are used to build libc
and
must not be compromised with custom or machine-specific
header information.
If you customize libc
through modified
headers all other applications that use
libc
thus become affected.
libc
header file (i.e.
meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc
).
The correct way to interface to a device or custom kernel is to use a separate package that provides the additional headers for the driver or other unique interfaces. When doing so, your application also becomes responsible for creating a dependency on that specific provider.
Consider the following:
Never modify
linux-libc-headers.inc
.
Consider that file to be part of the
libc
system, and not something
you use to access the kernel directly.
You should access libc
through
specific libc
calls.
Applications that must talk directly to devices should either provide necessary headers themselves, or establish a dependency on a special headers package that is specific to that driver.
For example, suppose you want to modify an existing header that adds I/O control or network support. If the modifications are used by a small number programs, providing a unique version of a header is easy and has little impact. When doing so, bear in mind the guidelines in the previous list.
libc
, and subsequently all
other applications on the system, use a
.bbappend
to modify the
linux-kernel-headers.inc
file.
However, take care to not make the changes
machine specific.
Consider a case where your kernel is older and you need
an older libc
ABI.
The headers installed by your recipe should still be a
standard mainline kernel, not your own custom one.
When you use custom kernel headers you need to get them from
STAGING_KERNEL_DIR
,
which is the directory with kernel headers that are
required to build out-of-tree modules.
Your recipe will also need the following:
do_configure[depends] += "virtual/kernel:do_shared_workdir"
During a build, the do_compile
task
happens after source is fetched, unpacked, and configured.
If the recipe passes through do_compile
successfully, nothing needs to be done.
However, if the compile step fails, you need to diagnose the failure. Here are some common issues that cause failures.
pkg-config
.
See the note in section
"Configuring the Recipe"
for additional information.
Parallel build failures: These failures manifest themselves as intermittent errors, or errors reporting that a file or directory that should be created by some other part of the build process could not be found. This type of failure can occur even if, upon inspection, the file or directory does exist after the build has failed, because that part of the build process happened in the wrong order.
To fix the problem, you need to either satisfy
the missing dependency in the Makefile or whatever
script produced the Makefile, or (as a workaround)
set
PARALLEL_MAKE
to an empty string:
PARALLEL_MAKE = ""
For information on parallel Makefile issues, see the "Debugging Parallel Make Races" section.
Improper host path usage:
This failure applies to recipes building for the target
or nativesdk
only.
The failure occurs when the compilation process uses
improper headers, libraries, or other files from the
host system when cross-compiling for the target.
To fix the problem, examine the
log.do_compile
file to identify
the host paths being used (e.g.
/usr/include
,
/usr/lib
, and so forth) and then
either add configure options, apply a patch, or do both.
Failure to find required
libraries/headers:
If a build-time dependency is missing because it has
not been declared in
DEPENDS
,
or because the dependency exists but the path used by
the build process to find the file is incorrect and the
configure step did not detect it, the compilation
process could fail.
For either of these failures, the compilation process
notes that files could not be found.
In these cases, you need to go back and add additional
options to the configure script as well as possibly
add additional build-time dependencies to
DEPENDS
.
Occasionally, it is necessary to apply a patch
to the source to ensure the correct paths are used.
If you need to specify paths to find files staged
into the sysroot from other recipes, use the variables
that the OpenEmbedded build system provides
(e.g.
STAGING_BINDIR
,
STAGING_INCDIR
,
STAGING_DATADIR
, and so forth).
During do_install
, the task copies the
built files along with their hierarchy to locations that
would mirror their locations on the target device.
The installation process copies files from the
${
S
}
,
${
B
}
,
and
${
WORKDIR
}
directories to the
${
D
}
directory to create the structure as it should appear on the
target system.
How your software is built affects what you must do to be sure your software is installed correctly. The following list describes what you must do for installation depending on the type of build system used by the software being built:
Autotools and CMake:
If the software your recipe is building uses Autotools
or CMake, the OpenEmbedded build
system understands how to install the software.
Consequently, you do not have to have a
do_install
task as part of your
recipe.
You just need to make sure the install portion of the
build completes with no issues.
However, if you wish to install additional files not
already being installed by
make install
, you should do this
using a do_install_append
function
using the install command as described in
the "Manual" bulleted item later in this list.
Other (using
make install
):
You need to define a
do_install
function in your
recipe.
The function should call
oe_runmake install
and will likely
need to pass in the destination directory as well.
How you pass that path is dependent on how the
Makefile
being run is written
(e.g. DESTDIR=${D}
,
PREFIX=${D}
,
INSTALLROOT=${D}
, and so forth).
For an example recipe using
make install
, see the
"Makefile-Based Package"
section.
Manual:
You need to define a
do_install
function in your
recipe.
The function must first use
install -d
to create the
directories under
${
D
}
.
Once the directories exist, your function can use
install
to manually install the
built software into the directories.
You can find more information on
install
at
http://www.gnu.org/software/coreutils/manual/html_node/install-invocation.html.
For the scenarios that do not use Autotools or
CMake, you need to track the installation
and diagnose and fix any issues until everything installs
correctly.
You need to look in the default location of
${D}
, which is
${WORKDIR}/image
, to be sure your
files have been installed correctly.
During the installation process, you might need to
modify some of the installed files to suit the target
layout.
For example, you might need to replace hard-coded paths
in an initscript with values of variables provided by
the build system, such as replacing
/usr/bin/
with
${bindir}
.
If you do perform such modifications during
do_install
, be sure to modify the
destination file after copying rather than before
copying.
Modifying after copying ensures that the build system
can re-execute do_install
if
needed.
oe_runmake install
, which can be
run directly or can be run indirectly by the
autotools
and
cmake
classes, runs make install
in
parallel.
Sometimes, a Makefile can have missing dependencies
between targets that can result in race conditions.
If you experience intermittent failures during
do_install
, you might be able to
work around them by disabling parallel Makefile
installs by adding the following to the recipe:
PARALLEL_MAKEINST = ""
See
PARALLEL_MAKEINST
for additional information.
If you want to install a service, which is a process that usually starts on boot and runs in the background, then you must include some additional definitions in your recipe.
If you are adding services and the service initialization
script or the service file itself is not installed, you must
provide for that installation in your recipe using a
do_install_append
function.
If your recipe already has a do_install
function, update the function near its end rather than
adding an additional do_install_append
function.
When you create the installation for your services, you need
to accomplish what is normally done by
make install
.
In other words, make sure your installation arranges the output
similar to how it is arranged on the target system.
The OpenEmbedded build system provides support for starting services two different ways:
SysVinit: SysVinit is a system and service manager that manages the init system used to control the very basic functions of your system. The init program is the first program started by the Linux kernel when the system boots. Init then controls the startup, running and shutdown of all other programs.
To enable a service using SysVinit, your recipe
needs to inherit the
update-rc.d
class.
The class helps facilitate safely installing the
package on the target.
You will need to set the
INITSCRIPT_PACKAGES
,
INITSCRIPT_NAME
,
and
INITSCRIPT_PARAMS
variables within your recipe.
systemd: System Management Daemon (systemd) was designed to replace SysVinit and to provide enhanced management of services. For more information on systemd, see the systemd homepage at http://freedesktop.org/wiki/Software/systemd/.
To enable a service using systemd, your recipe
needs to inherit the
systemd
class.
See the systemd.bbclass
file
located in your
Source Directory.
section for more information.
Successful packaging is a combination of automated processes performed by the OpenEmbedded build system and some specific steps you need to take. The following list describes the process:
Splitting Files:
The do_package
task splits the
files produced by the recipe into logical components.
Even software that produces a single binary might
still have debug symbols, documentation, and other
logical components that should be split out.
The do_package
task ensures
that files are split up and packaged correctly.
Running QA Checks:
The
insane
class adds a step to
the package generation process so that output quality
assurance checks are generated by the OpenEmbedded
build system.
This step performs a range of checks to be sure the
build's output is free of common problems that show
up during runtime.
For information on these checks, see the
insane
class and the
"QA Error and Warning Messages"
chapter in the Yocto Project Reference Manual.
Hand-Checking Your Packages:
After you build your software, you need to be sure
your packages are correct.
Examine the
${
WORKDIR
}/packages-split
directory and make sure files are where you expect
them to be.
If you discover problems, you can set
PACKAGES
,
FILES
,
do_install(_append)
, and so forth as
needed.
Splitting an Application into Multiple Packages: If you need to split an application into several packages, see the "Splitting an Application into Multiple Packages" section for an example.
Installing a Post-Installation Script: For an example showing how to install a post-installation script, see the "Post-Installation Scripts" section.
Marking Package Architecture: Depending on what your recipe is building and how it is configured, it might be important to mark the packages produced as being specific to a particular machine, or to mark them as not being specific to a particular machine or architecture at all.
By default, packages apply to any machine with the
same architecture as the target machine.
When a recipe produces packages that are
machine-specific (e.g. the
MACHINE
value is passed into the configure script or a patch
is applied only for a particular machine), you should
mark them as such by adding the following to the
recipe:
PACKAGE_ARCH = "${MACHINE_ARCH}"
On the other hand, if the recipe produces packages
that do not contain anything specific to the target
machine or architecture at all (e.g. recipes
that simply package script files or configuration
files), you should use the
allarch
class to do this for you by adding this to your
recipe:
inherit allarch
Ensuring that the package architecture is correct is not critical while you are doing the first few builds of your recipe. However, it is important in order to ensure that your recipe rebuilds (or does not rebuild) appropriately in response to changes in configuration, and to ensure that you get the appropriate packages installed on the target machine, particularly if you run separate builds for more than one target machine.
Recipes often need to use files provided by other recipes on
the build host.
For example, an application linking to a common library needs
access to the library itself and its associated headers.
The way this access is accomplished is by populating a sysroot
with files.
Each recipe has two sysroots in its work directory, one for
target files
(recipe-sysroot
) and one for files that
are native to the build host
(recipe-sysroot-native
).
STAGING_DIR
variable).
Recipes should never populate the sysroot directly (i.e. write
files into sysroot).
Instead, files should be installed into standard locations
during the
do_install
task within the
${
D
}
directory.
The reason for this limitation is that almost all files that
populate the sysroot are cataloged in manifests in order to
ensure the files can be removed later when a recipe is either
modified or removed.
Thus, the sysroot is able to remain free from stale files.
A subset of the files installed by the
do_install
task are used by the
do_populate_sysroot
task as defined by the the
SYSROOT_DIRS
variable to automatically populate the sysroot.
It is possible to modify the list of directories that populate
the sysroot.
The following example shows how you could add the
/opt
directory to the list of
directories within a recipe:
SYSROOT_DIRS += "/opt"
For a more complete description of the
do_populate_sysroot
task and its associated functions, see the
staging
class.
Sometimes the name of a recipe can lead to versioning
problems when the recipe is upgraded to a final release.
For example, consider the
irssi_0.8.16-rc1.bb
recipe file in
the list of example recipes in the
"Storing and Naming the Recipe"
section.
This recipe is at a release candidate stage (i.e.
"rc1").
When the recipe is released, the recipe filename becomes
irssi_0.8.16.bb
.
The version change from 0.8.16-rc1
to 0.8.16
is seen as a decrease by the
build system and package managers, so the resulting packages
will not correctly trigger an upgrade.
In order to ensure the versions compare properly, the
recommended convention is to set
PV
within the recipe to
"previous_version
+current_version
".
You can use an additional variable so that you can use the
current version elsewhere.
Here is an example:
REALPV = "0.8.16-rc1" PV = "0.8.15+${REALPV}"
Post-installation scripts run immediately after installing
a package on the target or during image creation when a
package is included in an image.
To add a post-installation script to a package, add a
pkg_postinst_
PACKAGENAME
()
function to
the recipe file (.bb
) and replace
PACKAGENAME
with the name of the package
you want to attach to the postinst
script.
To apply the post-installation script to the main package
for the recipe, which is usually what is required, specify
${
PN
}
in place of PACKAGENAME
.
A post-installation function has the following structure:
pkg_postinst_PACKAGENAME
() {
# Commands to carry out
}
The script defined in the post-installation function is called when the root filesystem is created. If the script succeeds, the package is marked as installed. If the script fails, the package is marked as unpacked and the script is executed when the image boots again.
Sometimes it is necessary for the execution of a post-installation script to be delayed until the first boot. For example, the script might need to be executed on the device itself. To delay script execution until boot time, use the following structure in the post-installation script:
pkg_postinst_PACKAGENAME
() {
if [ x"$D" = "x" ]; then
# Actions to carry out on the device go here
else
exit 1
fi
}
The previous example delays execution until the image boots
again because the environment variable D
points to the directory containing the image when
the root filesystem is created at build time but is unset
when executed on the first boot.
If you have recipes that use pkg_postinst
scripts and they require the use of non-standard native
tools that have dependencies during rootfs construction, you
need to use the
PACKAGE_WRITE_DEPS
variable in your recipe to list these tools.
If you do not use this variable, the tools might be missing and
execution of the post-installation script is deferred until
first boot.
Deferring the script to first boot is undesirable and for
read-only rootfs impossible.
pkg_preinst
,
pkg_prerm
, and
pkg_postrm
, respectively.
These scrips work in exactly the same way as does
pkg_postinst
with the exception that they
run at different times.
Also, because of when they run, they are not applicable to
being run at image creation time like
pkg_postinst
.
The final step for completing your recipe is to be sure that the software you built runs correctly. To accomplish runtime testing, add the build's output packages to your image and test them on the target.
For information on how to customize your image by adding specific packages, see the "Customizing Images" section.
To help summarize how to write a recipe, this section provides some examples given various scenarios:
Recipes that use local files
Using an Autotooled package
Using a Makefile-based package
Splitting an application into multiple packages
Adding binaries to an image
Building an application from a single file that is stored
locally (e.g. under files
) requires
a recipe that has the file listed in the
SRC_URI
variable.
Additionally, you need to manually write the
do_compile
and
do_install
tasks.
The S
variable defines the directory containing the source code,
which is set to
WORKDIR
in this case - the directory BitBake uses for the build.
SUMMARY = "Simple helloworld application" SECTION = "examples" LICENSE = "MIT" LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302" SRC_URI = "file://helloworld.c" S = "${WORKDIR}" do_compile() { ${CC} helloworld.c -o helloworld } do_install() { install -d ${D}${bindir} install -m 0755 helloworld ${D}${bindir} }
By default, the helloworld
,
helloworld-dbg
, and
helloworld-dev
packages are built.
For information on how to customize the packaging process,
see the
"Splitting an Application into Multiple Packages"
section.
Applications that use Autotools such as autoconf
and
automake
require a recipe that has a source archive listed in
SRC_URI
and
also inherit the
autotools
class, which contains the definitions of all the steps
needed to build an Autotool-based application.
The result of the build is automatically packaged.
And, if the application uses NLS for localization, packages with local information are
generated (one package per language).
Following is one example: (hello_2.3.bb
)
SUMMARY = "GNU Helloworld application" SECTION = "examples" LICENSE = "GPLv2+" LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe" SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz" inherit autotools gettext
The variable
LIC_FILES_CHKSUM
is used to track source license changes as described in the
"Tracking License Changes" section.
You can quickly create Autotool-based recipes in a manner similar to the previous example.
Applications that use GNU make
also require a recipe that has
the source archive listed in
SRC_URI
.
You do not need to add a do_compile
step since by default BitBake
starts the make
command to compile the application.
If you need additional make
options, you should store them in the
EXTRA_OEMAKE
or
PACKAGECONFIG_CONFARGS
variables.
BitBake passes these options into the GNU make
invocation.
Note that a do_install
task is still required.
Otherwise, BitBake runs an empty do_install
task by default.
Some applications might require extra parameters to be passed to the compiler.
For example, the application might need an additional header path.
You can accomplish this by adding to the
CFLAGS
variable.
The following example shows this:
CFLAGS_prepend = "-I ${S}/include "
In the following example, mtd-utils
is a makefile-based package:
SUMMARY = "Tools for managing memory technology devices" SECTION = "base" DEPENDS = "zlib lzo e2fsprogs util-linux" HOMEPAGE = "http://www.linux-mtd.infradead.org/" LICENSE = "GPLv2+" LIC_FILES_CHKSUM = "file://COPYING;md5=0636e73ff0215e8d672dc4c32c317bb3 \ file://include/common.h;beginline=1;endline=17;md5=ba05b07912a44ea2bf81ce409380049c" # Use the latest version at 26 Oct, 2013 SRCREV = "9f107132a6a073cce37434ca9cda6917dd8d866b" SRC_URI = "git://git.infradead.org/mtd-utils.git \ file://add-exclusion-to-mkfs-jffs2-git-2.patch \ " PV = "1.5.1+git${SRCPV}" S = "${WORKDIR}/git" EXTRA_OEMAKE = "'CC=${CC}' 'RANLIB=${RANLIB}' 'AR=${AR}' 'CFLAGS=${CFLAGS} -I${S}/include -DWITHOUT_XATTR' 'BUILDDIR=${S}'" do_install () { oe_runmake install DESTDIR=${D} SBINDIR=${sbindir} MANDIR=${mandir} INCLUDEDIR=${includedir} } PACKAGES =+ "mtd-utils-jffs2 mtd-utils-ubifs mtd-utils-misc" FILES_mtd-utils-jffs2 = "${sbindir}/mkfs.jffs2 ${sbindir}/jffs2dump ${sbindir}/jffs2reader ${sbindir}/sumtool" FILES_mtd-utils-ubifs = "${sbindir}/mkfs.ubifs ${sbindir}/ubi*" FILES_mtd-utils-misc = "${sbindir}/nftl* ${sbindir}/ftl* ${sbindir}/rfd* ${sbindir}/doc* ${sbindir}/serve_image ${sbindir}/recv_image" PARALLEL_MAKE = "" BBCLASSEXTEND = "native"
You can use the variables
PACKAGES
and
FILES
to split an application into multiple packages.
Following is an example that uses the libxpm
recipe.
By default, this recipe generates a single package that contains the library along
with a few binaries.
You can modify the recipe to split the binaries into separate packages:
require xorg-lib-common.inc SUMMARY = "Xpm: X Pixmap extension library" LICENSE = "BSD" LIC_FILES_CHKSUM = "file://COPYING;md5=51f4270b012ecd4ab1a164f5f4ed6cf7" DEPENDS += "libxext libsm libxt" PE = "1" XORG_PN = "libXpm" PACKAGES =+ "sxpm cxpm" FILES_cxpm = "${bindir}/cxpm" FILES_sxpm = "${bindir}/sxpm"
In the previous example, we want to ship the sxpm
and cxpm
binaries in separate packages.
Since bindir
would be packaged into the main
PN
package by default, we prepend the PACKAGES
variable so additional package names are added to the start of list.
This results in the extra FILES_*
variables then containing information that define which files and
directories go into which packages.
Files included by earlier packages are skipped by latter packages.
Thus, the main PN
package
does not include the above listed files.
Sometimes, you need to add pre-compiled binaries to an
image.
For example, suppose that binaries for proprietary code
exist, which are created by a particular division of a
company.
Your part of the company needs to use those binaries as
part of an image that you are building using the
OpenEmbedded build system.
Since you only have the binaries and not the source code,
you cannot use a typical recipe that expects to fetch the
source specified in
SRC_URI
and then compile it.
One method is to package the binaries and then install them as part of the image. Generally, it is not a good idea to package binaries since, among other things, it can hinder the ability to reproduce builds and could lead to compatibility problems with ABI in the future. However, sometimes you have no choice.
The easiest solution is to create a recipe that uses
the
bin_package
class and to be sure that you are using default locations
for build artifacts.
In most cases, the bin_package
class
handles "skipping" the configure and compile steps as well
as sets things up to grab packages from the appropriate
area.
In particular, this class sets noexec
on both the
do_configure
and
do_compile
tasks, sets
FILES_${PN}
to "/" so that it picks
up all files, and sets up a
do_install
task, which effectively copies all files from
${S}
to ${D}
.
The bin_package
class works well when
the files extracted into ${S}
are
already laid out in the way they should be laid out
on the target.
For more information on these variables, see the
FILES
,
PN
,
S
,
and
D
variables in the Yocto Project Reference Manual's variable
glossary.
Using
DEPENDS
is a good idea even for components distributed
in binary form, and is often necessary for
shared libraries.
For a shared library, listing the library
dependencies in
DEPENDS
makes sure that
the libraries are available in the staging
sysroot when other recipes link against the
library, which might be necessary for
successful linking.
Using DEPENDS
also
allows runtime dependencies between packages
to be added automatically.
See the
"Automatically Added Runtime Dependencies"
section in the Yocto Project Reference Manual
for more information.
If you cannot use the bin_package
class, you need to be sure you are doing the following:
Create a recipe where the
do_configure
and
do_compile
tasks do nothing:
It is usually sufficient to just not define these
tasks in the recipe, because the default
implementations do nothing unless a Makefile is
found in
${
S
}
.
If
${S}
might contain a Makefile,
or if you inherit some class that replaces
do_configure
and
do_compile
with custom
versions, then you can use the
[
noexec
]
flag to turn the tasks into no-ops, as follows:
do_configure[noexec] = "1" do_compile[noexec] = "1"
Unlike
deleting the tasks
,
using the flag preserves the dependency chain from
the
do_fetch
, do_unpack
,
and
do_patch
tasks to the
do_install
task.
Make sure your
do_install
task installs the
binaries appropriately.
Ensure that you set up
FILES
(usually
FILES_${
PN
}
)
to point to the files you have installed, which of
course depends on where you have installed them
and whether those files are in different locations
than the defaults.
When writing recipes, it is good to conform to existing style guidelines. The OpenEmbedded Styleguide wiki page provides rough guidelines for preferred recipe style.
It is common for existing recipes to deviate a bit from this
style.
However, aiming for at least a consistent style is a good idea.
Some practices, such as omitting spaces around
=
operators in assignments or ordering
recipe components in an erratic way, are widely seen as poor
style.
Adding a new machine to the Yocto Project is a straightforward process. This section describes how to add machines that are similar to those that the Yocto Project already supports.
gcc/glibc
and to the site
information, which is beyond the scope of this manual.
For a complete example that shows how to add a new machine, see the "Creating a New BSP Layer Using the yocto-bsp Script" section in the Yocto Project Board Support Package (BSP) Developer's Guide.
To add a new machine, you need to add a new machine
configuration file to the layer's
conf/machine
directory.
This configuration file provides details about the device
you are adding.
The OpenEmbedded build system uses the root name of the
machine configuration file to reference the new machine.
For example, given a machine configuration file named
crownbay.conf
, the build system
recognizes the machine as "crownbay".
The most important variables you must set in your machine configuration file or include from a lower-level configuration file are as follows:
TARGET_ARCH
(e.g. "arm")
PREFERRED_PROVIDER_virtual/kernel
MACHINE_FEATURES
(e.g. "apm screen wifi")
You might also need these variables:
SERIAL_CONSOLES
(e.g. "115200;ttyS0 115200;ttyS1")
KERNEL_IMAGETYPE
(e.g. "zImage")
IMAGE_FSTYPES
(e.g. "tar.gz jffs2")
You can find full details on these variables in the reference
section.
You can leverage existing machine .conf
files from meta-yocto-bsp/conf/machine/
.
The OpenEmbedded build system needs to be able to build a kernel
for the machine.
You need to either create a new kernel recipe for this machine,
or extend an existing kernel recipe.
You can find several kernel recipe examples in the
Source Directory at
meta/recipes-kernel/linux
that you can use as references.
If you are creating a new kernel recipe, normal recipe-writing
rules apply for setting up a
SRC_URI
.
Thus, you need to specify any necessary patches and set
S
to point at the source code.
You need to create a do_configure
task that
configures the unpacked kernel with a
defconfig
file.
You can do this by using a make defconfig
command or, more commonly, by copying in a suitable
defconfig
file and then running
make oldconfig
.
