5 Classes

Class files are used to abstract common functionality and share it amongst multiple recipe (.bb) files. To use a class file, you simply make sure the recipe inherits the class. In most cases, when a recipe inherits a class it is enough to enable its features. There are cases, however, where in the recipe you might need to set variables or override some default behavior.

Any Metadata usually found in a recipe can also be placed in a class file. Class files are identified by the extension .bbclass and are usually placed in one of a set of subdirectories beneath the meta*/ directory found in the Source Directory:

  • classes-recipe/ - classes intended to be inherited by recipes individually

  • classes-global/ - classes intended to be inherited globally

  • classes/ - classes whose usage context is not clearly defined

Class files can also be pointed to by BUILDDIR (e.g. build/) in the same way as .conf files in the conf directory. Class files are searched for in BBPATH using the same method by which .conf files are searched.

This chapter discusses only the most useful and important classes. Other classes do exist within the meta/classes* directories in the Source Directory. You can reference the .bbclass files directly for more information.

5.1 allarch

The allarch class is inherited by recipes that do not produce architecture-specific output. The class disables functionality that is normally needed for recipes that produce executable binaries (such as building the cross-compiler and a C library as pre-requisites, and splitting out of debug symbols during packaging).

Note

Unlike some distro recipes (e.g. Debian), OpenEmbedded recipes that produce packages that depend on tunings through use of the RDEPENDS and TUNE_PKGARCH variables, should never be configured for all architectures using allarch. This is the case even if the recipes do not produce architecture-specific output.

Configuring such recipes for all architectures causes the do_package_write_* tasks to have different signatures for the machines with different tunings. Additionally, unnecessary rebuilds occur every time an image for a different MACHINE is built even when the recipe never changes.

By default, all recipes inherit the base and package classes, which enable functionality needed for recipes that produce executable output. If your recipe, for example, only produces packages that contain configuration files, media files, or scripts (e.g. Python and Perl), then it should inherit the allarch class.

5.2 archiver

The archiver class supports releasing source code and other materials with the binaries.

For more details on the source archiver, see the “Maintaining Open Source License Compliance During Your Product’s Lifecycle” section in the Yocto Project Development Tasks Manual. You can also see the ARCHIVER_MODE variable for information about the variable flags (varflags) that help control archive creation.

5.3 autotools*

The autotools* classes support packages built with the GNU Autotools.

The autoconf, automake, and libtool packages bring standardization. This class defines a set of tasks (e.g. configure, compile and so forth) that work for all Autotooled packages. It should usually be enough to define a few standard variables and then simply inherit autotools. These classes can also work with software that emulates Autotools. For more information, see the “Building an Autotooled Package” section in the Yocto Project Development Tasks Manual.

By default, the autotools* classes use out-of-tree builds (i.e. autotools.bbclass building with B != S).

If the software being built by a recipe does not support using out-of-tree builds, you should have the recipe inherit the autotools-brokensep class. The autotools-brokensep class behaves the same as the autotools* class but builds with B == S. This method is useful when out-of-tree build support is either not present or is broken.

Note

It is recommended that out-of-tree support be fixed and used if at all possible.

It’s useful to have some idea of how the tasks defined by the autotools* classes work and what they do behind the scenes.

  • do_configure — regenerates the configure script (using autoreconf) and then launches it with a standard set of arguments used during cross-compilation. You can pass additional parameters to configure through the EXTRA_OECONF or PACKAGECONFIG_CONFARGS variables.

  • do_compile — runs make with arguments that specify the compiler and linker. You can pass additional arguments through the EXTRA_OEMAKE variable.

  • do_install — runs make install and passes in ${D} as DESTDIR.

5.4 base

The base class is special in that every .bb file implicitly inherits the class. This class contains definitions for standard basic tasks such as fetching, unpacking, configuring (empty by default), compiling (runs any Makefile present), installing (empty by default) and packaging (empty by default). These tasks are often overridden or extended by other classes such as the autotools* class or the package class.

The class also contains some commonly used functions such as oe_runmake, which runs make with the arguments specified in EXTRA_OEMAKE variable as well as the arguments passed directly to oe_runmake.

5.5 bash-completion

Sets up packaging and dependencies appropriate for recipes that build software that includes bash-completion data.

5.6 bin_package

The bin_package class is a helper class for recipes that extract the contents of a binary package (e.g. an RPM) and install those contents rather than building the binary from source. The binary package is extracted and new packages in the configured output package format are created. Extraction and installation of proprietary binaries is a good example use for this class.

Note

For RPMs and other packages that do not contain a subdirectory, you should specify an appropriate fetcher parameter to point to the subdirectory. For example, if BitBake is using the Git fetcher (git://), the “subpath” parameter limits the checkout to a specific subpath of the tree. Here is an example where ${BP} is used so that the files are extracted into the subdirectory expected by the default value of S:

SRC_URI = "git://example.com/downloads/somepackage.rpm;branch=main;subpath=${BP}"

See the “Fetchers” section in the BitBake User Manual for more information on supported BitBake Fetchers.

5.7 binconfig

The binconfig class helps to correct paths in shell scripts.

Before pkg-config had become widespread, libraries shipped shell scripts to give information about the libraries and include paths needed to build software (usually named LIBNAME-config). This class assists any recipe using such scripts.

During staging, the OpenEmbedded build system installs such scripts into the sysroots/ directory. Inheriting this class results in all paths in these scripts being changed to point into the sysroots/ directory so that all builds that use the script use the correct directories for the cross compiling layout. See the BINCONFIG_GLOB variable for more information.

5.8 binconfig-disabled

An alternative version of the binconfig class, which disables binary configuration scripts by making them return an error in favor of using pkg-config to query the information. The scripts to be disabled should be specified using the BINCONFIG variable within the recipe inheriting the class.

5.9 buildhistory

The buildhistory class records a history of build output metadata, which can be used to detect possible regressions as well as used for analysis of the build output. For more information on using Build History, see the “Maintaining Build Output Quality” section in the Yocto Project Development Tasks Manual.

5.10 buildstats

The buildstats class records performance statistics about each task executed during the build (e.g. elapsed time, CPU usage, and I/O usage).

When you use this class, the output goes into the BUILDSTATS_BASE directory, which defaults to ${TMPDIR}/buildstats/. You can analyze the elapsed time using scripts/pybootchartgui/pybootchartgui.py, which produces a cascading chart of the entire build process and can be useful for highlighting bottlenecks.

Collecting build statistics is enabled by default through the USER_CLASSES variable from your local.conf file. Consequently, you do not have to do anything to enable the class. However, if you want to disable the class, simply remove “buildstats” from the USER_CLASSES list.

5.11 buildstats-summary

When inherited globally, prints statistics at the end of the build on sstate re-use. In order to function, this class requires the buildstats class be enabled.

5.12 cargo

The cargo class allows to compile Rust language programs using Cargo. Cargo is Rust’s package manager, allowing to fetch package dependencies and build your program.

Using this class makes it very easy to build Rust programs. All you need is to use the SRC_URI variable to point to a source repository which can be built by Cargo, typically one that was created by the cargo new command, containing a Cargo.toml file, a Cargo.lock file and a src subdirectory.

If you want to build and package tests of the program, inherit the ptest-cargo class instead of cargo.

You will find an example (that show also how to handle possible git source dependencies) in the zvariant_3.12.0.bb recipe. Another example, with only crate dependencies, is the uutils-coreutils recipe, which was generated by the cargo-bitbake tool.

This class inherits the cargo_common class.

5.13 cargo_c

The cargo_c class can be inherited by a recipe to generate a Rust library that can be called by C/C++ code. The recipe which inherits this class has to only replace inherit cargo by inherit cargo_c.

See the rust-c-lib-example_git.bb example recipe.

5.14 cargo_common

The cargo_common class is an internal class that is not intended to be used directly.

An exception is the “rust” recipe, to build the Rust compiler and runtime library, which is built by Cargo but cannot use the cargo class. This is why this class was introduced.

5.15 cargo-update-recipe-crates

The cargo-update-recipe-crates class allows recipe developers to update the list of Cargo crates in SRC_URI by reading the Cargo.lock file in the source tree.

To do so, create a recipe for your program, for example using devtool, make it inherit the cargo and cargo-update-recipe-crates and run:

bitbake -c update_crates recipe

This creates a recipe-crates.inc file that you can include in your recipe:

require ${BPN}-crates.inc

That’s also something you can achieve by using the cargo-bitbake tool.

5.16 ccache

The ccache class enables the C/C++ Compiler Cache for the build. This class is used to give a minor performance boost during the build.

See https://ccache.samba.org/ for information on the C/C++ Compiler Cache, and the ccache.bbclass file for details about how to enable this mechanism in your configuration file, how to disable it for specific recipes, and how to share ccache files between builds.

However, using the class can lead to unexpected side-effects. Thus, using this class is not recommended.

5.17 chrpath

The chrpath class is a wrapper around the “chrpath” utility, which is used during the build process for nativesdk, cross, and cross-canadian recipes to change RPATH records within binaries in order to make them relocatable.

5.18 cmake

The cmake class allows recipes to build software using the CMake build system. You can use the EXTRA_OECMAKE variable to specify additional configuration options to pass to the cmake command line.

By default, the cmake class uses Ninja instead of GNU make for building, which offers better build performance. If a recipe is broken with Ninja, then the recipe can set the OECMAKE_GENERATOR variable to Unix Makefiles to use GNU make instead.

If you need to install custom CMake toolchain files supplied by the application being built, you should install them (during do_install) to the preferred CMake Module directory: ${D}${datadir}/cmake/modules/.

5.19 cmake-qemu

The cmake-qemu class might be used instead of the cmake class. In addition to the features provided by the cmake class, the cmake-qemu class passes the CMAKE_CROSSCOMPILING_EMULATOR setting to cmake. This allows to use QEMU user-mode emulation for the execution of cross-compiled binaries on the host machine. For more information about CMAKE_CROSSCOMPILING_EMULATOR please refer to the related section of the CMake documentation.

Not all platforms are supported by QEMU. This class only works for machines with qemu-usermode in the Machine Features. Using QEMU user-mode therefore involves a certain risk, which is also the reason why this feature is not part of the main cmake class by default.

One use case is the execution of cross-compiled unit tests with CTest on the build machine. If CMAKE_CROSSCOMPILING_EMULATOR is configured:

cmake --build --target test

works transparently with QEMU user-mode.

If the CMake project is developed with this use case in mind this works very nicely. This also applies to an IDE configured to use cmake-native for cross-compiling.

5.20 cml1

The cml1 class provides basic support for the Linux kernel style build configuration system. “cml” stands for “Configuration Menu Language”, which originates from the Linux kernel but is also used in other projects such as U-Boot and BusyBox. It could have been called “kconfig” too.

5.21 compress_doc

Enables compression for man pages and info pages. This class is intended to be inherited globally. The default compression mechanism is gz (gzip) but you can select an alternative mechanism by setting the DOC_COMPRESS variable.

