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.
This version of the Yocto Project Development Tasks Manual is for the 2.5 release of the Yocto Project. To be sure you have the latest version of the manual for this release, go to the Yocto Project documentation page and select the manual from that site. Manuals from the site are more up-to-date than manuals derived from the Yocto Project released TAR files.
If you located this manual through a web search, the version of the manual might not be the one you want (e.g. the search might have returned a manual much older than the Yocto Project version with which you are working). You can see all Yocto Project major releases by visiting the Releases page. If you need a version of this manual for a different Yocto Project release, visit the Yocto Project documentation page and select the manual set by using the "ACTIVE RELEASES DOCUMENTATION" or "DOCUMENTS ARCHIVE" pull-down menus.
To report any inaccuracies or problems with this
manual, send an email to the Yocto Project
discussion group at
yocto@yoctoproject.com
or log into
the freenode #yocto
channel.
Revision History | |
---|---|
Revision 1.1 | 6 October 2011 |
The initial document released with the Yocto Project 1.1 Release. | |
Revision 1.2 | April 2012 |
Released with the Yocto Project 1.2 Release. | |
Revision 1.3 | October 2012 |
Released with the Yocto Project 1.3 Release. | |
Revision 1.4 | April 2013 |
Released with the Yocto Project 1.4 Release. | |
Revision 1.5 | October 2013 |
Released with the Yocto Project 1.5 Release. | |
Revision 1.5.1 | January 2014 |
Released with the Yocto Project 1.5.1 Release. | |
Revision 1.6 | April 2014 |
Released with the Yocto Project 1.6 Release. | |
Revision 1.7 | October 2014 |
Released with the Yocto Project 1.7 Release. | |
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 2.4 | October 2017 |
Released with the Yocto Project 2.4 Release. | |
Revision 2.5 | May 2018 |
Released with the Yocto Project 2.5 Release. |
Table of Contents
bitbake-layers
Scriptbitbake-layers
Scriptbmaptool
oe-pkgdata-util
Table of Contents
Welcome to the Yocto Project Development Tasks Manual! This manual provides relevant procedures necessary for developing in the Yocto Project environment (i.e. developing embedded Linux images and user-space applications that run on targeted devices). The manual groups related procedures into higher-level sections. Procedures can consist of high-level steps or low-level steps depending on the topic.
The following list describes what you can get from this manual:
Procedures that help you get going with the Yocto Project. For example, procedures that show you how to set up a build host and work with the Yocto Project source repositories.
Procedures that show you how to submit changes to the Yocto Project. Changes can be improvements, new features, or bug fixes.
Procedures related to "everyday" tasks you perform while developing images and applications using the Yocto Project. For example, procedures to create a layer, customize an image, write a new recipe, and so forth.
This manual will not give you the following:
Redundant Step-by-step Instructions: For example, the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual contains detailed instructions on how to install an SDK, which is used to develop applications for target hardware.
Reference or Conceptual 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 Not Specific to the Yocto Project: For example, exhaustive information on how to use the Source Control Manager Git is better covered with Internet searches and official Git Documentation than through the Yocto Project documentation.
Because this manual presents information for many different topics, supplemental information is recommended for full comprehension. For introductory information on the Yocto Project, see the Yocto Project Website. If you want to build an image with no knowledge of Yocto Project as a way of quickly testing it out, see the Yocto Project Quick Build document.
For a comprehensive list of links and other documentation, see the "Links and Related Documentation" section in the Yocto Project Reference Manual.
Table of Contents
This chapter provides procedures related to getting set up to use the Yocto Project. You can learn about creating a team environment that develops using the Yocto Project, how to set up a build host, how to locate Yocto Project source repositories, and how to create local Git repositories.
It might not be immediately clear how you can use the Yocto Project in a team development 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 you understand how to set up this type of environment, this section presents a procedure that gives you the information to learn how to get the results you want. The procedure is high-level and presents some of the project's most successful experiences, practices, solutions, and available technologies that work well. Keep in mind, the procedure here is a starting point. You can build off it and customize it to fit any particular working environment and set of practices.
Determine Who is Going to be Developing: You need to understand who is going to be doing anything related to the Yocto Project and what their roles would be. Making this determination is essential to completing the steps two and three, which are to get your equipment together and set up your development environment's hardware topology.
The following roles exist:
Application Development: These types of developers do application level work on top of an existing software stack.
Core System Development: These types of developers work on the contents of the operating system image itself.
Build Engineer: This type of developer manages Autobuilders and releases. Not all environments need a Build Engineer.
Test Engineer: This type of developer creates and manages automated tests needed to ensure all application and core system development meets desired quality standards.
Gather the Hardware: Based on the size and make-up of the team, get the hardware together. Any development, build, or test engineer should be using a system that is running a supported Linux distribution. Systems, in general, should be high performance (e.g. dual, six-core Xeons with 24 Gbytes of RAM and plenty of disk space). You can help ensure efficiency by having any machines used for testing or that run Autobuilders be as high performance as possible.
Understand the Hardware Topology of the Environment: Once you understand the hardware involved and the make-up of the team, you can understand the hardware topology of the development environment. You can get a visual idea of the machines and their roles across the development environment.
Use Git as Your Source Control Manager (SCM): 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.
Gitolite:
Information for gitolite
.
Interfaces, frontends, and tools: Documentation on how to create interfaces and frontends for Git.
Set up the Application Development Machines: As mentioned earlier, application developers are creating applications on top of existing software stacks. Following are some best practices for setting up machines that do application development:
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 Application Development and the Extensible Software Development Kit (eSDK)" manual.
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.
Set up the Core Development Machines: As mentioned earlier, these types of developers work on the contents of the operating system itself. Following are some best practices for setting up machines used for developing images:
Have the Yocto Project build system itself available on the developer workstations so developers can run their own builds and directly rebuild the software stack.
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).
Share layers amongst the developers of a particular project and contain the policy configuration that defines the project.
Set up an Autobuilder: Autobuilders are often the core of the development environment. 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.
Set up Test Machines: Use a small number of shared, high performance systems for testing purposes. Developers can use these systems for wider, more extensive testing while they continue to develop locally using their primary development system.
Document Policies and Change Flow:
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.
Development Environment Summary: Aside from the previous steps, some best practices exist within the Yocto Project development environment. Consider the following:
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 "Locating Yocto Project Source Files" 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 "Submitting a Change to the Yocto Project" 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 "Submitting a Change to the Yocto Project" section. For a description of the available mailing lists, see the "Mailing Lists" section in the Yocto Project Reference Manual.
This section provides procedures to set up your development host to use the Yocto Project. You can use the Yocto Project on a native Linux development host or you can use CROPS, which leverages Docker Containers, to prepare any Linux, Mac, or Windows development host.
Once your development host is set up to use the Yocto Project, further steps are necessary depending on what you want to accomplish. See the following references for information on how to prepare for Board Support Package (BSP) development, kernel development, and development using the Eclipse™ IDE:
BSP Development: See the "Preparing Your Build Host to Work With BSP Layers" section in the Yocto Project Board Support Package (BSP) Developer's Guide.
Kernel Development: See the "Preparing the Build Host to Work on the Kernel" section in the Yocto Project Linux Kernel Development Manual.
Eclipse Development: See the "Developing Applications Using Eclipse™" Chapter in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.
Follow these steps to prepare a native Linux machine as your Yocto Project development host:
Use a Supported Linux Distribution: 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.
Have Enough Free Memory: You should have at least 50 Gbytes of free disk space for building images.
Meet Minimal Version Requirements: 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 1.27 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.
Install Development Host Packages: Required development host packages vary depending on your build machine and what you want to do with the Yocto Project. Collectively, the number of required packages is large if you want to be able to cover all cases.
For lists of required packages for all scenarios, see the "Required Packages for the Host Development System" section in the Yocto Project Reference Manual.
Once you have completed the previous steps, you are ready to
continue using a given development path on your native Linux
machine.
If you are going to use BitBake, see the
"Cloning the poky
Repository"
section.
If you are going to use the Extensible SDK, see the
"Using the Extensible SDK"
Chapter in the Yocto Project Application Development and the
Extensible Software Development Kit (eSDK) manual.
If you want to work on the kernel, see the
Yocto Project Linux Kernel Development Manual.
If you are going to use Toaster, see the
"Setting Up and Using Toaster"
section in the Toaster User Manual.
With CROPS, which leverages Docker Containers, you can create a Yocto Project development environment that is operating system agnostic. You can set up a container in which you can develop using the Yocto Project on a Windows, Mac, or Linux machine.
Follow these general steps to prepare a Windows, Mac, or Linux machine as your Yocto Project development host:
Go to the Docker Installation Site: Docker is a software container platform that you need to install on the host development machine. To start the installation process, see the Docker Installation site.
Choose Your Docker Edition: Docker comes in several editions. For the Yocto Project, the stable community edition (i.e. "Docker CE Stable") is adequate. You can learn more about the Docker editions from the site.
Go to the Install Site for Your Platform: Click the link for the Docker edition associated with your development host machine's native software. For example, if your machine is running Microsoft Windows Version 10 and you want the Docker CE Stable edition, click that link under "Supported Platforms".
Understand What You Need: The install page has pre-requisites your machine must meet. Be sure you read through this page and make sure your machine meets the requirements to run Docker. If your machine does not meet the requirements, the page has instructions to handle exceptions. For example, to run Docker on Windows 10, you must have the pro version of the operating system. If you have the home version, you need to install the Docker Toolbox.
Another example is that a Windows machine needs to have Microsoft Hyper-V. If you have a legacy version of the the Microsoft operating system or for any other reason you do not have Microsoft Hyper-V, you would have to enter the BIOS and enable virtualization.
Install the Software: Once you have understood all the pre-requisites, you can download and install the appropriate software. Follow the instructions for your specific machine and the type of the software you need to install.
Optionally Orient Yourself With Docker: If you are unfamiliar with Docker and the container concept, you can learn more here - https://docs.docker.com/get-started/. You should be able to launch Docker or the Docker Toolbox and have a terminal shell on your development host.
Set Up the Containers to Use the Yocto Project: Go to https://github.com/crops/docker-win-mac-docs/wiki and follow the directions for your particular development host (i.e. Linux, Mac, or Windows).
Once you complete the setup instructions for your machine, you have the Poky, Extensible SDK, and Toaster containers available. You can click those links from the page and learn more about using each of those containers.
Once you have a container set up, everything is in place to
develop just as if you were running on a native Linux machine.
If you are going to use the Poky container, see the
"Cloning the poky
Repository"
section.
If you are going to use the Extensible SDK container, see the
"Using the Extensible SDK"
Chapter in the Yocto Project Application Development and the
Extensible Software Development Kit (eSDK) manual.
If you are going to use the Toaster container, see the
"Setting Up and Using Toaster"
section in the Toaster User Manual.
This section contains procedures related to locating Yocto Project files. You establish and use these local files to work on projects.
For concepts and introductory information about Git as it is used in the Yocto Project, see the "Git" section in the Yocto Project Overview and Concepts Manual.
For concepts on Yocto Project source repositories, see the "Yocto Project Source Repositories" section in the Yocto Project Overview and Concepts Manual."
Working from a copy of the upstream Yocto Project
Source Repositories
is the preferred method for obtaining and using a Yocto Project
release.
You can view the Yocto Project Source Repositories at
http://git.yoctoproject.org.
In particular, you can find the
poky
repository at
http://git.yoctoproject.org/cgit/cgit.cgi/poky/.
Use the following procedure to locate the latest upstream copy of
the poky
Git repository:
Access Repositories: Open a browser and go to http://git.yoctoproject.org to access the GUI-based interface into the Yocto Project source repositories.
Select the Repository:
Click on the repository in which you are interested (i.e.
poky
).
Find the URL Used to Clone the Repository:
At the bottom of the page, note the URL used to
clone
that repository (e.g.
http://git.yoctoproject.org/poky
).
poky
Repository"
section.
Yocto Project maintains an Index of Releases area that contains related files that contribute to the Yocto Project. Rather than Git repositories, these files are tarballs that represent snapshots in time of a given component.
Access the Index of Releases:
Open a browser and go to
http://downloads.yoctoproject.org/releases to access the
Index of Releases.
The list represents released components (e.g.
eclipse-plugin
,
sato
, and so on).
yocto
directory contains the
full array of released Poky tarballs.
The poky
directory in the
Index of Releases was historically used for very
early releases and exists now only for retroactive
completeness.
Select a Component:
Click on any released component in which you are interested
(e.g. yocto
).
Find the Tarball:
Drill down to find the associated tarball.
For example, click on yocto-2.5
to
view files associated with the Yocto Project 2.5
release (e.g. poky-sumo-20.0.0.tar.bz2
,
which is the released Poky tarball).
Download the Tarball: Click the tarball to download and save a snapshot of the given component.
The Yocto Project Website uses a "DOWNLOADS" page from which you can locate and download tarballs of any Yocto Project release. Rather than Git repositories, these files represent snapshot tarballs.
Go to the Yocto Project Website: Open The Yocto Project Website in your browser.
Get to the Downloads Area: Select the "DOWNLOADS" item from the pull-down "SOFTWARE" tab menu.
Select a Yocto Project Release: Use the menu next to "RELEASE" to display and choose a Yocto Project release (e.g. sumo, rocko, pyro, and so forth. For a "map" of Yocto Project releases to version numbers, see the Releases wiki page.
Download Tools or Board Support Packages (BSPs): From the "DOWNLOADS" page, you can download tools or BSPs as well. Just scroll down the page and look for what you need.
Yocto Project maintains an area for nightly builds that contains tarball releases at https://autobuilder.yocto.io//pub/nightly/. These builds include Yocto Project releases, SDK installation scripts, and experimental builds.
Should you ever want to access a nightly build of a particular Yocto Project component, use the following procedure:
Access the Nightly Builds: Open a browser and go to https://autobuilder.yocto.io//pub/nightly/ to access the Nightly Builds.
Select a Build: Click on any build by date in which you are interested.
Find the Tarball: Drill down to find the associated tarball.
Download the Tarball: Click the tarball to download and save a snapshot of the given component.
To use the Yocto Project, you need a release of the Yocto Project locally installed on your development system. The locally installed set of files is referred to as the Source Directory in the Yocto Project documentation.
You create your Source Directory by using
Git to clone a local
copy of the upstream poky
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.
poky
Repository¶
Follow these steps to create a local version of the
upstream
poky
Git repository.
Set Your Directory: Be in the directory where you want to create your local copy of poky.
Clone the Repository: The following command clones the repository and uses the default name "poky" for your local repository:
$ git clone git://git.yoctoproject.org/poky Cloning into 'poky'... remote: Counting objects: 367178, done. remote: Compressing objects: 100% (88161/88161), done. remote: Total 367178 (delta 272761), reused 366942 (delta 272525) Receiving objects: 100% (367178/367178), 133.26 MiB | 6.40 MiB/s, done. Resolving deltas: 100% (272761/272761), done. Checking connectivity... done.
Unless you specify a specific development branch or tag name, Git clones the "master" branch, which results in a snapshot of the latest development changes for "master". For information on how to check out a specific development branch or on how to check out a local branch based on a tag name, see the "Checking Out By Branch in Poky" and Checking Out By Tag in Poky" sections, respectively.
Once the repository is created, you can change to that directory and check its status. Here, the single "master" branch exists on your system and by default, it is checked out:
$ cd ~/poky $ git status On branch master Your branch is up-to-date with 'origin/master'. nothing to commit, working directory clean $ git branch * master
Your local repository of poky is identical to the upstream poky repository at the time from which it was cloned.
When you clone the upstream poky repository, you have access to all its development branches. Each development branch in a repository is unique as it forks off the "master" branch. To see and use the files of a particular development branch locally, you need to know the branch name and then specifically check out that development branch.
Switch to the Poky Directory:
If you have a local poky Git repository, switch to that
directory.
If you do not have the local copy of poky, see the
"Cloning the poky
Repository"
section.