By making use of inherit kernel
and
potentially some of the linux-*.inc
files,
most other functionality is centralized and the defaults of the
class normally work well.
If you are extending an existing kernel recipe, it is usually
a matter of adding a suitable defconfig
file.
The file needs to be added into a location similar to
defconfig
files used for other machines
in a given kernel recipe.
A possible way to do this is by listing the file in the
SRC_URI
and adding the machine to the
expression in
COMPATIBLE_MACHINE
:
COMPATIBLE_MACHINE = '(qemux86|qemumips)'
For more information on defconfig
files,
see the
"Changing the Configuration"
section in the Yocto Project Linux Kernel Development Manual.
A formfactor configuration file provides information about the target hardware for which the image is being built and information that the build system cannot obtain from other sources such as the kernel. Some examples of information contained in a formfactor configuration file include framebuffer orientation, whether or not the system has a keyboard, the positioning of the keyboard in relation to the screen, and the screen resolution.
The build system uses reasonable defaults in most cases.
However, if customization is
necessary, you need to create a machconfig
file
in the meta/recipes-bsp/formfactor/files
directory.
This directory contains directories for specific machines such as
qemuarm
and qemux86
.
For information about the settings available and the defaults, see the
meta/recipes-bsp/formfactor/files/config
file found in the
same area.
Following is an example for "qemuarm" machine:
HAVE_TOUCHSCREEN=1 HAVE_KEYBOARD=1 DISPLAY_CAN_ROTATE=0 DISPLAY_ORIENTATION=0 #DISPLAY_WIDTH_PIXELS=640 #DISPLAY_HEIGHT_PIXELS=480 #DISPLAY_BPP=16 DISPLAY_DPI=150 DISPLAY_SUBPIXEL_ORDER=vrgb
Bitbake also has functionality that allows you to build multiple targets at the same time, where each target uses a different configuration.
In order to accomplish this, you setup each of the configurations
you need to use in parallel by placing the configuration files in
your current build directory alongside the usual
local.conf
file.
Follow these guidelines to create an environment that supports multiple configurations:
Create Configuration Files: You need to create a single configuration file for each configuration for which you want to add support. These files would contain lines such as the following:
MACHINE = "A"
The files would contain any other variables that can be set and built in the same directory.
TMPDIR
to not conflict.
Furthermore, the configuration file must be located in the
current build directory in a directory named
multiconfig
under the build's
conf
directory where
local.conf
resides.
The reason for this restriction is because the
BBPATH
variable is not constructed
until the layers are parsed.
Consequently, using the configuration file as a
pre-configuration file is not possible unless it is
located in the current working directory.
Add the BitBake Multi-Config Variable to you Local Configuration File:
Use the
BBMULTICONFIG
variable in your conf/local.conf
configuration file to specify each separate configuration.
For example, the following line tells BitBake it should load
conf/multiconfig/configA.conf
,
conf/multiconfig/configB.conf
, and
conf/multiconfig/configC.conf
.
BBMULTICONFIG = "configA configB configC"
Launch BitBake: Use the following BitBake command form to launch the build:
$ bitbake [multiconfig:multiconfigname
:]target
[[[multiconfig:multiconfigname
:]target
] ... ]
Following is an example that supports building a minimal
image for configuration A alongside a standard
core-image-sato
, which takes its
configuration from local.conf
:
$ bitbake multiconfig:configA:core-image-minimal core-image-sato
Support for multiple configurations in this current release of the Yocto Project (Pyro 2.3.3) has some known issues:
No inter-multi-configuration dependencies exist.
Shared State (sstate) optimizations do not exist.
Consequently, if the build uses the same object twice
in, for example, two different
TMPDIR
directories, the build
will either load from an existing sstate cache at the
start or build the object twice.
Libraries are an integral part of your system. This section describes some common practices you might find helpful when working with libraries to build your system:
If you are building a library and the library offers static linking, you can control
which static library files (*.a
files) get included in the
built library.
The PACKAGES
and FILES_*
variables in the
meta/conf/bitbake.conf
configuration file define how files installed
by the do_install
task are packaged.
By default, the PACKAGES
variable includes
${PN}-staticdev
, which represents all static library files.
${PN}-dev
.
Following is part of the BitBake configuration file, where you can see how the static library files are defined:
PACKAGE_BEFORE_PN ?= "" PACKAGES = "${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKAGE_BEFORE_PN} ${PN}" PACKAGES_DYNAMIC = "^${PN}-locale-.*" FILES = "" FILES_${PN} = "${bindir}/* ${sbindir}/* ${libexecdir}/* ${libdir}/lib*${SOLIBS} \ ${sysconfdir} ${sharedstatedir} ${localstatedir} \ ${base_bindir}/* ${base_sbindir}/* \ ${base_libdir}/*${SOLIBS} \ ${base_prefix}/lib/udev/rules.d ${prefix}/lib/udev/rules.d \ ${datadir}/${BPN} ${libdir}/${BPN}/* \ ${datadir}/pixmaps ${datadir}/applications \ ${datadir}/idl ${datadir}/omf ${datadir}/sounds \ ${libdir}/bonobo/servers" FILES_${PN}-bin = "${bindir}/* ${sbindir}/*" FILES_${PN}-doc = "${docdir} ${mandir} ${infodir} ${datadir}/gtk-doc \ ${datadir}/gnome/help" SECTION_${PN}-doc = "doc" FILES_SOLIBSDEV ?= "${base_libdir}/lib*${SOLIBSDEV} ${libdir}/lib*${SOLIBSDEV}" FILES_${PN}-dev = "${includedir} ${FILES_SOLIBSDEV} ${libdir}/*.la \ ${libdir}/*.o ${libdir}/pkgconfig ${datadir}/pkgconfig \ ${datadir}/aclocal ${base_libdir}/*.o \ ${libdir}/${BPN}/*.la ${base_libdir}/*.la" SECTION_${PN}-dev = "devel" ALLOW_EMPTY_${PN}-dev = "1" RDEPENDS_${PN}-dev = "${PN} (= ${EXTENDPKGV})" FILES_${PN}-staticdev = "${libdir}/*.a ${base_libdir}/*.a ${libdir}/${BPN}/*.a" SECTION_${PN}-staticdev = "devel" RDEPENDS_${PN}-staticdev = "${PN}-dev (= ${EXTENDPKGV})"
The build system offers the ability to build libraries with different target optimizations or architecture formats and combine these together into one system image. You can link different binaries in the image against the different libraries as needed for specific use cases. This feature is called "Multilib."
An example would be where you have most of a system compiled in 32-bit mode using 32-bit libraries, but you have something large, like a database engine, that needs to be a 64-bit application and uses 64-bit libraries. Multilib allows you to get the best of both 32-bit and 64-bit libraries.
While the Multilib feature is most commonly used for 32 and 64-bit differences, the approach the build system uses facilitates different target optimizations. You could compile some binaries to use one set of libraries and other binaries to use a different set of libraries. The libraries could differ in architecture, compiler options, or other optimizations.
Several examples exist in the
meta-skeleton
layer found in the
Source Directory:
conf/multilib-example.conf
configuration file
conf/multilib-example2.conf
configuration file
recipes-multilib/images/core-image-multilib-example.bb
recipe
User-specific requirements drive the Multilib feature. Consequently, there is no one "out-of-the-box" configuration that likely exists to meet your needs.
In order to enable Multilib, you first need to ensure your recipe is
extended to support multiple libraries.
Many standard recipes are already extended and support multiple libraries.
You can check in the meta/conf/multilib.conf
configuration file in the
Source Directory to see how this is
done using the
BBCLASSEXTEND
variable.
Eventually, all recipes will be covered and this list will
not be needed.
For the most part, the Multilib class extension works automatically to
extend the package name from ${PN}
to
${MLPREFIX}${PN}
, where MLPREFIX
is the particular multilib (e.g. "lib32-" or "lib64-").
Standard variables such as
DEPENDS
,
RDEPENDS
,
RPROVIDES
,
RRECOMMENDS
,
PACKAGES
, and
PACKAGES_DYNAMIC
are automatically extended by the system.
If you are extending any manual code in the recipe, you can use the
${MLPREFIX}
variable to ensure those names are extended
correctly.
This automatic extension code resides in multilib.bbclass
.
After you have set up the recipes, you need to define the actual
combination of multiple libraries you want to build.
You accomplish this through your local.conf
configuration file in the
Build Directory.
An example configuration would be as follows:
MACHINE = "qemux86-64" require conf/multilib.conf MULTILIBS = "multilib:lib32" DEFAULTTUNE_virtclass-multilib-lib32 = "x86" IMAGE_INSTALL_append = " lib32-glib-2.0"
This example enables an
additional library named lib32
alongside the
normal target packages.
When combining these "lib32" alternatives, the example uses "x86" for tuning.
For information on this particular tuning, see
meta/conf/machine/include/ia32/arch-ia32.inc
.
The example then includes lib32-glib-2.0
in all the images, which illustrates one method of including a
multiple library dependency.
You can use a normal image build to include this dependency,
for example:
$ bitbake core-image-sato
You can also build Multilib packages specifically with a command like this:
$ bitbake lib32-glib-2.0
Generic implementation details as well as details that are specific to package management systems exist. Following are implementation details that exist regardless of the package management system:
The typical convention used for the
class extension code as used by
Multilib assumes that all package names specified
in
PACKAGES
that contain ${PN}
have
${PN}
at the start of the name.
When that convention is not followed and
${PN}
appears at
the middle or the end of a name, problems occur.
The
TARGET_VENDOR
value under Multilib will be extended to
"-vendor
mlmultilib
"
(e.g. "-pokymllib32" for a "lib32" Multilib with
Poky).
The reason for this slightly unwieldy contraction
is that any "-" characters in the vendor
string presently break Autoconf's
config.sub
, and
other separators are problematic for different
reasons.
For the RPM Package Management System, the following implementation details exist:
A unique architecture is defined for the Multilib packages,
along with creating a unique deploy folder under
tmp/deploy/rpm
in the
Build Directory.
For example, consider lib32
in a
qemux86-64
image.
The possible architectures in the system are "all", "qemux86_64",
"lib32_qemux86_64", and "lib32_x86".
The ${MLPREFIX}
variable is stripped from
${PN}
during RPM packaging.
The naming for a normal RPM package and a Multilib RPM package in a
qemux86-64
system resolves to something similar to
bash-4.1-r2.x86_64.rpm
and
bash-4.1.r2.lib32_x86.rpm
, respectively.
When installing a Multilib image, the RPM backend first installs the base image and then installs the Multilib libraries.
The build system relies on RPM to resolve the identical files in the two (or more) Multilib packages.
For the IPK Package Management System, the following implementation details exist:
The ${MLPREFIX}
is not stripped from
${PN}
during IPK packaging.
The naming for a normal RPM package and a Multilib IPK package in a
qemux86-64
system resolves to something like
bash_4.1-r2.x86_64.ipk
and
lib32-bash_4.1-rw_x86.ipk
, respectively.
The IPK deploy folder is not modified with
${MLPREFIX}
because packages with and without
the Multilib feature can exist in the same folder due to the
${PN}
differences.
IPK defines a sanity check for Multilib installation using certain rules for file comparison, overridden, etc.
Situations can exist where you need to install and use multiple versions of the same library on the same system at the same time. These situations almost always exist when a library API changes and you have multiple pieces of software that depend on the separate versions of the library. To accommodate these situations, you can install multiple versions of the same library in parallel on the same system.
The process is straightforward as long as the libraries use
proper versioning.
With properly versioned libraries, all you need to do to
individually specify the libraries is create separate,
appropriately named recipes where the
PN
part of the
name includes a portion that differentiates each library version
(e.g.the major part of the version number).
Thus, instead of having a single recipe that loads one version
of a library (e.g. clutter
), you provide
multiple recipes that result in different versions
of the libraries you want.
As an example, the following two recipes would allow the
two separate versions of the clutter
library to co-exist on the same system:
clutter-1.6_1.6.20.bb clutter-1.8_1.8.4.bb
Additionally, if you have other recipes that depend on a given
library, you need to use the
DEPENDS
variable to create the dependency.
Continuing with the same example, if you want to have a recipe
depend on the 1.8 version of the clutter
library, use the following in your recipe:
DEPENDS = "clutter-1.8"
GObject introspection is the standard mechanism for accessing GObject-based software from runtime environments. GObject is a feature of the GLib library that provides an object framework for the GNOME desktop and related software. GObject Introspection adds information to GObject that allows objects created within it to be represented across different programming languages. If you want to construct GStreamer pipelines using Python, or control UPnP infrastructure using Javascript and GUPnP, GObject introspection is the only way to do it.
This section describes the Yocto Project support for generating
and packaging GObject introspection data.
GObject introspection data is a description of the
API provided by libraries built on top of GLib framework,
and, in particular, that framework's GObject mechanism.
GObject Introspection Repository (GIR) files go to
-dev
packages,
typelib
files go to main packages as they
are packaged together with libraries that are introspected.
The data is generated when building such a library, by linking the library with a small executable binary that asks the library to describe itself, and then executing the binary and processing its output.
Generating this data in a cross-compilation environment is difficult because the library is produced for the target architecture, but its code needs to be executed on the build host. This problem is solved with the OpenEmbedded build system by running the code through QEMU, which allows precisely that. Unfortunately, QEMU does not always work perfectly as mentioned in the xxx section.
Enabling the generation of introspection data (GIR files) in your library package involves the following:
Inherit the
gobject-introspection
class.
Make sure introspection is not disabled anywhere in
the recipe or from anything the recipe includes.
Also, make sure that "gobject-introspection-data" is
not in
DISTRO_FEATURES_BACKFILL_CONSIDERED
and that "qemu-usermode" is not in
MACHINE_FEATURES_BACKFILL_CONSIDERED
.
If either of these conditions exist, nothing will
happen.
Try to build the recipe.
If you encounter build errors that look like
something is unable to find
.so
libraries, check where these
libraries are located in the source tree and add
the following to the recipe:
GIR_EXTRA_LIBS_PATH = "${B}/something
/.libs"
oe-core
repository that use that
GIR_EXTRA_LIBS_PATH
variable
as an example.
Look for any other errors, which probably mean that introspection support in a package is not entirely standard, and thus breaks down in a cross-compilation environment. For such cases, custom-made fixes are needed. A good place to ask and receive help in these cases is the Yocto Project mailing lists.
You might find that you do not want to generate introspection data. Or, perhaps QEMU does not work on your build host and target architecture combination. If so, you can use either of the following methods to disable GIR file generations:
Add the following to your distro configuration:
DISTRO_FEATURES_BACKFILL_CONSIDERED = "gobject-introspection-data"
Adding this statement disables generating introspection data using QEMU but will still enable building introspection tools and libraries (i.e. building them does not require the use of QEMU).
Add the following to your machine configuration:
MACHINE_FEATURES_BACKFILL_CONSIDERED = "qemu-usermode"
Adding this statement disables the use of QEMU when building packages for your machine. Currently, this feature is used only by introspection recipes and has the same effect as the previously described option.
If you disable introspection data, you can still obtain it through other means such as copying the data from a suitable sysroot, or by generating it on the target hardware. The OpenEmbedded build system does not currently provide specific support for these techniques.
Use the following procedure to test if generating introspection data is working in an image:
Make sure that "gobject-introspection-data" is not in
DISTRO_FEATURES_BACKFILL_CONSIDERED
and that "qemu-usermode" is not in
MACHINE_FEATURES_BACKFILL_CONSIDERED
.
Build core-image-sato
.
Launch a Terminal and then start Python in the terminal.
Enter the following in the terminal:
>>> from gi.repository import GLib >>> GLib.get_host_name()
For something a little more advanced, enter the following:
http://python-gtk-3-tutorial.readthedocs.org/en/latest/introduction.html
The following know issues exist for GObject Introspection Support:
qemu-ppc64
immediately crashes.
Consequently, you cannot build introspection data on
that architecture.
x32 is not supported by QEMU. Consequently, introspection data is disabled.
musl causes transient GLib binaries to crash on assertion failures. Consequently, generating introspection data is disabled.
Because QEMU is not able to run the binaries correctly,
introspection is disabled for some specific packages
under specific architectures (e.g.
gcr
,
libsecret
, and
webkit
).
QEMU usermode might not work properly when running 64-bit binaries under 32-bit host machines. In particular, "qemumips64" is known to not work under i686.
You might want to use an external toolchain as part of your development. If this is the case, the fundamental steps you need to accomplish are as follows:
Understand where the installed toolchain resides. For cases where you need to build the external toolchain, you would need to take separate steps to build and install the toolchain.
Make sure you add the layer that contains the toolchain to
your bblayers.conf
file through the
BBLAYERS
variable.
Set the
EXTERNAL_TOOLCHAIN
variable in your local.conf
file
to the location in which you installed the toolchain.
A good example of an external toolchain used with the Yocto Project
is Mentor Graphics®
Sourcery G++ Toolchain.
You can see information on how to use that particular layer in the
README
file at
http://github.com/MentorEmbedded/meta-sourcery/.
You can find further information by reading about the
TCMODE
variable in the Yocto Project Reference Manual's variable glossary.
Creating an image for a particular hardware target using the OpenEmbedded build system does not necessarily mean you can boot that image as is on your device. Physical devices accept and boot images in various ways depending on the specifics of the device. Usually, information about the hardware can tell you what image format the device requires. Should your device require multiple partitions on an SD card, flash, or an HDD, you can use the OpenEmbedded Image Creator, Wic, to create the properly partitioned image.
You can generate partitioned images
(image
.wic
)
two ways: using the OpenEmbedded build system and by running
the OpenEmbedded Image Creator Wic directly.
The former way is preferable as it is easier to use and understand.
The OpenEmbedded build system can generate partitioned images the same way as it generates any other image type. To generate a partitioned image, you need to modify two variables.
Include "wic" as part of the
IMAGE_FSTYPES
variable.
Include the name of the
wic kickstart file
as part of the
WKS_FILE
variable
Further steps to generate a partitioned image are the same as for any other image type. For information on image types, see the "Building Images" section.
The wic
command generates partitioned
images from existing OpenEmbedded build artifacts.
Image generation is driven by partitioning commands
contained in an Openembedded kickstart file
(.wks
) specified either directly on
the command line or as one of a selection of canned
.wks
files as shown with the
wic list images
command in the
"Using an Existing Kickstart File"
section.
When you apply the command to a given set of build
artifacts, the result is an image or set of images that
can be directly written onto media and used on a particular
system.
The wic
command and the infrastructure
it is based on is by definition incomplete.
The purpose of the command is to allow the generation of
customized images, and as such, was designed to be
completely extensible through a plug-in interface.
See the
"Plug-ins"
section for information on these plug-ins.
This section provides some background information on Wic,
describes what you need to have in
place to run the tool, provides instruction on how to use
the wic
utility,
and provides several examples.
This section provides some background on the
wic
utility.
While none of this information is required to use
Wic, you might find it interesting.
The name "Wic" is derived from OpenEmbedded Image Creator (oeic). The "oe" diphthong in "oeic" was promoted to the letter "w", because "oeic" is both difficult to remember and to pronounce.
Wic is loosely based on the
Meego Image Creator (mic
)
framework.
The Wic implementation has been
heavily modified to make direct use of OpenEmbedded
build artifacts instead of package installation and
configuration, which are already incorporated within
the OpenEmbedded artifacts.
Wic is a completely independent
standalone utility that initially provides
easier-to-use and more flexible replacements for an
existing functionality in OE Core's
image-live
class and mkefidisk.sh
script.
The difference between
Wic and those examples is
that with Wic the
functionality of those scripts is implemented
by a general-purpose partitioning language, which is
based on Redhat kickstart syntax.
In order to use the wic
utility
with the OpenEmbedded Build system, your system needs
to meet the following requirements:
The Linux distribution on your development host must support the Yocto Project. See the "Supported Linux Distributions" section in the Yocto Project Reference Manual for the list of distributions that support the Yocto Project.
The standard system utilities, such as
cp
, must be installed on your
development host system.
You need to have the build artifacts already
available, which typically means that you must
have already created an image using the
Openembedded build system (e.g.
core-image-minimal
).
While it might seem redundant to generate an image
in order to create an image using
Wic, the current version of
Wic requires the artifacts
in the form generated by the build system.
You must build several native tools, which are tools built to run on the build system:
$ bitbake parted-native dosfstools-native mtools-native
You must have sourced one of the build environment
setup scripts (i.e.
oe-init-build-env
or
oe-init-build-env-memres
)
found in the
Build Directory.
You can get general help for the wic
command by entering the wic
command
by itself or by entering the command with a help argument
as follows:
$ wic -h $ wic --help
Currently, Wic supports two commands:
create
and list
.
You can get help for these commands as follows:
$ wic helpcommand
withcommand
being eithercreate
orlist
.
You can also get detailed help on a number of topics
from the help system.
The output of wic --help
displays a list of available help
topics under a "Help topics" heading.
You can have the help system display the help text for
a given topic by prefacing the topic with
wic help
:
$ wic help help_topic
You can find out more about the images Wic creates using the existing kickstart files with the following form of the command:
$ wic list image
help
with
being either image
directdisk
or
mkefidisk
.
You can use Wic in two different modes, depending on how much control you need for specifying the Openembedded build artifacts that are used for creating the image: Raw and Cooked:
Raw Mode: You explicitly specify build artifacts through command-line arguments.
Cooked Mode:
The current
MACHINE
setting and image name are used to automatically
locate and provide the build artifacts.
Regardless of the mode you use, you need to have the build
artifacts ready and available.
Additionally, the environment must be set up using the
oe-init-build-env
or
oe-init-build-env-memres
script found in the
Build Directory.
The general form of the
wic
command in raw mode is:
$ wic createimage_name
.wks [options
] [...] Where:image_name
.wks An OpenEmbedded kickstart file. You can provide your own custom file or use a file from a set of existing files as described by further options. -oOUTDIR
, --outdir=OUTDIR
The name of a directory in which to create image. -iPROPERTIES_FILE
, --infile=PROPERTIES_FILE
The name of a file containing the values for image properties as a JSON file. -eIMAGE_NAME
, --image-name=IMAGE_NAME
The name of the image from which to use the artifacts (e.g.core-image-sato
). -rROOTFS_DIR
, --rootfs-dir=ROOTFS_DIR
The path to the/rootfs
directory to use as the.wks
rootfs source. -bBOOTIMG_DIR
, --bootimg-dir=BOOTIMG_DIR
The path to the directory containing the boot artifacts (e.g./EFI
or/syslinux
) to use as the.wks
bootimg source. -kKERNEL_DIR
, --kernel-dir=KERNEL_DIR
The path to the directory containing the kernel to use in the.wks
boot image. -nNATIVE_SYSROOT
, --native-sysroot=NATIVE_SYSROOT
The path to the native sysroot containing the tools to use to build the image. -s, --skip-build-check Skips the build check. -D, --debug Output debug information.
The general form of the wic
command
using Cooked Mode is:
$ wic createkickstart_file
-eimage_name
Where:kickstart_file
An OpenEmbedded kickstart file. You can provide your own custom file or a supplied file.image_name
Specifies the image built using the OpenEmbedded build system.
This form is the simplest and most user-friendly, as it
does not require specifying all individual parameters.
All you need to provide is your own
.wks
file or one provided with the
release.
If you do not want to create your own
.wks
file, you can use an existing
file provided by the Wic installation.
Use the following command to list the available files:
$ wic list images directdisk Create a 'pcbios' direct disk image mkefidisk Create an EFI disk image
When you use an existing file, you do not have to use the
.wks
extension.