5.22 copyleft_compliance

The copyleft_compliance class preserves source code for the purposes of license compliance. This class is an alternative to the archiver class and is still used by some users even though it has been deprecated in favor of the archiver class.

5.23 copyleft_filter

A class used by the archiver and copyleft_compliance classes for filtering licenses. The copyleft_filter class is an internal class and is not intended to be used directly.

5.24 core-image

The core-image class provides common definitions for the core-image-* image recipes, such as support for additional IMAGE_FEATURES.

5.25 cpan*

The cpan* classes support Perl modules.

Recipes for Perl modules are simple. These recipes usually only need to point to the source’s archive and then inherit the proper class file. Building is split into two methods depending on which method the module authors used.

  • Modules that use old Makefile.PL-based build system require cpan.bbclass in their recipes.

  • Modules that use Build.PL-based build system require using cpan_build.bbclass in their recipes.

Both build methods inherit the cpan-base class for basic Perl support.

5.26 create-spdx

The create-spdx class provides support for automatically creating SPDX SBOM documents based upon image and SDK contents.

This class is meant to be inherited globally from a configuration file:

INHERIT += "create-spdx"

The toplevel SPDX output file is generated in JSON format as a IMAGE-MACHINE.spdx.json file in tmp/deploy/images/MACHINE/ inside the Build Directory. There are other related files in the same directory, as well as in tmp/deploy/spdx.

The exact behaviour of this class, and the amount of output can be controlled by the SPDX_PRETTY, SPDX_ARCHIVE_PACKAGED, SPDX_ARCHIVE_SOURCES and SPDX_INCLUDE_SOURCES variables.

See the description of these variables and the “Creating a Software Bill of Materials” section in the Yocto Project Development Manual for more details.

5.27 cross

The cross class provides support for the recipes that build the cross-compilation tools.

5.28 cross-canadian

The cross-canadian class provides support for the recipes that build the Canadian Cross-compilation tools for SDKs. See the “Cross-Development Toolchain Generation” section in the Yocto Project Overview and Concepts Manual for more discussion on these cross-compilation tools.

5.29 crosssdk

The crosssdk class provides support for the recipes that build the cross-compilation tools used for building SDKs. See the “Cross-Development Toolchain Generation” section in the Yocto Project Overview and Concepts Manual for more discussion on these cross-compilation tools.

5.30 cve-check

The cve-check class looks for known CVEs (Common Vulnerabilities and Exposures) while building with BitBake. This class is meant to be inherited globally from a configuration file:

INHERIT += "cve-check"

To filter out obsolete CVE database entries which are known not to impact software from Poky and OE-Core, add following line to the build configuration file:

include cve-extra-exclusions.inc

You can also look for vulnerabilities in specific packages by passing -c cve_check to BitBake.

After building the software with Bitbake, CVE check output reports are available in tmp/deploy/cve and image specific summaries in tmp/deploy/images/*.cve or tmp/deploy/images/*.json files.

When building, the CVE checker will emit build time warnings for any detected issues which are in the state Unpatched, meaning that CVE issue seems to affect the software component and version being compiled and no patches to address the issue are applied. Other states for detected CVE issues are: Patched meaning that a patch to address the issue is already applied, and Ignored meaning that the issue can be ignored.

The Patched state of a CVE issue is detected from patch files with the format CVE-ID.patch, e.g. CVE-2019-20633.patch, in the SRC_URI and using CVE metadata of format CVE: CVE-ID in the commit message of the patch file.

If the recipe adds CVE-ID as flag of the CVE_STATUS variable with status mapped to Ignored, then the CVE state is reported as Ignored:

CVE_STATUS[CVE-2020-15523] = "not-applicable-platform: Issue only applies on Windows"

If CVE check reports that a recipe contains false positives or false negatives, these may be fixed in recipes by adjusting the CVE product name using CVE_PRODUCT and CVE_VERSION variables. CVE_PRODUCT defaults to the plain recipe name BPN which can be adjusted to one or more CVE database vendor and product pairs using the syntax:

CVE_PRODUCT = "flex_project:flex"

where flex_project is the CVE database vendor name and flex is the product name. Similarly if the default recipe version PV does not match the version numbers of the software component in upstream releases or the CVE database, then the CVE_VERSION variable can be used to set the CVE database compatible version number, for example:

CVE_VERSION = "2.39"

Any bugs or missing or incomplete information in the CVE database entries should be fixed in the CVE database via the NVD feedback form.

Users should note that security is a process, not a product, and thus also CVE checking, analyzing results, patching and updating the software should be done as a regular process. The data and assumptions required for CVE checker to reliably detect issues are frequently broken in various ways. These can only be detected by reviewing the details of the issues and iterating over the generated reports, and following what happens in other Linux distributions and in the greater open source community.

You will find some more details in the “Checking for Vulnerabilities” section in the Development Tasks Manual.

5.31 debian

The debian class renames output packages so that they follow the Debian naming policy (i.e. glibc becomes libc6 and glibc-devel becomes libc6-dev.) Renaming includes the library name and version as part of the package name.

If a recipe creates packages for multiple libraries (shared object files of .so type), use the LEAD_SONAME variable in the recipe to specify the library on which to apply the naming scheme.

5.32 deploy

The deploy class handles deploying files to the DEPLOY_DIR_IMAGE directory. The main function of this class is to allow the deploy step to be accelerated by shared state. Recipes that inherit this class should define their own do_deploy function to copy the files to be deployed to DEPLOYDIR, and use addtask to add the task at the appropriate place, which is usually after do_compile or do_install. The class then takes care of staging the files from DEPLOYDIR to DEPLOY_DIR_IMAGE.

5.33 devicetree

The devicetree class allows to build a recipe that compiles device tree source files that are not in the kernel tree.

The compilation of out-of-tree device tree sources is the same as the kernel in-tree device tree compilation process. This includes the ability to include sources from the kernel such as SoC dtsi files as well as C header files, such as gpio.h.

The do_compile task will compile two kinds of files:

  • Regular device tree sources with a .dts extension.

  • Device tree overlays, detected from the presence of the /plugin/; string in the file contents.

This class deploys the generated device tree binaries into ${DEPLOY_DIR_IMAGE}/devicetree/. This is similar to what the kernel-devicetree class does, with the added devicetree subdirectory to avoid name clashes. Additionally, the device trees are populated into the sysroot for access via the sysroot from within other recipes.

By default, all device tree sources located in DT_FILES_PATH directory are compiled. To select only particular sources, set DT_FILES to a space-separated list of files (relative to DT_FILES_PATH). For convenience, both .dts and .dtb extensions can be used.

An extra padding is appended to non-overlay device trees binaries. This can typically be used as extra space for adding extra properties at boot time. The padding size can be modified by setting DT_PADDING_SIZE to the desired size, in bytes.

See devicetree.bbclass sources for further variables controlling this class.

Here is an excerpt of an example recipes-kernel/linux/devicetree-acme.bb recipe inheriting this class:

inherit devicetree
COMPATIBLE_MACHINE = "^mymachine$"
SRC_URI:mymachine = "file://mymachine.dts"

5.34 devshell

The devshell class adds the do_devshell task. Distribution policy dictates whether to include this class. See the “Using a Development Shell” section in the Yocto Project Development Tasks Manual for more information about using devshell.

5.35 devupstream

The devupstream class uses BBCLASSEXTEND to add a variant of the recipe that fetches from an alternative URI (e.g. Git) instead of a tarball. Here is an example:

BBCLASSEXTEND = "devupstream:target"
SRC_URI:class-devupstream = "git://git.example.com/example;branch=main"
SRCREV:class-devupstream = "abcd1234"

Adding the above statements to your recipe creates a variant that has DEFAULT_PREFERENCE set to “-1”. Consequently, you need to select the variant of the recipe to use it. Any development-specific adjustments can be done by using the class-devupstream override. Here is an example:

DEPENDS:append:class-devupstream = " gperf-native"
do_configure:prepend:class-devupstream() {
    touch ${S}/README
}

The class currently only supports creating a development variant of the target recipe, not native or nativesdk variants.

The BBCLASSEXTEND syntax (i.e. devupstream:target) provides support for native and nativesdk variants. Consequently, this functionality can be added in a future release.

Support for other version control systems such as Subversion is limited due to BitBake’s automatic fetch dependencies (e.g. subversion-native).

5.36 externalsrc

The externalsrc class supports building software from source code that is external to the OpenEmbedded build system. Building software from an external source tree means that the build system’s normal fetch, unpack, and patch process is not used.

By default, the OpenEmbedded build system uses the S and B variables to locate unpacked recipe source code and to build it, respectively. When your recipe inherits the externalsrc class, you use the EXTERNALSRC and EXTERNALSRC_BUILD variables to ultimately define S and B.

By default, this class expects the source code to support recipe builds that use the B variable to point to the directory in which the OpenEmbedded build system places the generated objects built from the recipes. By default, the B directory is set to the following, which is separate from the source directory (S):

${WORKDIR}/${BPN}-{PV}/

See these variables for more information: WORKDIR, BPN, and PV,

For more information on the externalsrc class, see the comments in meta/classes/externalsrc.bbclass in the Source Directory. For information on how to use the externalsrc class, see the “Building Software from an External Source” section in the Yocto Project Development Tasks Manual.

5.37 extrausers

The extrausers class allows additional user and group configuration to be applied at the image level. Inheriting this class either globally or from an image recipe allows additional user and group operations to be performed using the EXTRA_USERS_PARAMS variable.

Note

The user and group operations added using the extrausers class are not tied to a specific recipe outside of the recipe for the image. Thus, the operations can be performed across the image as a whole. Use the useradd* class to add user and group configuration to a specific recipe.

Here is an example that uses this class in an image recipe:

inherit extrausers
EXTRA_USERS_PARAMS = "\
    useradd -p '' tester; \
    groupadd developers; \
    userdel nobody; \
    groupdel -g video; \
    groupmod -g 1020 developers; \
    usermod -s /bin/sh tester; \
    "

Here is an example that adds two users named “tester-jim” and “tester-sue” and assigns passwords. First on host, create the (escaped) password hash:

printf "%q" $(mkpasswd -m sha256crypt tester01)

The resulting hash is set to a variable and used in useradd command parameters:

inherit extrausers
PASSWD = "\$X\$ABC123\$A-Long-Hash"
EXTRA_USERS_PARAMS = "\
    useradd -p '${PASSWD}' tester-jim; \
    useradd -p '${PASSWD}' tester-sue; \
    "

Finally, here is an example that sets the root password:

inherit extrausers
EXTRA_USERS_PARAMS = "\
    usermod -p '${PASSWD}' root; \
    "

Note

From a security perspective, hardcoding a default password is not generally a good idea or even legal in some jurisdictions. It is recommended that you do not do this if you are building a production image.

5.38 features_check

The features_check class allows individual recipes to check for required and conflicting DISTRO_FEATURES, MACHINE_FEATURES or COMBINED_FEATURES.

This class provides support for the following variables:

If any conditions specified in the recipe using the above variables are not met, the recipe will be skipped, and if the build system attempts to build the recipe then an error will be triggered.