Determine Existing Branch Names:
$ git branch -a * master remotes/origin/1.1_M1 remotes/origin/1.1_M2 remotes/origin/1.1_M3 remotes/origin/1.1_M4 remotes/origin/1.2_M1 remotes/origin/1.2_M2 remotes/origin/1.2_M3 . . . remotes/origin/master-next remotes/origin/master-next2 remotes/origin/morty remotes/origin/pinky remotes/origin/purple remotes/origin/pyro remotes/origin/rocko
Checkout the Branch: Checkout the development branch in which you want to work. For example, to access the files for the Yocto Project 2.5 Release (Sumo), use the following command:
$ git checkout -b sumo origin/sumo Branch sumo set up to track remote branch sumo from origin. Switched to a new branch 'sumo'
The previous command checks out the "sumo" development branch and reports that the branch is tracking the upstream "origin/sumo" branch.
The following command displays the branches that are now part of your local poky repository. The asterisk character indicates the branch that is currently checked out for work:
$ git branch master * sumo
Similar to branches, the upstream repository uses tags to mark specific commits associated with significant points in a development branch (i.e. a release point or stage of a release). You might want to set up a local branch based on one of those points in the repository. The process is similar to checking out by branch name except you use tag names.
Switch to the Poky Directory:
If you have a local poky Git repository, switch to that
directory.
If you do not have the local copy of poky, see the
"Cloning the poky
Repository"
section.
Fetch the Tag Names: To checkout the branch based on a tag name, you need to fetch the upstream tags into your local repository:
$ git fetch --tags $
List the Tag Names: You can list the tag names now:
$ git tag 1.1_M1.final 1.1_M1.rc1 1.1_M1.rc2 1.1_M2.final 1.1_M2.rc1 . . . yocto-2.2 yocto-2.2.1 yocto-2.3 yocto-2.3.1 yocto-2.4 yocto_1.5_M5.rc8
Checkout the Branch:
$ git checkout tags/yocto-2.5 -b my_yocto_2.5 Switched to a new branch 'my_yocto_2.5' $ git branch master * my_yocto_2.5
The previous command creates and checks out a local
branch named "my_yocto_2.5", which is based on
the commit in the upstream poky repository that has
the same tag.
In this example, the files you have available locally
as a result of the checkout
command are a snapshot of the
"sumo" development branch at the point
where Yocto Project 2.5 was released.
Table of Contents
bitbake-layers
Scriptbitbake-layers
Scriptbmaptool
oe-pkgdata-util
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. For introductory information on the Yocto Project Layer Model, see the "The Yocto Project Layer Model" section in the Yocto Project Overview and Concepts Manual.
It is very easy to create your own layers to use with the
OpenEmbedded build system.
The Yocto Project ships with tools that speed up creating
layers.
This section describes the steps you perform by hand to create
layers so that you can better understand them.
For information about the layer-creation tools, see the
"Creating a New BSP Layer Using the bitbake-layers
Script"
section in the Yocto Project Board Support Package (BSP)
Developer's Guide and the
"Creating a General Layer Using the bitbake-layers
Script"
section further down in this manual.
Follow these general steps to create your layer without using tools:
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. You could find a layer that is identical or close to what you need.
Create a Directory:
Create the directory for your layer.
When you create the layer, be sure to create the
directory in an area not associated with the
Yocto Project
Source Directory
(e.g. the cloned poky
repository).
While not strictly required, prepend the name of the directory with the string "meta-". For example:
meta-mylayer meta-GUI_xyz meta-mymachine
With rare exceptions, a layer's name follows this form:
meta-root_name
Following this layer naming convention can save you trouble later when tools, components, or variables "assume" your layer name begins with "meta-". A notable example is in configuration files as shown in the following step where layer names without the "meta-" string are appended to several variables used in the configuration.
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
in the Yocto Project
Source Repositories
demonstrates the required syntax.
For your layer, you need to replace "yoctobsp" with
a unique identifier for your layer (e.g. "machinexyz"
for a layer named "meta-machinexyz"):
# 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 = "4" LAYERSERIES_COMPAT_yoctobsp = "sumo"
Following is an explanation of the layer configuration file:
BBPATH
:
Adds the layer's root directory to BitBake's
search path.
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.
BBFILES
:
Defines the location for all recipes in the
layer.
BBFILE_COLLECTIONS
:
Establishes the current layer through a
unique identifier that is used throughout the
OpenEmbedded build system to refer to the layer.
In this example, the identifier "yoctobsp" is
the representation for the container layer
named "meta-yocto-bsp".
BBFILE_PATTERN
:
Expands immediately during parsing to
provide the directory of the layer.
BBFILE_PRIORITY
:
Establishes a priority to use for
recipes in the layer when the OpenEmbedded build
finds recipes of the same name in different
layers.
LAYERVERSION
:
Establishes a version number for the layer.
You can use this version number to specify this
exact version of the layer as a dependency when
using the
LAYERDEPENDS
variable.
LAYERSERIES_COMPAT
:
Lists the
Yocto Project
releases for which the current version is
compatible.
This variable is a good way to indicate how
up-to-date your particular layer is.
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 list:
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.
Structure Your Layers: 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:
Modify 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.
Perform Steps to Apply for Yocto Project 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.
Follow the Layer Naming Convention:
Store custom layers in a Git repository that use the
meta-
format.
layer_name
Group Your Layers Locally:
Clone your repository alongside other cloned
meta
directories from the
Source Directory.
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 could allow you permission to use the Yocto Project Compatible Logo.
The Yocto Project Compatibility Program consists of a layer application process that requests permission to use the Yocto Project Compatibility Logo for your layer and application. The process consists of two parts:
Successfully passing a script
(yocto-check-layer
) that
when run against your layer, tests it against
constraints based on experiences of how layers have
worked in the real world and where pitfalls have been
found.
Getting a "PASS" result from the script is required for
successful compatibility registration.
Completion of an application acceptance form, which you can find at https://www.yoctoproject.org/webform/yocto-project-compatible-registration.
To be granted permission to use the logo, you need to satisfy the following:
Be able to check the box indicating that you got a "PASS" when running the script against your layer.
Answer "Yes" to the questions on the form or have an acceptable explanation for any questions answered "No".
Be a Yocto Project Member Organization.
The remainder of this section presents information on the
registration form and on the
yocto-check-layer
script.
Use the form to apply for your layer's 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-check-layer
Script¶
The yocto-check-layer
script
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.
You need to achieve a "PASS" result in order to have
your application form successfully processed.
The script divides tests into three areas: COMMON, BSP, 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-check-layer 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
:
# POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf # changes incompatibly POKY_BBLAYERS_CONF_VERSION = "2" BBPATH = "${TOPDIR}" BBFILES ?= "" BBLAYERS ?= " \ /home/user
/poky/meta \ /home/user
/poky/meta-poky \ /home/user
/poky/meta-yocto-bsp \ /home/user
/poky/meta-mylayer \ "
BitBake parses each conf/layer.conf
file
from the top down 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_2.5.bbappend
must apply to
someapp_2.5.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 and append the layer's root name:
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
bitbake-layers
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.
For help on the BitBake layer management tool, use the following command:
$ bitbake-layers --help NOTE: Starting bitbake server... usage: bitbake-layers [-d] [-q] [-F] [--color COLOR] [-h] <subcommand> ... BitBake layers utility optional arguments: -d, --debug Enable debug output -q, --quiet Print only errors -F, --force Force add without recipe parse verification --color COLOR Colorize output (where COLOR is auto, always, never) -h, --help show this help message and exit subcommands: <subcommand> show-layers show current configured layers. show-overlayed list overlayed recipes (where the same recipe exists in another layer) show-recipes list available recipes, showing the layer they are provided by show-appends list bbappend files and recipe files they apply to show-cross-depends Show dependencies between recipes that cross layer boundaries. add-layer Add one or more layers to bblayers.conf. remove-layer Remove one or more layers from bblayers.conf. flatten flatten layer configuration into a separate output directory. layerindex-fetch Fetches a layer from a layer index along with its dependent layers, and adds them to conf/bblayers.conf. layerindex-show-depends Find layer dependencies from layer index. create-layer Create a basic layer Use bitbake-layers <subcommand> --help to get help on a specific command
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-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-recipes:
Lists available recipes and the layers that provide them.
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" ...
layerindex-fetch
:
Fetches a layer from a layer index, along with its
dependent layers, and adds the layers to the
conf/bblayers.conf
file.
layerindex-show-depends
:
Finds layer dependencies from the layer index.
create-layer
:
Creates a basic layer.
bitbake-layers
Script¶
The bitbake-layers
script with the
create-layer
subcommand simplifies
creating a new general layer.
For information on BSP layers, see the "BSP Layers" section in the Yocto Project Board Specific (BSP) Developer's Guide.
In order to use a layer with the OpenEmbedded
build system, you need to add the layer to your
bblayers.conf
configuration
file.
See the
"Adding a Layer Using the bitbake-layers
Script"
section for more information.
The default mode of the script's operation with this subcommand is to create a layer with the following:
A layer priority of 6.
A conf
subdirectory that contains a
layer.conf
file.
A recipes-example
subdirectory
that contains a further subdirectory named
example
, which contains
an example.bb
recipe file.
A COPYING.MIT
,
which is the license statement for the layer.
The script assumes you want to use the MIT license,
which is typical for most layers, for the contents of
the layer itself.
A README
file, which is a file
describing the contents of your new layer.
In its simplest form, you can use the following command form
to create a layer.
The command creates a layer whose name corresponds to
your_layer_name
in the current
directory:
$ bitbake-layers create-layer your_layer_name
As an example, the following command creates a layer named
meta-scottrif
in your home directory:
$ cd /usr/home $ bitbake-layers create-layer meta-scottrif NOTE: Starting bitbake server... Add your new layer with 'bitbake-layers add-layer meta-scottrif'
If you want to set the priority of the layer to other than the
default value of "6", you can either use the
‐‐priority
option or you can
edit the
BBFILE_PRIORITY
value in the conf/layer.conf
after the
script creates it.
Furthermore, if you want to give the example recipe file
some name other than the default, you can
use the
‐‐example-recipe-name
option.
The easiest way to see how the
bitbake-layers create-layer
command
works is to experiment with the script.
You can also read the usage information by entering the
following:
$ bitbake-layers create-layer --help NOTE: Starting bitbake server... usage: bitbake-layers create-layer [-h] [--priority PRIORITY] [--example-recipe-name EXAMPLERECIPE] layerdir Create a basic layer positional arguments: layerdir Layer directory to create optional arguments: -h, --help show this help message and exit --priority PRIORITY, -p PRIORITY Layer directory to create --example-recipe-name EXAMPLERECIPE, -e EXAMPLERECIPE Filename of the example recipe
bitbake-layers
Script¶
Once you create your general layer, you must add it to your
bblayers.conf
file.
Adding the layer to this configuration file makes the
OpenEmbedded build system aware of your layer so that it can
search it for metadata.
Add your layer by using the
bitbake-layers add-layer
command:
$ bitbake-layers add-layer your_layer_name
Here is an example that adds a layer named
meta-scottrif
to the configuration file.
Following the command that adds the layer is another
bitbake-layers
command that shows the
layers that are in your bblayers.conf
file:
$ bitbake-layers add-layer meta-scottrif NOTE: Starting bitbake server... Parsing recipes: 100% |##########################################################| Time: 0:00:49 Parsing of 1441 .bb files complete (0 cached, 1441 parsed). 2055 targets, 56 skipped, 0 masked, 0 errors. $ bitbake-layers show-layers NOTE: Starting bitbake server... layer path priority ========================================================================== meta /home/scottrif/poky/meta 5 meta-poky /home/scottrif/poky/meta-poky 5 meta-yocto-bsp /home/scottrif/poky/meta-yocto-bsp 5 workspace /home/scottrif/poky/build/workspace 99 meta-scottrif /home/scottrif/poky/build/meta-scottrif 6
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
"A Closer Look at devtool
add"
section in the Yocto Project Application Development
and the Extensible Software Development Kit (eSDK) manual.
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
).
To get help on the tool, use the following command:
$ recipetool -h NOTE: Starting bitbake server... usage: recipetool [-d] [-q] [--color COLOR] [-h] <subcommand> ... OpenEmbedded recipe tool options: -d, --debug Enable debug output -q, --quiet Print only errors --color COLOR Colorize output (where COLOR is auto, always, never) -h, --help show this help message and exit subcommands: create Create a new recipe newappend Create a bbappend for the specified target in the specified layer setvar Set a variable within a recipe appendfile Create/update a bbappend to replace a target file appendsrcfiles Create/update a bbappend to add or replace source files appendsrcfile Create/update a bbappend to add or replace a source file Use recipetool <subcommand> --help to get help on a specific command
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 Layer 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
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 the build environment setup script (i.e.
oe-init-build-env
)
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 Yocto Project Development Environment" chapter of the Yocto Project Overview and Concepts 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 Overview and Concepts 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.
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" section in the Yocto Project Overview and Concepts 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
${
D
}
directory.
The reason for this limitation is that almost all files that
populate the sysroot are cataloged in manifests in order to
ensure the files can be removed later when a recipe is either
modified or removed.
Thus, the sysroot is able to remain free from stale files.
A subset of the files installed by the
do_install
task are used by the
do_populate_sysroot
task as defined by the the
SYSROOT_DIRS
variable to automatically populate the sysroot.
It is possible to modify the list of directories that populate
the sysroot.
The following example shows how you could add the
/opt
directory to the list of
directories within a recipe:
SYSROOT_DIRS += "/opt"
For a more complete description of the
do_populate_sysroot
task and its associated functions, see the
staging
class.
Prior to a build, if you know that several different recipes
provide the same functionality, you can use a virtual provider
(i.e. virtual/*
) as a placeholder for the
actual provider.
The actual provider is determined at build-time.
A common scenario where a virtual provider is used would be
for the kernel recipe.
Suppose you have three kernel recipes whose
PN
values map to kernel-big
,
kernel-mid
, and
kernel-small
.
Furthermore, each of these recipes in some way uses a
PROVIDES
statement that essentially identifies itself as being able
to provide virtual/kernel
.
Here is one way through the
kernel
class:
PROVIDES += "${@ "virtual/kernel" if (d.getVar("KERNEL_PACKAGE_NAME") == "kernel") else "" }"
Any recipe that inherits the kernel
class
is going to utilize a PROVIDES
statement
that identifies that recipe as being able to provide the
virtual/kernel
item.
Now comes the time to actually build an image and you need a
kernel recipe, but which one?
You can configure your build to call out the kernel recipe
you want by using the
PREFERRED_PROVIDER
variable.
As an example, consider the
x86-base.inc
include file, which is a machine
(i.e. MACHINE
)
configuration file.
This include file is the reason all x86-based machines use the
linux-yocto
kernel.
Here are the relevant lines from the include file:
PREFERRED_PROVIDER_virtual/kernel ??= "linux-yocto" PREFERRED_VERSION_linux-yocto ??= "4.15%"
When you use a virtual provider, you do not have to
"hard code" a recipe name as a build dependency.
You can use the
DEPENDS
variable to state the build is dependent on
virtual/kernel
for example:
DEPENDS = "virtual/kernel"
During the build, the OpenEmbedded build system picks
the correct recipe needed for the
virtual/kernel
dependency based on the
PREFERRED_PROVIDER
variable.
If you want to use the small kernel mentioned at the beginning
of this section, configure your build as follows:
PREFERRED_PROVIDER_virtual/kernel ??= "kernel-small"
PROVIDES
a virtual/*
item that is ultimately
not selected through
PREFERRED_PROVIDER
does not get built.
Preventing these recipes from building is usually the
desired behavior since this mechanism's purpose is to
select between mutually exclusive alternative providers.
The following lists specific examples of virtual providers:
virtual/kernel
:
Provides the name of the kernel recipe to use when
building a kernel image.
virtual/bootloader
:
Provides the name of the bootloader to use when
building an image.
virtual/mesa
:
Provides gbm.pc
.
virtual/egl
:
Provides egl.pc
and possibly
wayland-egl.pc
.
virtual/libgl
:
Provides gl.pc
(i.e. libGL).
virtual/libgles1
:
Provides glesv1_cm.pc
(i.e. libGLESv1_CM).
virtual/libgles2
:
Provides glesv2.pc
(i.e. libGLESv2).
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 in the Yocto Project Overview and Concepts Manual.
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 Overview and
Concepts 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.
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 (${VARNAME
}):
Use the ${
syntax to access the contents of a variable:
VARNAME
}
SRC_URI = "${SOURCEFORGE_MIRROR}/libpng/zlib-${PV}.tar.gz"
:=
operator instead of
=
when you make the
assignment, but this is not generally needed.