Here is an example in Raw Mode that uses the
directdisk
file:
$ wic create directdisk -rrootfs_dir
-bbootimg_dir
\ -kkernel_dir
-nnative_sysroot
Here are the actual partition language commands
used in the mkefidisk.wks
file to
generate an image:
# short-description: Create an EFI disk image # long-description: Creates a partitioned EFI disk image that the user # can directly dd to boot media. part /boot --source bootimg-efi --ondisk sda --label msdos --active --align 1024 part / --source rootfs --ondisk sda --fstype=ext3 --label platform --align 1024 part swap --ondisk sda --size 44 --label swap1 --fstype=swap bootloader --timeout=10 --append="rootwait rootfstype=ext3 console=ttyPCH0,115200 console=tty0 vmalloc=256MB snd-hda-intel.enable_msi=0"
This section provides several examples that show how to use
the wic
utility.
All the examples assume the list of requirements in the
"Requirements"
section have been met.
The examples assume the previously generated image is
core-image-minimal
.
This example runs in Cooked Mode and uses the
mkefidisk
kickstart file:
$ wic create mkefidisk -e core-image-minimal
Checking basic build environment...
Done.
Creating image(s)...
Info: The new image(s) can be found here:
current_directory
/build/mkefidisk-201310230946-sda.direct
The following build artifacts were used to create the image(s):
ROOTFS_DIR: /home/trz/yocto/yocto-image/build/tmp/work/minnow-poky-linux/core-image-minimal/1.0-r0/rootfs
BOOTIMG_DIR: /home/trz/yocto/yocto-image/build/tmp/work/minnow-poky-linux/core-image-minimal/1.0-r0/core-image-minimal-1.0/hddimg
KERNEL_DIR: /home/trz/yocto/yocto-image/build/tmp/sysroots/minnow/usr/src/kernel
NATIVE_SYSROOT: /home/trz/yocto/yocto-image/build/tmp/sysroots/x86_64-linux
The image(s) were created using OE kickstart file:
/home/trz/yocto/yocto-image/scripts/lib/image/canned-wks/mkefidisk.wks
The previous example shows the easiest way to create
an image by running in Cooked Mode and using the
-e
option with an existing
kickstart file.
All that is necessary is to specify the image used to
generate the artifacts.
Your local.conf
needs to have the
MACHINE
variable set to the machine you are using, which is
"minnow" in this example.
The output specifies the exact image created as well as
where it was created, which is in the current
directory by default.
The output also names the artifacts used and the exact
.wks
script that was used to
generate the image.
Continuing with the example, you can now write the
image to a USB stick, or whatever media for which you
built your image, and boot the resulting media.
You can write the image by using
bmaptool
or
dd
:
$ oe-run-native bmaptool copy build/mkefidisk-201310230946-sda.direct /dev/sdX
or
$ sudo dd if=build/mkefidisk-201310230946-sda.direct of=/dev/sdX
bmaptool
to flash a device
with an image, see the
"Flashing Images Using bmaptool
"
section.
Because partitioned image creation is
driven by the kickstart file, it is easy to affect
image creation by changing the parameters in the file.
This next example demonstrates that through modification
of the directdisk
kickstart file.
As mentioned earlier, you can use the command
wic list images
to show the list
of existing kickstart files.
The directory in which these files reside is
scripts/lib/image/canned-wks/
located in the
Source Directory.
Because the available files reside in this directory,
you can create and add your own custom files to the
directory.
Subsequent use of the
wic list images
command would then
include your kickstart files.
In this example, the existing
directdisk
file already does most
of what is needed.
However, for the hardware in this example, the image
will need to boot from sdb
instead
of sda
, which is what the
directdisk
kickstart file uses.
The example begins by making a copy of the
directdisk.wks
file in the
scripts/lib/image/canned-wks
directory and then by changing the lines that specify
the target disk from which to boot.
$ cp /home/trz/yocto/yocto-image/scripts/lib/image/canned-wks/directdisk.wks \ /home/trz/yocto/yocto-image/scripts/lib/image/canned-wks/directdisksdb.wks
Next, the example modifies the
directdisksdb.wks
file and changes
all instances of "--ondisk sda
"
to "--ondisk sdb
".
The example changes the following two lines and leaves
the remaining lines untouched:
part /boot --source bootimg-pcbios --ondisk sdb --label boot --active --align 1024 part / --source rootfs --ondisk sdb --fstype=ext3 --label platform --align 1024
Once the lines are changed, the example generates the
directdisksdb
image.
The command points the process at the
core-image-minimal
artifacts for
the Next Unit of Computing (nuc)
MACHINE
the local.conf
.
$ wic create directdisksdb -e core-image-minimal
Checking basic build environment...
Done.
Creating image(s)...
Info: The new image(s) can be found here:
current_directory
/build/directdisksdb-201310231131-sdb.direct
The following build artifacts were used to create the image(s):
ROOTFS_DIR: /home/trz/yocto/yocto-image/build/tmp/work/nuc-poky-linux/core-image-minimal/1.0-r0/rootfs
BOOTIMG_DIR: /home/trz/yocto/yocto-image/build/tmp/sysroots/nuc/usr/share
KERNEL_DIR: /home/trz/yocto/yocto-image/build/tmp/sysroots/nuc/usr/src/kernel
NATIVE_SYSROOT: /home/trz/yocto/yocto-image/build/tmp/sysroots/x86_64-linux
The image(s) were created using OE kickstart file:
/home/trz/yocto/yocto-image/scripts/lib/image/canned-wks/directdisksdb.wks
Continuing with the example, you can now directly
dd
the image to a USB stick, or
whatever media for which you built your image,
and boot the resulting media:
$ sudo dd if=build/directdisksdb-201310231131-sdb.direct of=/dev/sdb 86018+0 records in 86018+0 records out 44041216 bytes (44 MB) copied, 13.0734 s, 3.4 MB/s [trz at empanada tmp]$ sudo eject /dev/sdb
core-image-minimal
and crownbay-noemgd
¶
This example creates an image based on
core-image-minimal
and a
crownbay-noemgd
MACHINE
that works right out of the box.
$ wic create directdisk -e core-image-minimal
Checking basic build environment...
Done.
Creating image(s)...
Info: The new image(s) can be found here:
current_directory
/build/directdisk-201309252350-sda.direct
The following build artifacts were used to create the image(s):
ROOTFS_DIR: /home/trz/yocto/yocto-image/build/tmp/work/crownbay_noemgd-poky-linux/core-image-minimal/1.0-r0/rootfs
BOOTIMG_DIR: /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/share
KERNEL_DIR: /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/src/kernel
NATIVE_SYSROOT: /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/src/kernel
The image(s) were created using OE kickstart file:
/home/trz/yocto/yocto-image/scripts/lib/image/canned-wks/directdisk.wks
This next example manually specifies each build artifact
(runs in Raw Mode) and uses a modified kickstart file.
The example also uses the -o
option
to cause Wic to create the output
somewhere other than the default output directory,
which is the current directory:
$ wic create ~/test.wks -o /home/trz/testwic --rootfs-dir \ /home/trz/yocto/yocto-image/build/tmp/work/crownbay_noemgd-poky-linux/core-image-minimal/1.0-r0/rootfs \ --bootimg-dir /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/share \ --kernel-dir /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/src/kernel \ --native-sysroot /home/trz/yocto/yocto-image/build/tmp/sysroots/x86_64-linux Creating image(s)... Info: The new image(s) can be found here: /home/trz/testwic/build/test-201309260032-sda.direct The following build artifacts were used to create the image(s): ROOTFS_DIR: /home/trz/yocto/yocto-image/build/tmp/work/crownbay_noemgd-poky-linux/core-image-minimal/1.0-r0/rootfs BOOTIMG_DIR: /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/share KERNEL_DIR: /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/src/kernel NATIVE_SYSROOT: /home/trz/yocto/yocto-image/build/tmp/sysroots/crownbay-noemgd/usr/src/kernel The image(s) were created using OE kickstart file: /home/trz/test.wks
For this example,
MACHINE
did not have to be specified in the
local.conf
file since the
artifact is manually specified.
Plug-ins allow Wic functionality to be extended and specialized by users. This section documents the plug-in interface, which is currently restricted to source plug-ins.
Source plug-ins provide a mechanism to customize
various aspects of the image generation process in
Wic, mainly the contents of
partitions.
The plug-ins provide a mechanism for mapping values
specified in .wks
files using the
--source
keyword to a
particular plug-in implementation that populates a
corresponding partition.
WKS_FILE_DEPENDS
variable.
A source plug-in is created as a subclass of
SourcePlugin
.
The plug-in file containing it is added to
scripts/lib/wic/plugins/source/
to
make the plug-in implementation available to the
Wic implementation.
For more information, see
scripts/lib/wic/pluginbase.py
.
Source plug-ins can also be implemented and added by
external layers.
As such, any plug-ins found in a
scripts/lib/wic/plugins/source/
directory in an external layer are also made
available.
When the Wic implementation needs
to invoke a partition-specific implementation, it looks
for the plug-in that has the same name as the
--source
parameter given to
that partition.
For example, if the partition is set up as follows:
part /boot --source bootimg-pcbios ...
The methods defined as class members of the plug-in
having the matching bootimg-pcbios.name
class member are used.
To be more concrete, here is the plug-in definition that
matches a
--source bootimg-pcbios
usage,
along with an example
method called by the Wic implementation
when it needs to invoke an implementation-specific
partition-preparation function:
class BootimgPcbiosPlugin(SourcePlugin): name = 'bootimg-pcbios' @classmethod def do_prepare_partition(self, part, ...)
If the subclass itself does not implement a function, a
default version in a superclass is located and
used, which is why all plug-ins must be derived from
SourcePlugin
.
The SourcePlugin
class defines the
following methods, which is the current set of methods
that can be implemented or overridden by
--source
plug-ins.
Any methods not implemented by a
SourcePlugin
subclass inherit the
implementations present in the
SourcePlugin
class.
For more information, see the
SourcePlugin
source for details:
do_prepare_partition()
:
Called to do the actual content population for a
partition.
In other words, the method prepares the final
partition image that is incorporated into the
disk image.
do_configure_partition()
:
Called before
do_prepare_partition()
.
This method is typically used to create custom
configuration files for a partition (e.g. syslinux
or grub configuration files).
do_install_disk()
:
Called after all partitions have been prepared and
assembled into a disk image.
This method provides a hook to allow finalization
of a disk image, (e.g. writing an MBR).
do_stage_partition()
:
Special content-staging hook called before
do_prepare_partition()
.
This method is normally empty.
Typically, a partition just uses the passed-in
parameters (e.g. the unmodified value of
bootimg_dir
).
However, in some cases things might need to be
more tailored.
As an example, certain files might additionally
need to be taken from
bootimg_dir + /boot
.
This hook allows those files to be staged in a
customized fashion.
get_bitbake_var()
allows you to access non-standard variables
that you might want to use for this.
This scheme is extensible.
Adding more hooks is a simple matter of adding more
plug-in methods to SourcePlugin
and
derived classes.
The code that then needs to call the plug-in methods uses
plugin.get_source_plugin_methods()
to find the method or methods needed by the call.
Retrieval of those methods is accomplished
by filling up a dict with keys
containing the method names of interest.
On success, these will be filled in with the actual
methods.
Please see the Wic
implementation for examples and details.
.wks
) Reference¶
The current Wic implementation supports
only the basic kickstart partitioning commands:
partition
(or part
for short) and bootloader
.
The following is a list of the commands, their syntax, and meanings. The commands are based on the Fedora kickstart versions but with modifications to reflect Wic capabilities. You can see the original documentation for those commands at the following links:
Either of these commands create a partition on the system and use the following syntax:
part [mntpoint
] partition [mntpoint
]
If you do not provide
mntpoint
, Wic creates a
partition but does not mount it.
The
is where the partition will be mounted and must be of
one of the following forms:
mntpoint
/
:
For example, "/", "/usr", or "/home"
path
swap
:
The created partition is used as swap space.
Specifying a mntpoint
causes
the partition to automatically be mounted.
Wic achieves this by adding entries to the filesystem
table (fstab) during image generation.
In order for wic to generate a valid fstab, you must
also provide one of the --ondrive
,
--ondisk
, or
--use-uuid
partition options as
part of the command.
Here is an example using "/" as the mountpoint.
The command uses "--ondisk" to force the partition onto
the sdb
disk:
part / --source rootfs --ondisk sdb --fstype=ext3 --label platform --align 1024
Here is a list that describes other supported options
you can use with the part
and
partition
commands:
--size
:
The minimum partition size in MBytes.
Specify an integer value such as 500.
Do not append the number with "MB".
You do not need this option if you use
--source
.
--source
:
This option is a
Wic-specific option that
names the source of the data that populates
the partition.
The most common value for this option is
"rootfs", but you can use any value that maps to
a valid source plug-in.
For information on the source plug-ins, see the
"Plug-ins"
section.
If you use
--source rootfs
,
Wic creates a partition as
large as needed and to fill it with the contents
of the root filesystem pointed to by the
-r
command-line option
or the equivalent rootfs derived from the
-e
command-line
option.
The filesystem type used to create the
partition is driven by the value of the
--fstype
option
specified for the partition.
See the entry on
--fstype
that
follows for more information.
If you use
--source
,
Wic creates a partition as
large as needed and fills it with the contents
of the partition that is generated by the
specified plug-in name using the data pointed
to by the plugin-name
-r
command-line
option or the equivalent rootfs derived from the
-e
command-line
option.
Exactly what those contents and filesystem type
end up being are dependent on the given plug-in
implementation.
If you do not use the
--source
option, the
wic
command creates an
empty partition.
Consequently, you must use the
--size
option to specify
the size of the empty partition.
--ondisk
or --ondrive
:
Forces the partition to be created on a
particular disk.
--fstype
:
Sets the file system type for the partition.
Valid values are:
ext4
ext3
ext2
btrfs
squashfs
swap
--fsoptions
:
Specifies a free-form string of options to be
used when mounting the filesystem.
This string will be copied into the
/etc/fstab
file of the
installed system and should be enclosed in
quotes.
If not specified, the default string
is "defaults".
--label label
:
Specifies the label to give to the filesystem to
be made on the partition.
If the given label is already in use by another
filesystem, a new label is created for the
partition.
--active
:
Marks the partition as active.
--align (in KBytes)
:
This option is a
Wic-specific option that
says to start a partition on an
x
KBytes
boundary.
--no-table
:
This option is a
Wic-specific option.
Using the option reserves space for the
partition and causes it to become populated.
However, the partition is not added to the
partition table.
--extra-space
:
This option is a
Wic-specific option that
adds extra space after the space filled by the
content of the partition.
The final size can go beyond the size specified
by the --size
option.
The default value is 10 Mbytes.
--overhead-factor
:
This option is a
Wic-specific option that
multiplies the size of the partition by the
option's value.
You must supply a value greater than or equal to
"1".
The default value is "1.3".
--part-type
:
This option is a
Wic-specific option that
specifies the partition type globally
unique identifier (GUID) for GPT partitions.
You can find the list of partition type GUIDs
at
http://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_type_GUIDs.
--use-uuid
:
This option is a
Wic-specific option that
causes Wic to generate a
random GUID for the partition.
The generated identifier is used in the
bootloader configuration to specify the root
partition.
--uuid
:
This option is a
Wic-specific
option that specifies the partition UUID.
This command specifies how the bootloader should be configured and supports the following options:
--source
plug-ins that implement bootloader functionality.
The bootloader command essentially provides a
means of modifying bootloader configuration.
--timeout
:
Specifies the number of seconds before the
bootloader times out and boots the default
option.
--append
:
Specifies kernel parameters.
These parameters will be added to the syslinux
APPEND
or
grub
kernel command line.
--configfile
:
Specifies a user-defined configuration file for
the bootloader.
You can provide a full pathname for the file or
a file that exists in the
canned-wks
folder.
This option overrides all other bootloader
options.
initramfs is the successor of Initial RAM Disk (initrd). It is a "copy in and out" (cpio) archive of the initial file system that gets loaded into memory during the Linux startup process. Because Linux uses the contents of the archive during initialization, the initramfs needs to contain all of the device drivers and tools needed to mount the final root filesystem.
To build an initramfs image and bundle it into the kernel, set the
INITRAMFS_IMAGE_BUNDLE
variable in your local.conf
file, and set the
INITRAMFS_IMAGE
variable in your machine.conf
file:
INITRAMFS_IMAGE_BUNDLE = "1"
INITRAMFS_IMAGE = "image_recipe_name
"
Setting the INITRAMFS_IMAGE_BUNDLE
flag causes the initramfs created by the recipe and defined by
INITRAMFS_IMAGE
to be unpacked into the
${B}/usr/
directory.
The unpacked initramfs is then passed to the kernel's
Makefile
using the
CONFIG_INITRAMFS_SOURCE
variable, allowing initramfs to be built in to the kernel
normally.
INITRAMFS_IMAGE
variable rather than the
INITRAMFS_TASK
variable.
Setting INITRAMFS_TASK
is supported for
backward compatibility.
However, use of this variable has circular dependency
problems.
See the
INITRAMFS_IMAGE_BUNDLE
variable for additional information on these dependency
problems.
The recipe that INITRAMFS_IMAGE
points to must produce a .cpio.gz
,
.cpio.tar
, .cpio.lz4
,
.cpio.lzma
, or
.cpio.xz
file.
You can ensure you produce one of these .cpio.*
files by setting the
INITRAMFS_FSTYPES
variable in your configuration file to one or more of the above
file types.
PACKAGE_INSTALL
rather than
IMAGE_INSTALL
.
PACKAGE_INSTALL
gives more direct control
of what is added to the image as compared to the defaults you
might not necessarily want that are set by the
image
or
core-image
classes.
Configuring the Yocto Project kernel consists of making sure the
.config
file has all the right information
in it for the image you are building.
You can use the menuconfig
tool and
configuration fragments to make sure your
.config
file is just how you need it.
You can also save known configurations in a
defconfig
file that the build system can use
for kernel configuration.
This section describes how to use menuconfig
,
create and use configuration fragments, and how to interactively
modify your .config
file to create the
leanest kernel configuration file possible.
For more information on kernel configuration, see the "Changing the Configuration" section in the Yocto Project Linux Kernel Development Manual.
menuconfig
¶
The easiest way to define kernel configurations is to set them through the
menuconfig
tool.
This tool provides an interactive method with which
to set kernel configurations.
For general information on menuconfig
, see
http://en.wikipedia.org/wiki/Menuconfig.
To use the menuconfig
tool in the Yocto Project development
environment, you must launch it using BitBake.
Thus, the environment must be set up using the
oe-init-build-env
or
oe-init-build-env-memres
script found in the
Build Directory.
You must also be sure of the state of your build in the
Source Directory.
The following commands run menuconfig
assuming the Source Directory's top-level folder is
~/poky
:
$ cd poky $ source oe-init-build-env $ bitbake linux-yocto -c kernel_configme -f $ bitbake linux-yocto -c menuconfig
Once menuconfig
comes up, its standard
interface allows you to interactively examine and configure
all the kernel configuration parameters.
After making your changes, simply exit the tool and save your
changes to create an updated version of the
.config
configuration file.
Consider an example that configures the linux-yocto-3.14
kernel.
The OpenEmbedded build system recognizes this kernel as
linux-yocto
.
Thus, the following commands from the shell in which you previously sourced the
environment initialization script cleans the shared state cache and the
WORKDIR
directory and then runs menuconfig
:
$ bitbake linux-yocto -c menuconfig
Once menuconfig
launches, use the interface
to navigate through the selections to find the configuration settings in
which you are interested.
For example, consider the CONFIG_SMP
configuration setting.
You can find it at Processor Type and Features
under
the configuration selection Symmetric Multi-processing Support
.
After highlighting the selection, use the arrow keys to select or deselect
the setting.
When you are finished with all your selections, exit out and save them.
Saving the selections updates the .config
configuration file.
This is the file that the OpenEmbedded build system uses to configure the
kernel during the build.
You can find and examine this file in the Build Directory in
tmp/work/
.
The actual .config
is located in the area where the
specific kernel is built.
For example, if you were building a Linux Yocto kernel based on the
Linux 3.14 kernel and you were building a QEMU image targeted for
x86
architecture, the
.config
file would be located here:
poky/build/tmp/work/qemux86-poky-linux/linux-yocto-3.14.11+git1+84f... ...656ed30-r1/linux-qemux86-standard-build
linux-yocto-3.14...
might differ.
Within the .config
file, you can see the kernel settings.
For example, the following entry shows that symmetric multi-processor support
is not set:
# CONFIG_SMP is not set
A good method to isolate changed configurations is to use a combination of the
menuconfig
tool and simple shell commands.
Before changing configurations with menuconfig
, copy the
existing .config
and rename it to something else,
use menuconfig
to make
as many changes as you want and save them, then compare the renamed configuration
file against the newly created file.
You can use the resulting differences as your base to create configuration fragments
to permanently save in your kernel layer.
.config
and don't just
rename it.
The build system needs an existing .config
from which to work.
defconfig
File¶
A defconfig
file is simply a
.config
renamed to "defconfig".
You can use a defconfig
file
to retain a known set of kernel configurations from which the
OpenEmbedded build system can draw to create the final
.config
file.
defconfig
or
.config
file.
The OpenEmbedded build system creates the final
.config
file used to configure the
kernel.
To create a defconfig
, start with a
complete, working Linux kernel .config
file.
Copy that file to the appropriate
${
PN
}
directory in your layer's
recipes-kernel/linux
directory, and rename
the copied file to "defconfig".
Then, add the following lines to the linux-yocto
.bbappend
file in your layer:
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" SRC_URI += "file://defconfig"
The
SRC_URI
tells the build system how to search for the file, while the
FILESEXTRAPATHS
extends the
FILESPATH
variable (search directories) to include the
${PN}
directory you created to hold the
configuration changes.
defconfig
file before applying any
subsequent configuration fragments.
The final kernel configuration is a combination of the
configurations in the defconfig
file and any configuration fragments you provide.
You need to realize that if you have any configuration
fragments, the build system applies these on top of and
after applying the existing defconfig file configurations.
For more information on configuring the kernel, see the "Changing the Configuration" and "Generating Configuration Files" sections, both in the Yocto Project Linux Kernel Development Manual.
Configuration fragments are simply kernel options that appear in a file
placed where the OpenEmbedded build system can find and apply them.
Syntactically, the configuration statement is identical to what would appear
in the .config
file, which is in the
Build Directory:
tmp/work/arch
-poky-linux/linux-yocto-release_specific_string
/linux-arch
-build_type
It is simple to create a configuration fragment.
For example, issuing the following from the shell creates a configuration fragment
file named my_smp.cfg
that enables multi-processor support
within the kernel:
$ echo "CONFIG_SMP=y" >> my_smp.cfg
.cfg
extension in order for the
OpenEmbedded build system to recognize them as a
configuration fragment.
Where do you put your configuration fragment files?
You can place these files in the same area pointed to by
SRC_URI
.
The OpenEmbedded build system picks up the configuration and
adds it to the kernel's configuration.
For example, suppose you had a set of configuration options
in a file called myconfig.cfg
.
If you put that file inside a directory named
linux-yocto
that resides in the same
directory as the kernel's append file and then add a
SRC_URI
statement such as the following
to the kernel's append file, those configuration options
will be picked up and applied when the kernel is built.
SRC_URI += "file://myconfig.cfg"
As mentioned earlier, you can group related configurations into multiple files and
name them all in the SRC_URI
statement as well.
For example, you could group separate configurations specifically for Ethernet and graphics
into their own files and add those by using a SRC_URI
statement like the
following in your append file:
SRC_URI += "file://myconfig.cfg \ file://eth.cfg \ file://gfx.cfg"
You can make sure the .config
file is as lean or efficient as
possible by reading the output of the kernel configuration fragment audit,
noting any issues, making changes to correct the issues, and then repeating.
As part of the kernel build process, the
do_kernel_configcheck
task runs.
This task validates the kernel configuration by checking the final
.config
file against the input files.
During the check, the task produces warning messages for the following
issues:
Requested options that did not make the final
.config
file.
Configuration items that appear twice in the same configuration fragment.
Configuration items tagged as "required" that were overridden.
A board overrides a non-board specific option.