5.39 fontcache

The fontcache class generates the proper post-install and post-remove (postinst and postrm) scriptlets for font packages. These scriptlets call fc-cache (part of Fontconfig) to add the fonts to the font information cache. Since the cache files are architecture-specific, fc-cache runs using QEMU if the postinst scriptlets need to be run on the build host during image creation.

If the fonts being installed are in packages other than the main package, set FONT_PACKAGES to specify the packages containing the fonts.

5.40 fs-uuid

The fs-uuid class extracts UUID from ${ROOTFS}, which must have been built by the time that this function gets called. The fs-uuid class only works on ext file systems and depends on tune2fs.

5.41 gconf

The gconf class provides common functionality for recipes that need to install GConf schemas. The schemas will be put into a separate package (${PN}-gconf) that is created automatically when this class is inherited. This package uses the appropriate post-install and post-remove (postinst/postrm) scriptlets to register and unregister the schemas in the target image.

5.42 gettext

The gettext class provides support for building software that uses the GNU gettext internationalization and localization system. All recipes building software that use gettext should inherit this class.

5.43 github-releases

For recipes that fetch release tarballs from github, the github-releases class sets up a standard way for checking available upstream versions (to support devtool upgrade and the Automated Upgrade Helper (AUH)).

To use it, add “github-releases” to the inherit line in the recipe, and if the default value of GITHUB_BASE_URI is not suitable, then set your own value in the recipe. You should then use ${GITHUB_BASE_URI} in the value you set for SRC_URI within the recipe.

5.44 gnomebase

The gnomebase class is the base class for recipes that build software from the GNOME stack. This class sets SRC_URI to download the source from the GNOME mirrors as well as extending FILES with the typical GNOME installation paths.

5.45 go

The go class supports building Go programs. The behavior of this class is controlled by the mandatory GO_IMPORT variable, and by the optional GO_INSTALL and GO_INSTALL_FILTEROUT ones.

To build a Go program with the Yocto Project, you can use the go-helloworld_0.1.bb recipe as an example.

5.46 go-mod

The go-mod class allows to use Go modules, and inherits the go class.

See the associated GO_WORKDIR variable.

5.47 gobject-introspection

Provides support for recipes building software that supports GObject introspection. This functionality is only enabled if the “gobject-introspection-data” feature is in DISTRO_FEATURES as well as “qemu-usermode” being in MACHINE_FEATURES.

Note

This functionality is backfilled by default and, if not applicable, should be disabled through DISTRO_FEATURES_BACKFILL_CONSIDERED or MACHINE_FEATURES_BACKFILL_CONSIDERED, respectively.

5.48 grub-efi

The grub-efi class provides grub-efi-specific functions for building bootable images.

This class supports several variables:

  • INITRD: Indicates list of filesystem images to concatenate and use as an initial RAM disk (initrd) (optional).

  • ROOTFS: Indicates a filesystem image to include as the root filesystem (optional).

  • GRUB_GFXSERIAL: Set this to “1” to have graphics and serial in the boot menu.

  • LABELS: A list of targets for the automatic configuration.

  • APPEND: An override list of append strings for each LABEL.

  • GRUB_OPTS: Additional options to add to the configuration (optional). Options are delimited using semi-colon characters (;).

  • GRUB_TIMEOUT: Timeout before executing the default LABEL (optional).

5.49 gsettings

The gsettings class provides common functionality for recipes that need to install GSettings (glib) schemas. The schemas are assumed to be part of the main package. Appropriate post-install and post-remove (postinst/postrm) scriptlets are added to register and unregister the schemas in the target image.

5.50 gtk-doc

The gtk-doc class is a helper class to pull in the appropriate gtk-doc dependencies and disable gtk-doc.

5.51 gtk-icon-cache

The gtk-icon-cache class generates the proper post-install and post-remove (postinst/postrm) scriptlets for packages that use GTK+ and install icons. These scriptlets call gtk-update-icon-cache to add the fonts to GTK+’s icon cache. Since the cache files are architecture-specific, gtk-update-icon-cache is run using QEMU if the postinst scriptlets need to be run on the build host during image creation.

5.52 gtk-immodules-cache

The gtk-immodules-cache class generates the proper post-install and post-remove (postinst/postrm) scriptlets for packages that install GTK+ input method modules for virtual keyboards. These scriptlets call gtk-update-icon-cache to add the input method modules to the cache. Since the cache files are architecture-specific, gtk-update-icon-cache is run using QEMU if the postinst scriptlets need to be run on the build host during image creation.

If the input method modules being installed are in packages other than the main package, set GTKIMMODULES_PACKAGES to specify the packages containing the modules.

5.53 gzipnative

The gzipnative class enables the use of different native versions of gzip and pigz rather than the versions of these tools from the build host.

5.54 icecc

The icecc class supports Icecream, which facilitates taking compile jobs and distributing them among remote machines.

The class stages directories with symlinks from gcc and g++ to icecc, for both native and cross compilers. Depending on each configure or compile, the OpenEmbedded build system adds the directories at the head of the PATH list and then sets the ICECC_CXX and ICECC_CC variables, which are the paths to the g++ and gcc compilers, respectively.

For the cross compiler, the class creates a tar.gz file that contains the Yocto Project toolchain and sets ICECC_VERSION, which is the version of the cross-compiler used in the cross-development toolchain, accordingly.

The class handles all three different compile stages (i.e native, cross-kernel and target) and creates the necessary environment tar.gz file to be used by the remote machines. The class also supports SDK generation.

If ICECC_PATH is not set in your local.conf file, then the class tries to locate the icecc binary using which. If ICECC_ENV_EXEC is set in your local.conf file, the variable should point to the icecc-create-env script provided by the user. If you do not point to a user-provided script, the build system uses the default script provided by the recipe icecc-create-env_0.1.bb.

Note

This script is a modified version and not the one that comes with icecream.

If you do not want the Icecream distributed compile support to apply to specific recipes or classes, you can ask them to be ignored by Icecream by listing the recipes and classes using the ICECC_RECIPE_DISABLE and ICECC_CLASS_DISABLE variables, respectively, in your local.conf file. Doing so causes the OpenEmbedded build system to handle these compilations locally.

Additionally, you can list recipes using the ICECC_RECIPE_ENABLE variable in your local.conf file to force icecc to be enabled for recipes using an empty PARALLEL_MAKE variable.

Inheriting the icecc class changes all sstate signatures. Consequently, if a development team has a dedicated build system that populates SSTATE_MIRRORS and they want to reuse sstate from SSTATE_MIRRORS, then all developers and the build system need to either inherit the icecc class or nobody should.

At the distribution level, you can inherit the icecc class to be sure that all builders start with the same sstate signatures. After inheriting the class, you can then disable the feature by setting the ICECC_DISABLED variable to “1” as follows:

INHERIT_DISTRO:append = " icecc"
ICECC_DISABLED ??= "1"

This practice makes sure everyone is using the same signatures but also requires individuals that do want to use Icecream to enable the feature individually as follows in your local.conf file:

ICECC_DISABLED = ""

5.55 image

The image class helps support creating images in different formats. First, the root filesystem is created from packages using one of the rootfs*.bbclass files (depending on the package format used) and then one or more image files are created.

  • The IMAGE_FSTYPES variable controls the types of images to generate.

  • The IMAGE_INSTALL variable controls the list of packages to install into the image.

For information on customizing images, see the “Customizing Images” section in the Yocto Project Development Tasks Manual. For information on how images are created, see the “Images” section in the Yocto Project Overview and Concepts Manual.

5.56 image-buildinfo

The image-buildinfo class writes a plain text file containing build information to the target filesystem at ${sysconfdir}/buildinfo by default (as specified by IMAGE_BUILDINFO_FILE). This can be useful for manually determining the origin of any given image. It writes out two sections:

  1. Build Configuration: a list of variables and their values (specified by IMAGE_BUILDINFO_VARS, which defaults to DISTRO and DISTRO_VERSION)

  2. Layer Revisions: the revisions of all of the layers used in the build.

Additionally, when building an SDK it will write the same contents to /buildinfo by default (as specified by SDK_BUILDINFO_FILE).

5.57 image_types

The image_types class defines all of the standard image output types that you can enable through the IMAGE_FSTYPES variable. You can use this class as a reference on how to add support for custom image output types.

By default, the image class automatically enables the image_types class. The image class uses the IMGCLASSES variable as follows:

IMGCLASSES = "rootfs_${IMAGE_PKGTYPE} image_types ${IMAGE_CLASSES}"
IMGCLASSES += "${@['populate_sdk_base', 'populate_sdk_ext']['linux' in d.getVar("SDK_OS")]}"
IMGCLASSES += "${@bb.utils.contains_any('IMAGE_FSTYPES', 'live iso hddimg', 'image-live', '', d)}"
IMGCLASSES += "${@bb.utils.contains('IMAGE_FSTYPES', 'container', 'image-container', '', d)}"
IMGCLASSES += "image_types_wic"
IMGCLASSES += "rootfs-postcommands"
IMGCLASSES += "image-postinst-intercepts"
inherit ${IMGCLASSES}

The image_types class also handles conversion and compression of images.

Note

To build a VMware VMDK image, you need to add “wic.vmdk” to IMAGE_FSTYPES. This would also be similar for Virtual Box Virtual Disk Image (“vdi”) and QEMU Copy On Write Version 2 (“qcow2”) images.

5.58 image-live

This class controls building “live” (i.e. HDDIMG and ISO) images. Live images contain syslinux for legacy booting, as well as the bootloader specified by EFI_PROVIDER if MACHINE_FEATURES contains “efi”.

Normally, you do not use this class directly. Instead, you add “live” to IMAGE_FSTYPES.

5.59 insane

The insane class adds a step to the package generation process so that output quality assurance checks are generated by the OpenEmbedded build system. A range of checks are performed that check the build’s output for common problems that show up during runtime. Distribution policy usually dictates whether to include this class.

You can configure the sanity checks so that specific test failures either raise a warning or an error message. Typically, failures for new tests generate a warning. Subsequent failures for the same test would then generate an error message once the metadata is in a known and good condition. See the “QA Error and Warning Messages” Chapter for a list of all the warning and error messages you might encounter using a default configuration.

Use the WARN_QA and ERROR_QA variables to control the behavior of these checks at the global level (i.e. in your custom distro configuration). However, to skip one or more checks in recipes, you should use INSANE_SKIP. For example, to skip the check for symbolic link .so files in the main package of a recipe, add the following to the recipe. You need to realize that the package name override, in this example ${PN}, must be used:

INSANE_SKIP:${PN} += "dev-so"

Please keep in mind that the QA checks are meant to detect real or potential problems in the packaged output. So exercise caution when disabling these checks.

The tests you can list with the WARN_QA and ERROR_QA variables are:

  • already-stripped: Checks that produced binaries have not already been stripped prior to the build system extracting debug symbols. It is common for upstream software projects to default to stripping debug symbols for output binaries. In order for debugging to work on the target using -dbg packages, this stripping must be disabled.