Quote All Assignments ("value
"):
Use double quotes around values in all variable
assignments (e.g.
"
).
Following is an example:
value
"
VAR1 = "${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).
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.
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 bitbake-layers
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
Over time, upstream developers publish new versions for software
built by layer recipes.
It is recommended to keep recipes up-to-date with upstream
version releases.
You can use the Automated Upgrade Helper (AUH) to set up
automatic version upgrades.
Alternatively, you can use devtool upgrade
to set up semi-automatic version upgrades.
Finally, you can even manually upgrade a recipe by editing the
recipe itself.
The AUH utility works in conjunction with the OpenEmbedded build system in order to automatically generate upgrades for recipes based on new versions being published upstream. Use AUH when you want to create a service that performs the upgrades automatically and optionally sends you an email with the results.
AUH allows you to update several recipes with a single use. You can also optionally perform build and integration tests using images with the results saved to your hard drive and emails of results optionally sent to recipe maintainers. Finally, AUH creates Git commits with appropriate commit messages in the layer's tree for the changes made to recipes.
devtool upgrade
or upgrade your
recipes manually:
When AUH cannot complete the upgrade sequence.
This situation usually results because custom
patches carried by the recipe cannot be
automatically rebased to the new version.
In this case, devtool upgrade
allows you to manually resolve conflicts.
When for any reason you want fuller control over the upgrade process. For example, when you want special arrangements for testing.
The following steps describe how to set up the AUH utility:
Be Sure the Development Host is Set Up: You need to be sure that your development host is set up to use the Yocto Project. For information on how to set up your host, see the "Preparing the Build Host" section.
Make Sure Git is Configured: The AUH utility requires Git to be configured because AUH uses Git to save upgrades. Thus, you must have Git user and email configured. The following command shows your configurations:
$ git config --list
If you do not have the user and email configured, you can use the following commands to do so:
$ git config --global user.namesome_name
$ git config --global user.emailusername
@domain
.com
Clone the AUH Repository: To use AUH, you must clone the repository onto your development host. The following command uses Git to create a local copy of the repository on your system:
$ git clone git://git.yoctoproject.org/auto-upgrade-helper Cloning into 'auto-upgrade-helper'... remote: Counting objects: 768, done. remote: Compressing objects: 100% (300/300), done. remote: Total 768 (delta 499), reused 703 (delta 434) Receiving objects: 100% (768/768), 191.47 KiB | 98.00 KiB/s, done. Resolving deltas: 100% (499/499), done. Checking connectivity... done.
AUH is not part of the OpenEmbedded-Core (OE-Core) or Poky repositories.
Create a Dedicated Build Directory:
Run the
oe-init-build-env
script to create a fresh build directory that you
use exclusively for running the AUH utility:
$ cd ~/poky
$ source oe-init-build-env your_AUH_build_directory
Re-using an existing build directory and its configurations is not recommended as existing settings could cause AUH to fail or behave undesirably.
Make Configurations in Your Local Configuration File:
Several settings need to exist in the
local.conf
file in the build
directory you just created for AUH.
Make these following configurations:
Enable "distrodata" as follows:
INHERIT =+ "distrodata"
If you want to enable
Build History,
which is optional, you need the following
lines in the
conf/local.conf
file:
INHERIT =+ "buildhistory" BUILDHISTORY_COMMIT = "1"
With this configuration and a successful
upgrade, a build history "diff" file appears in
the
upgrade-helper/work/recipe/buildhistory-diff.txt
file found in your build directory.
If you want to enable testing through the
testimage
class, which is optional, you need to have the
following set in your
conf/local.conf
file:
INHERIT += "testimage"
local.conf
file:
DISTRO_FEATURES_append = " ptest"
Optionally Start a vncserver: If you are running in a server without an X11 session, you need to start a vncserver:
$ vncserver :1 $ export DISPLAY=:1
Create and Edit an AUH Configuration File:
You need to have the
upgrade-helper/upgrade-helper.conf
configuration file in your build directory.
You can find a sample configuration file in the
AUH source repository.
Read through the sample file and make
configurations as needed.
For example, if you enabled build history in your
local.conf
as described earlier,
you must enable it in
upgrade-helper.conf
.
Also, if you are using the default
maintainers.inc
file supplied
with Poky and located in
meta-yocto
and you do not set a
"maintainers_whitelist" or "global_maintainer_override"
in the upgrade-helper.conf
configuration, and you specify "-e all" on the
AUH command-line, the utility automatically sends out
emails to all the default maintainers.
Please avoid this.
This next set of examples describes how to use the AUH:
Upgrading a Specific Recipe: To upgrade a specific recipe, use the following form:
$ upgrade-helper.py recipe_name
For example, this command upgrades the
xmodmap
recipe:
$ upgrade-helper.py xmodmap
Upgrading a Specific Recipe to a Particular Version: To upgrade a specific recipe to a particular version, use the following form:
$ upgrade-helper.pyrecipe_name
-tversion
For example, this command upgrades the
xmodmap
recipe to version
1.2.3:
$ upgrade-helper.py xmodmap -t 1.2.3
Upgrading all Recipes to the Latest Versions and Suppressing Email Notifications: To upgrade all recipes to their most recent versions and suppress the email notifications, use the following command:
$ upgrade-helper.py all
Upgrading all Recipes to the Latest Versions and Send Email Notifications: To upgrade all recipes to their most recent versions and send email messages to maintainers for each attempted recipe as well as a status email, use the following command:
$ upgrade-helper.py -e all
Once you have run the AUH utility, you can find the results in the AUH build directory:
${BUILDDIR}/upgrade-helper/timestamp
The AUH utility also creates recipe update commits from successful upgrade attempts in the layer tree.
You can easily set up to run the AUH utility on a regular
basis by using a cron job.
See the
weeklyjob.sh
file distributed with the utility for an example.
devtool upgrade
¶
As mentioned earlier, an alternative method for upgrading
recipes to newer versions is to use
devtool upgrade
.
You can read about devtool upgrade
in
general in the
"Use devtool upgrade
to Create a Version of the Recipe that Supports a Newer Version of the Software"
section in the Yocto Project Application Development and the
Extensible Software Development Kit (eSDK) Manual.
To see all the command-line options available with
devtool upgrade
, use the following help
command:
$ devtool upgrade -h
If you want to find out what version a recipe is currently at upstream without any attempt to upgrade your local version of the recipe, you can use the following command:
$ devtool latest-version recipe_name
As mentioned in the previous section describing AUH,
devtool upgrade
works in a
less-automated manner than AUH.
Specifically, devtool upgrade
only
works on a single recipe that you name on the command line,
cannot perform build and integration testing using images,
and does not automatically generate commits for changes in
the source tree.
Despite all these "limitations",
devtool upgrade
updates the recipe file
to the new upstream version and attempts to rebase custom
patches contained by the recipe as needed.
devtool upgrade
behind the scenes making AUH somewhat of a "wrapper"
application for devtool upgrade
.
A typical scenario involves having used Git to clone an
upstream repository that you use during build operations.
Because you are (or have) built the recipe in the past, the
layer is likely added to your configuration already.
If for some reason, the layer is not added, you could add
it easily using the
bitbake-layers
script.
For example, suppose you use the nano.bb
recipe from the meta-oe
layer in the
meta-openembedded
repository.
For this example, assume that the layer has been cloned into
following area:
/home/scottrif/meta-openembedded
The following command from your
Build Directory
adds the layer to your build configuration (i.e.
${BUILDDIR}/conf/bblayers.conf
):
$ bitbake-layers add-layer /home/scottrif/meta-openembedded/meta-oe NOTE: Starting bitbake server... Parsing recipes: 100% |##########################################| Time: 0:00:55 Parsing of 1431 .bb files complete (0 cached, 1431 parsed). 2040 targets, 56 skipped, 0 masked, 0 errors. Removing 12 recipes from the x86_64 sysroot: 100% |##############| Time: 0:00:00 Removing 1 recipes from the x86_64_i586 sysroot: 100% |##########| Time: 0:00:00 Removing 5 recipes from the i586 sysroot: 100% |#################| Time: 0:00:00 Removing 5 recipes from the qemux86 sysroot: 100% |##############| Time: 0:00:00
For this example, assume that the nano.bb
recipe that is upstream has a 2.9.3 version number.
However, the version in the local repository is 2.7.4.
The following command from your build directory automatically
upgrades the recipe for you:
-V
option is not necessary.
Omitting the version number causes
devtool upgrade
to upgrade the recipe
to the most recent version.
$ devtool upgrade nano -V 2.9.3 NOTE: Starting bitbake server... NOTE: Creating workspace layer in /home/scottrif/poky/build/workspace Parsing recipes: 100% |##########################################| Time: 0:00:46 Parsing of 1431 .bb files complete (0 cached, 1431 parsed). 2040 targets, 56 skipped, 0 masked, 0 errors. NOTE: Extracting current version source... NOTE: Resolving any missing task queue dependencies . . . NOTE: Executing SetScene Tasks NOTE: Executing RunQueue Tasks NOTE: Tasks Summary: Attempted 74 tasks of which 72 didn't need to be rerun and all succeeded. Adding changed files: 100% |#####################################| Time: 0:00:00 NOTE: Upgraded source extracted to /home/scottrif/poky/build/workspace/sources/nano NOTE: New recipe is /home/scottrif/poky/build/workspace/recipes/nano/nano_2.9.3.bb
Continuing with this example, you can use
devtool build
to build the newly upgraded
recipe:
$ devtool build nano NOTE: Starting bitbake server... Loading cache: 100% |################################################################################################| Time: 0:00:01 Loaded 2040 entries from dependency cache. Parsing recipes: 100% |##############################################################################################| Time: 0:00:00 Parsing of 1432 .bb files complete (1431 cached, 1 parsed). 2041 targets, 56 skipped, 0 masked, 0 errors. NOTE: Resolving any missing task queue dependencies . . . NOTE: Executing SetScene Tasks NOTE: Executing RunQueue Tasks NOTE: nano: compiling from external source tree /home/scottrif/poky/build/workspace/sources/nano NOTE: Tasks Summary: Attempted 520 tasks of which 304 didn't need to be rerun and all succeeded.
Within the devtool upgrade
workflow,
opportunity exists to deploy and test your rebuilt software.
For this example, however, running
devtool finish
cleans up the workspace
once the source in your workspace is clean.
This usually means using Git to stage and submit commits
for the changes generated by the upgrade process.
Once the tree is clean, you can clean things up in this
example with the following command from the
${BUILDDIR}/workspace/sources/nano
directory:
$ devtool finish nano meta-oe NOTE: Starting bitbake server... Loading cache: 100% |################################################################################################| Time: 0:00:00 Loaded 2040 entries from dependency cache. Parsing recipes: 100% |##############################################################################################| Time: 0:00:01 Parsing of 1432 .bb files complete (1431 cached, 1 parsed). 2041 targets, 56 skipped, 0 masked, 0 errors. NOTE: Adding new patch 0001-nano.bb-Stuff-I-changed-when-upgrading-nano.bb.patch NOTE: Updating recipe nano_2.9.3.bb NOTE: Removing file /home/scottrif/meta-openembedded/meta-oe/recipes-support/nano/nano_2.7.4.bb NOTE: Moving recipe file to /home/scottrif/meta-openembedded/meta-oe/recipes-support/nano NOTE: Leaving source tree /home/scottrif/poky/build/workspace/sources/nano as-is; if you no longer need it then please delete it manually
Using the devtool finish
command cleans
up the workspace and creates a patch file based on your
commits.
The tool puts all patch files back into the source directory
in a sub-directory named nano
in this
case.
If for some reason you choose not to upgrade recipes using the
Auto Upgrade Helper (AUH)
or by using
devtool upgrade
,
you can manually edit the recipe files to upgrade the versions.
devtool upgrade
, both of which
automate some steps and provide guidance for others needed
for the manual process.
To manually upgrade recipe versions, follow these general steps:
Change the Version:
Rename the recipe such that the version (i.e. the
PV
part of the recipe name) changes appropriately.
If the version is not part of the recipe name, change
the value as it is set for PV
within the recipe itself.
Update SRCREV
if Needed:
If the source code your recipe builds is fetched from
Git or some other version control system, update
SRCREV
to point to the commit hash that matches the new
version.
Build the Software: Try to build the recipe using BitBake. Typical build failures include the following:
License statements were updated for the new
version.
For this case, you need to review any changes
to the license and update the values of
LICENSE
and
LIC_FILES_CHKSUM
as needed.
Custom patches carried by the older version of the recipe might fail to apply to the new version. For these cases, you need to review the failures. Patches might not be necessary for the new version of the software if the upgraded version has fixed those issues. If a patch is necessary and failing, you need to rebase it into the new version.
Optionally Attempt to Build for Several Architectures:
Once you successfully build the new software for a
given architecture, you could test the build for
other architectures by changing the
MACHINE
variable and rebuilding the software.
This optional step is especially important if the
recipe is to be released publicly.
Check the Upstream Change Log or Release Notes: Checking both these reveals if new features exist that could break backwards-compatibility. If so, you need to take steps to mitigate or eliminate that situation.
Optionally Create a Bootable Image and Test: If you want, you can test the new software by booting it onto actual hardware.
Create a Commit with the Change in the Layer Repository: After all builds work and any testing is successful, you can create commits for any changes in the layer holding your upgraded recipe.
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.
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
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
devtool
workflow
as described in the Yocto Project Application Development
and the Extensible Software Development Kit (eSDK) manual
is a safer development flow 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
test 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
"Conserving Disk Space During Builds"
section.
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"
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 section describes various build procedures. For example, the steps needed for a simple build, a target that uses multiple configurations, building an image for more than one machine, and so forth.
In the development environment, you need to build an image whenever you change hardware support, add or change system libraries, or add or change services that have dependencies. Several methods exist that allow you to build an image within the Yocto Project. This section presents the basic steps you need to build a simple image using BitBake from a build host running Linux.
For information on how to build an image using Toaster, see the Toaster User Manual.
For information on how to use
devtool
to build images, see
the
"Using devtool
in Your SDK Workflow"
section in the Yocto Project Application
Development and the Extensible Software Development
Kit (eSDK) manual.
For a quick example on how to build an image using the OpenEmbedded build system, see the Yocto Project Quick Build document.
The build process creates an entire Linux distribution from
source and places it in your
Build Directory
under tmp/deploy/images
.
For detailed information on the build process using BitBake,
see the
"Images"
section in the Yocto Project Overview and Concepts Manual.
The following figure and list overviews the build process:
Set up Your Host Development System to Support Development Using the Yocto Project: See the "Setting Up to Use the Yocto Project" section for options on how to get a build host ready to use the Yocto Project.
Initialize the Build Environment:
Initialize the build environment by sourcing the build
environment script (i.e.
oe-init-build-env
):
$ source oe-init-build-env [build_dir
]
When you use the initialization script, the
OpenEmbedded build system uses
build
as the default Build
Directory in your current work directory.
You can use a build_dir
argument with the script to specify a different build
directory.
~/build/x86
for a
qemux86
target, and
~/build/arm
for a
qemuarm
target.
Make Sure Your local.conf
File is Correct:
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:
Build the image using the bitbake
command:
$ bitbake target
The target
is the name of the
recipe you want to build.
Common targets are the images in
meta/recipes-core/images
,
meta/recipes-sato/images
, and so
forth all found in the
Source Directory.
Or, the target can be the name of a recipe for a
specific piece of software such as BusyBox.
For more details about the images the OpenEmbedded build
system supports, see the
"Images"
chapter in the Yocto Project Reference Manual.
As an example, the following command builds the
core-image-minimal
image:
$ bitbake core-image-minimal
Once an image has been built, it often needs to be
installed.
The images and kernels built by the OpenEmbedded
build system are placed in the Build Directory in
tmp/deploy/images
.
For information on how to run pre-built images such as
qemux86
and qemuarm
,
see the
Yocto Project Application Development and the Extensible Software Development Kit (eSDK)
manual.
For information about how to install these images,
see the documentation for your particular board or
machine.
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 (Sumo 2.5) 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.
An initial RAM filesystem (initramfs) image provides a temporary root filesystem used for early system initialization (e.g. loading of modules needed to locate and mount the "real" root filesystem).