Listed options not valid for the kernel being processed. In other words, the option does not appear anywhere.
do_kernel_configcheck
task can
also optionally report if an option is overridden during
processing.
For each output warning, a message points to the file that contains a list of the options and a pointer to the configuration fragment that defines them. Collectively, the files are the key to streamlining the configuration.
To streamline the configuration, do the following:
Start with a full configuration that you know works - it builds and boots successfully. This configuration file will be your baseline.
Separately run the
do_kernel_configme
and
do_kernel_configcheck
tasks.
Take the resulting list of files from the
do_kernel_configcheck
task
warnings and do the following:
Drop values that are redefined in the fragment
but do not change the final
.config
file.
Analyze and potentially drop values from the
.config
file that override
required configurations.
Analyze and potentially remove non-board specific options.
Remove repeated and invalid options.
After you have worked through the output of the kernel
configuration audit, you can re-run the
do_kernel_configme
and
do_kernel_configcheck
tasks to
see the results of your changes.
If you have more issues, you can deal with them as
described in the previous step.
Iteratively working through steps two through four eventually yields
a minimal, streamlined configuration file.
Once you have the best .config
, you can build the Linux
Yocto kernel.
This section describes part of the kernel configuration audit
phase that most developers can ignore.
During this part of the audit phase, the contents of the final
.config
file are compared against the
fragments specified by the system.
These fragments can be system fragments, distro fragments,
or user specified configuration elements.
Regardless of their origin, the OpenEmbedded build system
warns the user if a specific option is not included in the
final kernel configuration.
In order to not overwhelm the user with configuration warnings, by default the system only reports on missing "hardware" options because a missing hardware option could mean a boot failure or that important hardware is not available.
To determine whether or not a given option is "hardware" or "non-hardware", the kernel Metadata contains files that classify individual or groups of options as either hardware or non-hardware. To better show this, consider a situation where the Yocto Project kernel cache contains the following files:
kernel-cache/features/drm-psb/hardware.cfg kernel-cache/features/kgdb/hardware.cfg kernel-cache/ktypes/base/hardware.cfg kernel-cache/bsp/mti-malta32/hardware.cfg kernel-cache/bsp/fsl-mpc8315e-rdb/hardware.cfg kernel-cache/bsp/qemu-ppc32/hardware.cfg kernel-cache/bsp/qemuarma9/hardware.cfg kernel-cache/bsp/mti-malta64/hardware.cfg kernel-cache/bsp/arm-versatile-926ejs/hardware.cfg kernel-cache/bsp/common-pc/hardware.cfg kernel-cache/bsp/common-pc-64/hardware.cfg kernel-cache/features/rfkill/non-hardware.cfg kernel-cache/ktypes/base/non-hardware.cfg kernel-cache/features/aufs/non-hardware.kcf kernel-cache/features/ocf/non-hardware.kcf kernel-cache/ktypes/base/non-hardware.kcf kernel-cache/ktypes/base/hardware.kcf kernel-cache/bsp/qemu-ppc32/hardware.kcf
The following list provides explanations for the various files:
hardware.kcf
:
Specifies a list of kernel Kconfig files that contain
hardware options only.
non-hardware.kcf
:
Specifies a list of kernel Kconfig files that contain
non-hardware options only.
hardware.cfg
:
Specifies a list of kernel
CONFIG_
options that are hardware,
regardless of whether or not they are within a Kconfig
file specified by a hardware or non-hardware
Kconfig file (i.e. hardware.kcf
or
non-hardware.kcf
).
non-hardware.cfg
:
Specifies a list of kernel
CONFIG_
options that are
not hardware, regardless of whether or not they are
within a Kconfig file specified by a hardware or
non-hardware Kconfig file (i.e.
hardware.kcf
or
non-hardware.kcf
).
Here is a specific example using the
kernel-cache/bsp/mti-malta32/hardware.cfg
:
CONFIG_SERIAL_8250 CONFIG_SERIAL_8250_CONSOLE CONFIG_SERIAL_8250_NR_UARTS CONFIG_SERIAL_8250_PCI CONFIG_SERIAL_CORE CONFIG_SERIAL_CORE_CONSOLE CONFIG_VGA_ARB
The kernel configuration audit automatically detects these
files (hence the names must be exactly the ones discussed here),
and uses them as inputs when generating warnings about the
final .config
file.
A user-specified kernel Metadata repository, or recipe space
feature, can use these same files to classify options that are
found within its .cfg
files as hardware
or non-hardware, to prevent the OpenEmbedded build system from
producing an error or warning when an option is not in the
final .config
file.
Patching the kernel involves changing or adding configurations to an existing kernel, changing or adding recipes to the kernel that are needed to support specific hardware features, or even altering the source code itself.
yocto-kernel
script
found in the Source Directory
under scripts
to manage kernel patches and configuration.
See the "Managing kernel Patches and Config Items with yocto-kernel"
section in the Yocto Project Board Support Packages (BSP) Developer's Guide for
more information.
This example creates a simple patch by adding some QEMU emulator console
output at boot time through printk
statements in the kernel's
calibrate.c
source code file.
Applying the patch and booting the modified image causes the added
messages to appear on the emulator's console.
The example assumes a clean build exists for the qemux86
machine in a
Source Directory
named poky
.
Furthermore, the Build Directory is
build
and is located in poky
and
the kernel is based on the Linux 3.4 kernel.
Also, for more information on patching the kernel, see the "Applying Patches" section in the Yocto Project Linux Kernel Development Manual.
The first step is to create a layer so you can isolate your
changes.
Rather than use the yocto-layer
script
to create the layer, this example steps through the process
by hand.
If you want information on the script that creates a general
layer, see the
"Creating a General Layer Using the yocto-layer Script"
section.
These two commands create a directory you can use for your layer:
$ cd ~/poky $ mkdir meta-mylayer
Creating a directory that follows the Yocto Project layer naming conventions sets up the layer for your changes. The layer is where you place your configuration files, append files, and patch files. To learn more about creating a layer and filling it with the files you need, see the "Understanding and Creating Layers" section.
Each time you build a kernel image, the kernel source code is fetched and unpacked into the following directory:
${S}/linux
See the "Finding Temporary Source Code"
section and the
S
variable
for more information about where source is kept during a build.
For this example, we are going to patch the
init/calibrate.c
file
by adding some simple console printk
statements that we can
see when we boot the image using QEMU.
Two methods exist by which you can create the patch:
devtool
and
Quilt.
For kernel patches, the Git workflow is more appropriate.
This section assumes the Git workflow and shows the steps specific to
this example.
Change the working directory:
Change to where the kernel source code is before making
your edits to the calibrate.c
file:
$ cd ~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-${PV}-${PR}/linux
Because you are working in an established Git repository, you must be in this directory in order to commit your changes and create the patch file.
Edit the source file:
Edit the init/calibrate.c
file to have the
following changes:
void calibrate_delay(void) { unsigned long lpj; static bool printed; int this_cpu = smp_processor_id(); printk("*************************************\n"); printk("* *\n"); printk("* HELLO YOCTO KERNEL *\n"); printk("* *\n"); printk("*************************************\n"); if (per_cpu(cpu_loops_per_jiffy, this_cpu)) { . . .
Stage and commit your changes: These Git commands display the modified file, stage it, and then commit the file:
$ git status $ git add init/calibrate.c $ git commit -m "calibrate: Add printk example"
Generate the patch file:
This Git command creates the a patch file named
0001-calibrate-Add-printk-example.patch
in the current directory.
$ git format-patch -1
These steps get your layer set up for the build:
Create additional structure: Create the additional layer structure:
$ cd ~/poky/meta-mylayer $ mkdir conf $ mkdir recipes-kernel $ mkdir recipes-kernel/linux $ mkdir recipes-kernel/linux/linux-yocto
The conf
directory holds your configuration files, while the
recipes-kernel
directory holds your append file and
your patch file.
Create the layer configuration file:
Move to the meta-mylayer/conf
directory and create
the layer.conf
file as follows:
# We have a conf and classes directory, add to BBPATH BBPATH .= ":${LAYERDIR}" # We have recipes-* directories, add to BBFILES BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \ ${LAYERDIR}/recipes-*/*/*.bbappend" BBFILE_COLLECTIONS += "mylayer" BBFILE_PATTERN_mylayer = "^${LAYERDIR}/" BBFILE_PRIORITY_mylayer = "5"
Notice mylayer
as part of the last three
statements.
Create the kernel recipe append file:
Move to the meta-mylayer/recipes-kernel/linux
directory and create
the linux-yocto_3.4.bbappend
file as follows:
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" SRC_URI += "file://0001-calibrate-Add-printk-example.patch"
The FILESEXTRAPATHS
and SRC_URI
statements enable the OpenEmbedded build system to find the patch file.
For more information on using append files, see the
"Using .bbappend Files in Your Layer"
section.
Put the patch file in your layer:
Move the 0001-calibrate-Add-printk-example.patch
file to
the meta-mylayer/recipes-kernel/linux/linux-yocto
directory.
Do the following to make sure the build parameters are set up for the example. Once you set up these build parameters, they do not have to change unless you change the target architecture of the machine you are building:
Build for the correct target architecture: Your
selected MACHINE
definition within the local.conf
file in the
Build Directory
specifies the target architecture used when building the Linux kernel.
By default, MACHINE
is set to
qemux86
, which specifies a 32-bit
Intel® Architecture
target machine suitable for the QEMU emulator.
Identify your meta-mylayer
layer: The
BBLAYERS
variable in the
bblayers.conf
file found in the
poky/build/conf
directory needs to have the path to your local
meta-mylayer
layer.
By default, the BBLAYERS
variable contains paths to
meta
, meta-poky
, and
meta-yocto-bsp
in the
poky
Git repository.
Add the path to your meta-mylayer
location:
BBLAYERS ?= " \ $HOME/poky/meta \ $HOME/poky/meta-poky \ $HOME/poky/meta-yocto-bsp \ $HOME/poky/meta-mylayer \ "
The following steps build your modified kernel image:
Be sure your build environment is initialized:
Your environment should be set up since you previously sourced
the
oe-init-build-env
script.
If it is not, source the script again from poky
.
$ cd ~/poky $ source oe-init-build-env
Clean up:
Be sure to clean the shared state out by using BitBake
to run from within the Build Directory the
do_cleansstate
task as follows:
$ bitbake -c cleansstate linux-yocto
tmp/deploy
directory inside the
Build Directory.
Always use the various BitBake clean tasks to
clear out previous build artifacts.
For information on the clean tasks, see the
"do_clean
",
"do_cleanall
",
and
"do_cleansstate
"
sections all in the Yocto Project Reference
Manual.
Build the image: Next, build the kernel image using this command:
$ bitbake -k linux-yocto
These steps boot the image and allow you to see the changes
Boot the image: Boot the modified image in the QEMU emulator using this command:
$ runqemu qemux86
Verify the changes:
Log into the machine using root
with no password and then
use the following shell command to scroll through the console's boot output.
# dmesg | less
You should see the results of your printk
statements
as part of the output.
Security is of increasing concern for embedded devices. Consider the issues and problems discussed in just this sampling of work found across the Internet:
"Security Risks of Embedded Systems" by Bruce Schneier
"Internet Census 2012" by Carna Botnet
"Security Issues for Embedded Devices" by Jake Edge
When securing your image is of concern, there are steps, tools, and variables that you can consider to help you reach the security goals you need for your particular device. Not all situations are identical when it comes to making an image secure. Consequently, this section provides some guidance and suggestions for consideration when you want to make your image more secure.
General considerations exist that help you create more secure images. You should consider the following suggestions to help make your device more secure:
Scan additional code you are adding to the system (e.g. application code) by using static analysis tools. Look for buffer overflows and other potential security problems.
Pay particular attention to the security for any web-based administration interface.
Web interfaces typically need to perform administrative functions and tend to need to run with elevated privileges. Thus, the consequences resulting from the interface's security becoming compromised can be serious. Look for common web vulnerabilities such as cross-site-scripting (XSS), unvalidated inputs, and so forth.
As with system passwords, the default credentials for accessing a web-based interface should not be the same across all devices. This is particularly true if the interface is enabled by default as it can be assumed that many end-users will not change the credentials.
Ensure you can update the software on the device to mitigate vulnerabilities discovered in the future. This consideration especially applies when your device is network-enabled.
Ensure you remove or disable debugging functionality before producing the final image. For information on how to do this, see the "Considerations Specific to the OpenEmbedded Build System" section.
Ensure you have no network services listening that are not needed.
Remove any software from the image that is not needed.
Enable hardware support for secure boot functionality when your device supports this functionality.
The Yocto Project has security flags that you can enable that
help make your build output more secure.
The security flags are in the
meta/conf/distro/include/security_flags.inc
file in your
Source Directory
(e.g. poky
).
Use the following line in your
local.conf
file or in your custom
distribution configuration file to enable the security
compiler and linker flags for your build:
require conf/distro/include/security_flags.inc
You can take some steps that are specific to the OpenEmbedded build system to make your images more secure:
Ensure "debug-tweaks" is not one of your selected
IMAGE_FEATURES
.
When creating a new project, the default is to provide you
with an initial local.conf
file that
enables this feature using the
EXTRA_IMAGE_FEATURES
variable with the line:
EXTRA_IMAGE_FEATURES = "debug-tweaks"
To disable that feature, simply comment out that line in your
local.conf
file, or
make sure IMAGE_FEATURES
does not contain
"debug-tweaks" before producing your final image.
Among other things, leaving this in place sets the
root password as blank, which makes logging in for
debugging or inspection easy during
development but also means anyone can easily log in
during production.
It is possible to set a root password for the image and also to set passwords for any extra users you might add (e.g. administrative or service type users). When you set up passwords for multiple images or users, you should not duplicate passwords.
To set up passwords, use the
extrausers
class, which is the preferred method.
For an example on how to set up both root and user
passwords, see the
"extrausers.bbclass
"
section.
Consider enabling a Mandatory Access Control (MAC)
framework such as SMACK or SELinux and tuning it
appropriately for your device's usage.
You can find more information in the
meta-selinux
layer.
The Yocto Project provides tools for making your image
more secure.
You can find these tools in the
meta-security
layer of the
Yocto Project Source Repositories.
When you build an image using the Yocto Project and do not alter any distribution Metadata, you are creating a Poky distribution. If you wish to gain more control over package alternative selections, compile-time options, and other low-level configurations, you can create your own distribution.
To create your own distribution, the basic steps consist of creating your own distribution layer, creating your own distribution configuration file, and then adding any needed code and Metadata to the layer. The following steps provide some more detail:
Create a layer for your new distro:
Create your distribution layer so that you can keep your
Metadata and code for the distribution separate.
It is strongly recommended that you create and use your own
layer for configuration and code.
Using your own layer as compared to just placing
configurations in a local.conf
configuration file makes it easier to reproduce the same
build configuration when using multiple build machines.
See the
"Creating a General Layer Using the yocto-layer Script"
section for information on how to quickly set up a layer.
Create the distribution configuration file:
The distribution configuration file needs to be created in
the conf/distro
directory of your
layer.
You need to name it using your distribution name
(e.g. mydistro.conf
).
You can split out parts of your configuration file
into include files and then "require" them from within
your distribution configuration file.
Be sure to place the include files in the
conf/distro/include
directory of
your layer.
A common example usage of include files would be to
separate out the selection of desired version and revisions
for individual recipes.
Your configuration file needs to set the following required variables:
DISTRO_NAME
DISTRO_VERSION
These following variables are optional and you typically set them from the distribution configuration file:
DISTRO_FEATURES
DISTRO_EXTRA_RDEPENDS
DISTRO_EXTRA_RRECOMMENDS
TCLIBC
conf/distro/defaultsetup.conf
as
a reference and just include variables that differ
as compared to defaultsetup.conf
.
Alternatively, you can create a distribution
configuration file from scratch using the
defaultsetup.conf
file
or configuration files from other distributions
such as Poky or Angstrom as references.
Provide miscellaneous variables:
Be sure to define any other variables for which you want to
create a default or enforce as part of the distribution
configuration.
You can include nearly any variable from the
local.conf
file.
The variables you use are not limited to the list in the
previous bulleted item.
Point to Your distribution configuration file:
In your local.conf
file in the
Build Directory,
set your
DISTRO
variable to point to your distribution's configuration file.
For example, if your distribution's configuration file is
named mydistro.conf
, then you point
to it as follows:
DISTRO = "mydistro"
Add more to the layer if necessary: Use your layer to hold other information needed for the distribution:
Add recipes for installing
distro-specific configuration files that are not
already installed by another recipe.
If you have distro-specific configuration files
that are included by an existing recipe, you should
add an append file (.bbappend
)
for those.
For general information and recommendations
on how to add recipes to your layer, see the
"Creating Your Own Layer"
and
"Best Practices to Follow When Creating Layers"
sections.
Add any image recipes that are specific to your distribution.
Add a psplash
append file for a branded splash screen.
For information on append files, see the
"Using .bbappend Files in Your Layer"
section.
Add any other append files to make custom changes that are specific to individual recipes.
If you are producing your own customized version
of the build system for use by other users, you might
want to customize the message shown by the setup script or
you might want to change the template configuration files (i.e.
local.conf
and
bblayers.conf
) that are created in
a new build directory.
The OpenEmbedded build system uses the environment variable
TEMPLATECONF
to locate the directory
from which it gathers configuration information that ultimately
ends up in the
Build Directory's
conf
directory.
By default, TEMPLATECONF
is set as
follows in the poky
repository:
TEMPLATECONF=${TEMPLATECONF:-meta-poky/conf}
This is the directory used by the build system to find templates
from which to build some key configuration files.
If you look at this directory, you will see the
bblayers.conf.sample
,
local.conf.sample
, and
conf-notes.txt
files.
The build system uses these files to form the respective
bblayers.conf
file,
local.conf
file, and display the list of
BitBake targets when running the setup script.
To override these default configuration files with
configurations you want used within every new
Build Directory, simply set the
TEMPLATECONF
variable to your directory.
The TEMPLATECONF
variable is set in the
.templateconf
file, which is in the
top-level
Source Directory
folder (e.g. poky
).
Edit the .templateconf
so that it can locate
your directory.
Best practices dictate that you should keep your
template configuration directory in your custom distribution layer.
For example, suppose you have a layer named
meta-mylayer
located in your home directory
and you want your template configuration directory named
myconf
.
Changing the .templateconf
as follows
causes the OpenEmbedded build system to look in your directory
and base its configuration files on the
*.sample
configuration files it finds.
The final configuration files (i.e.
local.conf
and
bblayers.conf
ultimately still end up in
your Build Directory, but they are based on your
*.sample
files.
TEMPLATECONF=${TEMPLATECONF:-meta-mylayer/myconf}
Aside from the *.sample
configuration files,
the conf-notes.txt
also resides in the
default meta-poky/conf
directory.
The scripts that set up the build environment
(i.e.
oe-init-build-env
and
oe-init-build-env-memres
)
use this file to display BitBake targets as part of the script
output.
Customizing this conf-notes.txt
file is a
good way to make sure your list of custom targets appears
as part of the script's output.
Here is the default list of targets displayed as a result of running either of the setup scripts:
You can now run 'bitbake <target>' Common targets are: core-image-minimal core-image-sato meta-toolchain meta-ide-support
Changing the listed common targets is as easy as editing your
version of conf-notes.txt
in your
custom template configuration directory and making sure you
have TEMPLATECONF
set to your directory.
Very small distributions have some significant advantages such as requiring less on-die or in-package memory (cheaper), better performance through efficient cache usage, lower power requirements due to less memory, faster boot times, and reduced development overhead. Some real-world examples where a very small distribution gives you distinct advantages are digital cameras, medical devices, and small headless systems.
This section presents information that shows you how you can
trim your distribution to even smaller sizes than the
poky-tiny
distribution, which is around
5 Mbytes, that can be built out-of-the-box using the Yocto Project.
The following list presents the overall steps you need to consider and perform to create distributions with smaller root filesystems, achieve faster boot times, maintain your critical functionality, and avoid initial RAM disks:
Before you can reach your destination, you need to know where you are going. Here is an example list that you can use as a guide when creating very small distributions:
Determine how much space you need (e.g. a kernel that is 1 Mbyte or less and a root filesystem that is 3 Mbytes or less).
Find the areas that are currently taking 90% of the space and concentrate on reducing those areas.
Do not create any difficult "hacks" to achieve your goals.
Leverage the device-specific options.
Work in a separate layer so that you keep changes isolated. For information on how to create layers, see the "Understanding and Creating Layers" section.
It is easiest to have something to start with when creating
your own distribution.
You can use the Yocto Project out-of-the-box to create the
poky-tiny
distribution.
Ultimately, you will want to make changes in your own
distribution that are likely modeled after
poky-tiny
.
poky-tiny
in your build,
set the
DISTRO
variable in your
local.conf
file to "poky-tiny"
as described in the
"Creating Your Own Distribution"
section.
Understanding some memory concepts will help you reduce the
system size.
Memory consists of static, dynamic, and temporary memory.
Static memory is the TEXT (code), DATA (initialized data
in the code), and BSS (uninitialized data) sections.
Dynamic memory represents memory that is allocated at runtime:
stacks, hash tables, and so forth.
Temporary memory is recovered after the boot process.
This memory consists of memory used for decompressing
the kernel and for the __init__
functions.
To help you see where you currently are with kernel and root
filesystem sizes, you can use two tools found in the
Source Directory in
the scripts/tiny/
directory:
ksize.py
: Reports
component sizes for the kernel build objects.
dirsize.py
: Reports
component sizes for the root filesystem.
This next tool and command help you organize configuration fragments and view file dependencies in a human-readable form:
merge_config.sh
:
Helps you manage configuration files and fragments
within the kernel.
With this tool, you can merge individual configuration
fragments together.
The tool allows you to make overrides and warns you
of any missing configuration options.
The tool is ideal for allowing you to iterate on
configurations, create minimal configurations, and
create configuration files for different machines
without having to duplicate your process.
The merge_config.sh
script is
part of the Linux Yocto kernel Git repositories
(i.e. linux-yocto-3.14
,
linux-yocto-3.10
,
linux-yocto-3.8
, and so forth)
in the
scripts/kconfig
directory.
For more information on configuration fragments, see the "Generating Configuration Files" section of the Yocto Project Linux Kernel Development Manual and the "Creating Configuration Fragments" section, which is in this manual.
bitbake -u taskexp -g
:
Using the BitBake command with these options brings up
a Dependency Explorer from which you can view file
dependencies.
Understanding these dependencies allows you to make
informed decisions when cutting out various pieces of the
kernel and root filesystem.bitbake_target
The root filesystem is made up of packages for booting, libraries, and applications. To change things, you can configure how the packaging happens, which changes the way you build them. You can also modify the filesystem itself or select a different filesystem.
First, find out what is hogging your root filesystem by running the
dirsize.py
script from your root directory:
$ cd root-directory-of-image
$ dirsize.py 100000 > dirsize-100k.log
$ cat dirsize-100k.log
You can apply a filter to the script to ignore files under a certain size. The previous example filters out any files below 100 Kbytes. The sizes reported by the tool are uncompressed, and thus will be smaller by a relatively constant factor in a compressed root filesystem. When you examine your log file, you can focus on areas of the root filesystem that take up large amounts of memory.
You need to be sure that what you eliminate does not cripple the functionality you need. One way to see how packages relate to each other is by using the Dependency Explorer UI with the BitBake command:
$ cdimage-directory
$ bitbake -u taskexp -gimage
Use the interface to select potential packages you wish to eliminate and see their dependency relationships.
When deciding how to reduce the size, get rid of packages that
result in minimal impact on the feature set.
For example, you might not need a VGA display.
Or, you might be able to get by with devtmpfs
and mdev
instead of
udev
.
Use your local.conf
file to make changes.
For example, to eliminate udev
and
glib
, set the following in the
local configuration file:
VIRTUAL-RUNTIME_dev_manager = ""
Finally, you should consider exactly the type of root
filesystem you need to meet your needs while also reducing
its size.