  • arch: Checks the Executable and Linkable Format (ELF) type, bit size, and endianness of any binaries to ensure they match the target architecture. This test fails if any binaries do not match the type since there would be an incompatibility. The test could indicate that the wrong compiler or compiler options have been used. Sometimes software, like bootloaders, might need to bypass this check.

  • buildpaths: Checks for paths to locations on the build host inside the output files. Not only can these leak information about the build environment, they also hinder binary reproducibility.

  • build-deps: Determines if a build-time dependency that is specified through DEPENDS, explicit RDEPENDS, or task-level dependencies exists to match any runtime dependency. This determination is particularly useful to discover where runtime dependencies are detected and added during packaging. If no explicit dependency has been specified within the metadata, at the packaging stage it is too late to ensure that the dependency is built, and thus you can end up with an error when the package is installed into the image during the do_rootfs task because the auto-detected dependency was not satisfied. An example of this would be where the update-rc.d class automatically adds a dependency on the initscripts-functions package to packages that install an initscript that refers to /etc/init.d/functions. The recipe should really have an explicit RDEPENDS for the package in question on initscripts-functions so that the OpenEmbedded build system is able to ensure that the initscripts recipe is actually built and thus the initscripts-functions package is made available.

  • configure-gettext: Checks that if a recipe is building something that uses automake and the automake files contain an AM_GNU_GETTEXT directive, that the recipe also inherits the gettext class to ensure that gettext is available during the build.

  • compile-host-path: Checks the do_compile log for indications that paths to locations on the build host were used. Using such paths might result in host contamination of the build output.

  • debug-deps: Checks that all packages except -dbg packages do not depend on -dbg packages, which would cause a packaging bug.

  • debug-files: Checks for .debug directories in anything but the -dbg package. The debug files should all be in the -dbg package. Thus, anything packaged elsewhere is incorrect packaging.

  • dep-cmp: Checks for invalid version comparison statements in runtime dependency relationships between packages (i.e. in RDEPENDS, RRECOMMENDS, RSUGGESTS, RPROVIDES, RREPLACES, and RCONFLICTS variable values). Any invalid comparisons might trigger failures or undesirable behavior when passed to the package manager.

  • desktop: Runs the desktop-file-validate program against any .desktop files to validate their contents against the specification for .desktop files.

  • dev-deps: Checks that all packages except -dev or -staticdev packages do not depend on -dev packages, which would be a packaging bug.

  • dev-so: Checks that the .so symbolic links are in the -dev package and not in any of the other packages. In general, these symlinks are only useful for development purposes. Thus, the -dev package is the correct location for them. In very rare cases, such as dynamically loaded modules, these symlinks are needed instead in the main package.

  • empty-dirs: Checks that packages are not installing files to directories that are normally expected to be empty (such as /tmp) The list of directories that are checked is specified by the QA_EMPTY_DIRS variable.

  • file-rdeps: Checks that file-level dependencies identified by the OpenEmbedded build system at packaging time are satisfied. For example, a shell script might start with the line #!/bin/bash. This line would translate to a file dependency on /bin/bash. Of the three package managers that the OpenEmbedded build system supports, only RPM directly handles file-level dependencies, resolving them automatically to packages providing the files. However, the lack of that functionality in the other two package managers does not mean the dependencies do not still need resolving. This QA check attempts to ensure that explicitly declared RDEPENDS exist to handle any file-level dependency detected in packaged files.

  • files-invalid: Checks for FILES variable values that contain “//”, which is invalid.

  • host-user-contaminated: Checks that no package produced by the recipe contains any files outside of /home with a user or group ID that matches the user running BitBake. A match usually indicates that the files are being installed with an incorrect UID/GID, since target IDs are independent from host IDs. For additional information, see the section describing the do_install task.

  • incompatible-license: Report when packages are excluded from being created due to being marked with a license that is in INCOMPATIBLE_LICENSE.

  • install-host-path: Checks the do_install log for indications that paths to locations on the build host were used. Using such paths might result in host contamination of the build output.

  • installed-vs-shipped: Reports when files have been installed within do_install but have not been included in any package by way of the FILES variable. Files that do not appear in any package cannot be present in an image later on in the build process. Ideally, all installed files should be packaged or not installed at all. These files can be deleted at the end of do_install if the files are not needed in any package.

  • invalid-chars: Checks that the recipe metadata variables DESCRIPTION, SUMMARY, LICENSE, and SECTION do not contain non-UTF-8 characters. Some package managers do not support such characters.

  • invalid-packageconfig: Checks that no undefined features are being added to PACKAGECONFIG. For example, any name “foo” for which the following form does not exist:

    PACKAGECONFIG[foo] = "..."
    
  • la: Checks .la files for any TMPDIR paths. Any .la file containing these paths is incorrect since libtool adds the correct sysroot prefix when using the files automatically itself.

  • ldflags: Ensures that the binaries were linked with the LDFLAGS options provided by the build system. If this test fails, check that the LDFLAGS variable is being passed to the linker command.

  • libdir: Checks for libraries being installed into incorrect (possibly hardcoded) installation paths. For example, this test will catch recipes that install /lib/bar.so when ${base_libdir} is “lib32”. Another example is when recipes install /usr/lib64/foo.so when ${libdir} is “/usr/lib”.

  • libexec: Checks if a package contains files in /usr/libexec. This check is not performed if the libexecdir variable has been set explicitly to /usr/libexec.

  • mime: Check that if a package contains mime type files (.xml files in ${datadir}/mime/packages) that the recipe also inherits the mime class in order to ensure that these get properly installed.

  • mime-xdg: Checks that if a package contains a .desktop file with a ‘MimeType’ key present, that the recipe inherits the mime-xdg class that is required in order for that to be activated.

  • missing-update-alternatives: Check that if a recipe sets the ALTERNATIVE variable that the recipe also inherits update-alternatives such that the alternative will be correctly set up.

  • packages-list: Checks for the same package being listed multiple times through the PACKAGES variable value. Installing the package in this manner can cause errors during packaging.

  • patch-fuzz: Checks for fuzz in patch files that may allow them to apply incorrectly if the underlying code changes.

  • patch-status-core: Checks that the Upstream-Status is specified and valid in the headers of patches for recipes in the OE-Core layer.

  • patch-status-noncore: Checks that the Upstream-Status is specified and valid in the headers of patches for recipes in layers other than OE-Core.

  • perllocalpod: Checks for perllocal.pod being erroneously installed and packaged by a recipe.

  • perm-config: Reports lines in fs-perms.txt that have an invalid format.

  • perm-line: Reports lines in fs-perms.txt that have an invalid format.

  • perm-link: Reports lines in fs-perms.txt that specify ‘link’ where the specified target already exists.

  • perms: Currently, this check is unused but reserved.

  • pkgconfig: Checks .pc files for any TMPDIR/WORKDIR paths. Any .pc file containing these paths is incorrect since pkg-config itself adds the correct sysroot prefix when the files are accessed.

  • pkgname: Checks that all packages in PACKAGES have names that do not contain invalid characters (i.e. characters other than 0-9, a-z, ., +, and -).

  • pkgv-undefined: Checks to see if the PKGV variable is undefined during do_package.

  • pkgvarcheck: Checks through the variables RDEPENDS, RRECOMMENDS, RSUGGESTS, RCONFLICTS, RPROVIDES, RREPLACES, FILES, ALLOW_EMPTY, pkg_preinst, pkg_postinst, pkg_prerm and pkg_postrm, and reports if there are variable sets that are not package-specific. Using these variables without a package suffix is bad practice, and might unnecessarily complicate dependencies of other packages within the same recipe or have other unintended consequences.

  • pn-overrides: Checks that a recipe does not have a name (PN) value that appears in OVERRIDES. If a recipe is named such that its PN value matches something already in OVERRIDES (e.g. PN happens to be the same as MACHINE or DISTRO), it can have unexpected consequences. For example, assignments such as FILES:${PN} = "xyz" effectively turn into FILES = "xyz".

  • rpaths: Checks for rpaths in the binaries that contain build system paths such as TMPDIR. If this test fails, bad -rpath options are being passed to the linker commands and your binaries have potential security issues.

  • shebang-size: Check that the shebang line (#! in the first line) in a packaged script is not longer than 128 characters, which can cause an error at runtime depending on the operating system.

  • split-strip: Reports that splitting or stripping debug symbols from binaries has failed.

  • staticdev: Checks for static library files (*.a) in non-staticdev packages.

  • src-uri-bad: Checks that the SRC_URI value set by a recipe does not contain a reference to ${PN} (instead of the correct ${BPN}) nor refers to unstable Github archive tarballs.

  • symlink-to-sysroot: Checks for symlinks in packages that point into TMPDIR on the host. Such symlinks will work on the host, but are clearly invalid when running on the target.

  • textrel: Checks for ELF binaries that contain relocations in their .text sections, which can result in a performance impact at runtime. See the explanation for the ELF binary message in “QA Error and Warning Messages” for more information regarding runtime performance issues.

  • unhandled-features-check: check that if one of the variables that the features_check class supports (e.g. REQUIRED_DISTRO_FEATURES) is set by a recipe, then the recipe also inherits features_check in order for the requirement to actually work.

  • unimplemented-ptest: Checks that ptests are implemented for upstream tests.

  • unlisted-pkg-lics: Checks that all declared licenses applying for a package are also declared on the recipe level (i.e. any license in LICENSE:* should appear in LICENSE).

  • useless-rpaths: Checks for dynamic library load paths (rpaths) in the binaries that by default on a standard system are searched by the linker (e.g. /lib and /usr/lib). While these paths will not cause any breakage, they do waste space and are unnecessary.

  • usrmerge: If usrmerge is in DISTRO_FEATURES, this check will ensure that no package installs files to root (/bin, /sbin, /lib, /lib64) directories.

  • var-undefined: Reports when variables fundamental to packaging (i.e. WORKDIR, DEPLOY_DIR, D, PN, and PKGD) are undefined during do_package.

  • version-going-backwards: If the buildhistory class is enabled, reports when a package being written out has a lower version than the previously written package under the same name. If you are placing output packages into a feed and upgrading packages on a target system using that feed, the version of a package going backwards can result in the target system not correctly upgrading to the “new” version of the package.

    Note

    This is only relevant when you are using runtime package management on your target system.

  • xorg-driver-abi: Checks that all packages containing Xorg drivers have ABI dependencies. The xserver-xorg recipe provides driver ABI names. All drivers should depend on the ABI versions that they have been built against. Driver recipes that include xorg-driver-input.inc or xorg-driver-video.inc will automatically get these versions. Consequently, you should only need to explicitly add dependencies to binary driver recipes.

5.60 kernel

The kernel class handles building Linux kernels. The class contains code to build all kernel trees. All needed headers are staged into the STAGING_KERNEL_DIR directory to allow out-of-tree module builds using the module class.

If a file named defconfig is listed in SRC_URI, then by default do_configure copies it as .config in the build directory, so it is automatically used as the kernel configuration for the build. This copy is not performed in case .config already exists there: this allows recipes to produce a configuration by other means in do_configure:prepend.