Follow these steps to create an initramfs image:
Create the initramfs Image Recipe:
You can reference the
core-image-minimal-initramfs.bb
recipe found in the meta/recipes-core
directory of the
Source Directory
as an example from which to work.
Decide if You Need to Bundle the initramfs Image
Into the Kernel Image:
If you want the initramfs image that is built to be
bundled in with the kernel image, set the
INITRAMFS_IMAGE_BUNDLE
variable to "1" in your local.conf
configuration file and set the
INITRAMFS_IMAGE
variable in the recipe that builds the kernel image.
Setting the INITRAMFS_IMAGE_BUNDLE
flag causes the initramfs image to be unpacked
into the ${B}/usr/
directory.
The unpacked initramfs image is then passed to the kernel's
Makefile
using the
CONFIG_INITRAMFS_SOURCE
variable, allowing the initramfs image to be built into
the kernel normally.
INITRD_IMAGE
,
INITRD_LIVE
, and
INITRD_IMAGE_LIVE
variables.
For more information, see the
image-live.bbclass
file.
Optionally Add Items to the initramfs Image
Through the initramfs Image Recipe:
If you add items to the initramfs image by way of its
recipe, you should use
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.
Build the Kernel Image and the initramfs
Image:
Build your kernel image using BitBake.
Because the initramfs image recipe is a dependency of the
kernel image, the initramfs image is built as well and
bundled with the kernel image if you used the
INITRAMFS_IMAGE_BUNDLE
variable described earlier.
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 "Creating Configuration Fragments" section in the Yocto Project Linux Kernel Development 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 how NXP (formerly Freescale) allows
for the easy reuse of binary packages in their layer
meta-freescale
.
In this example, the
fsl-dynamic-packagearch
class shares GPU packages for i.MX53 boards because
all boards share the AMD GPU.
The i.MX6-based boards can do the same because all boards
share the Vivante GPU.
This class inspects the BitBake datastore to identify if
the package provides or depends on one of the
sub-architecture values.
If so, the class sets the
PACKAGE_ARCH
value based on the MACHINE_SUBARCH
value.
If the package does not provide or depend on one of the
sub-architecture values but it matches a value in the
machine-specific filter, it sets
MACHINE_ARCH
.
This behavior reduces the number of packages built and
saves build time by reusing binaries.
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_CONSOLES
,
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.
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
"
Build time can be an issue. By default, the build system uses simple controls to try and maximize build efficiency. In general, the default settings for all the following variables result in the most efficient build times when dealing with single socket systems (i.e. a single CPU). If you have multiple CPUs, you might try increasing the default values to gain more speed. See the descriptions in the glossary for each variable for more information:
BB_NUMBER_THREADS
:
The maximum number of threads BitBake simultaneously executes.
BB_NUMBER_PARSE_THREADS
:
The number of threads BitBake uses during parsing.
PARALLEL_MAKE
:
Extra options passed to the make
command
during the
do_compile
task in order to specify parallel compilation on the
local build host.
PARALLEL_MAKEINST
:
Extra options passed to the make
command
during the
do_install
task in order to specify parallel installation on the
local build host.
As mentioned, these variables all scale to the number of processor cores available on the build system. For single socket systems, this auto-scaling ensures that the build system fundamentally takes advantage of potential parallel operations during the build based on the build machine's capabilities.
Following are additional factors that can affect build speed:
File system type:
The file system type that the build is being performed on can
also influence performance.
Using ext4
is recommended as compared
to ext2
and ext3
due to ext4
improved features
such as extents.
Disabling the updating of access time using
noatime
:
The noatime
mount option prevents the
build system from updating file and directory access times.
Setting a longer commit: Using the "commit=" mount option increases the interval in seconds between disk cache writes. Changing this interval from the five second default to something longer increases the risk of data loss but decreases the need to write to the disk, thus increasing the build performance.
Choosing the packaging backend: Of the available packaging backends, IPK is the fastest. Additionally, selecting a singular packaging backend also helps.
Using tmpfs
for
TMPDIR
as a temporary file system:
While this can help speed up the build, the benefits are
limited due to the compiler using
-pipe
.
The build system goes to some lengths to avoid
sync()
calls into the
file system on the principle that if there was a significant
failure, the
Build Directory
contents could easily be rebuilt.
Inheriting the
rm_work
class:
Inheriting this class has shown to speed up builds due to
significantly lower amounts of data stored in the data
cache as well as on disk.
Inheriting this class also makes cleanup of
TMPDIR
faster, at the expense of being easily able to dive into the
source code.
File system maintainers have recommended that the fastest way
to clean up large numbers of files is to reformat partitions
rather than delete files due to the linear nature of
partitions.
This, of course, assumes you structure the disk partitions and
file systems in a way that this is practical.
Aside from the previous list, you should keep some trade offs in mind that can help you speed up the build:
Remove items from
DISTRO_FEATURES
that you might not need.
Exclude debug symbols and other debug information:
If you do not need these symbols and other debug information,
disabling the *-dbg
package generation
can speed up the build.
You can disable this generation by setting the
INHIBIT_PACKAGE_DEBUG_SPLIT
variable to "1".
Disable static library generation for recipes derived from
autoconf
or libtool
:
Following is an example showing how to disable static
libraries and still provide an override to handle exceptions:
STATICLIBCONF = "--disable-static" STATICLIBCONF_sqlite3-native = "" EXTRA_OECONF += "${STATICLIBCONF}"
Some recipes need static libraries in order to work
correctly (e.g. pseudo-native
needs sqlite3-native
).
Overrides, as in the previous example, account for
these kinds of exceptions.
Some packages have packaging code that assumes the presence of the static libraries. If so, you might need to exclude them as well.
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"
x32 processor-specific Application Binary Interface (x32 psABI) is a native 32-bit processor-specific ABI for Intel® 64 (x86-64) architectures. An ABI defines the calling conventions between functions in a processing environment. The interface determines what registers are used and what the sizes are for various C data types.
Some processing environments prefer using 32-bit applications even when running on Intel 64-bit platforms. Consider the i386 psABI, which is a very old 32-bit ABI for Intel 64-bit platforms. The i386 psABI does not provide efficient use and access of the Intel 64-bit processor resources, leaving the system underutilized. Now consider the x86_64 psABI. This ABI is newer and uses 64-bits for data sizes and program pointers. The extra bits increase the footprint size of the programs, libraries, and also increases the memory and file system size requirements. Executing under the x32 psABI enables user programs to utilize CPU and system resources more efficiently while keeping the memory footprint of the applications low. Extra bits are used for registers but not for addressing mechanisms.
The Yocto Project supports the final specifications of x32 psABI as follows:
You can create packages and images in x32 psABI format on x86_64 architecture targets.
You can successfully build recipes with the x32 toolchain.
You can create and boot
core-image-minimal
and
core-image-sato
images.
RPM Package Manager (RPM) support exists for x32 binaries.
Support for large images exists.
To use the x32 psABI, you need to edit your
conf/local.conf
configuration file as
follows:
MACHINE = "qemux86-64" DEFAULTTUNE = "x86-64-x32" baselib = "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE', True) \ or 'INVALID'), True) or 'lib'}"
Once you have set up your configuration file, use BitBake to build an image that supports the x32 psABI. Here is an example:
$ bitbake core-image-sato
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.
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
kickstart 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.
.wks
) Reference"
Chapter in the Yocto Project Reference Manual.
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
"Using the Wic Plug-Ins Interface"
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, provides information on using the Wic plug-ins interface, and provides several examples that show how to use Wic.
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 must have sourced the build environment
setup script (i.e.
oe-init-build-env
)
found in the
Build Directory.
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 OpenEmbedded build
system.
You must build several native tools, which are built to run on the build system:
$ bitbake parted-native dosfstools-native mtools-native
Include "wic" as part of the
IMAGE_FSTYPES
variable.
Include the name of the
wic kickstart file
as part of the
WKS_FILE
variable
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 $ wic help
Currently, Wic supports seven commands:
cp
, create
,
help
, list
,
ls
, rm
, and
write
.
You can get help for all these commands except "help" by
using the following form:
$ wic help command
For example, the following command returns help for the
write
command:
$ wic help write
Wic supports help for three topics:
overview
,
plugins
, and
kickstart
.
You can get help for any topic using the following form:
$ wic help topic
For example, the following returns overview help for Wic:
$ wic help overview
One additional level of help exists for Wic.
You can get help on individual images through the
list
command.
You can use the list
command to return the
available Wic images as follows:
$ wic list images mpc8315e-rdb Create SD card image for MPC8315E-RDB genericx86 Create an EFI disk image for genericx86* beaglebone-yocto Create SD card image for Beaglebone edgerouter Create SD card image for Edgerouter qemux86-directdisk Create a qemu machine 'pcbios' direct disk image directdisk-gpt Create a 'pcbios' direct disk image mkefidisk Create an EFI disk image directdisk Create a 'pcbios' direct disk image systemd-bootdisk Create an EFI disk image with systemd-boot mkhybridiso Create a hybrid ISO image sdimage-bootpart Create SD card image with a boot partition directdisk-multi-rootfs Create multi rootfs image using rootfs plugin directdisk-bootloader-config Create a 'pcbios' direct disk image with custom bootloader config
Once you know the list of available Wic images, you can use
help
with the command to get help on a
particular image.
For example, the following command returns help on the
"beaglebone-yocto" image:
$ wic list beaglebone-yocto help Creates a partitioned SD card image for Beaglebone. Boot files are located in the first vfat partition.
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 Wic command-line arguments.
Cooked Mode:
The current
MACHINE
setting and image name are used to automatically
locate and provide the build artifacts.
You just supply a kickstart file and the name
of the image from which to use artifacts.
Regardless of the mode you use, you need to have the build artifacts ready and available.
Running Wic in raw mode allows you to specify all the
partitions through the wic
command line.
The primary use for raw mode is if you have built
your kernel outside of the Yocto Project
Build Directory.
In other words, you can point to arbitrary kernel,
root filesystem locations, and so forth.
Contrast this behavior with cooked mode where Wic
looks in the Build Directory (e.g.
tmp/deploy/images/
machine
).
The general form of the
wic
command in raw mode is:
$ wic createwks_file
options
... Where:wks_file
: 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. optional arguments: -h, --help show this help message and exit -oOUTDIR
, --outdirOUTDIR
name of directory to create image in -eIMAGE_NAME
, --image-nameIMAGE_NAME
name of the image to use the artifacts from e.g. core- image-sato -rROOTFS_DIR
, --rootfs-dirROOTFS_DIR
path to the /rootfs dir to use as the .wks rootfs source -bBOOTIMG_DIR
, --bootimg-dirBOOTIMG_DIR
path to the dir containing the boot artifacts (e.g. /EFI or /syslinux dirs) to use as the .wks bootimg source -kKERNEL_DIR
, --kernel-dirKERNEL_DIR
path to the dir containing the kernel to use in the .wks bootimg -nNATIVE_SYSROOT
, --native-sysrootNATIVE_SYSROOT
path to the native sysroot containing the tools to use to build the image -s, --skip-build-check skip the build check -f, --build-rootfs build rootfs -c {gzip,bzip2,xz}, --compress-with {gzip,bzip2,xz} compress image with specified compressor -m, --bmap generate .bmap --no-fstab-update Do not change fstab file. -vVARS_DIR
, --varsVARS_DIR
directory with <image>.env files that store bitbake variables -D, --debug output debug information
Running Wic in cooked mode leverages off artifacts in
the Build Directory.
In other words, you do not have to specify kernel or
root filesystem locations as part of the command.
All you need to provide is a kickstart file and the
name of the image from which to use artifacts by using
the "-e" option.
Wic looks in the Build Directory (e.g.
tmp/deploy/images/
machine
)
for artifacts.
The general form of the wic
command using Cooked Mode is as follows:
$ wic createwks_file
-eIMAGE_NAME
Where:wks_file
: An OpenEmbedded kickstart file. You can provide your own custom file or use a file from a set of existing files provided with the Yocto Project release. required argument: -eIMAGE_NAME
, --image-nameIMAGE_NAME
name of the image to use the artifacts from e.g. core- image-sato
If you do not want to create your own kickstart file, you can use an existing file provided by the Wic installation. As shipped, kickstart files can be found in the Yocto Project Source Repositories in the following two locations:
poky/meta-yocto-bsp/wic poky/scripts/lib/wic/canned-wks
Use the following command to list the available kickstart files:
$ wic list images mpc8315e-rdb Create SD card image for MPC8315E-RDB genericx86 Create an EFI disk image for genericx86* beaglebone-yocto Create SD card image for Beaglebone edgerouter Create SD card image for Edgerouter qemux86-directdisk Create a qemu machine 'pcbios' direct disk image directdisk-gpt Create a 'pcbios' direct disk image mkefidisk Create an EFI disk image directdisk Create a 'pcbios' direct disk image systemd-bootdisk Create an EFI disk image with systemd-boot mkhybridiso Create a hybrid ISO image sdimage-bootpart Create SD card image with a boot partition directdisk-multi-rootfs Create multi rootfs image using rootfs plugin directdisk-bootloader-config Create a 'pcbios' direct disk image with custom bootloader config
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 genericx86.wks
file to
generate an image:
# short-description: Create an EFI disk image for genericx86* # long-description: Creates a partitioned EFI disk image for genericx86* machines part /boot --source bootimg-efi --sourceparams="loader=grub-efi" --ondisk sda --label msdos --active --align 1024 part / --source rootfs --ondisk sda --fstype=ext4 --label platform --align 1024 --use-uuid part swap --ondisk sda --size 44 --label swap1 --fstype=swap bootloader --ptable gpt --timeout=5 --append="rootfstype=ext4 console=ttyS0,115200 console=tty0"
You can extend and specialize Wic functionality by using Wic plug-ins. This section explains the Wic plug-in interface.
Source plug-ins provide a mechanism to customize partition
content during the Wic image generation process.
You can use source plug-ins to map values that you specify
using --source
commands in kickstart
files (i.e. *.wks
) to a plug-in
implementation used to populate a given partition.
WKS_FILE_DEPENDS
variable.
Source plug-ins are subclasses defined in plug-in files. As shipped, the Yocto Project provides several plug-in files. You can see the source plug-in files that ship with the Yocto Project here. Each of these plug-in files contains source plug-ins that are designed to populate a specific Wic image partition.
Source plug-ins are subclasses of the
SourcePlugin
class, which is
defined in the
poky/scripts/lib/wic/pluginbase.py
file.
For example, the BootimgEFIPlugin
source plug-in found in the
bootimg-efi.py
file is a subclass of
the SourcePlugin
class, which is found
in the pluginbase.py
file.
You can also implement source plug-ins in a layer outside
of the Source Repositories (external layer).
To do so, be sure that your plug-in files are located in
a directory whose path is
scripts/lib/wic/plugins/source/
within your external layer.
When the plug-in files are located there, the source
plug-ins they contain are made available to Wic.
When the Wic implementation needs to invoke a
partition-specific implementation, it looks for the plug-in
with the same name as the --source
parameter used in the kickstart file given to that
partition.
For example, if the partition is set up using the following
command in a kickstart file:
part /boot --source bootimg-pcbios --ondisk sda --label boot --active --align 1024
The methods defined as class members of the matching
source plug-in (i.e. bootimg-pcbios
)
in the bootimg-pcbios.py
plug-in file
are used.
To be more concrete, here is the corresponding plug-in
definition from the bootimg-pcbios.py
file for the previous command along with an example
method called by the Wic implementation when it needs to
prepare a partition using an implementation-specific
function:
. . . class BootimgPcbiosPlugin(SourcePlugin): """ Create MBR boot partition and install syslinux on it. """ name = 'bootimg-pcbios' . . . @classmethod def do_prepare_partition(cls, part, source_params, creator, cr_workdir, oe_builddir, bootimg_dir, kernel_dir, rootfs_dir, native_sysroot): """ Called to do the actual content population for a partition i.e. it 'prepares' the partition to be incorporated into the image. In this case, prepare content for legacy bios boot partition. """ . . .
If a subclass (plug-in) itself does not implement a
particular function, Wic locates and uses the default
version in the superclass.
It is for this reason that all source plug-ins are derived
from the SourcePlugin
class.
The SourcePlugin
class defined in
the pluginbase.py
file defines
a set of methods that source plug-ins can implement or
override.