For example, consider cramfs
,
squashfs
, ubifs
,
ext2
, or an initramfs
using initramfs
.
Be aware that ext3
requires a 1 Mbyte
journal.
If you are okay with running read-only, you do not need this
journal.
The kernel is built by including policies for hardware-independent aspects. What subsystems do you enable? For what architecture are you building? Which drivers do you build by default?
Run the ksize.py
script from the top-level
Linux build directory to get an idea of what is making up
the kernel:
$ cd top-level-linux-build-directory
$ ksize.py > ksize.log
$ cat ksize.log
When you examine the log, you will see how much space is
taken up with the built-in .o
files for
drivers, networking, core kernel files, filesystem, sound,
and so forth.
The sizes reported by the tool are uncompressed, and thus
will be smaller by a relatively constant factor in a compressed
kernel image.
Look to reduce the areas that are large and taking up around
the "90% rule."
To examine, or drill down, into any particular area, use the
-d
option with the script:
$ ksize.py -d > ksize.log
Using this option breaks out the individual file information for each area of the kernel (e.g. drivers, networking, and so forth).
Use your log file to see what you can eliminate from the kernel based on features you can let go. For example, if you are not going to need sound, you do not need any drivers that support sound.
After figuring out what to eliminate, you need to reconfigure
the kernel to reflect those changes during the next build.
You could run menuconfig
and make all your
changes at once.
However, that makes it difficult to see the effects of your
individual eliminations and also makes it difficult to replicate
the changes for perhaps another target device.
A better method is to start with no configurations using
allnoconfig
, create configuration
fragments for individual changes, and then manage the
fragments into a single configuration file using
merge_config.sh
.
The tool makes it easy for you to iterate using the
configuration change and build cycle.
Each time you make configuration changes, you need to rebuild the kernel and check to see what impact your changes had on the overall size.
Packaging requirements add size to the image. One way to reduce the size of the image is to remove all the packaging requirements from the image. This reduction includes both removing the package manager and its unique dependencies as well as removing the package management data itself.
To eliminate all the packaging requirements for an image,
be sure that "package-management" is not part of your
IMAGE_FEATURES
statement for the image.
When you remove this feature, you are removing the package
manager as well as its dependencies from the root filesystem.
Depending on your particular circumstances, other areas that you can trim likely exist. The key to finding these areas is through tools and methods described here combined with experimentation and iteration. Here are a couple of areas to experiment with:
glibc
:
In general, follow this process:
Remove glibc
features from
DISTRO_FEATURES
that you think you do not need.
Build your distribution.
If the build fails due to missing
symbols in a package, determine if you can
reconfigure the package to not need those
features.
For example, change the configuration to not
support wide character support as is done for
ncurses
.
Or, if support for those characters is needed,
determine what glibc
features provide the support and restore the
configuration.
Rebuild and repeat the process.
busybox
:
For BusyBox, use a process similar as described for
glibc
.
A difference is you will need to boot the resulting
system to see if you are able to do everything you
expect from the running system.
You need to be sure to integrate configuration fragments
into Busybox because BusyBox handles its own core
features and then allows you to add configuration
fragments on top.
If you have not reached your goals on system size, you need to iterate on the process. The process is the same. Use the tools and see just what is taking up 90% of the root filesystem and the kernel. Decide what you can eliminate without limiting your device beyond what you need.
Depending on your system, a good place to look might be Busybox, which provides a stripped down version of Unix tools in a single, executable file. You might be able to drop virtual terminal services or perhaps ipv6.
A common scenario developers face is creating images for several
different machines that use the same software environment.
In this situation, it is tempting to set the
tunings and optimization flags for each build specifically for
the targeted hardware (i.e. "maxing out" the tunings).
Doing so can considerably add to build times and package feed
maintenance collectively for the machines.
For example, selecting tunes that are extremely specific to a
CPU core used in a system might enable some micro optimizations
in GCC for that particular system but would otherwise not gain
you much of a performance difference across the other systems
as compared to using a more general tuning across all the builds
(e.g. setting
DEFAULTTUNE
specifically for each machine's build).
Rather than "max out" each build's tunings, you can take steps that
cause the OpenEmbedded build system to reuse software across the
various machines where it makes sense.
If build speed and package feed maintenance are considerations, you should consider the points in this section that can help you optimize your tunings to best consider build times and package feed maintenance.
Share the Build Directory:
If at all possible, share the
TMPDIR
across builds.
The Yocto Project supports switching between different
MACHINE
values in the same TMPDIR
.
This practice is well supported and regularly used by
developers when building for multiple machines.
When you use the same TMPDIR
for
multiple machine builds, the OpenEmbedded build system can
reuse the existing native and often cross-recipes for
multiple machines.
Thus, build time decreases.
DISTRO
settings change or fundamental configuration settings
such as the filesystem layout, you need to work with
a clean TMPDIR
.
Sharing TMPDIR
under these
circumstances might work but since it is not
guaranteed, you should use a clean
TMPDIR
.
Enable the Appropriate Package Architecture: By default, the OpenEmbedded build system enables three levels of package architectures: "all", "tune" or "package", and "machine". Any given recipe usually selects one of these package architectures (types) for its output. Depending for what a given recipe creates packages, making sure you enable the appropriate package architecture can directly impact the build time.
A recipe that just generates scripts can enable
"all" architecture because there are no binaries to build.
To specifically enable "all" architecture, be sure your
recipe inherits the
allarch
class.
This class is useful for "all" architectures because it
configures many variables so packages can be used across
multiple architectures.
If your recipe needs to generate packages that are
machine-specific or when one of the build or runtime
dependencies is already machine-architecture dependent,
which makes your recipe also machine-architecture dependent,
make sure your recipe enables the "machine" package
architecture through the
MACHINE_ARCH
variable:
PACKAGE_ARCH = "${MACHINE_ARCH}"
When you do not specifically enable a package
architecture through the
PACKAGE_ARCH
,
The OpenEmbedded build system defaults to the
TUNE_PKGARCH
setting:
PACKAGE_ARCH = "${TUNE_PKGARCH}"
Choose a Generic Tuning File if Possible:
Some tunes are more generic and can run on multiple targets
(e.g. an armv5
set of packages could
run on armv6
and
armv7
processors in most cases).
Similarly, i486
binaries could work
on i586
and higher processors.
You should realize, however, that advances on newer
processor versions would not be used.
If you select the same tune for several different machines, the OpenEmbedded build system reuses software previously built, thus speeding up the overall build time. Realize that even though a new sysroot for each machine is generated, the software is not recompiled and only one package feed exists.
Manage Granular Level Packaging:
Sometimes cases exist where injecting another level
of package architecture beyond the three higher levels
noted earlier can be useful.
For example, consider the emgd
graphics stack in the
meta-intel
layer.
In this layer, a subset of software exists that is
compiled against something different from the rest of the
generic packages.
You can examine the key code in the
Source Repositories
"daisy" branch in
classes/emgd-gl.bbclass
.
For a specific set of packages, the code redefines
PACKAGE_ARCH
.
PACKAGE_EXTRA_ARCHS
is then appended with this extra tune name in
meta-intel-emgd.inc
.
The result is that when searching for packages, the
build system uses a four-level search and the packages
in this new level are preferred as compared to the standard
tune.
The overall result is that the build system reuses most
software from the common tune except for specific cases
as needed.
Use Tools to Debug Issues:
Sometimes you can run into situations where software is
being rebuilt when you think it should not be.
For example, the OpenEmbedded build system might not be
using shared state between machines when you think it
should be.
These types of situations are usually due to references
to machine-specific variables such as
MACHINE
,
SERIAL_CONSOLE
,
XSERVER
,
MACHINE_FEATURES
,
and so forth in code that is supposed to only be
tune-specific or when the recipe depends
(DEPENDS
,
RDEPENDS
,
RRECOMMENDS
,
RSUGGESTS
,
and so forth) on some other recipe that already has
PACKAGE_ARCH
defined as "${MACHINE_ARCH}".
For such cases, you can use some tools to help you sort out the situation:
sstate-diff-machines.sh
:
You can find this tool in the
scripts
directory of the
Source Repositories.
See the comments in the script for information on
how to use the tool.
BitBake's "-S printdiff" Option:
Using this option causes BitBake to try to
establish the closest signature match it can
(e.g. in the shared state cache) and then run
bitbake-diffsigs
over the
matches to determine the stamps and delta where
these two stamp trees diverge.
This section describes a few tasks that involve packages:
You might find it necessary to prevent specific packages from being installed into an image. If so, you can use several variables to direct the build system to essentially ignore installing recommended packages or to not install a package at all.
The following list introduces variables you can use to
prevent packages from being installed into your image.
Each of these variables only works with IPK and RPM
package types.
Support for Debian packages does not exist.
Also, you can use these variables from your
local.conf
file or attach them to a
specific image recipe by using a recipe name override.
For more detail on the variables, see the descriptions in the
Yocto Project Reference Manual's glossary chapter.
BAD_RECOMMENDATIONS
:
Use this variable to specify "recommended-only"
packages that you do not want installed.
NO_RECOMMENDATIONS
:
Use this variable to prevent all "recommended-only"
packages from being installed.
PACKAGE_EXCLUDE
:
Use this variable to prevent specific packages from
being installed regardless of whether they are
"recommended-only" or not.
You need to realize that the build process could
fail with an error when you
prevent the installation of a package whose presence
is required by an installed package.
This section provides some background on how binary package versioning is accomplished and presents some of the services, variables, and terminology involved.
In order to understand binary package versioning, you need to consider the following:
Binary Package: The binary package that is eventually built and installed into an image.
Binary Package Version: The binary package version is composed of two components - a version and a revision.
PE
)
is involved but this discussion for the most part
ignores PE
.
The version and revision are taken from the
PV
and
PR
variables, respectively.
PV
: The recipe version.
PV
represents the version of the
software being packaged.
Do not confuse PV
with the
binary package version.
PR
: The recipe revision.
SRCPV
:
The OpenEmbedded build system uses this string
to help define the value of PV
when the source code revision needs to be included
in it.
PR Service: A network-based service that helps automate keeping package feeds compatible with existing package manager applications such as RPM, APT, and OPKG.
Whenever the binary package content changes, the binary package
version must change.
Changing the binary package version is accomplished by changing
or "bumping" the PR
and/or
PV
values.
Increasing these values occurs one of two ways:
Automatically using a Package Revision Service (PR Service).
Manually incrementing the
PR
and/or
PV
variables.
Given a primary challenge of any build system and its users is how to maintain a package feed that is compatible with existing package manager applications such as RPM, APT, and OPKG, using an automated system is much preferred over a manual system. In either system, the main requirement is that binary package version numbering increases in a linear fashion and that a number of version components exist that support that linear progression. For information on how to ensure package revisioning remains linear, see the "Automatically Incrementing a Binary Package Revision Number" section.
The following three sections provide related information on the
PR Service, the manual method for "bumping"
PR
and/or PV
, and
on how to ensure binary package revisioning remains linear.
As mentioned, attempting to maintain revision numbers in the Metadata is error prone, inaccurate, and causes problems for people submitting recipes. Conversely, the PR Service automatically generates increasing numbers, particularly the revision field, which removes the human element.
The Yocto Project uses variables in order of
decreasing priority to facilitate revision numbering (i.e.
PE
,
PV
, and
PR
for epoch, version, and revision, respectively).
The values are highly dependent on the policies and
procedures of a given distribution and package feed.
Because the OpenEmbedded build system uses
"signatures",
which are unique to a given build, the build system
knows when to rebuild packages.
All the inputs into a given task are represented by a
signature, which can trigger a rebuild when different.
Thus, the build system itself does not rely on the
PR
, PV
, and
PE
numbers to trigger a rebuild.
The signatures, however, can be used to generate
these values.
The PR Service works with both
OEBasic
and
OEBasicHash
generators.
The value of PR
bumps when the
checksum changes and the different generator mechanisms
change signatures under different circumstances.
As implemented, the build system includes values from
the PR Service into the PR
field as
an addition using the form ".x
" so
r0
becomes r0.1
,
r0.2
and so forth.
This scheme allows existing PR
values
to be used for whatever reasons, which include manual
PR
bumps, should it be necessary.
By default, the PR Service is not enabled or running. Thus, the packages generated are just "self consistent". The build system adds and removes packages and there are no guarantees about upgrade paths but images will be consistent and correct with the latest changes.
The simplest form for a PR Service is for it to exist
for a single host development system that builds the
package feed (building system).
For this scenario, you can enable a local PR Service by
setting
PRSERV_HOST
in your local.conf
file in the
Build Directory:
PRSERV_HOST = "localhost:0"
Once the service is started, packages will automatically
get increasing PR
values and
BitBake takes care of starting and stopping the server.
If you have a more complex setup where multiple host
development systems work against a common, shared package
feed, you have a single PR Service running and it is
connected to each building system.
For this scenario, you need to start the PR Service using
the bitbake-prserv
command:
bitbake-prserv --hostip
--portport
--start
In addition to hand-starting the service, you need to
update the local.conf
file of each
building system as described earlier so each system
points to the server and port.
It is also recommended you use build history, which adds
some sanity checks to binary package versions, in
conjunction with the server that is running the PR Service.
To enable build history, add the following to each building
system's local.conf
file:
# It is recommended to activate "buildhistory" for testing the PR service INHERIT += "buildhistory" BUILDHISTORY_COMMIT = "1"
For information on build history, see the "Maintaining Build Output Quality" section in the Yocto Project Reference Manual.
The OpenEmbedded build system does not maintain
PR
information as part of the
shared state (sstate) packages.
If you maintain an sstate feed, its expected that either
all your building systems that contribute to the sstate
feed use a shared PR Service, or you do not run a PR
Service on any of your building systems.
Having some systems use a PR Service while others do
not leads to obvious problems.
For more information on shared state, see the "Shared State Cache" section in the Yocto Project Reference Manual.
The alternative to setting up a PR Service is to manually
"bump" the
PR
variable.
If a committed change results in changing the package
output, then the value of the PR variable needs to be
increased (or "bumped") as part of that commit.
For new recipes you should add the PR
variable and set its initial value equal to "r0", which is
the default.
Even though the default value is "r0", the practice of
adding it to a new recipe makes it harder to forget to bump
the variable when you make changes to the recipe in future.
If you are sharing a common .inc
file
with multiple recipes, you can also use the
INC_PR
variable to ensure that the recipes sharing the
.inc
file are rebuilt when the
.inc
file itself is changed.
The .inc
file must set
INC_PR
(initially to "r0"), and all
recipes referring to it should set PR
to "${INC_PR}.0" initially, incrementing the last number
when the recipe is changed.
If the .inc
file is changed then its
INC_PR
should be incremented.
When upgrading the version of a binary package, assuming the
PV
changes, the PR
variable should be
reset to "r0" (or "${INC_PR}.0" if you are using
INC_PR
).
Usually, version increases occur only to binary packages.
However, if for some reason PV
changes
but does not increase, you can increase the
PE
variable (Package Epoch).
The PE
variable defaults to "0".
Binary package version numbering strives to follow the Debian Version Field Policy Guidelines. These guidelines define how versions are compared and what "increasing" a version means.
When fetching a repository, BitBake uses the
SRCREV
variable to determine the specific source code revision
from which to build.
You set the SRCREV
variable to
AUTOREV
to cause the OpenEmbedded build system to automatically use the
latest revision of the software:
SRCREV = "${AUTOREV}"
Furthermore, you need to reference SRCPV
in PV
in order to automatically update
the version whenever the revision of the source code
changes.
Here is an example:
PV = "1.0+git${SRCPV}"
The OpenEmbedded build system substitutes
SRCPV
with the following:
AUTOINC+source_code_revision
The build system replaces the AUTOINC
with
a number.
The number used depends on the state of the PR Service:
If PR Service is enabled, the build system increments
the number, which is similar to the behavior of
PR
.
This behavior results in linearly increasing package
versions, which is desirable.
Here is an example:
hello-world-git_0.0+git0+b6558dd387-r0.0_armv7a-neon.ipk hello-world-git_0.0+git1+dd2f5c3565-r0.0_armv7a-neon.ipk
If PR Service is not enabled, the build system
replaces the AUTOINC
placeholder with zero (i.e. "0").
This results in changing the package version since
the source revision is included.
However, package versions are not increased linearly.
Here is an example:
hello-world-git_0.0+git0+b6558dd387-r0.0_armv7a-neon.ipk hello-world-git_0.0+git0+dd2f5c3565-r0.0_armv7a-neon.ipk
In summary, the OpenEmbedded build system does not track the
history of binary package versions for this purpose.
AUTOINC
, in this case, is comparable to
PR
.
If PR server is not enabled, AUTOINC
in the package version is simply replaced by "0".
If PR server is enabled, the build system keeps track of the
package versions and bumps the number when the package
revision changes.
Many pieces of software split functionality into optional modules (or plug-ins) and the plug-ins that are built might depend on configuration options. To avoid having to duplicate the logic that determines what modules are available in your recipe or to avoid having to package each module by hand, the OpenEmbedded build system provides functionality to handle module packaging dynamically.
To handle optional module packaging, you need to do two things:
Ensure the module packaging is actually done.
Ensure that any dependencies on optional modules from other recipes are satisfied by your recipe.
To ensure the module packaging actually gets done, you use
the do_split_packages
function within
the populate_packages
Python function
in your recipe.
The do_split_packages
function
searches for a pattern of files or directories under a
specified path and creates a package for each one it finds
by appending to the
PACKAGES
variable and setting the appropriate values for
FILES_packagename
,
RDEPENDS_packagename
,
DESCRIPTION_packagename
, and so forth.
Here is an example from the lighttpd
recipe:
python populate_packages_prepend () { lighttpd_libdir = d.expand('${libdir}') do_split_packages(d, lighttpd_libdir, '^mod_(.*)\.so$', 'lighttpd-module-%s', 'Lighttpd module for %s', extra_depends='') }
The previous example specifies a number of things in the
call to do_split_packages
.
A directory within the files installed
by your recipe through do_install
in which to search.
A regular expression used to match module files in that directory. In the example, note the parentheses () that mark the part of the expression from which the module name should be derived.
A pattern to use for the package names.
A description for each package.
An empty string for
extra_depends
, which disables
the default dependency on the main
lighttpd
package.
Thus, if a file in ${libdir}
called mod_alias.so
is found,
a package called lighttpd-module-alias
is created for it and the
DESCRIPTION
is set to "Lighttpd module for alias".
Often, packaging modules is as simple as the previous
example.
However, more advanced options exist that you can use
within do_split_packages
to modify its
behavior.
And, if you need to, you can add more logic by specifying
a hook function that is called for each package.
It is also perfectly acceptable to call
do_split_packages
multiple times if
you have more than one set of modules to package.
For more examples that show how to use
do_split_packages
, see the
connman.inc
file in the
meta/recipes-connectivity/connman/
directory of the poky
source repository.
You can also find examples in
meta/classes/kernel.bbclass
.
Following is a reference that shows
do_split_packages
mandatory and
optional arguments:
Mandatory arguments root The path in which to search file_regex Regular expression to match searched files. Use parentheses () to mark the part of this expression that should be used to derive the module name (to be substituted where %s is used in other function arguments as noted below) output_pattern Pattern to use for the package names. Must include %s. description Description to set for each package. Must include %s. Optional arguments postinst Postinstall script to use for all packages (as a string) recursive True to perform a recursive search - default False hook A hook function to be called for every match. The function will be called with the following arguments (in the order listed): f Full path to the file/directory match pkg The package name file_regex As above output_pattern As above modulename The module name derived using file_regex extra_depends Extra runtime dependencies (RDEPENDS) to be set for all packages. The default value of None causes a dependency on the main package (${PN}) - if you do not want this, pass empty string '' for this parameter. aux_files_pattern Extra item(s) to be added to FILES for each package. Can be a single string item or a list of strings for multiple items. Must include %s. postrm postrm script to use for all packages (as a string) allow_dirs True to allow directories to be matched - default False prepend If True, prepend created packages to PACKAGES instead of the default False which appends them match_path match file_regex on the whole relative path to the root rather than just the file name aux_files_pattern_verbatim Extra item(s) to be added to FILES for each package, using the actual derived module name rather than converting it to something legal for a package name. Can be a single string item or a list of strings for multiple items. Must include %s. allow_links True to allow symlinks to be matched - default False summary Summary to set for each package. Must include %s; defaults to description if not set.
The second part for handling optional module packaging
is to ensure that any dependencies on optional modules
from other recipes are satisfied by your recipe.
You can be sure these dependencies are satisfied by
using the
PACKAGES_DYNAMIC
variable.
Here is an example that continues with the
lighttpd
recipe shown earlier:
PACKAGES_DYNAMIC = "lighttpd-module-.*"
The name specified in the regular expression can of
course be anything.
In this example, it is lighttpd-module-
and is specified as the prefix to ensure that any
RDEPENDS
and RRECOMMENDS
on a package name starting with the prefix are satisfied
during build time.
If you are using do_split_packages
as described in the previous section, the value you put in
PACKAGES_DYNAMIC
should correspond to
the name pattern specified in the call to
do_split_packages
.
During a build, BitBake always transforms a recipe into one or
more packages.
For example, BitBake takes the bash
recipe
and currently produces the bash-dbg
,
bash-staticdev
,
bash-dev
, bash-doc
,
bash-locale
, and
bash
packages.
Not all generated packages are included in an image.
In several situations, you might need to update, add, remove, or query the packages on a target device at runtime (i.e. without having to generate a new image). Examples of such situations include:
You want to provide in-the-field updates to deployed devices (e.g. security updates).
You want to have a fast turn-around development cycle for one or more applications that run on your device.
You want to temporarily install the "debug" packages of various applications on your device so that debugging can be greatly improved by allowing access to symbols and source debugging.
You want to deploy a more minimal package selection of your device but allow in-the-field updates to add a larger selection for customization.
In all these situations, you have something similar to a more traditional Linux distribution in that in-field devices are able to receive pre-compiled packages from a server for installation or update. Being able to install these packages on a running, in-field device is what is termed "runtime package management".
In order to use runtime package management, you need a host/server machine that serves up the pre-compiled packages plus the required metadata. You also need package manipulation tools on the target. The build machine is a likely candidate to act as the server. However, that machine does not necessarily have to be the package server. The build machine could push its artifacts to another machine that acts as the server (e.g. Internet-facing).
A simple build that targets just one device produces
more than one package database.
In other words, the packages produced by a build are separated
out into a couple of different package groupings based on
criteria such as the target's CPU architecture, the target
board, or the C library used on the target.
For example, a build targeting the qemuarm
device produces the following three package databases:
all
, armv5te
, and
qemuarm
.
If you wanted your qemuarm
device to be
aware of all the packages that were available to it,
you would need to point it to each of these databases
individually.
In a similar way, a traditional Linux distribution usually is
configured to be aware of a number of software repositories
from which it retrieves packages.
Using runtime package management is completely optional and not required for a successful build or deployment in any way. But if you want to make use of runtime package management, you need to do a couple things above and beyond the basics. The remainder of this section describes what you need to do.
This section describes build considerations of which you need to be aware in order to provide support for runtime package management.
When BitBake generates packages, it needs to know
what format or formats to use.
In your configuration, you use the
PACKAGE_CLASSES
variable to specify the format:
Open the local.conf
file
inside your
Build Directory
(e.g. ~/poky/build/conf/local.conf
).
Select the desired package format as follows:
PACKAGE_CLASSES ?= “package_packageformat
”
where packageformat
can be "ipk", "rpm", and "deb", which are the
supported package formats.
If you would like your image to start off with a basic
package database containing the packages in your current
build as well as to have the relevant tools available on the
target for runtime package management, you can include
"package-management" in the
IMAGE_FEATURES
variable.
Including "package-management" in this
configuration variable ensures that when the image
is assembled for your target, the image includes
the currently-known package databases as well as
the target-specific tools required for runtime
package management to be performed on the target.