Each built kernel module is packaged separately and inter-module dependencies are created by parsing the modinfo output. If all modules are required, then installing the kernel-modules package installs all packages with modules and various other kernel packages such as kernel-vmlinux.

The kernel class contains logic that allows you to embed an initial RAM filesystem (Initramfs) image when you build the kernel image. For information on how to build an Initramfs, see the “Building an Initial RAM Filesystem (Initramfs) Image” section in the Yocto Project Development Tasks Manual.

Various other classes are used by the kernel and module classes internally including the kernel-arch, module-base, and linux-kernel-base classes.

5.61 kernel-arch

The kernel-arch class sets the ARCH environment variable for Linux kernel compilation (including modules).

5.62 kernel-devicetree

The kernel-devicetree class, which is inherited by the kernel class, supports device tree generation.

Its behavior is mainly controlled by the following variables:

5.63 kernel-fitimage

The kernel-fitimage class provides support to pack a kernel image, device trees, a U-boot script, an Initramfs bundle and a RAM disk into a single FIT image. In theory, a FIT image can support any number of kernels, U-boot scripts, Initramfs bundles, RAM disks and device-trees. However, kernel-fitimage currently only supports limited usecases: just one kernel image, an optional U-boot script, an optional Initramfs bundle, an optional RAM disk, and any number of device trees.

To create a FIT image, it is required that KERNEL_CLASSES is set to include “kernel-fitimage” and one of KERNEL_IMAGETYPE, KERNEL_ALT_IMAGETYPE or KERNEL_IMAGETYPES to include “fitImage”.

The options for the device tree compiler passed to mkimage -D when creating the FIT image are specified using the UBOOT_MKIMAGE_DTCOPTS variable.

Only a single kernel can be added to the FIT image created by kernel-fitimage and the kernel image in FIT is mandatory. The address where the kernel image is to be loaded by U-Boot is specified by UBOOT_LOADADDRESS and the entrypoint by UBOOT_ENTRYPOINT. Setting FIT_ADDRESS_CELLS to “2” is necessary if such addresses are 64 bit ones.

Multiple device trees can be added to the FIT image created by kernel-fitimage and the device tree is optional. The address where the device tree is to be loaded by U-Boot is specified by UBOOT_DTBO_LOADADDRESS for device tree overlays and by UBOOT_DTB_LOADADDRESS for device tree binaries.

Only a single RAM disk can be added to the FIT image created by kernel-fitimage and the RAM disk in FIT is optional. The address where the RAM disk image is to be loaded by U-Boot is specified by UBOOT_RD_LOADADDRESS and the entrypoint by UBOOT_RD_ENTRYPOINT. The ramdisk is added to the FIT image when INITRAMFS_IMAGE is specified and requires that INITRAMFS_IMAGE_BUNDLE is not set to 1.

Only a single Initramfs bundle can be added to the FIT image created by kernel-fitimage and the Initramfs bundle in FIT is optional. In case of Initramfs, the kernel is configured to be bundled with the root filesystem in the same binary (example: zImage-initramfs-MACHINE.bin). When the kernel is copied to RAM and executed, it unpacks the Initramfs root filesystem. The Initramfs bundle can be enabled when INITRAMFS_IMAGE is specified and requires that INITRAMFS_IMAGE_BUNDLE is set to 1. The address where the Initramfs bundle is to be loaded by U-boot is specified by UBOOT_LOADADDRESS and the entrypoint by UBOOT_ENTRYPOINT.

Only a single U-boot boot script can be added to the FIT image created by kernel-fitimage and the boot script is optional. The boot script is specified in the ITS file as a text file containing U-boot commands. When using a boot script the user should configure the U-boot do_install task to copy the script to sysroot. So the script can be included in the FIT image by the kernel-fitimage class. At run-time, U-boot CONFIG_BOOTCOMMAND define can be configured to load the boot script from the FIT image and execute it.

The FIT image generated by the kernel-fitimage class is signed when the variables UBOOT_SIGN_ENABLE, UBOOT_MKIMAGE_DTCOPTS, UBOOT_SIGN_KEYDIR and UBOOT_SIGN_KEYNAME are set appropriately. The default values used for FIT_HASH_ALG and FIT_SIGN_ALG in kernel-fitimage are “sha256” and “rsa2048” respectively. The keys for signing the FIT image can be generated using the kernel-fitimage class when both FIT_GENERATE_KEYS and UBOOT_SIGN_ENABLE are set to “1”.

5.64 kernel-grub

The kernel-grub class updates the boot area and the boot menu with the kernel as the priority boot mechanism while installing a RPM to update the kernel on a deployed target.

5.65 kernel-module-split

The kernel-module-split class provides common functionality for splitting Linux kernel modules into separate packages.

5.66 kernel-uboot

The kernel-uboot class provides support for building from vmlinux-style kernel sources.

5.67 kernel-uimage

The kernel-uimage class provides support to pack uImage.

5.68 kernel-yocto

The kernel-yocto class provides common functionality for building from linux-yocto style kernel source repositories.

5.69 kernelsrc

The kernelsrc class sets the Linux kernel source and version.

5.70 lib_package

The lib_package class supports recipes that build libraries and produce executable binaries, where those binaries should not be installed by default along with the library. Instead, the binaries are added to a separate ${PN}-bin package to make their installation optional.

5.71 libc*

The libc* classes support recipes that build packages with libc:

  • The libc-common class provides common support for building with libc.

  • The libc-package class supports packaging up glibc and eglibc.

5.72 license

The license class provides license manifest creation and license exclusion. This class is enabled by default using the default value for the INHERIT_DISTRO variable.

5.73 linux-kernel-base

The linux-kernel-base class provides common functionality for recipes that build out of the Linux kernel source tree. These builds goes beyond the kernel itself. For example, the Perf recipe also inherits this class.

5.74 linuxloader

Provides the function linuxloader(), which gives the value of the dynamic loader/linker provided on the platform. This value is used by a number of other classes.

5.75 logging

The logging class provides the standard shell functions used to log messages for various BitBake severity levels (i.e. bbplain, bbnote, bbwarn, bberror, bbfatal, and bbdebug).

This class is enabled by default since it is inherited by the base class.

5.76 meson

The meson class allows to create recipes that build software using the Meson build system. You can use the MESON_BUILDTYPE, MESON_TARGET and EXTRA_OEMESON variables to specify additional configuration options to be passed using the meson command line.

5.77 metadata_scm

The metadata_scm class provides functionality for querying the branch and revision of a Source Code Manager (SCM) repository.

The base class uses this class to print the revisions of each layer before starting every build. The metadata_scm class is enabled by default because it is inherited by the base class.

5.78 migrate_localcount

The migrate_localcount class verifies a recipe’s localcount data and increments it appropriately.

5.79 mime

The mime class generates the proper post-install and post-remove (postinst/postrm) scriptlets for packages that install MIME type files. These scriptlets call update-mime-database to add the MIME types to the shared database.

5.80 mime-xdg

The mime-xdg class generates the proper post-install and post-remove (postinst/postrm) scriptlets for packages that install .desktop files containing MimeType entries. These scriptlets call update-desktop-database to add the MIME types to the database of MIME types handled by desktop files.

Thanks to this class, when users open a file through a file browser on recently created images, they don’t have to choose the application to open the file from the pool of all known applications, even the ones that cannot open the selected file.

If you have recipes installing their .desktop files as absolute symbolic links, the detection of such files cannot be done by the current implementation of this class. In this case, you have to add the corresponding package names to the MIME_XDG_PACKAGES variable.

5.81 mirrors

The mirrors class sets up some standard MIRRORS entries for source code mirrors. These mirrors provide a fall-back path in case the upstream source specified in SRC_URI within recipes is unavailable.

This class is enabled by default since it is inherited by the base class.

5.82 module

The module class provides support for building out-of-tree Linux kernel modules. The class inherits the module-base and kernel-module-split classes, and implements the do_compile and do_install tasks. The class provides everything needed to build and package a kernel module.

For general information on out-of-tree Linux kernel modules, see the “Incorporating Out-of-Tree Modules” section in the Yocto Project Linux Kernel Development Manual.

5.83 module-base

The module-base class provides the base functionality for building Linux kernel modules. Typically, a recipe that builds software that includes one or more kernel modules and has its own means of building the module inherits this class as opposed to inheriting the module class.

5.84 multilib*

The multilib* classes provide support for building libraries with different target optimizations or target architectures and installing them side-by-side in the same image.

For more information on using the Multilib feature, see the “Combining Multiple Versions of Library Files into One Image” section in the Yocto Project Development Tasks Manual.

5.85 native

The native class provides common functionality for recipes that build tools to run on the Build Host (i.e. tools that use the compiler or other tools from the build host).

You can create a recipe that builds tools that run natively on the host a couple different ways:

  • Create a myrecipe-native.bb recipe that inherits the native class. If you use this method, you must order the inherit statement in the recipe after all other inherit statements so that the native class is inherited last.

    Note

    When creating a recipe this way, the recipe name must follow this naming convention:

    myrecipe-native.bb
    

    Not using this naming convention can lead to subtle problems caused by existing code that depends on that naming convention.

  • Create or modify a target recipe that contains the following:

    BBCLASSEXTEND = "native"
    

    Inside the recipe, use :class-native and :class-target overrides to specify any functionality specific to the respective native or target case.

Although applied differently, the native class is used with both methods. The advantage of the second method is that you do not need to have two separate recipes (assuming you need both) for native and target. All common parts of the recipe are automatically shared.

5.86 nativesdk

The nativesdk class provides common functionality for recipes that wish to build tools to run as part of an SDK (i.e. tools that run on SDKMACHINE).

You can create a recipe that builds tools that run on the SDK machine a couple different ways:

  • Create a nativesdk-myrecipe.bb recipe that inherits the nativesdk class. If you use this method, you must order the inherit statement in the recipe after all other inherit statements so that the nativesdk class is inherited last.

  • Create a nativesdk variant of any recipe by adding the following:

    BBCLASSEXTEND = "nativesdk"
    

    Inside the recipe, use :class-nativesdk and :class-target overrides to specify any functionality specific to the respective SDK machine or target case.

Note

When creating a recipe, you must follow this naming convention:

nativesdk-myrecipe.bb

Not doing so can lead to subtle problems because there is code that depends on the naming convention.

Although applied differently, the nativesdk class is used with both methods. The advantage of the second method is that you do not need to have two separate recipes (assuming you need both) for the SDK machine and the target. All common parts of the recipe are automatically shared.

5.87 nopackages

Disables packaging tasks for those recipes and classes where packaging is not needed.

5.88 npm

Provides support for building Node.js software fetched using the node package manager (NPM).

Note

Currently, recipes inheriting this class must use the npm:// fetcher to have dependencies fetched and packaged automatically.

For information on how to create NPM packages, see the “Creating Node Package Manager (NPM) Packages” section in the Yocto Project Development Tasks Manual.

5.89 oelint

The oelint class is an obsolete lint checking tool available in meta/classes in the Source Directory.

There are some classes that could be generally useful in OE-Core but are never actually used within OE-Core itself. The oelint class is one such example. However, being aware of this class can reduce the proliferation of different versions of similar classes across multiple layers.