Any plug-ins (subclass of
SourcePlugin
) that do not implement
a particular method inherit the implementation of the
method from the SourcePlugin
class.
For more information, see the
SourcePlugin
class in the
pluginbase.py
file for details:
The following list describes the methods implemented in the
SourcePlugin
class:
do_prepare_partition()
:
Called to populate a partition with actual content.
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()
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
behavior.
You can extend the source plug-in mechanism.
To add more hooks, create more source plug-in methods
within SourcePlugin
and the
corresponding derived subclasses.
The code that calls the plug-in methods uses the
plugin.get_source_plugin_methods()
function to find the method or methods needed by the call.
Retrieval of those methods is accomplished by filling up
a dict with keys that contain the method names of interest.
On success, these will be filled in with the actual
methods.
See the Wic implementation for examples and details.
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 INFO: Building wic-tools... . . . INFO: The new image(s) can be found here: ./mkefidisk-201804191017-sda.direct The following build artifacts were used to create the image(s): ROOTFS_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs BOOTIMG_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share KERNEL_DIR: /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86 NATIVE_SYSROOT: /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native INFO: The image(s) were created using OE kickstart file: /home/stephano/build/master/openembedded-core/scripts/lib/wic/canned-wks/mkefidisk.wks
The previous example shows the easiest way to create
an image by running in cooked mode and supplying
a kickstart file and the "-e" option to point to the
existing build artifacts.
Your local.conf
file needs to have
the
MACHINE
variable set to the machine you are using, which is
"qemux86" in this example.
Once the image builds, the output provides image location, artifact use, and kickstart file information.
Continuing with the example, you can now write the
image from the Build Directory onto a USB stick, or
whatever media for which you built your image, and boot
from the media.
You can write the image by using
bmaptool
or
dd
:
$ oe-run-native bmaptool copy mkefidisk-201804191017-sda.direct /dev/sdX
or
$ sudo dd if=mkefidisk-201804191017-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-gpt
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 the
directdisk-gpt.wks
file resides is
scripts/lib/image/canned-wks/
,
which is located in the
Source Directory
(e.g. poky
).
Because 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-gpt
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-gpt
kickstart file
uses.
The example begins by making a copy of the
directdisk-gpt.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/stephano/poky/scripts/lib/wic/canned-wks/directdisk-gpt.wks \ /home/stephano/poky/scripts/lib/wic/canned-wks/directdisksdb-gpt.wks
Next, the example modifies the
directdisksdb-gpt.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=ext4 --label platform --align 1024 --use-uuid
Once the lines are changed, the example generates the
directdisksdb-gpt
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-gpt -e core-image-minimal INFO: Building wic-tools... . . . Initialising tasks: 100% |#######################################| Time: 0:00:01 NOTE: Executing SetScene Tasks NOTE: Executing RunQueue Tasks NOTE: Tasks Summary: Attempted 1161 tasks of which 1157 didn't need to be rerun and all succeeded. INFO: Creating image(s)... INFO: The new image(s) can be found here: ./directdisksdb-gpt-201710090938-sdb.direct The following build artifacts were used to create the image(s): ROOTFS_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs BOOTIMG_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share KERNEL_DIR: /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86 NATIVE_SYSROOT: /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native INFO: The image(s) were created using OE kickstart file: /home/stephano/poky/scripts/lib/wic/canned-wks/directdisksdb-gpt.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=directdisksdb-gpt-201710090938-sdb.direct of=/dev/sdb 140966+0 records in 140966+0 records out 72174592 bytes (72 MB, 69 MiB) copied, 78.0282 s, 925 kB/s $ sudo eject /dev/sdb
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 /home/stephano/my_yocto/test.wks -o /home/stephano/testwic \ --rootfs-dir /home/stephano/build/master/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/rootfs \ --bootimg-dir /home/stephano/build/master/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share \ --kernel-dir /home/stephano/build/master/build/tmp/deploy/images/qemux86 \ --native-sysroot /home/stephano/build/master/build/tmp/work/i586-poky-linux/wic-tools/1.0-r0/recipe-sysroot-native INFO: Creating image(s)... INFO: The new image(s) can be found here: /home/stephano/testwic/test-201710091445-sdb.direct The following build artifacts were used to create the image(s): ROOTFS_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs BOOTIMG_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share KERNEL_DIR: /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86 NATIVE_SYSROOT: /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native INFO: The image(s) were created using OE kickstart file: /home/stephano/my_yocto/test.wks
For this example,
MACHINE
did not have to be specified in the
local.conf
file since the
artifact is manually specified.
Wic image manipulation allows you to shorten turnaround time during image development. For example, you can use Wic to delete the kernel partition of a Wic image and then insert a newly built kernel. This saves you time from having to rebuild the entire image each time you modify the kernel.
mtools
package installed.
The following example examines the contents of the Wic image, deletes the existing kernel, and then inserts a new kernel:
List the Partitions:
Use the wic ls
command to list
all the partitions in the Wic image:
$ wic ls tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic Num Start End Size Fstype 1 1048576 25041919 23993344 fat16 2 25165824 72157183 46991360 ext4
The previous output shows two partitions in the
core-image-minimal-qemux86.wic
image.
Examine a Particular Partition:
Use the wic ls
command again
but in a different form to examine a particular
partition.
$ wic help command
For example, the following command shows you
the various ways to use the
wic ls
command:
$ wic help ls
The following command shows what is in Partition one:
$ wic ls tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1 Volume in drive : is boot Volume Serial Number is E894-1809 Directory for ::/ libcom32 c32 186500 2017-10-09 16:06 libutil c32 24148 2017-10-09 16:06 syslinux cfg 220 2017-10-09 16:06 vesamenu c32 27104 2017-10-09 16:06 vmlinuz 6904608 2017-10-09 16:06 5 files 7 142 580 bytes 16 582 656 bytes free
The previous output shows five files, with the
vmlinuz
being the kernel.
~/.mtoolsrc
file and
be sure to have the line “mtools_skip_check=1“
in the file.
Then, run the Wic command again:
ERROR: _exec_cmd: /usr/bin/mdir -i /tmp/wic-parttfokuwra ::/ returned '1' instead of 0 output: Total number of sectors (47824) not a multiple of sectors per track (32)! Add mtools_skip_check=1 to your .mtoolsrc file to skip this test
Remove the Old Kernel:
Use the wic rm
command to
remove the vmlinuz
file
(kernel):
$ wic rm tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1/vmlinuz
Add In the New Kernel:
Use the wic cp
command to
add the updated kernel to the Wic image.
Depending on how you built your kernel, it could
be in different places.
If you used devtool
and
an SDK to build your kernel, it resides in the
tmp/work
directory of the
extensible SDK.
If you used make
to build the
kernel, the kernel will be in the
workspace/sources
area.
The following example assumes
devtool
was used to build
the kernel:
cp ~/poky_sdk/tmp/work/qemux86-poky-linux/linux-yocto/4.12.12+git999-r0/linux-yocto-4.12.12+git999/arch/x86/boot/bzImage \ ~/poky/build/tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1/vmlinuz
Once the new kernel is added back into the image,
you can use the dd
command or
bmaptool
to flash your wic image onto an SD card
or USB stick and test your target.
bmaptool
is
generally 10 to 20 times faster than using
dd
.
bmaptool
¶A fast and easy way to flash an image to a bootable device is to use Bmaptool, which is integrated into the OpenEmbedded build system. Bmaptool is a generic tool that creates a file's block map (bmap) and then uses that map to copy the file. As compared to traditional tools such as dd or cp, Bmaptool can copy (or flash) large files like raw system image files much faster.
If you are using Ubuntu or Debian distributions, you
can install the 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
If you are unable to install the
bmap-tools
package, you will
need to build Bmaptool before using it.
Use the following command:
$ bitbake bmap-tools-native
Following, is an example that shows how to flash a Wic image. Realize that while this example uses a Wic image, you can use Bmaptool to flash any type of image. Use these steps to flash an image using Bmaptool:
Update your local.conf
File:
You need to have the following set in your
local.conf
file before building
your image:
IMAGE_FSTYPES += "wic wic.bmap"
Get Your Image:
Either have your image ready (pre-built with the
IMAGE_FSTYPES
setting previously mentioned) or take the step to build
the image:
$ bitbake image
Flash the Device:
Flash the device with the image by using Bmaptool
depending on your particular setup.
The following commands assume the image resides in the
Build Directory's deploy/images/
area:
If you have write access to the media, use this command form:
$ oe-run-native bmap-tools-native bmaptool copybuild-directory
/tmp/deploy/images/machine
/image
.wic /dev/sdX
If you do not have write access to the media, set your permissions first and then use the same command form:
$ sudo chmod 666 /dev/sdX
$ oe-run-native bmap-tools-native bmaptool copybuild-directory
/tmp/deploy/images/machine
/image
.wic /dev/sdX
For help on the bmaptool
command, use the
following command:
$ bmaptool --help
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 bitbake-layers
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
"Following Best Practices 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
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 script that sets up the build environment
(i.e.
oe-init-build-env
)
uses 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.
To help conserve disk space during builds, you can add the
following statement to your project's
local.conf
configuration file found in the
Build Directory:
INHERIT += "rm_work"
Adding this statement deletes the work directory used for building
a recipe once the recipe is built.
For more information on "rm_work", see the
rm_work
class in the Yocto Project Reference Manual.
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.
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 Overview and Concepts 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 produces a number of packages (e.g.
bash
, bash-bashbug
,
bash-completion
,
bash-completion-dbg
,
bash-completion-dev
,
bash-completion-extra
,
bash-dbg
, and so forth).
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 or 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). In fact, doing so is advantageous for a production environment as getting the packages away from the development system's build directory prevents accidental overwrites.
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 qemux86
device produces the following three package databases:
noarch
, i586
, and
qemux86
.
If you wanted your qemux86
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", "deb", or "tar" 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 existing package, it is always a good idea to re-generate the package index after the build by using the following command:
$ bitbake package-index
It might be tempting to build the package and the package index at the same time with a command such as the following:
$ bitbake some-package
package-index
Do not do this as BitBake does not schedule the package index for after the completion of the package you are building. Consequently, you cannot be sure of the package index including information for the package you just built. Thus, be sure to run the package update step separately after building any packages.
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 RPM, then your RPM packages are available in
tmp/deploy/rpm
.
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
Dandified Packaging Tool
(DNF) performs runtime package management of RPM
packages.
In order to use DNF for runtime package management,
you must perform an initial setup on the target
machine for cases where the
PACKAGE_FEED_*
variables were not
set as part of the image that is running on the
target.
This means if you built your image and did not not use
these variables as part of the build and your image is
now running on the target, you need to perform the
steps in this section if you want to use runtime
package management.
PACKAGE_FEED_*
variables, see
PACKAGE_FEED_ARCHS
,
PACKAGE_FEED_BASE_PATHS
,
and
PACKAGE_FEED_URIS
in the Yocto Project Reference Manual variables
glossary.
On the target, you must inform DNF that package
databases are available.
You do this by creating a file named
/etc/yum.repos.d/oe-packages.repo
and defining the oe-packages
.
As an example, assume the target is able to use the
following package databases:
all
, i586
,
and qemux86
from a server named
my.server
.
The specifics for setting up the web server are up to
you.
The critical requirement is that the URIs in the
target repository configuration point to the
correct remote location for the feeds.
deploy
directory.
However, for production use, it is better to copy
the package directories to a location outside of
the build area and use that location.
Doing so avoids situations where the build system
overwrites or changes the
deploy
directory.
When telling DNF where to look for the package databases, you must declare individual locations per architecture or a single location used for all architectures. You cannot do both:
Create an Explicit List of Architectures: Define individual base URLs to identify where each package database is located:
[oe-packages] baseurl=http://my.server/rpm/i586 http://my.server/rpm/qemux86 http://my.server/rpm/all
This example informs DNF about individual package databases for all three architectures.
Create a Single (Full) Package Index: Define a single base URL that identifies where a full package database is located:
[oe-packages] baseurl=http://my.server/rpm
This example informs DNF about a single package database that contains all the package index information for all supported architectures.
Once you have informed DNF where to find the package databases, you need to fetch them:
# dnf makecache
DNF is now able to find, install, and upgrade packages from the specified repository or repositories.
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 signed package feeds for IPK and RPM 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 shows you how you can use mirrors to speed up fetching source files and how you can pre-fetch files all of which leads to more efficient use of resources and time.
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 target
runall="fetch"
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 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
).
Many factors can influence the quality of a build. For example, if you upgrade a recipe to use a new version of an upstream software package or you experiment with some new configuration options, subtle changes can occur that you might not detect until later. Consider the case where your recipe is using a newer version of an upstream package. In this case, a new version of a piece of software might introduce an optional dependency on another library, which is auto-detected. If that library has already been built when the software is building, the software will link to the built library and that library will be pulled into your image along with the new software even if you did not want the library.
The
buildhistory
class exists to help you maintain the quality of your build
output.
You can use the class to highlight unexpected and possibly
unwanted changes in the build output.
When you enable build history, it records information about the
contents of each package and image and then commits that
information to a local Git repository where you can examine
the information.
The remainder of this section describes the following:
How you can enable and disable build history
How to understand what the build history contains
How to limit the information used for build history
How to examine the build history from both a command-line and web interface
Build history is disabled by default.
To enable it, add the following INHERIT
statement and set the
BUILDHISTORY_COMMIT
variable to "1" at the end of your
conf/local.conf
file found in the
Build Directory:
INHERIT += "buildhistory" BUILDHISTORY_COMMIT = "1"
Enabling build history as previously described causes the OpenEmbedded build system to collect build output information and commit it as a single commit to a local Git repository.
You can disable build history by removing the previous
statements from your conf/local.conf
file.
Build history information is kept in
${
TOPDIR
}/buildhistory
in the Build Directory as defined by the
BUILDHISTORY_DIR
variable.
The following is an example abbreviated listing:
At the top level, a metadata-revs
file exists that lists the revisions of the repositories for
the enabled layers when the build was produced.
The rest of the data splits into separate
packages
, images
and sdk
directories, the contents of
which are described as follows.
The history for each package contains a text file that has
name-value pairs with information about the package.
For example,
buildhistory/packages/i586-poky-linux/busybox/busybox/latest
contains the following:
PV = 1.22.1 PR = r32 RPROVIDES = RDEPENDS = glibc (>= 2.20) update-alternatives-opkg RRECOMMENDS = busybox-syslog busybox-udhcpc update-rc.d PKGSIZE = 540168 FILES = /usr/bin/* /usr/sbin/* /usr/lib/busybox/* /usr/lib/lib*.so.* \ /etc /com /var /bin/* /sbin/* /lib/*.so.* /lib/udev/rules.d \ /usr/lib/udev/rules.d /usr/share/busybox /usr/lib/busybox/* \ /usr/share/pixmaps /usr/share/applications /usr/share/idl \ /usr/share/omf /usr/share/sounds /usr/lib/bonobo/servers FILELIST = /bin/busybox /bin/busybox.nosuid /bin/busybox.suid /bin/sh \ /etc/busybox.links.nosuid /etc/busybox.links.suid
Most of these name-value pairs correspond to variables
used to produce the package.
The exceptions are FILELIST
, which
is the actual list of files in the package, and
PKGSIZE
, which is the total size of
files in the package in bytes.
A file also exists that corresponds to the recipe from
which the package came (e.g.
buildhistory/packages/i586-poky-linux/busybox/latest
):
PV = 1.22.1 PR = r32 DEPENDS = initscripts kern-tools-native update-rc.d-native \ virtual/i586-poky-linux-compilerlibs virtual/i586-poky-linux-gcc \ virtual/libc virtual/update-alternatives PACKAGES = busybox-ptest busybox-httpd busybox-udhcpd busybox-udhcpc \ busybox-syslog busybox-mdev busybox-hwclock busybox-dbg \ busybox-staticdev busybox-dev busybox-doc busybox-locale busybox
Finally, for those recipes fetched from a version control
system (e.g., Git), a file exists that lists source
revisions that are specified in the recipe and lists
the actual revisions used during the build.
Listed and actual revisions might differ when
SRCREV
is set to
${AUTOREV
}.