However, this is not strictly necessary.
You could start your image off without any databases
but only include the required on-target package
tool(s).
As an example, you could include "opkg" in your
IMAGE_INSTALL
variable if you are using the IPK package format.
You can then initialize your target's package database(s)
later once your image is up and running.
Whenever you perform any sort of build step that can potentially generate a package or modify an existing package, it is always a good idea to re-generate the package index with:
$ bitbake package-index
Realize that it is not sufficient to simply do the following:
$ bitbake some-package
package-index
The reason for this restriction is because BitBake does not
properly schedule the package-index
target fully after any other target has completed.
Thus, be sure to run the package update step separately.
You can use the
PACKAGE_FEED_ARCHS
,
PACKAGE_FEED_BASE_PATHS
,
and
PACKAGE_FEED_URIS
variables to pre-configure target images to use a package
feed.
If you do not define these variables, then manual steps
as described in the subsequent sections are necessary to
configure the target.
You should set these variables before building the image
in order to produce a correctly configured image.
When your build is complete, your packages reside in the
${TMPDIR}/deploy/
directory.
For example, if
packageformat
${
TMPDIR
}
is tmp
and your selected package type
is IPK, then your IPK packages are available in
tmp/deploy/ipk
.
Although other protocols are possible, a server using HTTP typically serves packages. If you want to use HTTP, then set up and configure a web server such as Apache 2, lighttpd, or SimpleHTTPServer on the machine serving the packages.
To keep things simple, this section describes how to set up a SimpleHTTPServer web server to share package feeds from the developer's machine. Although this server might not be the best for a production environment, the setup is simple and straight forward. Should you want to use a different server more suited for production (e.g. Apache 2, Lighttpd, or Nginx), take the appropriate steps to do so.
From within the build directory where you have built an
image based on your packaging choice (i.e. the
PACKAGE_CLASSES
setting), simply start the server.
The following example assumes a build directory of
~/poky/build/tmp/deploy/rpm
and a
PACKAGE_CLASSES
setting of
"package_rpm":
$ cd ~/poky/build/tmp/deploy/rpm $ python -m SimpleHTTPServer
Setting up the target differs depending on the package management system. This section provides information for RPM, IPK, and DEB.
The dnf
application performs
runtime package management of RPM packages.
You must perform an initial setup for
dnf
on the target machine
if the
PACKAGE_FEED_ARCHS
,
PACKAGE_FEED_BASE_PATHS
,
and
PACKAGE_FEED_URIS
variables have not been set or the target image was
built before the variables were set.
As an example, assume the target is able to use the
following package databases:
all
, i586
,
and qemux86
from a server named
my.server
.
You must inform dnf
of the
availability of these databases by creating a
/etc/yum.repos.d/oe-packages.repo
file with the following content:
[oe-packages] baseurl="http://my.server/rpm/i586 http://my.server/rpm/qemux86 http://my.server/rpm/all"
From the target machine, fetch the repository:
# dnf makecache
After everything is set up, dnf
is able to find, install, and upgrade packages from
the specified repository.
The opkg
application performs
runtime package management of IPK packages.
You must perform an initial setup for
opkg
on the target machine
if the
PACKAGE_FEED_ARCHS
,
PACKAGE_FEED_BASE_PATHS
, and
PACKAGE_FEED_URIS
variables have not been set or the target image was
built before the variables were set.
The opkg
application uses
configuration files to find available package
databases.
Thus, you need to create a configuration file inside
the /etc/opkg/
direction, which
informs opkg
of any repository
you want to use.
As an example, suppose you are serving packages from a
ipk/
directory containing the
i586
,
all
, and
qemux86
databases through an
HTTP server named my.server
.
On the target, create a configuration file
(e.g. my_repo.conf
) inside the
/etc/opkg/
directory containing
the following:
src/gz all http://my.server/ipk/all src/gz i586 http://my.server/ipk/i586 src/gz qemux86 http://my.server/ipk/qemux86
Next, instruct opkg
to fetch
the repository information:
# opkg update
The opkg
application is now able
to find, install, and upgrade packages from the
specified repository.
The apt
application performs
runtime package management of DEB packages.
This application uses a source list file to find
available package databases.
You must perform an initial setup for
apt
on the target machine
if the
PACKAGE_FEED_ARCHS
,
PACKAGE_FEED_BASE_PATHS
, and
PACKAGE_FEED_URIS
variables have not been set or the target image was
built before the variables were set.
To inform apt
of the repository
you want to use, you might create a list file (e.g.
my_repo.list
) inside the
/etc/apt/sources.list.d/
directory.
As an example, suppose you are serving packages from a
deb/
directory containing the
i586
,
all
, and
qemux86
databases through an
HTTP server named my.server
.
The list file should contain:
deb http://my.server/deb/all ./ deb http://my.server/deb/i586 ./ deb http://my.server/deb/qemux86 ./
Next, instruct the apt
application to fetch the repository information:
# apt-get update
After this step, apt
is able
to find, install, and upgrade packages from the
specified repository.
In order to add security to RPM packages used during a build, you can take steps to securely sign them. Once a signature is verified, the OpenEmbedded build system can use the package in the build. If security fails for a signed package, the build system aborts the build.
This section describes how to sign RPM packages during a build and how to use signed package feeds (repositories) when doing a build.
To enable signing RPM packages, you must set up the
following configurations in either your
local.config
or
distro.config
file:
# Inherit sign_rpm.bbclass to enable signing functionality INHERIT += " sign_rpm" # Define the GPG key that will be used for signing. RPM_GPG_NAME = "key_name
" # Provide passphrase for the key RPM_GPG_PASSPHRASE = "passphrase
"
key_name
and
passphrase
Aside from the
RPM_GPG_NAME
and
RPM_GPG_PASSPHRASE
variables in the
previous example, two optional variables related to signing
exist:
GPG_BIN
:
Specifies a gpg
binary/wrapper
that is executed when the package is signed.
GPG_PATH
:
Specifies the gpg
home
directory used when the package is signed.
In addition to being able to sign RPM packages, you can also enable the OpenEmbedded build system to be able to handle previously signed package feeds for IPK packages.
The steps you need to take to enable signed package feed
use are similar to the steps used to sign RPM packages.
You must define the following in your
local.config
or
distro.config
file:
INHERIT += "sign_package_feed" PACKAGE_FEED_GPG_NAME = "key_name
" PACKAGE_FEED_GPG_PASSPHRASE_FILE = "path_to_file_containing_passphrase
"
For signed package feeds, the passphrase must exist in a
separate file, which is pointed to by the
PACKAGE_FEED_GPG_PASSPHRASE_FILE
variable.
Regarding security, keeping a plain text passphrase out of
the configuration is more secure.
Aside from the
PACKAGE_FEED_GPG_NAME
and
PACKAGE_FEED_GPG_PASSPHRASE_FILE
variables, three optional variables related to signed
package feeds exist:
GPG_BIN
:
Specifies a gpg
binary/wrapper
that is executed when the package is signed.
GPG_PATH
:
Specifies the gpg
home
directory used when the package is signed.
PACKAGE_FEED_GPG_SIGNATURE_TYPE
:
Specifies the type of gpg
signature.
This variable applies only to RPM and IPK package
feeds.
Allowable values for the
PACKAGE_FEED_GPG_SIGNATURE_TYPE
are "ASC", which is the default and specifies ascii
armored, and "BIN", which specifies binary.
A Package Test (ptest) runs tests against packages built
by the OpenEmbedded build system on the target machine.
A ptest contains at least two items: the actual test, and
a shell script (run-ptest
) that starts
the test.
The shell script that starts the test must not contain
the actual test - the script only starts the test.
On the other hand, the test can be anything from a simple
shell script that runs a binary and checks the output to
an elaborate system of test binaries and data files.
The test generates output in the format used by Automake:
result
:testname
where the result can be PASS
,
FAIL
, or SKIP
,
and the testname can be any identifying string.
For a list of Yocto Project recipes that are already enabled with ptest, see the Ptest wiki page.
ptest
class.
To add package testing to your build, add the
DISTRO_FEATURES
and EXTRA_IMAGE_FEATURES
variables to your local.conf
file,
which is found in the
Build Directory:
DISTRO_FEATURES_append = " ptest" EXTRA_IMAGE_FEATURES += "ptest-pkgs"
Once your build is complete, the ptest files are installed
into the
/usr/lib/
directory within the image, where
package
/ptest
is the name of the package.
package
The ptest-runner
package installs a
shell script that loops through all installed ptest test
suites and runs them in sequence.
Consequently, you might want to add this package to
your image.
In order to enable a recipe to run installed ptests on target hardware, you need to prepare the recipes that build the packages you want to test. Here is what you have to do for each recipe:
Be sure the recipe
inherits the
ptest
class:
Include the following line in each recipe:
inherit ptest
Create run-ptest
:
This script starts your test.
Locate the script where you will refer to it
using
SRC_URI
.
Here is an example that starts a test for
dbus
:
#!/bin/sh cd test make -k runtest-TESTS
Ensure dependencies are
met:
If the test adds build or runtime dependencies
that normally do not exist for the package
(such as requiring "make" to run the test suite),
use the
DEPENDS
and
RDEPENDS
variables in your recipe in order for the package
to meet the dependencies.
Here is an example where the package has a runtime
dependency on "make":
RDEPENDS_${PN}-ptest += "make"
Add a function to build the test suite: Not many packages support cross-compilation of their test suites. Consequently, you usually need to add a cross-compilation function to the package.
Many packages based on Automake compile and
run the test suite by using a single command
such as make check
.
However, the host make check
builds and runs on the same computer, while
cross-compiling requires that the package is built
on the host but executed for the target
architecture (though often, as in the case for
ptest, the execution occurs on the host).
The built version of Automake that ships with the
Yocto Project includes a patch that separates
building and execution.
Consequently, packages that use the unaltered,
patched version of make check
automatically cross-compiles.
Regardless, you still must add a
do_compile_ptest
function to
build the test suite.
Add a function similar to the following to your
recipe:
do_compile_ptest() { oe_runmake buildtest-TESTS }
Ensure special configurations
are set:
If the package requires special configurations
prior to compiling the test code, you must
insert a do_configure_ptest
function into the recipe.
Install the test
suite:
The ptest
class
automatically copies the file
run-ptest
to the target and
then runs make install-ptest
to run the tests.
If this is not enough, you need to create a
do_install_ptest
function and
make sure it gets called after the
"make install-ptest" completes.
The OpenEmbedded build system works with source files located
through the
SRC_URI
variable.
When you build something using BitBake, a big part of the operation
is locating and downloading all the source tarballs.
For images, downloading all the source for various packages can
take a significant amount of time.
This section presents information for working with source files that can lead to more efficient use of resources and time.
As mentioned, a good deal that goes into a Yocto Project build is simply downloading all of the source tarballs. Maybe you have been working with another build system (OpenEmbedded or Angstrom) for which you have built up a sizable directory of source tarballs. Or, perhaps someone else has such a directory for which you have read access. If so, you can save time by adding statements to your configuration file so that the build process checks local directories first for existing tarballs before checking the Internet.
Here is an efficient way to set it up in your
local.conf
file:
SOURCE_MIRROR_URL ?= "file:///home/you/your-download-dir/" INHERIT += "own-mirrors" BB_GENERATE_MIRROR_TARBALLS = "1" # BB_NO_NETWORK = "1"
In the previous example, the
BB_GENERATE_MIRROR_TARBALLS
variable causes the OpenEmbedded build system to generate
tarballs of the Git repositories and store them in the
DL_DIR
directory.
Due to performance reasons, generating and storing these
tarballs is not the build system's default behavior.
You can also use the
PREMIRRORS
variable.
For an example, see the variable's glossary entry in the
Yocto Project Reference Manual.
Another technique you can use to ready yourself for a
successive string of build operations, is to pre-fetch
all the source files without actually starting a build.
This technique lets you work through any download issues
and ultimately gathers all the source files into your
download directory
build/downloads
,
which is located with
DL_DIR
.
Use the following BitBake command form to fetch all the necessary sources without starting the build:
$ bitbake -c fetchall target
This variation of the BitBake command guarantees that you have all the sources for that BitBake target should you disconnect from the Internet and want to do the build later offline.
By default, the OpenEmbedded build system uses the Build Directory when building source code. The build process involves fetching the source files, unpacking them, and then patching them if necessary before the build takes place.
Situations exist where you might want to build software from source
files that are external to and thus outside of the
OpenEmbedded build system.
For example, suppose you have a project that includes a new BSP with
a heavily customized kernel.
And, you want to minimize exposing the build system to the
development team so that they can focus on their project and
maintain everyone's workflow as much as possible.
In this case, you want a kernel source directory on the development
machine where the development occurs.
You want the recipe's
SRC_URI
variable to point to the external directory and use it as is, not
copy it.
To build from software that comes from an external source, all you
need to do is inherit the
externalsrc
class and then set the
EXTERNALSRC
variable to point to your external source code.
Here are the statements to put in your
local.conf
file:
INHERIT += "externalsrc" EXTERNALSRC_pn-myrecipe
= "path-to-your-source-tree
"
This next example shows how to accomplish the same thing by setting
EXTERNALSRC
in the recipe itself or in the
recipe's append file:
EXTERNALSRC = "path
" EXTERNALSRC_BUILD = "path
"
externalsrc
class.
By default, externalsrc.bbclass
builds
the source code in a directory separate from the external source
directory as specified by
EXTERNALSRC
.
If you need to have the source built in the same directory in
which it resides, or some other nominated directory, you can set
EXTERNALSRC_BUILD
to point to that directory:
EXTERNALSRC_BUILD_pn-myrecipe
= "path-to-your-source-tree
"
By default, the Yocto Project uses SysVinit as the initialization manager. However, support also exists for systemd, which is a full replacement for init with parallel starting of services, reduced shell overhead and other features that are used by many distributions.
If you want to use SysVinit, you do not have to do anything. But, if you want to use systemd, you must take some steps as described in the following sections.
Set the these variables in your distribution configuration file as follows:
DISTRO_FEATURES_append = " systemd" VIRTUAL-RUNTIME_init_manager = "systemd"
You can also prevent the SysVinit distribution feature from being automatically enabled as follows:
DISTRO_FEATURES_BACKFILL_CONSIDERED = "sysvinit"
Doing so removes any redundant SysVinit scripts.
To remove initscripts from your image altogether, set this variable also:
VIRTUAL-RUNTIME_initscripts = ""
For information on the backfill variable, see
DISTRO_FEATURES_BACKFILL_CONSIDERED
.
Set these variables in your distribution configuration file as follows:
DISTRO_FEATURES_append = " systemd" VIRTUAL-RUNTIME_init_manager = "systemd"
Doing so causes your main image to use the
packagegroup-core-boot.bb
recipe and
systemd.
The rescue/minimal image cannot use this package group.
However, it can install SysVinit
and the appropriate packages will have support for both
systemd and SysVinit.
The Yocto Project provides multiple ways to manage the device
manager (/dev
):
Persistent and Pre-Populated/dev
:
For this case, the /dev
directory
is persistent and the required device nodes are created
during the build.
Use devtmpfs
with a Device Manager:
For this case, the /dev
directory
is provided by the kernel as an in-memory file system and
is automatically populated by the kernel at runtime.
Additional configuration of device nodes is done in user
space by a device manager like
udev
or
busybox-mdev
.
/dev
¶
To use the static method for device population, you need to
set the
USE_DEVFS
variable to "0" as follows:
USE_DEVFS = "0"
The content of the resulting /dev
directory is defined in a Device Table file.
The
IMAGE_DEVICE_TABLES
variable defines the Device Table to use and should be set
in the machine or distro configuration file.
Alternatively, you can set this variable in your
local.conf
configuration file.
If you do not define the
IMAGE_DEVICE_TABLES
variable, the default
device_table-minimal.txt
is used:
IMAGE_DEVICE_TABLES = "device_table-mymachine.txt"
The population is handled by the makedevs
utility during image creation:
devtmpfs
and a Device Manager¶
To use the dynamic method for device population, you need to
use (or be sure to set) the
USE_DEVFS
variable to "1", which is the default:
USE_DEVFS = "1"
With this setting, the resulting /dev
directory is populated by the kernel using
devtmpfs
.
Make sure the corresponding kernel configuration variable
CONFIG_DEVTMPFS
is set when building
you build a Linux kernel.
All devices created by devtmpfs
will be
owned by root
and have permissions
0600
.
To have more control over the device nodes, you can use a
device manager like udev
or
busybox-mdev
.
You choose the device manager by defining the
VIRTUAL-RUNTIME_dev_manager
variable
in your machine or distro configuration file.
Alternatively, you can set this variable in your
local.conf
configuration file:
VIRTUAL-RUNTIME_dev_manager = "udev" # Some alternative values # VIRTUAL-RUNTIME_dev_manager = "busybox-mdev" # VIRTUAL-RUNTIME_dev_manager = "systemd"
If you're working on a recipe that pulls from an external Source Code Manager (SCM), it is possible to have the OpenEmbedded build system notice new recipe changes added to the SCM and then build the resulting packages that depend on the new recipes by using the latest versions. This only works for SCMs from which it is possible to get a sensible revision number for changes. Currently, you can do this with Apache Subversion (SVN), Git, and Bazaar (BZR) repositories.
To enable this behavior, the
PV
of the recipe needs to reference
SRCPV
.
Here is an example:
PV = "1.2.3+git${SRCPV}"
Then, you can add the following to your
local.conf
:
SRCREV_pn-PN
= "${AUTOREV}"
PN
is the name of the recipe for which you want to enable automatic source
revision updating.
If you do not want to update your local configuration file, you can add the following directly to the recipe to finish enabling the feature:
SRCREV = "${AUTOREV}"
The Yocto Project provides a distribution named
poky-bleeding
, whose configuration
file contains the line:
require conf/distro/include/poky-floating-revisions.inc
This line pulls in the listed include file that contains numerous lines of exactly that form:
#SRCREV_pn-opkg-native ?= "${AUTOREV}" #SRCREV_pn-opkg-sdk ?= "${AUTOREV}" #SRCREV_pn-opkg ?= "${AUTOREV}" #SRCREV_pn-opkg-utils-native ?= "${AUTOREV}" #SRCREV_pn-opkg-utils ?= "${AUTOREV}" SRCREV_pn-gconf-dbus ?= "${AUTOREV}" SRCREV_pn-matchbox-common ?= "${AUTOREV}" SRCREV_pn-matchbox-config-gtk ?= "${AUTOREV}" SRCREV_pn-matchbox-desktop ?= "${AUTOREV}" SRCREV_pn-matchbox-keyboard ?= "${AUTOREV}" SRCREV_pn-matchbox-panel-2 ?= "${AUTOREV}" SRCREV_pn-matchbox-themes-extra ?= "${AUTOREV}" SRCREV_pn-matchbox-terminal ?= "${AUTOREV}" SRCREV_pn-matchbox-wm ?= "${AUTOREV}" SRCREV_pn-settings-daemon ?= "${AUTOREV}" SRCREV_pn-screenshot ?= "${AUTOREV}" . . .
These lines allow you to experiment with building a distribution that tracks the latest development source for numerous packages.
poky-bleeding
distribution
is not tested on a regular basis.
Keep this in mind if you use it.
Suppose, for security reasons, you need to disable your target device's root filesystem's write permissions (i.e. you need a read-only root filesystem). Or, perhaps you are running the device's operating system from a read-only storage device. For either case, you can customize your image for that behavior.
To create the read-only root filesystem, simply add the
"read-only-rootfs" feature to your image.
Using either of the following statements in your
image recipe or from within the
local.conf
file found in the
Build Directory
causes the build system to create a read-only root filesystem:
IMAGE_FEATURES = "read-only-rootfs"
or
EXTRA_IMAGE_FEATURES += "read-only-rootfs"
For more information on how to use these variables, see the
"Customizing Images Using Custom IMAGE_FEATURES
and EXTRA_IMAGE_FEATURES
"
section.
For information on the variables, see
IMAGE_FEATURES
and EXTRA_IMAGE_FEATURES
.
It is very important that you make sure all
post-Installation (pkg_postinst
) scripts
for packages that are installed into the image can be run
at the time when the root filesystem is created during the
build on the host system.
These scripts cannot attempt to run during first-boot on the
target device.
With the "read-only-rootfs" feature enabled,
the build system checks during root filesystem creation to make
sure all post-installation scripts succeed.
If any of these scripts still need to be run after the root
filesystem is created, the build immediately fails.
These build-time checks ensure that the build fails
rather than the target device fails later during its
initial boot operation.
Most of the common post-installation scripts generated by the build system for the out-of-the-box Yocto Project are engineered so that they can run during root filesystem creation (e.g. post-installation scripts for caching fonts). However, if you create and add custom scripts, you need to be sure they can be run during this file system creation.
Here are some common problems that prevent post-installation scripts from running during root filesystem creation:
Not using $D in front of absolute
paths:
The build system defines
$
D
when the root filesystem is created.
Furthermore, $D
is blank when the
script is run on the target device.
This implies two purposes for $D
:
ensuring paths are valid in both the host and target
environments, and checking to determine which
environment is being used as a method for taking
appropriate actions.
Attempting to run processes that are
specific to or dependent on the target
architecture:
You can work around these attempts by using native
tools, which run on the host system,
to accomplish the same tasks, or
by alternatively running the processes under QEMU,
which has the qemu_run_binary
function.
For more information, see the
qemu
class.
With the "read-only-rootfs" feature enabled,
any attempt by the target to write to the root filesystem at
runtime fails.
Consequently, you must make sure that you configure processes
and applications that attempt these types of writes do so
to directories with write access (e.g.
/tmp
or /var/run
).
The OpenEmbedded build system makes available a series of automated
tests for images to verify runtime functionality.
You can run these tests on either QEMU or actual target hardware.
Tests are written in Python making use of the
unittest
module, and the majority of them
run commands on the target system over SSH.
This section describes how you set up the environment to use these
tests, run available tests, and write and add your own tests.
For information on the test and QA infrastructure available within the Yocto Project, see the "Testing and Quality Assurance" section in the Yocto Project Reference Manual.
Depending on whether you are planning to run tests using QEMU or on the hardware, you have to take different steps to enable the tests. See the following subsections for information on how to enable both types of tests.
In order to run tests, you need to do the following:
Set up to avoid interaction
with sudo
for networking:
To accomplish this, you must do one of the
following:
Add
NOPASSWD
for your user
in /etc/sudoers
either for
all commands or just for
runqemu-ifup
.
You must provide the full path as that can
change if you are using multiple clones of the
source repository.
/etc/sudoers
.
Manually configure a tap interface for your system.
Run as root the script in
scripts/runqemu-gen-tapdevs
,
which should generate a list of tap devices.
This is the option typically chosen for
Autobuilder-type environments.
Set the
DISPLAY
variable:
You need to set this variable so that you have an X
server available (e.g. start
vncserver
for a headless machine).
Be sure your host's firewall
accepts incoming connections from
192.168.7.0/24:
Some of the tests (in particular DNF tests) start
an HTTP server on a random high number port,
which is used to serve files to the target.
The DNF module serves
${WORKDIR}/oe-rootfs-repo
so it can run DNF channel commands.
That means your host's firewall
must accept incoming connections from 192.168.7.0/24,
which is the default IP range used for tap devices
by runqemu
.
Be sure your host has the correct packages installed: Depending your host's distribution, you need to have the following packages installed:
Ubuntu and Debian:
sysstat
and
iproute2
OpenSUSE:
sysstat
and
iproute2
Fedora:
sysstat
and
iproute
CentOS:
sysstat
and
iproute
Once you start running the tests, the following happens:
A copy of the root filesystem is written
to ${WORKDIR}/testimage
.
The image is booted under QEMU using the
standard runqemu
script.
A default timeout of 500 seconds occurs
to allow for the boot process to reach the login prompt.
You can change the timeout period by setting
TEST_QEMUBOOT_TIMEOUT
in the local.conf
file.