5.90 overlayfs

It’s often desired in Embedded System design to have a read-only root filesystem. But a lot of different applications might want to have read-write access to some parts of a filesystem. It can be especially useful when your update mechanism overwrites the whole root filesystem, but you may want your application data to be preserved between updates. The overlayfs class provides a way to achieve that by means of overlayfs and at the same time keeping the base root filesystem read-only.

To use this class, set a mount point for a partition overlayfs is going to use as upper layer in your machine configuration. The underlying file system can be anything that is supported by overlayfs. This has to be done in your machine configuration:

OVERLAYFS_MOUNT_POINT[data] = "/data"

Note

  • QA checks fail to catch file existence if you redefine this variable in your recipe!

  • Only the existence of the systemd mount unit file is checked, not its contents.

  • To get more details on overlayfs, its internals and supported operations, please refer to the official documentation of the Linux kernel.

The class assumes you have a data.mount systemd unit defined elsewhere in your BSP (e.g. in systemd-machine-units recipe) and it’s installed into the image.

Then you can specify writable directories on a recipe basis (e.g. in my-application.bb):

OVERLAYFS_WRITABLE_PATHS[data] = "/usr/share/my-custom-application"

To support several mount points you can use a different variable flag. Assuming we want to have a writable location on the file system, but do not need that the data survives a reboot, then we could have a mnt-overlay.mount unit for a tmpfs file system.

In your machine configuration:

OVERLAYFS_MOUNT_POINT[mnt-overlay] = "/mnt/overlay"

and then in your recipe:

OVERLAYFS_WRITABLE_PATHS[mnt-overlay] = "/usr/share/another-application"

On a practical note, your application recipe might require multiple overlays to be mounted before running to avoid writing to the underlying file system (which can be forbidden in case of read-only file system) To achieve that overlayfs provides a systemd helper service for mounting overlays. This helper service is named ${PN}-overlays.service and can be depended on in your application recipe (named application in the following example) systemd unit by adding to the unit the following:

[Unit]
After=application-overlays.service
Requires=application-overlays.service

Note

The class does not support the /etc directory itself, because systemd depends on it. In order to get /etc in overlayfs, see overlayfs-etc.

5.91 overlayfs-etc

In order to have the /etc directory in overlayfs a special handling at early boot stage is required. The idea is to supply a custom init script that mounts /etc before launching the actual init program, because the latter already requires /etc to be mounted.

Example usage in image recipe:

IMAGE_FEATURES += "overlayfs-etc"

Note

This class must not be inherited directly. Use IMAGE_FEATURES or EXTRA_IMAGE_FEATURES

Your machine configuration should define at least the device, mount point, and file system type you are going to use for overlayfs:

OVERLAYFS_ETC_MOUNT_POINT = "/data"
OVERLAYFS_ETC_DEVICE = "/dev/mmcblk0p2"
OVERLAYFS_ETC_FSTYPE ?= "ext4"

To control more mount options you should consider setting mount options (defaults is used by default):

OVERLAYFS_ETC_MOUNT_OPTIONS = "wsync"

The class provides two options for /sbin/init generation:

  • The default option is to rename the original /sbin/init to /sbin/init.orig and place the generated init under original name, i.e. /sbin/init. It has an advantage that you won’t need to change any kernel parameters in order to make it work, but it poses a restriction that package-management can’t be used, because updating the init manager would remove the generated script.

  • If you wish to keep original init as is, you can set:

    OVERLAYFS_ETC_USE_ORIG_INIT_NAME = "0"
    

    Then the generated init will be named /sbin/preinit and you would need to extend your kernel parameters manually in your bootloader configuration.

5.92 own-mirrors

The own-mirrors class makes it easier to set up your own PREMIRRORS from which to first fetch source before attempting to fetch it from the upstream specified in SRC_URI within each recipe.

To use this class, inherit it globally and specify SOURCE_MIRROR_URL. Here is an example:

INHERIT += "own-mirrors"
SOURCE_MIRROR_URL = "http://example.com/my-source-mirror"

You can specify only a single URL in SOURCE_MIRROR_URL.

5.93 package

The package class supports generating packages from a build’s output. The core generic functionality is in package.bbclass. The code specific to particular package types resides in these package-specific classes: package_deb, package_rpm, package_ipk.

You can control the list of resulting package formats by using the PACKAGE_CLASSES variable defined in your conf/local.conf configuration file, which is located in the Build Directory. When defining the variable, you can specify one or more package types. Since images are generated from packages, a packaging class is needed to enable image generation. The first class listed in this variable is used for image generation.

If you take the optional step to set up a repository (package feed) on the development host that can be used by DNF, you can install packages from the feed while you are running the image on the target (i.e. runtime installation of packages). For more information, see the “Using Runtime Package Management” section in the Yocto Project Development Tasks Manual.

The package-specific class you choose can affect build-time performance and has space ramifications. In general, building a package with IPK takes about thirty percent less time as compared to using RPM to build the same or similar package. This comparison takes into account a complete build of the package with all dependencies previously built. The reason for this discrepancy is because the RPM package manager creates and processes more Metadata than the IPK package manager. Consequently, you might consider setting PACKAGE_CLASSES to “package_ipk” if you are building smaller systems.

Before making your package manager decision, however, you should consider some further things about using RPM:

  • RPM starts to provide more abilities than IPK due to the fact that it processes more Metadata. For example, this information includes individual file types, file checksum generation and evaluation on install, sparse file support, conflict detection and resolution for Multilib systems, ACID style upgrade, and repackaging abilities for rollbacks.

  • For smaller systems, the extra space used for the Berkeley Database and the amount of metadata when using RPM can affect your ability to perform on-device upgrades.

You can find additional information on the effects of the package class at these two Yocto Project mailing list links:

5.94 package_deb

The package_deb class provides support for creating packages that use the Debian (i.e. .deb) file format. The class ensures the packages are written out in a .deb file format to the ${DEPLOY_DIR_DEB} directory.

This class inherits the package class and is enabled through the PACKAGE_CLASSES variable in the local.conf file.

5.95 package_ipk

The package_ipk class provides support for creating packages that use the IPK (i.e. .ipk) file format. The class ensures the packages are written out in a .ipk file format to the ${DEPLOY_DIR_IPK} directory.

This class inherits the package class and is enabled through the PACKAGE_CLASSES variable in the local.conf file.

5.96 package_rpm

The package_rpm class provides support for creating packages that use the RPM (i.e. .rpm) file format. The class ensures the packages are written out in a .rpm file format to the ${DEPLOY_DIR_RPM} directory.

This class inherits the package class and is enabled through the PACKAGE_CLASSES variable in the local.conf file.

5.97 packagedata

The packagedata class provides common functionality for reading pkgdata files found in PKGDATA_DIR. These files contain information about each output package produced by the OpenEmbedded build system.

This class is enabled by default because it is inherited by the package class.

5.98 packagegroup

The packagegroup class sets default values appropriate for package group recipes (e.g. PACKAGES, PACKAGE_ARCH, ALLOW_EMPTY, and so forth). It is highly recommended that all package group recipes inherit this class.

For information on how to use this class, see the “Customizing Images Using Custom Package Groups” section in the Yocto Project Development Tasks Manual.

Previously, this class was called the task class.

5.99 patch

The patch class provides all functionality for applying patches during the do_patch task.

This class is enabled by default because it is inherited by the base class.

5.100 perlnative

When inherited by a recipe, the perlnative class supports using the native version of Perl built by the build system rather than using the version provided by the build host.

5.101 pypi

The pypi class sets variables appropriately for recipes that build Python modules from PyPI, the Python Package Index. By default it determines the PyPI package name based upon BPN (stripping the “python-” or “python3-” prefix off if present), however in some cases you may need to set it manually in the recipe by setting PYPI_PACKAGE.

Variables set by the pypi class include SRC_URI, SECTION, HOMEPAGE, UPSTREAM_CHECK_URI, UPSTREAM_CHECK_REGEX and CVE_PRODUCT.

5.102 python_flit_core

The python_flit_core class enables building Python modules which declare the PEP-517 compliant flit_core.buildapi build-backend in the [build-system] section of pyproject.toml (See PEP-518).

Python modules built with flit_core.buildapi are pure Python (no C or Rust extensions).

Internally this uses the python_pep517 class.

5.103 python_pep517

The python_pep517 class builds and installs a Python wheel binary archive (see PEP-517).

Recipes wouldn’t inherit this directly, instead typically another class will inherit this and add the relevant native dependencies.

Examples of classes which do this are python_flit_core, python_setuptools_build_meta, and python_poetry_core.

5.104 python_poetry_core

The python_poetry_core class enables building Python modules which use the Poetry Core build system.

Internally this uses the python_pep517 class.

5.105 python_pyo3

The python_pyo3 class helps make sure that Python extensions written in Rust and built with PyO3, properly set up the environment for cross compilation.

This class is internal to the python-setuptools3_rust class and is not meant to be used directly in recipes.

5.106 python-setuptools3_rust

The python-setuptools3_rust class enables building Python extensions implemented in Rust with PyO3, which allows to compile and distribute Python extensions written in Rust as easily as if they were written in C.

This class inherits the setuptools3 and python_pyo3 classes.

5.107 pixbufcache

The pixbufcache class generates the proper post-install and post-remove (postinst/postrm) scriptlets for packages that install pixbuf loaders, which are used with gdk-pixbuf. These scriptlets call update_pixbuf_cache to add the pixbuf loaders to the cache. Since the cache files are architecture-specific, update_pixbuf_cache is run using QEMU if the postinst scriptlets need to be run on the build host during image creation.

If the pixbuf loaders being installed are in packages other than the recipe’s main package, set PIXBUF_PACKAGES to specify the packages containing the loaders.

5.108 pkgconfig

The pkgconfig class provides a standard way to get header and library information by using pkg-config. This class aims to smooth integration of pkg-config into libraries that use it.

During staging, BitBake installs pkg-config data into the sysroots/ directory. By making use of sysroot functionality within pkg-config, the pkgconfig class no longer has to manipulate the files.

5.109 populate_sdk

The populate_sdk class provides support for SDK-only recipes. For information on advantages gained when building a cross-development toolchain using the do_populate_sdk task, see the “Building an SDK Installer” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

5.110 populate_sdk_*

The populate_sdk_* classes support SDK creation and consist of the following classes:

  • populate_sdk_base: The base class supporting SDK creation under all package managers (i.e. DEB, RPM, and opkg).

  • populate_sdk_deb: Supports creation of the SDK given the Debian package manager.

  • populate_sdk_rpm: Supports creation of the SDK given the RPM package manager.

  • populate_sdk_ipk: Supports creation of the SDK given the opkg (IPK format) package manager.

  • populate_sdk_ext: Supports extensible SDK creation under all package managers.

The populate_sdk_base class inherits the appropriate populate_sdk_* (i.e. deb, rpm, and ipk) based on IMAGE_PKGTYPE.