Here is an example assuming
buildhistory/packages/qemux86-poky-linux/linux-yocto/latest_srcrev
):
# SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1" SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1" # SRCREV_meta = "a227f20eff056e511d504b2e490f3774ab260d6f" SRCREV_meta = "a227f20eff056e511d504b2e490f3774ab260d6f"
You can use the
buildhistory-collect-srcrevs
command with the -a
option to
collect the stored SRCREV
values
from build history and report them in a format suitable for
use in global configuration (e.g.,
local.conf
or a distro include file)
to override floating AUTOREV
values
to a fixed set of revisions.
Here is some example output from this command:
$ buildhistory-collect-srcrevs -a # i586-poky-linux SRCREV_pn-glibc = "b8079dd0d360648e4e8de48656c5c38972621072" SRCREV_pn-glibc-initial = "b8079dd0d360648e4e8de48656c5c38972621072" SRCREV_pn-opkg-utils = "53274f087565fd45d8452c5367997ba6a682a37a" SRCREV_pn-kmod = "fd56638aed3fe147015bfa10ed4a5f7491303cb4" # x86_64-linux SRCREV_pn-gtk-doc-stub-native = "1dea266593edb766d6d898c79451ef193eb17cfa" SRCREV_pn-dtc-native = "65cc4d2748a2c2e6f27f1cf39e07a5dbabd80ebf" SRCREV_pn-update-rc.d-native = "eca680ddf28d024954895f59a241a622dd575c11" SRCREV_glibc_pn-cross-localedef-native = "b8079dd0d360648e4e8de48656c5c38972621072" SRCREV_localedef_pn-cross-localedef-native = "c833367348d39dad7ba018990bfdaffaec8e9ed3" SRCREV_pn-prelink-native = "faa069deec99bf61418d0bab831c83d7c1b797ca" SRCREV_pn-opkg-utils-native = "53274f087565fd45d8452c5367997ba6a682a37a" SRCREV_pn-kern-tools-native = "23345b8846fe4bd167efdf1bd8a1224b2ba9a5ff" SRCREV_pn-kmod-native = "fd56638aed3fe147015bfa10ed4a5f7491303cb4" # qemux86-poky-linux SRCREV_machine_pn-linux-yocto = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1" SRCREV_meta_pn-linux-yocto = "a227f20eff056e511d504b2e490f3774ab260d6f" # all-poky-linux SRCREV_pn-update-rc.d = "eca680ddf28d024954895f59a241a622dd575c11"
buildhistory-collect-srcrevs
command:
By default, only values where the
SRCREV
was not hardcoded
(usually when AUTOREV
is used) are reported.
Use the -a
option to
see all SRCREV
values.
The output statements might not have any effect
if overrides are applied elsewhere in the
build system configuration.
Use the -f
option to add
the forcevariable
override
to each output line if you need to work around
this restriction.
The script does apply special handling when
building for multiple machines.
However, the script does place a comment before
each set of values that specifies which
triplet to which they belong as previously
shown (e.g.,
i586-poky-linux
).
The files produced for each image are as follows:
image-files:
A directory containing selected files from the root
filesystem.
The files are defined by
BUILDHISTORY_IMAGE_FILES
.
build-id.txt:
Human-readable information about the build
configuration and metadata source revisions.
This file contains the full build header as printed
by BitBake.
*.dot:
Dependency graphs for the image that are
compatible with graphviz
.
files-in-image.txt:
A list of files in the image with permissions,
owner, group, size, and symlink information.
image-info.txt:
A text file containing name-value pairs with
information about the image.
See the following listing example for more
information.
installed-package-names.txt:
A list of installed packages by name only.
installed-package-sizes.txt:
A list of installed packages ordered by size.
installed-packages.txt:
A list of installed packages with full package
filenames.
Here is an example of image-info.txt
:
DISTRO = poky DISTRO_VERSION = 1.7 USER_CLASSES = buildstats image-mklibs image-prelink IMAGE_CLASSES = image_types IMAGE_FEATURES = debug-tweaks IMAGE_LINGUAS = IMAGE_INSTALL = packagegroup-core-boot run-postinsts BAD_RECOMMENDATIONS = NO_RECOMMENDATIONS = PACKAGE_EXCLUDE = ROOTFS_POSTPROCESS_COMMAND = write_package_manifest; license_create_manifest; \ write_image_manifest ; buildhistory_list_installed_image ; \ buildhistory_get_image_installed ; ssh_allow_empty_password; \ postinst_enable_logging; rootfs_update_timestamp ; ssh_disable_dns_lookup ; IMAGE_POSTPROCESS_COMMAND = buildhistory_get_imageinfo ; IMAGESIZE = 6900
Other than IMAGESIZE
, which is the
total size of the files in the image in Kbytes, the
name-value pairs are variables that may have influenced the
content of the image.
This information is often useful when you are trying to
determine why a change in the package or file
listings has occurred.
As you can see, build history produces image information,
including dependency graphs, so you can see why something
was pulled into the image.
If you are just interested in this information and not
interested in collecting specific package or SDK
information, you can enable writing only image information
without any history by adding the following to your
conf/local.conf
file found in the
Build Directory:
INHERIT += "buildhistory" BUILDHISTORY_COMMIT = "0" BUILDHISTORY_FEATURES = "image"
Here, you set the
BUILDHISTORY_FEATURES
variable to use the image feature only.
Build history collects similar information on the contents
of SDKs
(e.g. bitbake -c populate_sdk imagename
)
as compared to information it collects for images.
Furthermore, this information differs depending on whether
an extensible or standard SDK is being produced.
The following list shows the files produced for SDKs:
files-in-sdk.txt:
A list of files in the SDK with permissions,
owner, group, size, and symlink information.
This list includes both the host and target parts
of the SDK.
sdk-info.txt:
A text file containing name-value pairs with
information about the SDK.
See the following listing example for more
information.
sstate-task-sizes.txt:
A text file containing name-value pairs with
information about task group sizes
(e.g. do_populate_sysroot
tasks have a total size).
The sstate-task-sizes.txt
file
exists only when an extensible SDK is created.
sstate-package-sizes.txt:
A text file containing name-value pairs with
information for the shared-state packages and
sizes in the SDK.
The sstate-package-sizes.txt
file exists only when an extensible SDK is created.
sdk-files:
A folder that contains copies of the files
mentioned in
BUILDHISTORY_SDK_FILES
if the
files are present in the output.
Additionally, the default value of
BUILDHISTORY_SDK_FILES
is
specific to the extensible SDK although you can
set it differently if you would like to pull in
specific files from the standard SDK.
The default files are
conf/local.conf
,
conf/bblayers.conf
,
conf/auto.conf
,
conf/locked-sigs.inc
, and
conf/devtool.conf
.
Thus, for an extensible SDK, these files get
copied into the sdk-files
directory.
The following information appears under
each of the host
and target
directories
for the portions of the SDK that run on the host
and on the target, respectively:
depends.dot:
Dependency graph for the SDK that is
compatible with
graphviz
.
installed-package-names.txt:
A list of installed packages by name only.
installed-package-sizes.txt:
A list of installed packages ordered by size.
installed-packages.txt:
A list of installed packages with full
package filenames.
Here is an example of sdk-info.txt
:
DISTRO = poky DISTRO_VERSION = 1.3+snapshot-20130327 SDK_NAME = poky-glibc-i686-arm SDK_VERSION = 1.3+snapshot SDKMACHINE = SDKIMAGE_FEATURES = dev-pkgs dbg-pkgs BAD_RECOMMENDATIONS = SDKSIZE = 352712
Other than SDKSIZE
, which is the
total size of the files in the SDK in Kbytes, the
name-value pairs are variables that might have influenced
the content of the SDK.
This information is often useful when you are trying to
determine why a change in the package or file listings
has occurred.
You can examine build history output from the command line or from a web interface.
To see any changes that have occurred (assuming you have
BUILDHISTORY_COMMIT
= "1"
),
you can simply use any Git command that allows you to
view the history of a repository.
Here is one method:
$ git log -p
You need to realize, however, that this method does show changes that are not significant (e.g. a package's size changing by a few bytes).
A command-line tool called
buildhistory-diff
does exist, though,
that queries the Git repository and prints just the
differences that might be significant in human-readable
form.
Here is an example:
$ ~/poky/poky/scripts/buildhistory-diff . HEAD^ Changes to images/qemux86_64/glibc/core-image-minimal (files-in-image.txt): /etc/anotherpkg.conf was added /sbin/anotherpkg was added * (installed-package-names.txt): * anotherpkg was added Changes to images/qemux86_64/glibc/core-image-minimal (installed-package-names.txt): anotherpkg was added packages/qemux86_64-poky-linux/v86d: PACKAGES: added "v86d-extras" * PR changed from "r0" to "r1" * PV changed from "0.1.10" to "0.1.12" packages/qemux86_64-poky-linux/v86d/v86d: PKGSIZE changed from 110579 to 144381 (+30%) * PR changed from "r0" to "r1" * PV changed from "0.1.10" to "0.1.12"
buildhistory-diff
tool
requires the GitPython
package.
Be sure to install it using Pip3 as follows:
$ pip3 install GitPython --userAlternatively, you can install
python3-git
using the appropriate
distribution package manager (e.g.
apt-get
, dnf
,
or zipper
).
To see changes to the build history using a web interface,
follow the instruction in the README
file here.
http://git.yoctoproject.org/cgit/cgit.cgi/buildhistory-web/.
Here is a sample screenshot of the interface:
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.
Be sure to use an absolute path when calling this script with sudo.
The package recipe
qemu-helper-native
is required to run this script.
Build the package using the
following command:
$ bitbake qemu-helper-native
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 } ] }
The exact method for debugging build failures depends on the nature of the problem and on the system's area from which the bug originates. Standard debugging practices such as comparison against the last known working version with examination of the changes and the re-application of steps to identify the one causing the problem are valid for the Yocto Project just as they are for any other system. Even though it is impossible to detail every possible potential failure, this section provides some general tips to aid in debugging given a variety of situations.
The following list shows the debugging topics in the remainder of this section:
"Viewing Logs from Failed Tasks" describes how to find and view logs from tasks that failed during the build process.
"Viewing Variable Values"
describes how to use the BitBake -e
option to examine variable values after a recipe has been
parsed.
"Viewing Package Information with oe-pkgdata-util
"
describes how to use the
oe-pkgdata-util
utility to query
PKGDATA_DIR
and display package-related information for built
packages.
"Viewing Dependencies Between Recipes and Tasks"
describes how to use the BitBake -g
option to display recipe dependency information used
during the build.
"Viewing Task Variable Dependencies"
describes how to use the
bitbake-dumpsig
command in
conjunction with key subdirectories in the
Build Directory
to determine variable dependencies.
"Running Specific Tasks"
describes how to use several BitBake options (e.g.
-c
, -C
, and
-f
) to run specific tasks in the
build chain.
It can be useful to run tasks "out-of-order" when trying
isolate build issues.
"General BitBake Problems"
describes how to use BitBake's -D
debug output option to reveal more about what BitBake is
doing during the build.
"Building with No Dependencies"
describes how to use the BitBake -b
option to build a recipe while ignoring dependencies.
"Recipe Logging Mechanisms" describes how to use the many recipe logging functions to produce debugging output and report errors and warnings.
"Debugging Parallel Make Races" describes how to debug situations where the build consists of several parts that are run simultaneously and 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.
"Debugging With the GNU Project Debugger (GDB) Remotely" describes how to use GDB to allow you to examine running programs, which can help you fix problems.
"Debugging with the GNU Project Debugger (GDB) on the Target" describes how to use GDB directly on target hardware for debugging.
"Other Debugging Tips" describes miscellaneous debugging tips that can be useful.
For debugging information within the popular Eclipse™ IDE, see the "Working within Eclipse" section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.
You can find the log for a task in the file
${
WORKDIR
}/temp/log.do_
taskname
.
For example, the log for the
do_compile
task of the QEMU minimal image for the x86 machine
(qemux86
) might be in
tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_compile
.
To see the commands
BitBake
ran to generate a log, look at the corresponding
run.do_
taskname
file in the same directory.
log.do_
taskname
and
run.do_
taskname
are actually symbolic links to
log.do_
taskname
.
pid
and
log.run_
taskname
.
pid
,
where pid
is the PID the task had
when it ran.
The symlinks always point to the files corresponding to the most
recent run.
BitBake's -e
option is used to display
variable values after parsing.
The following command displays the variable values after the
configuration files (i.e. local.conf
,
bblayers.conf
,
bitbake.conf
and so forth) have been
parsed:
$ bitbake -e
The following command displays variable values after a specific recipe has been parsed. The variables include those from the configuration as well:
$ bitbake -e recipename
Each recipe has its own private set of variables (datastore). Internally, after parsing the configuration, a copy of the resulting datastore is made prior to parsing each recipe. This copying implies that variables set in one recipe will not be visible to other recipes.
Likewise, each task within a recipe gets a private datastore based on the recipe datastore, which means that variables set within one task will not be visible to other tasks.
In the output of bitbake -e
, each
variable is preceded by a description of how the variable
got its value, including temporary values that were later
overriden.
This description also includes variable flags (varflags) set on
the variable.
The output can be very helpful during debugging.
Variables that are exported to the environment are preceded by
export
in the output of
bitbake -e
.
See the following example:
export CC="i586-poky-linux-gcc -m32 -march=i586 --sysroot=/home/ulf/poky/build/tmp/sysroots/qemux86"
In addition to variable values, the output of the
bitbake -e
and
bitbake -e
recipe
commands includes the following information:
The output starts with a tree listing all configuration
files and classes included globally, recursively listing
the files they include or inherit in turn.
Much of the behavior of the OpenEmbedded build system
(including the behavior of the
normal recipe build tasks)
is implemented in the
base
class and the classes it inherits, rather than being
built into BitBake itself.
After the variable values, all functions appear in the
output.
For shell functions, variables referenced within the
function body are expanded.
If a function has been modified using overrides or
using override-style operators like
_append
and
_prepend
, then the final assembled
function body appears in the output.
oe-pkgdata-util
¶
You can use the oe-pkgdata-util
command-line utility to query
PKGDATA_DIR
and display various package-related information.
When you use the utility, you must use it to view information
on packages that have already been built.
Following are a few of the available
oe-pkgdata-util
subcommands.
oe-pkgdata-util list-pkgs [
pattern
]
:
Lists all packages that have been built, optionally
limiting the match to packages that match
pattern
.
oe-pkgdata-util list-pkg-files
package
...
:
Lists the files and directories contained in the given
packages.
A different way to view the contents of a package is
to look at the
${
WORKDIR
}/packages-split
directory of the recipe that generates the
package.
This directory is created by the
do_package
task and has one subdirectory for each package the
recipe generates, which contains the files stored in
that package.
If you want to inspect the
${WORKDIR}/packages-split
directory, make sure that
rm_work
is not enabled when you build the recipe.
oe-pkgdata-util find-path
path
...
:
Lists the names of the packages that contain the given
paths.
For example, the following tells us that
/usr/share/man/man1/make.1
is contained in the make-doc
package:
$ oe-pkgdata-util find-path /usr/share/man/man1/make.1 make-doc: /usr/share/man/man1/make.1
oe-pkgdata-util lookup-recipe
package
...
:
Lists the name of the recipes that
produce the given packages.
For more information on the oe-pkgdata-util
command, use the help facility:
$ oe-pkgdata-util ‐‐help
$ oe-pkgdata-util subcommand
--help
Sometimes it can be hard to see why BitBake wants to build other recipes before the one you have specified. Dependency information can help you understand why a recipe is built.
To generate dependency information for a recipe, run the following command:
$ bitbake -g recipename
This command writes the following files in the current directory:
pn-buildlist
: A list of
recipes/targets involved in building
recipename
.
"Involved" here means that at least one task from the
recipe needs to run when building
recipename
from scratch.
Targets that are in
ASSUME_PROVIDED
are not listed.
task-depends.dot
: A graph showing
dependencies between tasks.
The graphs are in
DOT
format and can be converted to images (e.g. using the
dot
tool from
Graphviz).
DOT files use a plain text format.
The graphs generated using the
bitbake -g
command are often so
large as to be difficult to read without special
pruning (e.g. with Bitbake's
-I
option) and processing.
Despite the form and size of the graphs, the
corresponding .dot
files can
still be possible to read and provide useful
information.