Once the boot process is reached and the
login prompt appears, the tests run.
The full boot log is written to
${WORKDIR}/testimage/qemu_boot_log
.
Each test module loads in the order found
in TEST_SUITES
.
You can find the full output of the commands run over
SSH in
${WORKDIR}/testimgage/ssh_target_log
.
If no failures occur, the task running the
tests ends successfully.
You can find the output from the
unittest
in the task log at
${WORKDIR}/temp/log.do_testimage
.
The OpenEmbedded build system can run tests on real hardware, and for certain devices it can also deploy the image to be tested onto the device beforehand.
For automated deployment, a "master image" is installed onto the hardware once as part of setup. Then, each time tests are to be run, the following occurs:
The master image is booted into and used to write the image to be tested to a second partition.
The device is then rebooted using an external script that you need to provide.
The device boots into the image to be tested.
When running tests (independent of whether the image has been deployed automatically or not), the device is expected to be connected to a network on a pre-determined IP address. You can either use static IP addresses written into the image, or set the image to use DHCP and have your DHCP server on the test network assign a known IP address based on the MAC address of the device.
In order to run tests on hardware, you need to set
TEST_TARGET
to an appropriate value.
For QEMU, you do not have to change anything, the default
value is "QemuTarget".
For running tests on hardware, the following options exist:
"SimpleRemoteTarget": Choose "SimpleRemoteTarget" if you are going to run tests on a target system that is already running the image to be tested and is available on the network. You can use "SimpleRemoteTarget" in conjunction with either real hardware or an image running within a separately started QEMU or any other virtual machine manager.
"Systemd-bootTarget":
Choose "Systemd-bootTarget" if your hardware is
an EFI-based machine with
systemd-boot
as bootloader and
core-image-testmaster
(or something similar) is installed.
Also, your hardware under test must be in a
DHCP-enabled network that gives it the same IP
address for each reboot.
If you choose "Systemd-bootTarget", there are additional requirements and considerations. See the "Selecting Systemd-bootTarget" section, which follows, for more information.
"BeagleBoneTarget":
Choose "BeagleBoneTarget" if you are deploying
images and running tests on the BeagleBone
"Black" or original "White" hardware.
For information on how to use these tests, see the
comments at the top of the BeagleBoneTarget
meta-yocto-bsp/lib/oeqa/controllers/beaglebonetarget.py
file.
"EdgeRouterTarget":
Choose "EdgeRouterTarget" is you are deploying
images and running tests on the Ubiquiti Networks
EdgeRouter Lite.
For information on how to use these tests, see the
comments at the top of the EdgeRouterTarget
meta-yocto-bsp/lib/oeqa/controllers/edgeroutertarget.py
file.
"GrubTarget":
Choose the "supports deploying images and running
tests on any generic PC that boots using GRUB.
For information on how to use these tests, see the
comments at the top of the GrubTarget
meta-yocto-bsp/lib/oeqa/controllers/grubtarget.py
file.
"your-target
":
Create your own custom target if you want to run
tests when you are deploying images and running
tests on a custom machine within your BSP layer.
To do this, you need to add a Python unit that
defines the target class under
lib/oeqa/controllers/
within
your layer.
You must also provide an empty
__init__.py
.
For examples, see files in
meta-yocto-bsp/lib/oeqa/controllers/
.
If you did not set TEST_TARGET
to
"Systemd-bootTarget", then you do not need any information
in this section.
You can skip down to the
"Running Tests"
section.
If you did set TEST_TARGET
to
"Systemd-bootTarget", you also need to perform a one-time
setup of your master image by doing the following:
Set EFI_PROVIDER
:
Be sure that EFI_PROVIDER
is as follows:
EFI_PROVIDER = "systemd-boot"
Build the master image:
Build the core-image-testmaster
image.
The core-image-testmaster
recipe is provided as an example for a
"master" image and you can customize the image
recipe as you would any other recipe.
Here are the image recipe requirements:
Inherits
core-image
so that kernel modules are installed.
Installs normal linux utilities
not busybox ones (e.g.
bash
,
coreutils
,
tar
,
gzip
, and
kmod
).
Uses a custom Initial RAM Disk (initramfs) image with a custom installer. A normal image that you can install usually creates a single rootfs partition. This image uses another installer that creates a specific partition layout. Not all Board Support Packages (BSPs) can use an installer. For such cases, you need to manually create the following partition layout on the target:
First partition mounted
under /boot
,
labeled "boot".
The main rootfs
partition where this image gets
installed, which is mounted under
/
.
Another partition labeled "testrootfs" where test images get deployed.
Install image: Install the image that you just built on the target system.
The final thing you need to do when setting
TEST_TARGET
to "Systemd-bootTarget" is
to set up the test image:
Set up your local.conf
file:
Make sure you have the following statements in
your local.conf
file:
IMAGE_FSTYPES += "tar.gz" INHERIT += "testimage" TEST_TARGET = "Systemd-bootTarget" TEST_TARGET_IP = "192.168.2.3"
Build your test image: Use BitBake to build the image:
$ bitbake core-image-sato
For most hardware targets other than SimpleRemoteTarget, you can control power:
You can use
TEST_POWERCONTROL_CMD
together with
TEST_POWERCONTROL_EXTRA_ARGS
as a command that runs on the host and does power
cycling.
The test code passes one argument to that command:
off, on or cycle (off then on).
Here is an example that could appear in your
local.conf
file:
TEST_POWERCONTROL_CMD = "powercontrol.exp test 10.11.12.1 nuc1"
In this example, the expect script does the following:
ssh test@10.11.12.1 "pyctl nuc1 arg
"
It then runs a Python script that controls power
for a label called nuc1
.
TEST_POWERCONTROL_CMD
and
TEST_POWERCONTROL_EXTRA_ARGS
for your own setup.
The one requirement is that it accepts
"on", "off", and "cycle" as the last argument.
When no command is defined, it connects to the device over SSH and uses the classic reboot command to reboot the device. Classic reboot is fine as long as the machine actually reboots (i.e. the SSH test has not failed). It is useful for scenarios where you have a simple setup, typically with a single board, and where some manual interaction is okay from time to time.
If you have no hardware to automatically perform power
control but still wish to experiment with automated
hardware testing, you can use the dialog-power-control
script that shows a dialog prompting you to perform the
required power action.
This script requires either KDialog or Zenity to be
installed.
To use this script, set the
TEST_POWERCONTROL_CMD
variable as follows:
TEST_POWERCONTROL_CMD = "${COREBASE}/scripts/contrib/dialog-power-control"
For test target classes requiring a serial console
to interact with the bootloader (e.g. BeagleBoneTarget,
EdgeRouterTarget, and GrubTarget), you need to
specify a command to use to connect to the serial console
of the target machine by using the
TEST_SERIALCONTROL_CMD
variable and optionally the
TEST_SERIALCONTROL_EXTRA_ARGS
variable.
These cases could be a serial terminal program if the
machine is connected to a local serial port, or a
telnet
or
ssh
command connecting to a remote
console server.
Regardless of the case, the command simply needs to
connect to the serial console and forward that connection
to standard input and output as any normal terminal
program does.
For example, to use the picocom terminal program on
serial device /dev/ttyUSB0
at 115200bps, you would set the variable as follows:
TEST_SERIALCONTROL_CMD = "picocom /dev/ttyUSB0 -b 115200"
For local devices where the serial port device disappears
when the device reboots, an additional "serdevtry" wrapper
script is provided.
To use this wrapper, simply prefix the terminal command
with
${COREBASE}/scripts/contrib/serdevtry
:
TEST_SERIALCONTROL_CMD = "${COREBASE}/scripts/contrib/serdevtry picocom -b 115200 /dev/ttyUSB0"
You can start the tests automatically or manually:
Automatically running tests:
To run the tests automatically after the
OpenEmbedded build system successfully creates an image,
first set the
TEST_IMAGE
variable to "1" in your local.conf
file in the
Build Directory:
TEST_IMAGE = "1"
Next, build your image. If the image successfully builds, the tests will be run:
bitbake core-image-sato
Manually running tests:
To manually run the tests, first globally inherit the
testimage
class by editing your local.conf
file:
INHERIT += "testimage"
Next, use BitBake to run the tests:
bitbake -c testimage image
All test files reside in
meta/lib/oeqa/runtime
in the
Source Directory.
A test name maps directly to a Python module.
Each test module may contain a number of individual tests.
Tests are usually grouped together by the area
tested (e.g tests for systemd reside in
meta/lib/oeqa/runtime/systemd.py
).
You can add tests to any layer provided you place them in the
proper area and you extend
BBPATH
in the local.conf
file as normal.
Be sure that tests reside in
.
layer
/lib/oeqa/runtime
meta/lib/oeqa/runtime
.
You can change the set of tests run by appending or overriding
TEST_SUITES
variable in local.conf
.
Each name in TEST_SUITES
represents a
required test for the image.
Test modules named within TEST_SUITES
cannot be skipped even if a test is not suitable for an image
(e.g. running the RPM tests on an image without
rpm
).
Appending "auto" to TEST_SUITES
causes the
build system to try to run all tests that are suitable for the
image (i.e. each test module may elect to skip itself).
The order you list tests in TEST_SUITES
is important and influences test dependencies.
Consequently, tests that depend on other tests should be added
after the test on which they depend.
For example, since the ssh
test
depends on the
ping
test, "ssh" needs to come after
"ping" in the list.
The test class provides no re-ordering or dependency handling.
unittest
rules apply.
Here are some things to keep in mind when running tests:
The default tests for the image are defined as:
DEFAULT_TEST_SUITES_pn-image
= "ping ssh df connman syslog xorg scp vnc date rpm dnf dmesg"
Add your own test to the list of the by using the following:
TEST_SUITES_append = " mytest"
Run a specific list of tests as follows:
TEST_SUITES = "test1 test2 test3"
Remember, order is important. Be sure to place a test that is dependent on another test later in the order.
You can export tests so that they can run independently of
the build system.
Exporting tests is required if you want to be able to hand
the test execution off to a scheduler.
You can only export tests that are defined in
TEST_SUITES
.
If your image is already built, make sure the following are set
in your local.conf
file:
INHERIT +="testexport" TEST_TARGET_IP = "IP-address-for-the-test-target
" TEST_SERVER_IP = "IP-address-for-the-test-server
"
You can then export the tests with the following BitBake command form:
$ bitbake image
-c testexport
Exporting the tests places them in the
Build Directory in
tmp/testexport/
image
,
which is controlled by the
TEST_EXPORT_DIR
variable.
You can now run the tests outside of the build environment:
$ cd tmp/testexport/image
$ ./runexported.py testdata.json
Here is a complete example that shows IP addresses and uses
the core-image-sato
image:
INHERIT +="testexport" TEST_TARGET_IP = "192.168.7.2" TEST_SERVER_IP = "192.168.7.1"
Use BitBake to export the tests:
$ bitbake core-image-sato -c testexport
Run the tests outside of the build environment using the following:
$ cd tmp/testexport/core-image-sato $ ./runexported.py testdata.json
As mentioned previously, all new test files need to be in the
proper place for the build system to find them.
New tests for additional functionality outside of the core
should be added to the layer that adds the functionality, in
(as long as
layer
/lib/oeqa/runtimeBBPATH
is extended in the layer's
layer.conf
file as normal).
Just remember the following:
Filenames need to map directly to test (module) names.
Do not use module names that collide with existing core tests.
Minimally, an empty
__init__.py
file must exist
in the runtime directory.
To create a new test, start by copying an existing module
(e.g. syslog.py
or
gcc.py
are good ones to use).
Test modules can use code from
meta/lib/oeqa/utils
, which are helper
classes.
df.py
and
date.py
modules for examples.
You will notice that all test classes inherit
oeRuntimeTest
, which is found in
meta/lib/oetest.py
.
This base class offers some helper attributes, which are
described in the following sections:
Class methods are as follows:
hasPackage(pkg)
:
Returns "True" if pkg
is in the
installed package list of the image, which is based
on the manifest file that is generated during the
do_rootfs
task.
hasFeature(feature)
:
Returns "True" if the feature is in
IMAGE_FEATURES
or
DISTRO_FEATURES
.
Class attributes are as follows:
pscmd
:
Equals "ps -ef" if procps
is
installed in the image.
Otherwise, pscmd
equals
"ps" (busybox).
tc
:
The called test context, which gives access to the
following attributes:
d
:
The BitBake datastore, which allows you to
use stuff such as
oeRuntimeTest.tc.d.getVar("VIRTUAL-RUNTIME_init_manager")
.
testslist
and testsrequired
:
Used internally.
The tests do not need these.
filesdir
:
The absolute path to
meta/lib/oeqa/runtime/files
,
which contains helper files for tests meant
for copying on the target such as small
files written in C for compilation.
target
:
The target controller object used to deploy
and start an image on a particular target
(e.g. QemuTarget, SimpleRemote, and
Systemd-bootTarget).
Tests usually use the following:
ip
:
The target's IP address.
server_ip
:
The host's IP address, which is
usually used by the DNF test
suite.
run(cmd, timeout=None)
:
The single, most used method.
This command is a wrapper for:
ssh root@host "cmd"
.
The command returns a tuple:
(status, output), which are what
their names imply - the return code
of "cmd" and whatever output
it produces.
The optional timeout argument
represents the number of seconds the
test should wait for "cmd" to
return.
If the argument is "None", the
test uses the default instance's
timeout period, which is 300
seconds.
If the argument is "0", the test
runs until the command returns.
copy_to(localpath, remotepath)
:
scp localpath root@ip:remotepath
.
copy_from(remotepath, localpath)
:
scp root@host:remotepath localpath
.
A single instance attribute exists, which is
target
.
The target
instance attribute is
identical to the class attribute of the same name, which
is described in the previous section.
This attribute exists as both an instance and class
attribute so tests can use
self.target.run(cmd)
in instance
methods instead of
oeRuntimeTest.tc.target.run(cmd)
.
When a test requires a package built by BitBake, it is possible
to install that package.
Installing the package does not require a package manager be
installed in the device under test (DUT).
It does, however, require an SSH connection and the target must
be using the sshcontrol
class.
scp
to copy files
from the host to the target, which causes permissions and
special attributes to be lost.
A JSON file is used to define the packages needed by a test.
This file must be in the same path as the file used to define
the tests.
Furthermore, the filename must map directly to the test
module name with a .json
extension.
The JSON file must include an object with the test name as keys of an object or an array. This object (or array of objects) uses the following data:
"pkg" - A mandatory string that is the name of the package to be installed.
"rm" - An optional boolean, which defaults to "false", that specifies to remove the package after the test.
"extract" - An optional boolean, which defaults to "false", that specifies if the package must be extracted from the package format. When set to "true", the package is not automatically installed into the DUT.
Following is an example JSON file that handles test "foo" installing package "bar" and test "foobar" installing packages "foo" and "bar". Once the test is complete, the packages are removed from the DUT.
{ "foo": { "pkg": "bar" }, "foobar": [ { "pkg": "foo", "rm": true }, { "pkg": "bar", "rm": true } ] }
GDB allows you to examine running programs, which in turn helps you to understand and fix problems. It also allows you to perform post-mortem style analysis of program crashes. GDB is available as a package within the Yocto Project and is installed in SDK images by default. See the "Images" chapter in the Yocto Project Reference Manual for a description of these images. You can find information on GDB at http://sourceware.org/gdb/.
-dbg
) packages
for the applications you are going to debug.
Doing so makes extra debug symbols available that give you more
meaningful output.
Sometimes, due to memory or disk space constraints, it is not possible to use GDB directly on the remote target to debug applications. These constraints arise because GDB needs to load the debugging information and the binaries of the process being debugged. Additionally, GDB needs to perform many computations to locate information such as function names, variable names and values, stack traces and so forth - even before starting the debugging process. These extra computations place more load on the target system and can alter the characteristics of the program being debugged.
To help get past the previously mentioned constraints, you can use gdbserver, which runs on the remote target and does not load any debugging information from the debugged process. Instead, a GDB instance processes the debugging information that is run on a remote computer - the host GDB. The host GDB then sends control commands to gdbserver to make it stop or start the debugged program, as well as read or write memory regions of that debugged program. All the debugging information loaded and processed as well as all the heavy debugging is done by the host GDB. Offloading these processes gives the gdbserver running on the target a chance to remain small and fast.
Because the host GDB is responsible for loading the debugging information and for doing the necessary processing to make actual debugging happen, you have to make sure the host can access the unstripped binaries complete with their debugging information and also be sure the target is compiled with no optimizations. The host GDB must also have local access to all the libraries used by the debugged program. Because gdbserver does not need any local debugging information, the binaries on the remote target can remain stripped. However, the binaries must also be compiled without optimization so they match the host's binaries.
To remain consistent with GDB documentation and terminology, the binary being debugged on the remote target machine is referred to as the "inferior" binary. For documentation on GDB see the GDB site.
The following steps show you how to debug using the GNU project debugger.
Configure your build system to construct the companion debug filesystem:
In your local.conf
file, set
the following:
IMAGE_GEN_DEBUGFS = "1" IMAGE_FSTYPES_DEBUGFS = "tar.bz2"
These options cause the OpenEmbedded build system
to generate a special companion filesystem fragment,
which contains the matching source and debug symbols to
your deployable filesystem.
The build system does this by looking at what is in the
deployed filesystem, and pulling the corresponding
-dbg
packages.
The companion debug filesystem is not a complete filesystem, but only contains the debug fragments. This filesystem must be combined with the full filesystem for debugging. Subsequent steps in this procedure show how to combine the partial filesystem with the full filesystem.
Configure the system to include gdbserver in the target filesystem:
Make the following addition in either your
local.conf
file or in an image
recipe:
IMAGE_INSTALL_append = “ gdbserver"
The change makes sure the gdbserver
package is included.
Build the environment:
Use the following command to construct the image and the companion Debug Filesystem:
$ bitbake image
Build the cross GDB component and make it available for debugging. Build the SDK that matches the image. Building the SDK is best for a production build that can be used later for debugging, especially during long term maintenance:
$ bitbake -c populate_sdk image
Alternatively, you can build the minimal toolchain components that match the target. Doing so creates a smaller than typical SDK and only contains a minimal set of components with which to build simple test applications, as well as run the debugger:
$ bitbake meta-toolchain
A final method is to build Gdb itself within the build system:
$ bitbake gdb-cross-architecture
Doing so produces a temporary copy of
cross-gdb
you can use for
debugging during development.
While this is the quickest approach, the two previous
methods in this step are better when considering
long-term maintenance strategies.
bitbake gdb-cross
, the
OpenEmbedded build system suggests the actual
image (e.g. gdb-cross-i586
).
The suggestion is usually the actual name you want
to use.
Set up the debugfs
Run the following commands to set up the
debugfs
:
$ mkdir debugfs $ cd debugfs $ tar xvfjbuild-dir
/tmp-glibc/deploy/images/machine
/image
.rootfs.tar.bz2 $ tar xvfjbuild-dir
/tmp-glibc/deploy/images/machine
/image
-dbg.rootfs.tar.bz2
Set up GDB
Install the SDK (if you built one) and then
source the correct environment file.
Sourcing the environment file puts the SDK in your
PATH
environment variable.
If you are using the build system, Gdb is
located in
build-dir
/tmp/sysroots/host
/usr/bin/architecture
/architecture
-gdb
Boot the target:
For information on how to run QEMU, see the QEMU Documentation.
Debug a program:
Debugging a program involves running gdbserver
on the target and then running Gdb on the host.
The example in this step debugs
gzip
:
root@qemux86:~# gdbserver localhost:1234 /bin/gzip —help
For additional gdbserver options, see the GDB Server Documentation.
After running gdbserver on the target, you need to run Gdb on the host and configure it and connect to the target. Use these commands:
$ cddirectory-holding-the-debugfs-directory
$arch
-gdb (gdb) set sysroot debugfs (gdb) set substitute-path /usr/src/debug debugfs/usr/src/debug (gdb) target remoteIP-of-target
:1234
At this point, everything should automatically load (i.e. matching binaries, symbols and headers).
set
commands in the
previous example can be placed into the users
~/.gdbinit
file.
Upon starting, Gdb automatically runs whatever
commands are in that file.
Deploying without a full image rebuild:
In many cases, during development you want a quick method to deploy a new binary to the target and debug it, without waiting for a full image build.
One approach to solving this situation is to
just build the component you want to debug.
Once you have built the component, copy the
executable directly to both the target and the
host debugfs
.
If the binary is processed through the debug
splitting in OpenEmbedded, you should also
copy the debug items (i.e. .debug
contents and corresponding
/usr/src/debug
files)
from the work directory.
Here is an example:
$ bitbake bash $ bitbake -c devshell bash $ cd .. $ scp packages-split/bash/bin/bashtarget
:/bin/bash $ cp -a packages-split/bash-dbg/*path
/debugfs
The previous section addressed using GDB remotely for debugging purposes, which is the most usual case due to the inherent hardware limitations on many embedded devices. However, debugging in the target hardware itself is also possible with more powerful devices. This section describes what you need to do in order to support using GDB to debug on the target hardware.
To support this kind of debugging, you need do the following:
Ensure that GDB is on the target.
You can do this by adding "gdb" to
IMAGE_INSTALL
:
IMAGE_INSTALL_append = " gdb"
Alternatively, you can add "tools-debug" to
IMAGE_FEATURES
:
IMAGE_FEATURES_append = " tools-debug"
Ensure that debug symbols are present.
You can make sure these symbols are present by installing
-dbg
:
IMAGE_INSTALL_append = " packagename
-dbg"
Alternatively, you can do the following to include all the debug symbols:
IMAGE_FEATURES_append = " dbg-pkgs"
local.conf
file, you will reduce
optimization from
FULL_OPTIMIZATION
of "-O2" to
DEBUG_OPTIMIZATION
of "-O -fno-omit-frame-pointer":
DEBUG_BUILD = "1"Consider that this will reduce the application's performance and is recommended only for debugging purposes.
A parallel make
race occurs when the build
consists of several parts that are run simultaneously and
a situation occurs when the output or result of one
part is not ready for use with a different part of the build that
depends on that output.
Parallel make races are annoying and can sometimes be difficult
to reproduce and fix.
However, some simple tips and tricks exist that can help
you debug and fix them.
This section presents a real-world example of an error encountered
on the Yocto Project autobuilder and the process used to fix it.
make
race
condition, you can work around it by clearing either the
PARALLEL_MAKE
or
PARALLEL_MAKEINST
variables.
For this example, assume that you are building an image that depends on the "neard" package. And, during the build, BitBake runs into problems and creates the following output.