The base class ensures all source and destination directories are established and then populates the SDK. After populating the SDK, the populate_sdk_base class constructs two sysroots: ${SDK_ARCH}-nativesdk, which contains the cross-compiler and associated tooling, and the target, which contains a target root filesystem that is configured for the SDK usage. These two images reside in SDK_OUTPUT, which consists of the following:

${SDK_OUTPUT}/${SDK_ARCH}-nativesdk-pkgs
${SDK_OUTPUT}/${SDKTARGETSYSROOT}/target-pkgs

Finally, the base populate SDK class creates the toolchain environment setup script, the tarball of the SDK, and the installer.

The respective populate_sdk_deb, populate_sdk_rpm, and populate_sdk_ipk classes each support the specific type of SDK. These classes are inherited by and used with the populate_sdk_base class.

For more information on the cross-development toolchain generation, see the “Cross-Development Toolchain Generation” section in the Yocto Project Overview and Concepts Manual. For information on advantages gained when building a cross-development toolchain using the do_populate_sdk task, see the “Building an SDK Installer” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

5.111 prexport

The prexport class provides functionality for exporting PR values.

Note

This class is not intended to be used directly. Rather, it is enabled when using “bitbake-prserv-tool export”.

5.112 primport

The primport class provides functionality for importing PR values.

Note

This class is not intended to be used directly. Rather, it is enabled when using “bitbake-prserv-tool import”.

5.113 prserv

The prserv class provides functionality for using a PR service in order to automatically manage the incrementing of the PR variable for each recipe.

This class is enabled by default because it is inherited by the package class. However, the OpenEmbedded build system will not enable the functionality of this class unless PRSERV_HOST has been set.

5.114 ptest

The ptest class provides functionality for packaging and installing runtime tests for recipes that build software that provides these tests.

This class is intended to be inherited by individual recipes. However, the class’ functionality is largely disabled unless “ptest” appears in DISTRO_FEATURES. See the “Testing Packages With ptest” section in the Yocto Project Development Tasks Manual for more information on ptest.

5.115 ptest-cargo

The ptest-cargo class is a class which extends the cargo class and adds compile_ptest_cargo and install_ptest_cargo steps to respectively build and install test suites defined in the Cargo.toml file, into a dedicated -ptest package.

5.116 ptest-gnome

Enables package tests (ptests) specifically for GNOME packages, which have tests intended to be executed with gnome-desktop-testing.

For information on setting up and running ptests, see the “Testing Packages With ptest” section in the Yocto Project Development Tasks Manual.

5.117 python3-dir

The python3-dir class provides the base version, location, and site package location for Python 3.

5.118 python3native

The python3native class supports using the native version of Python 3 built by the build system rather than support of the version provided by the build host.

5.119 python3targetconfig

The python3targetconfig class supports using the native version of Python 3 built by the build system rather than support of the version provided by the build host, except that the configuration for the target machine is accessible (such as correct installation directories). This also adds a dependency on target python3, so should only be used where appropriate in order to avoid unnecessarily lengthening builds.

5.120 qemu

The qemu class provides functionality for recipes that either need QEMU or test for the existence of QEMU. Typically, this class is used to run programs for a target system on the build host using QEMU’s application emulation mode.

5.121 recipe_sanity

The recipe_sanity class checks for the presence of any host system recipe prerequisites that might affect the build (e.g. variables that are set or software that is present).

5.122 relocatable

The relocatable class enables relocation of binaries when they are installed into the sysroot.

This class makes use of the chrpath class and is used by both the cross and native classes.

5.123 remove-libtool

The remove-libtool class adds a post function to the do_install task to remove all .la files installed by libtool. Removing these files results in them being absent from both the sysroot and target packages.

If a recipe needs the .la files to be installed, then the recipe can override the removal by setting REMOVE_LIBTOOL_LA to “0” as follows:

REMOVE_LIBTOOL_LA = "0"

Note

The remove-libtool class is not enabled by default.

5.124 report-error

The report-error class supports enabling the error reporting tool”, which allows you to submit build error information to a central database.

The class collects debug information for recipe, recipe version, task, machine, distro, build system, target system, host distro, branch, commit, and log. From the information, report files using a JSON format are created and stored in ${LOG_DIR}/error-report.

5.125 rm_work

The rm_work class supports deletion of temporary workspace, which can ease your hard drive demands during builds.

The OpenEmbedded build system can use a substantial amount of disk space during the build process. A portion of this space is the work files under the ${TMPDIR}/work directory for each recipe. Once the build system generates the packages for a recipe, the work files for that recipe are no longer needed. However, by default, the build system preserves these files for inspection and possible debugging purposes. If you would rather have these files deleted to save disk space as the build progresses, you can enable rm_work by adding the following to your local.conf file, which is found in the Build Directory:

INHERIT += "rm_work"

If you are modifying and building source code out of the work directory for a recipe, enabling rm_work will potentially result in your changes to the source being lost. To exclude some recipes from having their work directories deleted by rm_work, you can add the names of the recipe or recipes you are working on to the RM_WORK_EXCLUDE variable, which can also be set in your local.conf file. Here is an example:

RM_WORK_EXCLUDE += "busybox glibc"

5.126 rootfs*

The rootfs* classes support creating the root filesystem for an image and consist of the following classes:

  • The rootfs-postcommands class, which defines filesystem post-processing functions for image recipes.

  • The rootfs_deb class, which supports creation of root filesystems for images built using .deb packages.

  • The rootfs_rpm class, which supports creation of root filesystems for images built using .rpm packages.

  • The rootfs_ipk class, which supports creation of root filesystems for images built using .ipk packages.

  • The rootfsdebugfiles class, which installs additional files found on the build host directly into the root filesystem.

The root filesystem is created from packages using one of the rootfs* files as determined by the PACKAGE_CLASSES variable.

For information on how root filesystem images are created, see the “Image Generation” section in the Yocto Project Overview and Concepts Manual.

5.127 rust

The rust class is an internal class which is just used in the “rust” recipe, to build the Rust compiler and runtime library. Except for this recipe, it is not intended to be used directly.

5.128 rust-common

The rust-common class is an internal class to the cargo_common and rust classes and is not intended to be used directly.

5.129 sanity

The sanity class checks to see if prerequisite software is present on the host system so that users can be notified of potential problems that might affect their build. The class also performs basic user configuration checks from the local.conf configuration file to prevent common mistakes that cause build failures. Distribution policy usually determines whether to include this class.

5.130 scons

The scons class supports recipes that need to build software that uses the SCons build system. You can use the EXTRA_OESCONS variable to specify additional configuration options you want to pass SCons command line.

5.131 sdl

The sdl class supports recipes that need to build software that uses the Simple DirectMedia Layer (SDL) library.

5.132 python_setuptools_build_meta

The python_setuptools_build_meta class enables building Python modules which declare the PEP-517 compliant setuptools.build_meta build-backend in the [build-system] section of pyproject.toml (See PEP-518).

Python modules built with setuptools.build_meta can be pure Python or include C or Rust extensions).

Internally this uses the python_pep517 class.

5.133 setuptools3

The setuptools3 class supports Python version 3.x extensions that use build systems based on setuptools (e.g. only have a setup.py and have not migrated to the official pyproject.toml format). If your recipe uses these build systems, the recipe needs to inherit the setuptools3 class.

Note

The setuptools3 class do_compile task now calls setup.py bdist_wheel to build the wheel binary archive format (See PEP-427).

A consequence of this is that legacy software still using deprecated distutils from the Python standard library cannot be packaged as wheels. A common solution is the replace from distutils.core import setup with from setuptools import setup.

Note

The setuptools3 class do_install task now installs the wheel binary archive. In current versions of setuptools the legacy setup.py install method is deprecated. If the setup.py cannot be used with wheels, for example it creates files outside of the Python module or standard entry points, then setuptools3_legacy should be used.

5.134 setuptools3_legacy

The setuptools3_legacy class supports Python version 3.x extensions that use build systems based on setuptools (e.g. only have a setup.py and have not migrated to the official pyproject.toml format). Unlike setuptools3, this uses the traditional setup.py build and install commands and not wheels. This use of setuptools like this is deprecated but still relatively common.

5.135 setuptools3-base

The setuptools3-base class provides a reusable base for other classes that support building Python version 3.x extensions. If you need functionality that is not provided by the setuptools3 class, you may want to inherit setuptools3-base. Some recipes do not need the tasks in the setuptools3 class and inherit this class instead.

5.136 sign_rpm

The sign_rpm class supports generating signed RPM packages.

5.137 siteconfig

The siteconfig class provides functionality for handling site configuration. The class is used by the autotools* class to accelerate the do_configure task.

5.138 siteinfo

The siteinfo class provides information about the targets that might be needed by other classes or recipes.

As an example, consider Autotools, which can require tests that must execute on the target hardware. Since this is not possible in general when cross compiling, site information is used to provide cached test results so these tests can be skipped over but still make the correct values available. The meta/site directory contains test results sorted into different categories such as architecture, endianness, and the libc used. Site information provides a list of files containing data relevant to the current build in the CONFIG_SITE variable that Autotools automatically picks up.

The class also provides variables like SITEINFO_ENDIANNESS and SITEINFO_BITS that can be used elsewhere in the metadata.

5.139 sstate

The sstate class provides support for Shared State (sstate). By default, the class is enabled through the INHERIT_DISTRO variable’s default value.

For more information on sstate, see the “Shared State Cache” section in the Yocto Project Overview and Concepts Manual.

5.140 staging

The staging class installs files into individual recipe work directories for sysroots. The class contains the following key tasks:

  • The do_populate_sysroot task, which is responsible for handing the files that end up in the recipe sysroots.

  • The do_prepare_recipe_sysroot task (a “partner” task to the populate_sysroot task), which installs the files into the individual recipe work directories (i.e. WORKDIR).

The code in the staging class is complex and basically works in two stages:

  • Stage One: The first stage addresses recipes that have files they want to share with other recipes that have dependencies on the originating recipe. Normally these dependencies are installed through the do_install task into ${D}. The do_populate_sysroot task copies a subset of these files into ${SYSROOT_DESTDIR}. This subset of files is controlled by the SYSROOT_DIRS, SYSROOT_DIRS_NATIVE, and SYSROOT_DIRS_IGNORE variables.

    Note

    Additionally, a recipe can customize the files further by declaring a processing function in the SYSROOT_PREPROCESS_FUNCS variable.

    A shared state (sstate) object is built from these files and the files are placed into a subdirectory of build/tmp/sysroots-components/. The files are scanned for hardcoded paths to the original installation location. If the location is found in text files, the hardcoded locations are replaced by tokens and a list of the files needing such replacements is created. These adjustments are referred to as “FIXMEs”. The list of files that are scanned for paths is controlled by the SSTATE_SCAN_FILES variable.

  • Stage Two: The second stage addresses recipes that want to use something from another recipe and declare a dependency on that recipe through the DEPENDS variable. The recipe will have a do_prepare_recipe_sysroot task and when this task executes, it creates the recipe-sysroot and recipe-sysroot-native in the recipe work directory (i.e. WORKDIR). The OpenEmbedded build system creates hard links to copies of the relevant files from sysroots-components into the recipe work directory.