As an example, the
task-depends.dot
file contains
lines such as the following:
"libxslt.do_configure" -> "libxml2.do_populate_sysroot"
The above example line reveals that the
do_configure
task in libxslt
depends on the
do_populate_sysroot
task in libxml2
, which is a
normal
DEPENDS
dependency between the two recipes.
For an example of how .dot
files can be processed, see the
scripts/contrib/graph-tool
Python script, which finds and displays paths
between graph nodes.
You can use a different method to view dependency information by using the following command:
$ bitbake -g -u taskexp recipename
This command displays a GUI window from which you can view
build-time and runtime dependencies for the recipes involved in
building recipename
.
As mentioned in the
"Checksums (Signatures)"
section of the BitBake User Manual, BitBake tries to
automatically determine what variables a task depends on so
that it can rerun the task if any values of the variables
change.
This determination is usually reliable.
However, if you do things like construct variable names at
runtime, then you might have to manually declare dependencies
on those variables using vardeps
as
described in the
"Variable Flags"
section of the BitBake User Manual.
If you are unsure whether a variable dependency is being picked up automatically for a given task, you can list the variable dependencies BitBake has determined by doing the following:
Build the recipe containing the task:
$ bitbake recipename
Inside the
STAMPS_DIR
directory, find the signature data
(sigdata
) file that corresponds
to the task.
The sigdata
files contain a pickled
Python database of all the metadata that went into
creating the input checksum for the task.
As an example, for the
do_fetch
task of the db
recipe, the
sigdata
file might be found in the
following location:
${BUILDDIR}/tmp/stamps/i586-poky-linux/db/6.0.30-r1.do_fetch.sigdata.7c048c18222b16ff0bcee2000ef648b1
For tasks that are accelerated through the shared state
(sstate)
cache, an additional siginfo
file
is written into
SSTATE_DIR
along with the cached task output.
The siginfo
files contain exactly
the same information as sigdata
files.
Run bitbake-dumpsig
on the
sigdata
or
siginfo
file.
Here is an example:
$ bitbake-dumpsig ${BUILDDIR}/tmp/stamps/i586-poky-linux/db/6.0.30-r1.do_fetch.sigdata.7c048c18222b16ff0bcee2000ef648b1
In the output of the above command, you will find a line like the following, which lists all the (inferred) variable dependencies for the task. This list also includes indirect dependencies from variables depending on other variables, recursively.
Task dependencies: ['PV', 'SRCREV', 'SRC_URI', 'SRC_URI[md5sum]', 'SRC_URI[sha256sum]', 'base_do_fetch']
base_do_fetch
)
also count as variable dependencies.
These functions in turn depend on the variables they
reference.
The output of bitbake-dumpsig
also
includes the value each variable had, a list of
dependencies for each variable, and
BB_HASHBASE_WHITELIST
information.
There is also a bitbake-diffsigs
command
for comparing two siginfo
or
sigdata
files.
This command can be helpful when trying to figure out what
changed between two versions of a task.
If you call bitbake-diffsigs
with just one
file, the command behaves like
bitbake-dumpsig
.
You can also use BitBake to dump out the signature construction information without executing tasks by using either of the following BitBake command-line options:
‐‐dump-signatures=SIGNATURE_HANDLER
-SSIGNATURE_HANDLER
SIGNATURE_HANDLER
are "none" and
"printdiff", which dump only the signature or compare the
dumped signature with the cached one, respectively.
Using BitBake with either of these options causes BitBake to
dump out sigdata
files in the
stamps
directory for every task it would
have executed instead of building the specified target package.
Seeing what metadata went into creating the input signature
of a shared state (sstate) task can be a useful debugging
aid.
This information is available in signature information
(siginfo
) files in
SSTATE_DIR
.
For information on how to view and interpret information in
siginfo
files, see the
"Viewing Task Variable Dependencies"
section.
For conceptual information on shared state, see the "Shared State" section in the Yocto Project Overview and Concepts Manual.
The OpenEmbedded build system uses checksums and shared state cache to avoid unnecessarily rebuilding tasks. Collectively, this scheme is known as "shared state code."
As with all schemes, this one has some drawbacks.
It is possible that you could make implicit changes to your
code that the checksum calculations do not take into
account.
These implicit changes affect a task's output but do not
trigger the shared state code into rebuilding a recipe.
Consider an example during which a tool changes its output.
Assume that the output of rpmdeps
changes.
The result of the change should be that all the
package
and
package_write_rpm
shared state cache
items become invalid.
However, because the change to the output is
external to the code and therefore implicit,
the associated shared state cache items do not become
invalidated.
In this case, the build process uses the cached items
rather than running the task again.
Obviously, these types of implicit changes can cause
problems.
To avoid these problems during the build, you need to understand the effects of any changes you make. Realize that changes you make directly to a function are automatically factored into the checksum calculation. Thus, these explicit changes invalidate the associated area of shared state cache. However, you need to be aware of any implicit changes that are not obvious changes to the code and could affect the output of a given task.
When you identify an implicit change, you can easily
take steps to invalidate the cache and force the tasks
to run.
The steps you can take are as simple as changing a
function's comments in the source code.
For example, to invalidate package shared state files,
change the comment statements of
do_package
or the comments of one of the functions it calls.
Even though the change is purely cosmetic, it causes the
checksum to be recalculated and forces the build system to
run the task again.
Any given recipe consists of a set of tasks.
The standard BitBake behavior in most cases is:
do_fetch
,
do_unpack
,
do_patch
,
do_configure
,
do_compile
,
do_install
,
do_package
,
do_package_write_*
, and
do_build
.
The default task is do_build
and any tasks
on which it depends build first.
Some tasks, such as do_devshell
, are not
part of the default build chain.
If you wish to run a task that is not part of the default build
chain, you can use the -c
option in
BitBake.
Here is an example:
$ bitbake matchbox-desktop -c devshell
The -c
option respects task dependencies,
which means that all other tasks (including tasks from other
recipes) that the specified task depends on will be run before
the task.
Even when you manually specify a task to run with
-c
, BitBake will only run the task if it
considers it "out of date".
See the
"Stamp Files and the Rerunning of Tasks"
section in the Yocto Project Overview and Concepts Manual for
how BitBake determines whether a task is "out of date".
If you want to force an up-to-date task to be rerun (e.g.
because you made manual modifications to the recipe's
WORKDIR
that you want to try out), then you can use the
-f
option.
-f
is never required when
running the
do_devshell
task is because the
[
nostamp
]
variable flag is already set for the task.
The following example shows one way you can use the
-f
option:
$ bitbake matchbox-desktop . . make some changes to the source code in the work directory . . $ bitbake matchbox-desktop -c compile -f $ bitbake matchbox-desktop
This sequence first builds and then recompiles
matchbox-desktop
.
The last command reruns all tasks (basically the packaging
tasks) after the compile.
BitBake recognizes that the do_compile
task was rerun and therefore understands that the other tasks
also need to be run again.
Another, shorter way to rerun a task and all
normal recipe build tasks
that depend on it is to use the -C
option.
-c
option, which is lower-cased.
Using this option invalidates the given task and then runs the
do_build
task, which is the default task if no task is given, and the
tasks on which it depends.
You could replace the final two commands in the previous example
with the following single command:
$ bitbake matchbox-desktop -C compile
Internally, the -f
and
-C
options work by tainting (modifying) the
input checksum of the specified task.
This tainting indirectly causes the task and its
dependent tasks to be rerun through the normal task dependency
mechanisms.
WARNING: /home/ulf/poky/meta/recipes-sato/matchbox-desktop/matchbox-desktop_2.1.bb.do_compile is tainted from a forced runThe purpose of the warning is to let you know that the work directory and build output might not be in the clean state they would be in for a "normal" build, depending on what actions you took. To get rid of such warnings, you can remove the work directory and rebuild the recipe, as follows:
$ bitbake matchbox-desktop -c clean $ bitbake matchbox-desktop
You can view a list of tasks in a given package by running the
do_listtasks
task as follows:
$ bitbake matchbox-desktop -c listtasks
The results appear as output to the console and are also in the
file ${WORKDIR}/temp/log.do_listtasks
.
You can see debug output from BitBake by using the
-D
option.
The debug output gives more information about what BitBake
is doing and the reason behind it.
Each -D
option you use increases the
logging level.
The most common usage is -DDD
.
The output from
bitbake -DDD -v
targetname
can reveal why BitBake chose a certain version of a package or
why BitBake picked a certain provider.
This command could also help you in a situation where you think
BitBake did something unexpected.
To build a specific recipe (.bb
file),
you can use the following command form:
$ bitbake -bsomepath
/somerecipe
.bb
This command form does not check for dependencies. Consequently, you should use it only when you know existing dependencies have been met.
The Yocto Project provides several logging functions for
producing debugging output and reporting errors and warnings.
For Python functions, the following logging functions exist.
All of these functions log to
${T}/log.do_
task
,
and can also log to standard output (stdout) with the right
settings:
bb.plain(
msg
)
:
Writes msg
as is to the
log while also logging to stdout.
bb.note(
msg
)
:
Writes "NOTE: msg
" to the
log.
Also logs to stdout if BitBake is called with "-v".
bb.debug(
level
,
msg
)
:
Writes "DEBUG: msg
" to the
log.
Also logs to stdout if the log level is greater than or
equal to level
.
See the
"-D"
option in the BitBake User Manual for more information.
bb.warn(
msg
)
:
Writes "WARNING: msg
" to the
log while also logging to stdout.
bb.error(
msg
)
:
Writes "ERROR: msg
" to the
log while also logging to standard out (stdout).
bb.fatal(
msg
)
:
This logging function is similar to
bb.error(
msg
)
but also causes the calling task to fail.
bb.fatal()
raises an exception,
which means you do not need to put a "return"
statement after the function.
The same logging functions are also available in shell
functions, under the names
bbplain
, bbnote
,
bbdebug
, bbwarn
,
bberror
, and bbfatal
.
The
logging
class implements these functions.
See that class in the
meta/classes
folder of the
Source Directory
for information.
When creating recipes using Python and inserting code that handles build logs, keep in mind the goal is to have informative logs while keeping the console as "silent" as possible. Also, if you want status messages in the log, use the "debug" loglevel.
Following is an example written in Python.
The code handles logging for a function that determines the
number of tasks needed to be run.
See the
"do_listtasks
"
section for additional information:
python do_listtasks() { bb.debug(2, "Starting to figure out the task list") if noteworthy_condition: bb.note("There are 47 tasks to run") bb.debug(2, "Got to point xyz") if warning_trigger: bb.warn("Detected warning_trigger, this might be a problem later.") if recoverable_error: bb.error("Hit recoverable_error, you really need to fix this!") if fatal_error: bb.fatal("fatal_error detected, unable to print the task list") bb.plain("The tasks present are abc") bb.debug(2, "Finished figuring out the tasklist") }
When creating recipes using Bash and inserting code that handles build logs, you have the same goals - informative with minimal console output. The syntax you use for recipes written in Bash is similar to that of recipes written in Python described in the previous section.
Following is an example written in Bash.
The code logs the progress of the do_my_function
function.
do_my_function() { bbdebug 2 "Running do_my_function" if [ exceptional_condition ]; then bbnote "Hit exceptional_condition" fi bbdebug 2 "Got to point xyz" if [ warning_trigger ]; then bbwarn "Detected warning_trigger, this might cause a problem later." fi if [ recoverable_error ]; then bberror "Hit recoverable_error, correcting" fi if [ fatal_error ]; then bbfatal "fatal_error detected" fi bbdebug 2 "Completed do_my_function" }
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 "Submitting a Change to the Yocto Project" section for more information.
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.
Here are some other tips that you might find useful:
When adding new packages, it is worth watching for
undesirable items making their way into compiler command
lines.
For example, you do not want references to local system
files like
/usr/lib/
or
/usr/include/
.
If you want to remove the psplash
boot splashscreen,
add psplash=false
to the kernel
command line.
Doing so prevents psplash
from
loading and thus allows you to see the console.
It is also possible to switch out of the splashscreen by
switching the virtual console (e.g. Fn+Left or Fn+Right
on a Zaurus).
Removing
TMPDIR
(usually tmp/
, within the
Build Directory)
can often fix temporary build issues.
Removing TMPDIR
is usually a
relatively cheap operation, because task output will be
cached in
SSTATE_DIR
(usually sstate-cache/
, which is
also in the Build Directory).
TMPDIR
might be a
workaround rather than a fix.
Consequently, trying to determine the underlying
cause of an issue before removing the directory is
a good idea.
Understanding how a feature is used in practice within existing recipes can be very helpful. It is recommended that you configure some method that allows you to quickly search through files.
Using GNU Grep, you can use the following shell
function to recursively search through common
recipe-related files, skipping binary files,
.git
directories, and the
Build Directory (assuming its name starts with
"build"):
g() { grep -Ir \ --exclude-dir=.git \ --exclude-dir='build*' \ --include='*.bb*' \ --include='*.inc*' \ --include='*.conf*' \ --include='*.py*' \ "$@" }
Following are some usage examples:
$ g FOO # Search recursively for "FOO" $ g -i foo # Search recursively for "foo", ignoring case $ g -w FOO # Search recursively for "FOO" as a word, ignoring e.g. "FOOBAR"
If figuring out how some feature works requires a lot of searching, it might indicate that the documentation should be extended or improved. In such cases, consider filing a documentation bug using the Yocto Project implementation of Bugzilla. For information on how to submit a bug against the Yocto Project, see the Yocto Project Bugzilla wiki page and the "Submitting a Defect Against the Yocto Project" section.
.bbclass
file).
Because the Yocto Project is an open-source, community-based project, you can effect changes to the project. This section presents procedures that show you how to submit a defect against the project and how to submit a change.
Use the Yocto Project implementation of Bugzilla to submit a defect (bug) against the Yocto Project. For additional information on this implementation of Bugzilla see the "Yocto Project Bugzilla" section in the Yocto Project Reference Manual. For more detail on any of the following steps, see the Yocto Project Bugzilla wiki page.
Use the following general steps to submit a bug"
Open the Yocto Project implementation of Bugzilla.
Click "File a Bug" to enter a new bug.
Choose the appropriate "Classification", "Product", and
"Component" for which the bug was found.
Bugs for the Yocto Project fall into one of several
classifications, which in turn break down into several
products and components.
For example, for a bug against the
meta-intel
layer, you would choose
"Build System, Metadata & Runtime", "BSPs", and
"bsps-meta-intel", respectively.
Choose the "Version" of the Yocto Project for which you found the bug (e.g. 2.5).
Determine and select the "Severity" of the bug. The severity indicates how the bug impacted your work.
Choose the "Hardware" that the bug impacts.
Choose the "Architecture" that the bug impacts.
Choose a "Documentation change" item for the bug. Fixing a bug might or might not affect the Yocto Project documentation. If you are unsure of the impact to the documentation, select "Don't Know".
Provide a brief "Summary" of the bug. Try to limit your summary to just a line or two and be sure to capture the essence of the bug.
Provide a detailed "Description" of the bug. You should provide as much detail as you can about the context, behavior, output, and so forth that surrounds the bug. You can even attach supporting files for output from logs by using the "Add an attachment" button.
Click the "Submit Bug" button submit the bug. A new Bugzilla number is assigned to the bug and the defect is logged in the bug tracking system.
Once you file a bug, the bug is processed by the Yocto Project Bug Triage Team and further details concerning the bug are assigned (e.g. priority and owner). You are the "Submitter" of the bug and any further categorization, progress, or comments on the bug result in Bugzilla sending you an automated email concerning the particular change or progress to the bug.
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.
The Yocto Project uses a mailing list and a 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.
You should send patches to the appropriate mailing list so that they
can be reviewed and merged by the appropriate maintainer.
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.
The "poky" repository, which is the Yocto Project's reference build environment, is a hybrid repository that contains several individual pieces (e.g. BitBake, Metadata, 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-*" trees: These trees contain Metadata. 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.
You can also push a change upstream and request a maintainer to pull the change into the component's upstream repository. You do this by pushing to a contribution repository that is upstream. See the "Git Workflows and the Yocto Project" section in the Yocto Project Overview and Concepts Manual for additional concepts on working in the Yocto Project development environment.
Two commonly used testing repositories exist for OpenEmbedded-Core:
"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.
The following sections provide procedures for submitting a change.