If you examine the output or the log file, you see the
failure during make
:
| DEBUG: SITE files ['endian-little', 'bit-32', 'ix86-common', 'common-linux', 'common-glibc', 'i586-linux', 'common'] | DEBUG: Executing shell function do_compile | NOTE: make -j 16 | make --no-print-directory all-am | /bin/mkdir -p include/near | /bin/mkdir -p include/near | /bin/mkdir -p include/near | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/types.h include/near/types.h | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/log.h include/near/log.h | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/plugin.h include/near/plugin.h | /bin/mkdir -p include/near | /bin/mkdir -p include/near | /bin/mkdir -p include/near | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/tag.h include/near/tag.h | /bin/mkdir -p include/near | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/adapter.h include/near/adapter.h | /bin/mkdir -p include/near | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/ndef.h include/near/ndef.h | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/tlv.h include/near/tlv.h | /bin/mkdir -p include/near | /bin/mkdir -p include/near | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/setting.h include/near/setting.h | /bin/mkdir -p include/near | /bin/mkdir -p include/near | /bin/mkdir -p include/near | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/device.h include/near/device.h | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/nfc_copy.h include/near/nfc_copy.h | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/snep.h include/near/snep.h | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/version.h include/near/version.h | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ 0.14-r0/neard-0.14/include/dbus.h include/near/dbus.h | ./src/genbuiltin nfctype1 nfctype2 nfctype3 nfctype4 p2p > src/builtin.h | i586-poky-linux-gcc -m32 -march=i586 --sysroot=/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/ build/build/tmp/sysroots/qemux86 -DHAVE_CONFIG_H -I. -I./include -I./src -I./gdbus -I/home/pokybuild/ yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/include/glib-2.0 -I/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/ lib/glib-2.0/include -I/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/ tmp/sysroots/qemux86/usr/include/dbus-1.0 -I/home/pokybuild/yocto-autobuilder/yocto-slave/ nightly-x86/build/build/tmp/sysroots/qemux86/usr/lib/dbus-1.0/include -I/home/pokybuild/yocto-autobuilder/ yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/include/libnl3 -DNEAR_PLUGIN_BUILTIN -DPLUGINDIR=\""/usr/lib/near/plugins"\" -DCONFIGDIR=\""/etc/neard\"" -O2 -pipe -g -feliminate-unused-debug-types -c -o tools/snep-send.o tools/snep-send.c | In file included from tools/snep-send.c:16:0: | tools/../src/near.h:41:23: fatal error: near/dbus.h: No such file or directory | #include <near/dbus.h> | ^ | compilation terminated. | make[1]: *** [tools/snep-send.o] Error 1 | make[1]: *** Waiting for unfinished jobs.... | make: *** [all] Error 2 | ERROR: oe_runmake failed
Because race conditions are intermittent, they do not manifest themselves every time you do the build. In fact, most times the build will complete without problems even though the potential race condition exists. Thus, once the error surfaces, you need a way to reproduce it.
In this example, compiling the "neard" package is causing the
problem.
So the first thing to do is build "neard" locally.
Before you start the build, set the
PARALLEL_MAKE
variable in your local.conf
file to
a high number (e.g. "-j 20").
Using a high value for PARALLEL_MAKE
increases the chances of the race condition showing up:
$ bitbake neard
Once the local build for "neard" completes, start a
devshell
build:
$ bitbake neard -c devshell
For information on how to use a
devshell
, see the
"Using a Development Shell"
section.
In the devshell
, do the following:
$ make clean $ make tools/snep-send.o
The devshell
commands cause the failure
to clearly be visible.
In this case, a missing dependency exists for the "neard"
Makefile target.
Here is some abbreviated, sample output with the
missing dependency clearly visible at the end:
i586-poky-linux-gcc -m32 -march=i586 --sysroot=/home/scott-lenovo/...... . . . tools/snep-send.c In file included from tools/snep-send.c:16:0: tools/../src/near.h:41:23: fatal error: near/dbus.h: No such file or directory #include <near/dbus.h> ^ compilation terminated. make: *** [tools/snep-send.o] Error 1 $
Because there is a missing dependency for the Makefile
target, you need to patch the
Makefile.am
file, which is generated
from Makefile.in
.
You can use Quilt to create the patch:
$ quilt new parallelmake.patch Patch patches/parallelmake.patch is now on top $ quilt add Makefile.am File Makefile.am added to patch patches/parallelmake.patch
For more information on using Quilt, see the "Using Quilt in Your Workflow" section.
At this point you need to make the edits to
Makefile.am
to add the missing
dependency.
For our example, you have to add the following line
to the file:
tools/snep-send.$(OBJEXT): include/near/dbus.h
Once you have edited the file, use the
refresh
command to create the patch:
$ quilt refresh Refreshed patch patches/parallelmake.patch
Once the patch file exists, you need to add it back to the
originating recipe folder.
Here is an example assuming a top-level
Source Directory
named poky
:
$ cp patches/parallelmake.patch poky/meta/recipes-connectivity/neard/neard
The final thing you need to do to implement the fix in the
build is to update the "neard" recipe (i.e.
neard-0.14.bb
) so that the
SRC_URI
statement includes the patch file.
The recipe file is in the folder above the patch.
Here is what the edited SRC_URI
statement would look like:
SRC_URI = "${KERNELORG_MIRROR}/linux/network/nfc/${BPN}-${PV}.tar.xz \ file://neard.in \ file://neard.service.in \ file://parallelmake.patch \ "
With the patch complete and moved to the correct folder and
the SRC_URI
statement updated, you can
exit the devshell
:
$ exit
With everything in place, you can get back to trying the build again locally:
$ bitbake neard
This build should succeed.
Now you can open up a devshell
again
and repeat the clean and make operations as follows:
$ bitbake neard -c devshell $ make clean $ make tools/snep-send.o
The build should work without issue.
As with all solved problems, if they originated upstream, you need to submit the fix for the recipe in OE-Core and upstream so that the problem is taken care of at its source. See the "How to Submit a Change" section for more information.
One of the concerns for a development organization using open source software is how to maintain compliance with various open source licensing during the lifecycle of the product. While this section does not provide legal advice or comprehensively cover all scenarios, it does present methods that you can use to assist you in meeting the compliance requirements during a software release.
With hundreds of different open source licenses that the Yocto Project tracks, it is difficult to know the requirements of each and every license. However, the requirements of the major FLOSS licenses can begin to be covered by assuming that three main areas of concern exist:
Source code must be provided.
License text for the software must be provided.
Compilation scripts and modifications to the source code must be provided.
There are other requirements beyond the scope of these three and the methods described in this section (e.g. the mechanism through which source code is distributed).
As different organizations have different methods of complying with open source licensing, this section is not meant to imply that there is only one single way to meet your compliance obligations, but rather to describe one method of achieving compliance. The remainder of this section describes methods supported to meet the previously mentioned three requirements. Once you take steps to meet these requirements, and prior to releasing images, sources, and the build system, you should audit all artifacts to ensure completeness.
${DEPLOY_DIR}/licenses/image_name-datestamp
to assist with any audits.
Compliance activities should begin before you generate the final image. The first thing you should look at is the requirement that tops the list for most compliance groups - providing the source. The Yocto Project has a few ways of meeting this requirement.
One of the easiest ways to meet this requirement is
to provide the entire
DL_DIR
used by the build.
This method, however, has a few issues.
The most obvious is the size of the directory since it includes
all sources used in the build and not just the source used in
the released image.
It will include toolchain source, and other artifacts, which
you would not generally release.
However, the more serious issue for most companies is accidental
release of proprietary software.
The Yocto Project provides an
archiver
class to help avoid some of these concerns.
Before you employ DL_DIR
or the
archiver
class, you need to decide how
you choose to provide source.
The source archiver
class can generate
tarballs and SRPMs and can create them with various levels of
compliance in mind.
One way of doing this (but certainly not the only way) is to
release just the source as a tarball.
You can do this by adding the following to the
local.conf
file found in the
Build Directory:
INHERIT += "archiver" ARCHIVER_MODE[src] = "original"
During the creation of your image, the source from all
recipes that deploy packages to the image is placed within
subdirectories of
DEPLOY_DIR/sources
based on the
LICENSE
for each recipe.
Releasing the entire directory enables you to comply with
requirements concerning providing the unmodified source.
It is important to note that the size of the directory can
get large.
A way to help mitigate the size issue is to only release tarballs for licenses that require the release of source. Let us assume you are only concerned with GPL code as identified by running the following script:
# Script to archive a subset of packages matching specific license(s) # Source and license files are copied into sub folders of package folder # Must be run from build folder #!/bin/bash src_release_dir="source-release" mkdir -p $src_release_dir for a in tmp/deploy/sources/*; do for d in $a/*; do # Get package name from path p=`basename $d` p=${p%-*} p=${p%-*} # Only archive GPL packages (update *GPL* regex for your license check) numfiles=`ls tmp/deploy/licenses/$p/*GPL* 2> /dev/null | wc -l` if [ $numfiles -gt 1 ]; then echo Archiving $p mkdir -p $src_release_dir/$p/source cp $d/* $src_release_dir/$p/source 2> /dev/null mkdir -p $src_release_dir/$p/license cp tmp/deploy/licenses/$p/* $src_release_dir/$p/license 2> /dev/null fi done done
At this point, you could create a tarball from the
gpl_source_release
directory and
provide that to the end user.
This method would be a step toward achieving compliance
with section 3a of GPLv2 and with section 6 of GPLv3.
One requirement that is often overlooked is inclusion
of license text.
This requirement also needs to be dealt with prior to
generating the final image.
Some licenses require the license text to accompany
the binary.
You can achieve this by adding the following to your
local.conf
file:
COPY_LIC_MANIFEST = "1" COPY_LIC_DIRS = "1" LICENSE_CREATE_PACKAGE = "1"
Adding these statements to the configuration file ensures that the licenses collected during package generation are included on your image.
Setting all three variables to "1" results in the
image having two copies of the same license file.
One copy resides in
/usr/share/common-licenses
and
the other resides in
/usr/share/license
.
The reason for this behavior is because
COPY_LIC_DIRS
and
COPY_LIC_MANIFEST
add a copy of the license when the image is built but do
not offer a path for adding licenses for newly installed
packages to an image.
LICENSE_CREATE_PACKAGE
adds a separate package and an upgrade path for adding
licenses to an image.
As the source archiver
class has already
archived the original
unmodified source that contains the license files,
you would have already met the requirements for inclusion
of the license information with source as defined by the GPL
and other open source licenses.
At this point, we have addressed all we need to prior to generating the image. The next two requirements are addressed during the final packaging of the release.
By releasing the version of the OpenEmbedded build system and the layers used during the build, you will be providing both compilation scripts and the source code modifications in one step.
If the deployment team has a BSP layer and a distro layer, and those those layers are used to patch, compile, package, or modify (in any way) any open source software included in your released images, you might be required to release those layers under section 3 of GPLv2 or section 1 of GPLv3. One way of doing that is with a clean checkout of the version of the Yocto Project and layers used during your build. Here is an example:
# We built using the pyro branch of the poky repo $ git clone -b pyro git://git.yoctoproject.org/poky $ cd poky # We built using the release_branch for our layers $ git clone -b release_branch git://git.mycompany.com/meta-my-bsp-layer $ git clone -b release_branch git://git.mycompany.com/meta-my-software-layer # clean up the .git repos $ find . -name ".git" -type d -exec rm -rf {} \;
One thing a development organization might want to consider
for end-user convenience is to modify
meta-poky/conf/bblayers.conf.sample
to
ensure that when the end user utilizes the released build
system to build an image, the development organization's
layers are included in the bblayers.conf
file automatically:
# LAYER_CONF_VERSION is increased each time build/conf/bblayers.conf # changes incompatibly LCONF_VERSION = "6" BBPATH = "${TOPDIR}" BBFILES ?= "" BBLAYERS ?= " \ ##OEROOT##/meta \ ##OEROOT##/meta-poky \ ##OEROOT##/meta-yocto-bsp \ ##OEROOT##/meta-mylayer \ "
Creating and providing an archive of the Metadata layers (recipes, configuration files, and so forth) enables you to meet your requirements to include the scripts to control compilation as well as any modifications to the original source.
The error reporting tool allows you to
submit errors encountered during builds to a central database.
Outside of the build environment, you can use a web interface to
browse errors, view statistics, and query for errors.
The tool works using a client-server system where the client
portion is integrated with the installed Yocto Project
Source Directory
(e.g. poky
).
The server receives the information collected and saves it in a
database.
A live instance of the error reporting server exists at http://errors.yoctoproject.org. This server exists so that when you want to get help with build failures, you can submit all of the information on the failure easily and then point to the URL in your bug report or send an email to the mailing list.
By default, the error reporting tool is disabled.
You can enable it by inheriting the
report-error
class by adding the following statement to the end of
your local.conf
file in your
Build Directory.
INHERIT += "report-error"
By default, the error reporting feature stores information in
${
LOG_DIR
}/error-report
.
However, you can specify a directory to use by adding the following
to your local.conf
file:
ERR_REPORT_DIR = "path"
Enabling error reporting causes the build process to collect the errors and store them in a file as previously described. When the build system encounters an error, it includes a command as part of the console output. You can run the command to send the error file to the server. For example, the following command sends the errors to an upstream server:
$ send-error-report /home/brandusa/project/poky/build/tmp/log/error-report/error_report_201403141617.txt
In the previous example, the errors are sent to a public database available at http://errors.yoctoproject.org, which is used by the entire community. If you specify a particular server, you can send the errors to a different database. Use the following command for more information on available options:
$ send-error-report --help
When sending the error file, you are prompted to review the data being sent as well as to provide a name and optional email address. Once you satisfy these prompts, the command returns a link from the server that corresponds to your entry in the database. For example, here is a typical link:
http://errors.yoctoproject.org/Errors/Details/9522/
Following the link takes you to a web interface where you can browse, query the errors, and view statistics.
To disable the error reporting feature, simply remove or comment
out the following statement from the end of your
local.conf
file in your
Build Directory.
INHERIT += "report-error"
If you want to set up your own error reporting server, you can obtain the code from the Git repository at http://git.yoctoproject.org/cgit/cgit.cgi/error-report-web/. Instructions on how to set it up are in the README document.
Quick EMUlator (QEMU) is an Open Source project the Yocto Project uses as part of its development "tool set". As such, the information in this chapter is limited to the Yocto Project integration of QEMU and not QEMU in general. For official information and documentation on QEMU, see the following references:
QEMU Website: The official website for the QEMU Open Source project.
Documentation: The QEMU user manual.
This chapter provides an overview of the Yocto Project's integration of QEMU, a description of how you use QEMU and its various options, running under a Network File System (NFS) server, and a few tips and tricks you might find helpful when using QEMU.
Within the context of the Yocto Project, QEMU is an emulator and virtualization machine that allows you to run a complete image you have built using the Yocto Project as just another task on your build system. QEMU is useful for running and testing images and applications on supported Yocto Project architectures without having actual hardware. Among other things, the Yocto Project uses QEMU to run automated Quality Assurance (QA) tests on final images shipped with each release.
QEMU is made available with the Yocto Project a number of ways. One method is to install a Software Development Kit (SDK). For more information on how to make sure you have QEMU available, see the Yocto Project Software Development Kit (SDK) Developer's Guide.
Running QEMU involves having your build environment set up, having the
right artifacts available, and understanding how to use the many
options that are available to you when you start QEMU using the
runqemu
command.
You run QEMU in the same environment from which you run BitBake.
This means you need to source a build environment script (i.e.
oe-init-build-env
or
oe-init-build-env-memres
).
runqemu
Command¶
The basic runqemu
command syntax is as
follows:
$ runqemu [option
] [...]
Based on what you provide on the command line,
runqemu
does a good job of figuring out what
you are trying to do.
For example, by default, QEMU looks for the most recently built
image according to the timestamp when it needs to look for an
image.
Minimally, through the use of options, you must provide either
a machine name, a virtual machine image
(*.vmdk
), or a kernel image
(*.bin
).
Following is a description of runqemu
options you can provide on the command line:
runqemu
provides appropriate error
messaging to help you correct the problem.
QEMUARCH
:
The QEMU machine architecture, which must be "qemux86",
"qemux86_64", "qemuarm", "qemumips", "qemumipsel",
“qemumips64", "qemush4", "qemuppc", "qemumicroblaze",
or "qemuzynq".
:
The virtual machine image, which must be a
VM
.vmdk
file.
Use this option when you want to boot a
.vmdk
image.
The image filename you provide must contain one of the
following strings: "qemux86-64", "qemux86", "qemuarm",
"qemumips64", "qemumips", "qemuppc", or "qemush4".
ROOTFS
:
A root filesystem that has one of the following
filetype extensions: "ext2", "ext3", "ext4", "jffs2",
"nfs", or "btrfs".
If the filename you provide for this option uses “nfs”, it
must provide an explicit root filesystem path.
KERNEL
:
A kernel image, which is a .bin
file.
When you provide a .bin
file,
runqemu
detects it and assumes the
file is a kernel image.
MACHINE
:
The architecture of the QEMU machine, which must be one
of the following: "qemux86",
"qemux86-64", "qemuarm", "qemumips", "qemumipsel",
“qemumips64", "qemush4", "qemuppc", "qemumicroblaze",
or "qemuzynq".
The MACHINE
and
QEMUARCH
options are basically
identical.
If you do not provide a MACHINE
option, runqemu
tries to determine
it based on other options.
ramfs
:
Indicates you are booting an initial RAM disk (initramfs)
image, which means the FSTYPE
is
cpio.gz
.
iso
:
Indicates you are booting an ISO image, which means the
FSTYPE
is
.iso
.
nographic
:
Disables the video console, which sets the console to
"ttys0".
serial
:
Enables a serial console on
/dev/ttyS0
.
biosdir
:
Establishes a custom directory for BIOS, VGA BIOS and
keymaps.
biosfilename
:
Establishes a custom BIOS name.
qemuparams=\"
:
Specifies custom QEMU parameters.
Use this option to pass options other than the simple
"kvm" and "serial" options.
xyz
\"
bootparams=\"
:
Specifies custom boot parameters for the kernel.
xyz
\"
audio
:
Enables audio in QEMU.
The MACHINE
option must be
either "qemux86" or "qemux86-64" in order for audio to be
enabled.
Additionally, the snd_intel8x0
or snd_ens1370
driver must be
installed in linux guest.
slirp
:
Enables "slirp" networking, which is a different way
of networking that does not need root access
but also is not as easy to use or comprehensive
as the default.
kvm
:
Enables KVM when running "qemux86" or "qemux86-64"
QEMU architectures.
For KVM to work, all the following conditions must be met:
Your MACHINE
must be either
qemux86" or "qemux86-64".
Your build host has to have the KVM modules
installed, which are
/dev/kvm
.
The build host /dev/kvm
directory has to be both writable and readable.
kvm-vhost
:
Enables KVM with VHOST support when running "qemux86" or "qemux86-64"
QEMU architectures.
For KVM with VHOST to work, the following conditions must
be met:
kvm option conditions must be met.
Your build host has to have virtio net device, which
are /dev/vhost-net
.
The build host /dev/vhost-net
directory has to be either readable or writable
and “slirp-enabled”.
publicvnc
:
Enables a VNC server open to all hosts.
For further understanding regarding option use with
runqemu
, consider some examples.
This example starts QEMU with
MACHINE
set to "qemux86".
Assuming a standard
Build Directory,
runqemu
automatically finds the
bzImage-qemux86.bin
image file and
the
core-image-minimal-qemux86-20140707074611.rootfs.ext3
(assuming the current build created a
core-image-minimal
image).
$ runqemu qemux86
This example produces the exact same results as the previous example. This command, however, specifically provides the image and root filesystem type.
$ runqemu qemux86 core-image-minimal ext3
This example specifies to boot an initial RAM disk image
and to enable audio in QEMU.
For this case, runqemu
set the
internal variable FSTYPE
to
"cpio.gz".
Also, for audio to be enabled, an appropriate driver must
be installed (see the previous description for the
audio
option for more information).
$ runqemu qemux86 ramfs audio
This example does not provide enough information for
QEMU to launch.
While the command does provide a root filesystem type, it
must also minimally provide a
MACHINE
,
KERNEL
, or
VM
option.
$ runqemu ext3
This example specifies to boot a virtual machine image
(.vmdk
file).
From the .vmdk
,
runqemu
determines the QEMU
architecture (MACHINE
) to be
"qemux86" and the root filesystem type to be "vmdk".
$ runqemu /home/scott-lenovo/vm/core-image-minimal-qemux86.vmdk
One method for running QEMU is to run it on an NFS server. This is useful when you need to access the same file system from both the build and the emulated system at the same time. It is also worth noting that the system does not need root privileges to run. It uses a user space NFS server to avoid that. This section describes how to set up for running QEMU using an NFS server and then how you can start and stop the server.
Once you are able to run QEMU in your environment, you can use the
runqemu-extract-sdk
script, which is located
in the scripts
directory along with
runqemu
script.
The runqemu-extract-sdk
takes a root
file system tarball and extracts it into a location that you
specify.
Then, when you run runqemu
, you can specify
the location that has the file system to pass it to QEMU.
Here is an example that takes a file system and extracts it to
a directory named test-nfs
:
runqemu-extract-sdk ./tmp/deploy/images/qemux86/core-image-sato-qemux86.tar.bz2 test-nfs
Once you have extracted the file system, you can run
runqemu
normally with the additional
location of the file system.
You can then also make changes to the files within
./test-nfs
and see those changes appear in the
image in real time.
Here is an example using the qemux86
image:
runqemu qemux86 ./test-nfs
You can manually start and stop the NFS share using these commands:
start
:
Starts the NFS share:
runqemu-export-rootfs start file-system-location
stop
:
Stops the NFS share:
runqemu-export-rootfs stop file-system-location
restart
:
Restarts the NFS share:
runqemu-export-rootfs restart file-system-location
The following list describes things you can do to make running QEMU in the context of the Yocto Project a better experience:
Switching Between Consoles:
When booting or running QEMU, you can switch between
supported consoles by using
Ctrl+Alt+number
.
For example, Ctrl+Alt+3 switches you to the serial console as
long as that console is enabled.
Being able to switch consoles is helpful, for example, if the
main QEMU console breaks for some reason.
Removing the Splash Screen: You can remove the splash screen when QEMU is booting by using Alt+left. Removing the splash screen allows you to see what is happening in the background.
Disabling the Cursor Grab: The default QEMU integration captures the cursor within the main window. It does this since standard mouse devices only provide relative input and not absolute coordinates. You then have to break out of the grab using the "Ctrl+Alt" key combination. However, the Yocto Project's integration of QEMU enables the wacom USB touch pad driver by default to allow input of absolute coordinates. This default means that the mouse can enter and leave the main window without the grab taking effect leading to a better user experience.
Welcome to the Yocto Project Software Development Kit (SDK) Developer's Guide. This manual provides information that explains how to use both the Yocto Project extensible and standard SDKs to develop applications and images. Additionally, the manual also provides information on how to use the popular Eclipse™ IDE as part of your application development workflow within the SDK environment.
All SDKs consist of the following:
Cross-Development Toolchain: This toolchain contains a compiler, debugger, and various miscellaneous tools.
Libraries, Headers, and Symbols: The libraries, headers, and symbols are specific to the image (i.e. they match the image).
Environment Setup Script:
This *.sh
file, once run, sets up the
cross-development environment by defining variables and
preparing for SDK use.
Additionally an extensible SDK has tools that allow you to easily add new applications and libraries to an image, modify the source of an existing component, test changes on the target hardware, and easily integrate an application into the OpenEmbedded build system.
You can use an SDK to independently develop and test code
that is destined to run on some target machine.
SDKs are completely self-contained.
The binaries are linked against their own copy of
libc
, which results in no dependencies
on the target system.
To achieve this, the pointer to the dynamic loader is
configured at install time since that path cannot be dynamically
altered.
This is the reason for a wrapper around the
populate_sdk
and
populate_sdk_ext
archives.
Another feature for the SDKs is that only one set of cross-compiler
toolchain binaries are produced for any given architecture.
This feature takes advantage of the fact that the target hardware can
be passed to gcc
as a set of compiler options.
Those options are set up by the environment script and contained in
variables such as
CC
and
LD
.
This reduces the space needed for the tools.
Understand, however, that a sysroot is still needed for every target
since those binaries are target-specific.
The SDK development environment consists of the following:
The self-contained SDK, which is an
architecture-specific cross-toolchain and
matching sysroots (target and native) all built by the
OpenEmbedded build system (e.g. the SDK).
The toolchain and sysroots are based on a
Metadata
configuration and extensions,
which allows you to cross-develop on the host machine for the
target hardware.
Additionally, the extensible SDK contains the
devtool
functionality.
The Quick EMUlator (QEMU), which lets you simulate target hardware. QEMU is not literally part of the SDK. You must build and include this emulator separately. However, QEMU plays an important role in the development process that revolves around use of the SDK.
The Eclipse IDE Yocto Plug-in. This plug-in is available for you if you are an Eclipse user. In the same manner as QEMU, the plug-in is not literally part of the SDK but is rather available for use as part of the development process.
Various performance-related tools that can enhance your development experience.