    Note

    If hard links are not possible, the build system uses actual copies.

    The build system then addresses any “FIXMEs” to paths as defined from the list created in the first stage.

    Finally, any files in ${bindir} within the sysroot that have the prefix “postinst-” are executed.

    Note

    Although such sysroot post installation scripts are not recommended for general use, the files do allow some issues such as user creation and module indexes to be addressed.

    Because recipes can have other dependencies outside of DEPENDS (e.g. do_unpack[depends] += "tar-native:do_populate_sysroot"), the sysroot creation function extend_recipe_sysroot is also added as a pre-function for those tasks whose dependencies are not through DEPENDS but operate similarly.

    When installing dependencies into the sysroot, the code traverses the dependency graph and processes dependencies in exactly the same way as the dependencies would or would not be when installed from sstate. This processing means, for example, a native tool would have its native dependencies added but a target library would not have its dependencies traversed or installed. The same sstate dependency code is used so that builds should be identical regardless of whether sstate was used or not. For a closer look, see the setscene_depvalid() function in the sstate class.

    The build system is careful to maintain manifests of the files it installs so that any given dependency can be installed as needed. The sstate hash of the installed item is also stored so that if it changes, the build system can reinstall it.

5.141 syslinux

The syslinux class provides syslinux-specific functions for building bootable images.

The class supports the following variables:

  • INITRD: Indicates list of filesystem images to concatenate and use as an initial RAM disk (initrd). This variable is optional.

  • ROOTFS: Indicates a filesystem image to include as the root filesystem. This variable is optional.

  • AUTO_SYSLINUXMENU: Enables creating an automatic menu when set to “1”.

  • LABELS: Lists targets for automatic configuration.

  • APPEND: Lists append string overrides for each label.

  • SYSLINUX_OPTS: Lists additional options to add to the syslinux file. Semicolon characters separate multiple options.

  • SYSLINUX_SPLASH: Lists a background for the VGA boot menu when you are using the boot menu.

  • SYSLINUX_DEFAULT_CONSOLE: Set to “console=ttyX” to change kernel boot default console.

  • SYSLINUX_SERIAL: Sets an alternate serial port. Or, turns off serial when the variable is set with an empty string.

  • SYSLINUX_SERIAL_TTY: Sets an alternate “console=tty…” kernel boot argument.

5.142 systemd

The systemd class provides support for recipes that install systemd unit files.

The functionality for this class is disabled unless you have “systemd” in DISTRO_FEATURES.

Under this class, the recipe or Makefile (i.e. whatever the recipe is calling during the do_install task) installs unit files into ${D}${systemd_unitdir}/system. If the unit files being installed go into packages other than the main package, you need to set SYSTEMD_PACKAGES in your recipe to identify the packages in which the files will be installed.

You should set SYSTEMD_SERVICE to the name of the service file. You should also use a package name override to indicate the package to which the value applies. If the value applies to the recipe’s main package, use ${PN}. Here is an example from the connman recipe:

SYSTEMD_SERVICE:${PN} = "connman.service"

Services are set up to start on boot automatically unless you have set SYSTEMD_AUTO_ENABLE to “disable”.

For more information on systemd, see the “Selecting an Initialization Manager” section in the Yocto Project Development Tasks Manual.

5.143 systemd-boot

The systemd-boot class provides functions specific to the systemd-boot bootloader for building bootable images. This is an internal class and is not intended to be used directly.

Note

The systemd-boot class is a result from merging the gummiboot class used in previous Yocto Project releases with the systemd project.

Set the EFI_PROVIDER variable to “systemd-boot” to use this class. Doing so creates a standalone EFI bootloader that is not dependent on systemd.

For information on more variables used and supported in this class, see the SYSTEMD_BOOT_CFG, SYSTEMD_BOOT_ENTRIES, and SYSTEMD_BOOT_TIMEOUT variables.

You can also see the Systemd-boot documentation for more information.

5.144 terminal

The terminal class provides support for starting a terminal session. The OE_TERMINAL variable controls which terminal emulator is used for the session.

Other classes use the terminal class anywhere a separate terminal session needs to be started. For example, the patch class assuming PATCHRESOLVE is set to “user”, the cml1 class, and the devshell class all use the terminal class.

5.145 testimage

The testimage class supports running automated tests against images using QEMU and on actual hardware. The classes handle loading the tests and starting the image. To use the classes, you need to perform steps to set up the environment.

To enable this class, add the following to your configuration:

IMAGE_CLASSES += "testimage"

The tests are commands that run on the target system over ssh. Each test is written in Python and makes use of the unittest module.

The testimage class runs tests on an image when called using the following:

$ bitbake -c testimage image

Alternatively, if you wish to have tests automatically run for each image after it is built, you can set TESTIMAGE_AUTO:

TESTIMAGE_AUTO = "1"

For information on how to enable, run, and create new tests, see the “Performing Automated Runtime Testing” section in the Yocto Project Development Tasks Manual.

5.146 testsdk

This class supports running automated tests against software development kits (SDKs). The testsdk class runs tests on an SDK when called using the following:

$ bitbake -c testsdk image

Note

Best practices include using IMAGE_CLASSES rather than INHERIT to inherit the testsdk class for automated SDK testing.

5.147 texinfo

This class should be inherited by recipes whose upstream packages invoke the texinfo utilities at build-time. Native and cross recipes are made to use the dummy scripts provided by texinfo-dummy-native, for improved performance. Target architecture recipes use the genuine Texinfo utilities. By default, they use the Texinfo utilities on the host system.

Note

If you want to use the Texinfo recipe shipped with the build system, you can remove “texinfo-native” from ASSUME_PROVIDED and makeinfo from SANITY_REQUIRED_UTILITIES.

5.148 toaster

The toaster class collects information about packages and images and sends them as events that the BitBake user interface can receive. The class is enabled when the Toaster user interface is running.

This class is not intended to be used directly.

5.149 toolchain-scripts

The toolchain-scripts class provides the scripts used for setting up the environment for installed SDKs.

5.150 typecheck

The typecheck class provides support for validating the values of variables set at the configuration level against their defined types. The OpenEmbedded build system allows you to define the type of a variable using the “type” varflag. Here is an example:

IMAGE_FEATURES[type] = "list"

5.151 uboot-config

The uboot-config class provides support for U-Boot configuration for a machine. Specify the machine in your recipe as follows:

UBOOT_CONFIG ??= <default>
UBOOT_CONFIG[foo] = "config,images,binary"

You can also specify the machine using this method:

UBOOT_MACHINE = "config"

See the UBOOT_CONFIG and UBOOT_MACHINE variables for additional information.

5.152 uboot-sign

The uboot-sign class provides support for U-Boot verified boot. It is intended to be inherited from U-Boot recipes.

The variables used by this class are:

See U-Boot’s documentation for details about verified boot and the signature process.

See also the description of kernel-fitimage class, which this class imitates.

5.153 uninative

Attempts to isolate the build system from the host distribution’s C library in order to make re-use of native shared state artifacts across different host distributions practical. With this class enabled, a tarball containing a pre-built C library is downloaded at the start of the build. In the Poky reference distribution this is enabled by default through meta/conf/distro/include/yocto-uninative.inc. Other distributions that do not derive from poky can also “require conf/distro/include/yocto-uninative.inc” to use this. Alternatively if you prefer, you can build the uninative-tarball recipe yourself, publish the resulting tarball (e.g. via HTTP) and set UNINATIVE_URL and UNINATIVE_CHECKSUM appropriately. For an example, see the meta/conf/distro/include/yocto-uninative.inc.

The uninative class is also used unconditionally by the extensible SDK. When building the extensible SDK, uninative-tarball is built and the resulting tarball is included within the SDK.

5.154 update-alternatives

The update-alternatives class helps the alternatives system when multiple sources provide the same command. This situation occurs when several programs that have the same or similar function are installed with the same name. For example, the ar command is available from the busybox, binutils and elfutils packages. The update-alternatives class handles renaming the binaries so that multiple packages can be installed without conflicts. The ar command still works regardless of which packages are installed or subsequently removed. The class renames the conflicting binary in each package and symlinks the highest priority binary during installation or removal of packages.

To use this class, you need to define a number of variables:

These variables list alternative commands needed by a package, provide pathnames for links, default links for targets, and so forth. For details on how to use this class, see the comments in the update-alternatives.bbclass file.

Note

You can use the update-alternatives command directly in your recipes. However, this class simplifies things in most cases.

5.155 update-rc.d

The update-rc.d class uses update-rc.d to safely install an initialization script on behalf of the package. The OpenEmbedded build system takes care of details such as making sure the script is stopped before a package is removed and started when the package is installed.

Three variables control this class: INITSCRIPT_PACKAGES, INITSCRIPT_NAME and INITSCRIPT_PARAMS. See the variable links for details.

5.156 useradd*

The useradd* classes support the addition of users or groups for usage by the package on the target. For example, if you have packages that contain system services that should be run under their own user or group, you can use these classes to enable creation of the user or group. The meta-skeleton/recipes-skeleton/useradd/useradd-example.bb recipe in the Source Directory provides a simple example that shows how to add three users and groups to two packages.

The useradd_base class provides basic functionality for user or groups settings.

The useradd* classes support the USERADD_PACKAGES, USERADD_PARAM, GROUPADD_PARAM, and GROUPMEMS_PARAM variables.

The useradd-staticids class supports the addition of users or groups that have static user identification (uid) and group identification (gid) values.

The default behavior of the OpenEmbedded build system for assigning uid and gid values when packages add users and groups during package install time is to add them dynamically. This works fine for programs that do not care what the values of the resulting users and groups become. In these cases, the order of the installation determines the final uid and gid values. However, if non-deterministic uid and gid values are a problem, you can override the default, dynamic application of these values by setting static values. When you set static values, the OpenEmbedded build system looks in BBPATH for files/passwd and files/group files for the values.

To use static uid and gid values, you need to set some variables. See the USERADDEXTENSION, USERADD_UID_TABLES, USERADD_GID_TABLES, and USERADD_ERROR_DYNAMIC variables. You can also see the useradd* class for additional information.

Note

You do not use the useradd-staticids class directly. You either enable or disable the class by setting the USERADDEXTENSION variable. If you enable or disable the class in a configured system, TMPDIR might contain incorrect uid and gid values. Deleting the TMPDIR directory will correct this condition.

5.157 utility-tasks

The utility-tasks class provides support for various “utility” type tasks that are applicable to all recipes, such as do_clean and do_listtasks.

This class is enabled by default because it is inherited by the base class.

5.158 utils

The utils class provides some useful Python functions that are typically used in inline Python expressions (e.g. ${@...}). One example use is for bb.utils.contains().

This class is enabled by default because it is inherited by the base class.

5.159 vala

The vala class supports recipes that need to build software written using the Vala programming language.

5.160 waf

The waf class supports recipes that need to build software that uses the Waf build system. You can use the EXTRA_OECONF or PACKAGECONFIG_CONFARGS variables to specify additional configuration options to be passed on the Waf command line.