Follow this procedure to push a change to an upstream "contrib" Git repository:
Make Your Changes Locally: Make your changes in your local Git repository. You should make small, controlled, isolated 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.
Stage Your Changes:
Stage your changes by using the git add
command on each file you changed.
Commit Your Changes:
Commit the change by using the
git commit
command.
Make sure your commit information follows standards by
following these accepted conventions:
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.
Provide a single-line summary of the change. and, if more explanation is needed, provide more detail in the body of the commit. 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
Push Your Commits to a "Contrib" Upstream: If you have arranged for permissions to push to an upstream contrib repository, push the change to that repository:
$ git pushupstream_remote_repo
local_branch_name
For example, suppose you have permissions to push into the
upstream meta-intel-contrib
repository and you are working in a local branch named
your_name
/README
.
The following command pushes your local commits to the
meta-intel-contrib
upstream
repository and puts the commit in a branch named
your_name
/README
:
$ git push meta-intel-contrib your_name
/README
Determine Who to Notify: Determine the maintainer or the mailing list that you need to notify for the change.
Before submitting any change, you need to be sure who the maintainer is or what mailing list that you need to notify. Use either these methods to find out:
Maintenance File:
Examine the maintainers.inc
file, which is located in the
Source Directory
at
meta/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 everyone who has committed grouped by name. From the list, you can see who is responsible for the bulk of the changes against the file.
Examine the List of Mailing Lists: For a list of the Yocto Project and related mailing lists, see the "Mailing lists" section in the Yocto Project Reference Manual.
Make a Pull Request: Notify the maintainer or the mailing list 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
(e.g. ~/poky/scripts
).
Using these scripts correctly formats the requests without introducing any whitespace or HTML formatting. The maintainer that receives your patches either directly or through the mailing list needs to be able to save and apply them directly from your emails. Using these scripts is the preferred method for sending patches.
First, create the pull request. For example, the following command runs the script, specifies the upstream repository in the contrib directory into which you pushed the change, and provides a subject line in the created patch files:
$ ~/poky/scripts/create-pull-request -u meta-intel-contrib -s "Updated Manual Section Reference in README"
Running this script forms
*.patch
files in a folder named
pull-
PID
in the current directory.
One of the patch files is a cover letter.
Before running the
send-pull-request
script, you must
edit the cover letter patch to insert information about
your change.
After editing the cover letter, send the pull request.
For example, the following command runs the script and
specifies the patch directory and email address.
In this example, the email address is a mailing list:
$ ~/poky/scripts/send-pull-request -p ~/meta-intel/pull-10565 -t meta-intel@yoctoproject.org
You need to follow the prompts as the script is interactive.
-h
argument as follows:
$ poky/scripts/create-pull-request -h $ poky/scripts/send-pull-request -h
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 at the beginning of this section. For a description of all 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 Locally: Make your changes in your local Git repository. You should make small, controlled, isolated 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.
Stage Your Changes:
Stage your changes by using the git add
command on each file you changed.
Commit Your Changes:
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 Step 3 in the previous section for information on how to provide commit information that meets Yocto Project commit message standards.
Format the Commit:
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:
Import the files into your mail client by using the
git send-email
command.
git send-email
,
you must have the proper Git packages installed on
your host.
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
~/.gitconfig
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 using
email 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.
As mentioned in the "Licensing" section in the Yocto Project Overview and Concepts Manual, open source projects are open to the public and they consequently have different licensing structures in place. This section describes the mechanism by which the OpenEmbedded build system tracks changes to licensing text and covers how to maintain open source license compliance during your project's lifecycle. The section also describes how to enable commercially licensed recipes, which by default are disabled.
The license of an upstream project might change in the future.
In order to prevent these changes going unnoticed, the
LIC_FILES_CHKSUM
variable tracks changes to the license text. The checksums are
validated at the end of the configure step, and if the
checksums do not match, the build will fail.
LIC_FILES_CHKSUM
Variable¶
The LIC_FILES_CHKSUM
variable contains checksums of the license text in the
source code for the recipe.
Following is an example of how to specify
LIC_FILES_CHKSUM
:
LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \ file://licfile1.txt;beginline=5;endline=29;md5=yyyy \ file://licfile2.txt;endline=50;md5=zzzz \ ..."
When using "beginline" and "endline", realize
that line numbering begins with one and not
zero.
Also, the included lines are inclusive (i.e.
lines five through and including 29 in the
previous example for
licfile1.txt
).
When a license check fails, the selected license text is included as part of the QA message. Using this output, you can determine the exact start and finish for the needed license text.
The build system uses the
S
variable as the default directory when searching files
listed in LIC_FILES_CHKSUM
.
The previous example employs the default directory.
Consider this next example:
LIC_FILES_CHKSUM = "file://src/ls.c;beginline=5;endline=16;\ md5=bb14ed3c4cda583abc85401304b5cd4e" LIC_FILES_CHKSUM = "file://${WORKDIR}/license.html;md5=5c94767cedb5d6987c902ac850ded2c6"
The first line locates a file in
${S}/src/ls.c
and isolates lines five
through 16 as license text.
The second line refers to a file in
WORKDIR
.
Note that LIC_FILES_CHKSUM
variable is
mandatory for all recipes, unless the
LICENSE
variable is set to "CLOSED".
As mentioned in the previous section, the
LIC_FILES_CHKSUM
variable lists all
the important files that contain the license text for the
source code.
It is possible to specify a checksum for an entire file,
or a specific section of a file (specified by beginning and
ending line numbers with the "beginline" and "endline"
parameters, respectively).
The latter is useful for source files with a license
notice header, README documents, and so forth.
If you do not use the "beginline" parameter, then it is
assumed that the text begins on the first line of the file.
Similarly, if you do not use the "endline" parameter,
it is assumed that the license text ends with the last
line of the file.
The "md5" parameter stores the md5 checksum of the license text. If the license text changes in any way as compared to this parameter then a mismatch occurs. This mismatch triggers a build failure and notifies the developer. Notification allows the developer to review and address the license text changes. Also note that if a mismatch occurs during the build, the correct md5 checksum is placed in the build log and can be easily copied to the recipe.
There is no limit to how many files you can specify using
the LIC_FILES_CHKSUM
variable.
Generally, however, every project requires a few
specifications for license tracking.
Many projects have a "COPYING" file that stores the
license information for all the source code files.
This practice allows you to just track the "COPYING"
file as long as it is kept up to date.
If you specify an empty or invalid "md5" parameter, BitBake returns an md5 mis-match error and displays the correct "md5" parameter value during the build. The correct parameter is also captured in the build log.
If the whole file contains only license text, you do not need to use the "beginline" and "endline" parameters.
By default, the OpenEmbedded build system disables
components that have commercial or other special licensing
requirements.
Such requirements are defined on a
recipe-by-recipe basis through the
LICENSE_FLAGS
variable definition in the affected recipe.
For instance, the
poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly
recipe contains the following statement:
LICENSE_FLAGS = "commercial"
Here is a slightly more complicated example that contains both an explicit recipe name and version (after variable expansion):
LICENSE_FLAGS = "license_${PN}_${PV}"
In order for a component restricted by a
LICENSE_FLAGS
definition to be enabled and
included in an image, it needs to have a matching entry in the
global
LICENSE_FLAGS_WHITELIST
variable, which is a variable typically defined in your
local.conf
file.
For example, to enable the
poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly
package, you could add either the string
"commercial_gst-plugins-ugly" or the more general string
"commercial" to LICENSE_FLAGS_WHITELIST
.
See the
"License Flag Matching"
section for a full
explanation of how LICENSE_FLAGS
matching
works.
Here is the example:
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly"
Likewise, to additionally enable the package built from the
recipe containing
LICENSE_FLAGS = "license_${PN}_${PV}"
,
and assuming that the actual recipe name was
emgd_1.10.bb
, the following string would
enable that package as well as the original
gst-plugins-ugly
package:
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly license_emgd_1.10"
As a convenience, you do not need to specify the complete license string in the whitelist for every package. You can use an abbreviated form, which consists of just the first portion or portions of the license string before the initial underscore character or characters. A partial string will match any license that contains the given string as the first portion of its license. For example, the following whitelist string will also match both of the packages previously mentioned as well as any other packages that have licenses starting with "commercial" or "license".
LICENSE_FLAGS_WHITELIST = "commercial license"
License flag matching allows you to control what recipes
the OpenEmbedded build system includes in the build.
Fundamentally, the build system attempts to match
LICENSE_FLAGS
strings found in recipes
against LICENSE_FLAGS_WHITELIST
strings found in the whitelist.
A match causes the build system to include a recipe in the
build, while failure to find a match causes the build
system to exclude a recipe.
In general, license flag matching is simple. However, understanding some concepts will help you correctly and effectively use matching.
Before a flag
defined by a particular recipe is tested against the
contents of the whitelist, the expanded string
_${PN}
is appended to the flag.
This expansion makes each
LICENSE_FLAGS
value recipe-specific.
After expansion, the string is then matched against the
whitelist.
Thus, specifying
LICENSE_FLAGS = "commercial"
in recipe "foo", for example, results in the string
"commercial_foo"
.
And, to create a match, that string must appear in the
whitelist.
Judicious use of the LICENSE_FLAGS
strings and the contents of the
LICENSE_FLAGS_WHITELIST
variable
allows you a lot of flexibility for including or excluding
recipes based on licensing.
For example, you can broaden the matching capabilities by
using license flags string subsets in the whitelist.
usethispart_1.3
,
usethispart_1.4
, and so forth).
For example, simply specifying the string "commercial" in
the whitelist matches any expanded
LICENSE_FLAGS
definition that starts
with the string "commercial" such as "commercial_foo" and
"commercial_bar", which are the strings the build system
automatically generates for hypothetical recipes named
"foo" and "bar" assuming those recipes simply specify the
following:
LICENSE_FLAGS = "commercial"
Thus, you can choose to exhaustively enumerate each license flag in the whitelist and allow only specific recipes into the image, or you can use a string subset that causes a broader range of matches to allow a range of recipes into the image.
This scheme works even if the
LICENSE_FLAGS
string already
has _${PN}
appended.
For example, the build system turns the license flag
"commercial_1.2_foo" into "commercial_1.2_foo_foo" and
would match both the general "commercial" and the specific
"commercial_1.2_foo" strings found in the whitelist, as
expected.
Here are some other scenarios:
You can specify a versioned string in the recipe such as "commercial_foo_1.2" in a "foo" recipe. The build system expands this string to "commercial_foo_1.2_foo". Combine this license flag with a whitelist that has the string "commercial" and you match the flag along with any other flag that starts with the string "commercial".
Under the same circumstances, you can use "commercial_foo" in the whitelist and the build system not only matches "commercial_foo_1.2" but also matches any license flag with the string "commercial_foo", regardless of the version.
You can be very specific and use both the package and version parts in the whitelist (e.g. "commercial_foo_1.2") to specifically match a versioned recipe.
Other helpful variables related to commercial
license handling exist and are defined in the
poky/meta/conf/distro/include/default-distrovars.inc
file:
COMMERCIAL_AUDIO_PLUGINS ?= "" COMMERCIAL_VIDEO_PLUGINS ?= ""
If you want to enable these components, you can do so by
making sure you have statements similar to the following
in your local.conf
configuration file:
COMMERCIAL_AUDIO_PLUGINS = "gst-plugins-ugly-mad \ gst-plugins-ugly-mpegaudioparse" COMMERCIAL_VIDEO_PLUGINS = "gst-plugins-ugly-mpeg2dec \ gst-plugins-ugly-mpegstream gst-plugins-bad-mpegvideoparse" LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly commercial_gst-plugins-bad commercial_qmmp"
Of course, you could also create a matching whitelist
for those components using the more general "commercial"
in the whitelist, but that would also enable all the
other packages with LICENSE_FLAGS
containing "commercial", which you may or may not want:
LICENSE_FLAGS_WHITELIST = "commercial"
Specifying audio and video plug-ins as part of the
COMMERCIAL_AUDIO_PLUGINS
and
COMMERCIAL_VIDEO_PLUGINS
statements
(along with the enabling
LICENSE_FLAGS_WHITELIST
) includes the
plug-ins or components into built images, thus adding
support for media formats or components.
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 sumo branch of the poky repo $ git clone -b sumo 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:
# POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf # changes incompatibly POKY_BBLAYERS_CONF_VERSION = "2" 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.
Wayland is a computer display server protocol that provides a method for compositing window managers to communicate directly with applications and video hardware and expects them to communicate with input hardware using other libraries. Using Wayland with supporting targets can result in better control over graphics frame rendering than an application might otherwise achieve.
The Yocto Project provides the Wayland protocol libraries and the
reference
Weston
compositor as part of its release.
You can find the integrated packages in the
meta
layer of the
Source Directory.
Specifically, you can find the recipes that build both Wayland
and Weston at meta/recipes-graphics/wayland
.
You can build both the Wayland and Weston packages for use only with targets that accept the Mesa 3D and Direct Rendering Infrastructure, which is also known as Mesa DRI. This implies that you cannot build and use the packages if your target uses, for example, the Intel® Embedded Media and Graphics Driver (Intel® EMGD) that overrides Mesa DRI.
This section describes what you need to do to implement Wayland and use the Weston compositor when building an image for a supporting target.
To enable Wayland, you need to enable it to be built and enable it to be included (installed) in the image.
To cause Mesa to build the wayland-egl
platform and Weston to build Wayland with Kernel Mode
Setting
(KMS)
support, include the "wayland" flag in the
DISTRO_FEATURES
statement in your local.conf
file:
DISTRO_FEATURES_append = " wayland"
To install the Wayland feature into an image, you must
include the following
CORE_IMAGE_EXTRA_INSTALL
statement in your local.conf
file:
CORE_IMAGE_EXTRA_INSTALL += "wayland weston"
To run Weston inside X11, enabling it as described earlier and building a Sato image is sufficient. If you are running your image under Sato, a Weston Launcher appears in the "Utility" category.
Alternatively, you can run Weston through the command-line interpretor (CLI), which is better suited for development work. To run Weston under the CLI, you need to do the following after your image is built:
Run these commands to export
XDG_RUNTIME_DIR
:
mkdir -p /tmp/$USER-weston chmod 0700 /tmp/$USER-weston export XDG_RUNTIME_DIR=/tmp/$USER-weston
Launch Weston in the shell:
weston
Table of Contents
The Yocto Project uses an implementation of the Quick EMUlator (QEMU) Open Source project as part of the Yocto Project development "tool set". This chapter provides both procedures that show you how to use the Quick EMUlator (QEMU) and other QEMU information helpful for development purposes.
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.
This section provides a brief reference for the Yocto Project implementation of QEMU.
For official information and documentation on QEMU in general, see the following references:
QEMU Website: The official website for the QEMU Open Source project.
Documentation: The QEMU user manual.
To use QEMU, you need to have QEMU installed and initialized as well as have the proper artifacts (i.e. image files and root filesystems) available. Follow these general steps to run QEMU:
Install QEMU: QEMU is made available with the Yocto Project a number of ways. One method is to install a Software Development Kit (SDK). See "The QEMU Emulator" section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual for information on how to install QEMU.
Setting Up the Environment: How you set up the QEMU environment depends on how you installed QEMU:
If you cloned the poky
repository or you downloaded and unpacked a
Yocto Project release tarball, you can source
the build environment script (i.e.
oe-init-build-env
):
$ cd ~/poky $ source oe-init-build-env
If you installed a cross-toolchain, you can
run the script that initializes the toolchain.
For example, the following commands run the
initialization script from the default
poky_sdk
directory:
. ~/poky_sdk/environment-setup-core2-64-poky-linux
Ensure the Artifacts are in Place: You need to be sure you have a pre-built kernel that will boot in QEMU. You also need the target root filesystem for your target machine’s architecture:
If you have previously built an image for QEMU
(e.g. qemux86
,
qemuarm
, and so forth),
then the artifacts are in place in your
Build Directory.
If you have not built an image, you can go to the machines/qemu area and download a pre-built image that matches your architecture and can be run on QEMU.
See the "Extracting the Root Filesystem" section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual for information on how to extract a root filesystem.
Run QEMU:
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
(*wic.vmdk
), or a kernel image
(*.bin
).
Here are some additional examples to help illustrate further QEMU:
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).