12 Variables Glossary

This chapter lists common variables used in the OpenEmbedded build system and gives an overview of their function and contents.

A B C D E F G H I K L M N O P R S T U V W X

ABIEXTENSION 

Extension to the Application Binary Interface (ABI) field of the GNU canonical architecture name (e.g. “eabi”).

ABI extensions are set in the machine include files. For example, the meta/conf/machine/include/arm/arch-arm.inc file sets the following extension:

ABIEXTENSION = "eabi"

ALLOW_EMPTY 

Specifies whether to produce an output package even if it is empty. By default, BitBake does not produce empty packages. This default behavior can cause issues when there is an RDEPENDS or some other hard runtime requirement on the existence of the package.

Like all package-controlling variables, you must always use them in conjunction with a package name override, as in:

ALLOW_EMPTY:${PN} = "1"
ALLOW_EMPTY:${PN}-dev = "1"
ALLOW_EMPTY:${PN}-staticdev = "1"

ALTERNATIVE 

Lists commands in a package that need an alternative binary naming scheme. Sometimes the same command is provided in multiple packages. When this occurs, the OpenEmbedded build system needs to use the alternatives system to create a different binary naming scheme so the commands can co-exist.

To use the variable, list out the package’s commands that are also provided by another package. For example, if the busybox package has four such commands, you identify them as follows:

ALTERNATIVE:busybox = "sh sed test bracket"

For more information on the alternatives system, see the “update-alternatives” section.

ALTERNATIVE_LINK_NAME 

Used by the alternatives system to map duplicated commands to actual locations. For example, if the bracket command provided by the busybox package is duplicated through another package, you must use the ALTERNATIVE_LINK_NAME variable to specify the actual location:

ALTERNATIVE_LINK_NAME[bracket] = "/usr/bin/["

In this example, the binary for the bracket command (i.e. [) from the busybox package resides in /usr/bin/.

Note

If ALTERNATIVE_LINK_NAME is not defined, it defaults to ${bindir}/name.

For more information on the alternatives system, see the “update-alternatives” section.

ALTERNATIVE_PRIORITY 

Used by the alternatives system to create default priorities for duplicated commands. You can use the variable to create a single default regardless of the command name or package, a default for specific duplicated commands regardless of the package, or a default for specific commands tied to particular packages. Here are the available syntax forms:

ALTERNATIVE_PRIORITY = "priority"
ALTERNATIVE_PRIORITY[name] = "priority"
ALTERNATIVE_PRIORITY_pkg[name] = "priority"

For more information on the alternatives system, see the “update-alternatives” section.

ALTERNATIVE_TARGET 

Used by the alternatives system to create default link locations for duplicated commands. You can use the variable to create a single default location for all duplicated commands regardless of the command name or package, a default for specific duplicated commands regardless of the package, or a default for specific commands tied to particular packages. Here are the available syntax forms:

ALTERNATIVE_TARGET = "target"
ALTERNATIVE_TARGET[name] = "target"
ALTERNATIVE_TARGET_pkg[name] = "target"

Note

If ALTERNATIVE_TARGET is not defined, it inherits the value from the ALTERNATIVE_LINK_NAME variable.

If ALTERNATIVE_LINK_NAME and ALTERNATIVE_TARGET are the same, the target for ALTERNATIVE_TARGET has “.{BPN}” appended to it.

Finally, if the file referenced has not been renamed, the alternatives system will rename it to avoid the need to rename alternative files in the do_install task while retaining support for the command if necessary.

For more information on the alternatives system, see the “update-alternatives” section.

ANY_OF_DISTRO_FEATURES 

When inheriting the features_check class, this variable identifies a list of distribution features where at least one must be enabled in the current configuration in order for the OpenEmbedded build system to build the recipe. In other words, if none of the features listed in ANY_OF_DISTRO_FEATURES appear in DISTRO_FEATURES within the current configuration, then the recipe will be skipped, and if the build system attempts to build the recipe then an error will be triggered.

APPEND 

An override list of append strings for each target specified with LABELS.

See the grub-efi class for more information on how this variable is used.

AR 

The minimal command and arguments used to run ar.

ARCHIVER_MODE 

When used with the archiver class, determines the type of information used to create a released archive. You can use this variable to create archives of patched source, original source, configured source, and so forth by employing the following variable flags (varflags):

ARCHIVER_MODE[src] = "original"                   # Uses original (unpacked) source files.
ARCHIVER_MODE[src] = "patched"                    # Uses patched source files. This is the default.
ARCHIVER_MODE[src] = "configured"                 # Uses configured source files.
ARCHIVER_MODE[diff] = "1"                         # Uses patches between do_unpack and do_patch.
ARCHIVER_MODE[diff-exclude] ?= "file file ..."    # Lists files and directories to exclude from diff.
ARCHIVER_MODE[dumpdata] = "1"                     # Uses environment data.
ARCHIVER_MODE[recipe] = "1"                       # Uses recipe and include files.
ARCHIVER_MODE[srpm] = "1"                         # Uses RPM package files.

For information on how the variable works, see the meta/classes/archiver.bbclass file in the Source Directory.

AS 

Minimal command and arguments needed to run the assembler.

ASSUME_PROVIDED 

Lists recipe names (PN values) BitBake does not attempt to build. Instead, BitBake assumes these recipes have already been built.

In OpenEmbedded-Core, ASSUME_PROVIDED mostly specifies native tools that should not be built. An example is git-native, which when specified, allows for the Git binary from the host to be used rather than building git-native.

ASSUME_SHLIBS 

Provides additional shlibs provider mapping information, which adds to or overwrites the information provided automatically by the system. Separate multiple entries using spaces.

As an example, use the following form to add an shlib provider of shlibname in packagename with the optional version:

shlibname:packagename[_version]

Here is an example that adds a shared library named libEGL.so.1 as being provided by the libegl-implementation package:

ASSUME_SHLIBS = "libEGL.so.1:libegl-implementation"

AUTHOR 

The email address used to contact the original author or authors in order to send patches and forward bugs.

AUTO_LIBNAME_PKGS 

When the debian class is inherited, which is the default behavior, AUTO_LIBNAME_PKGS specifies which packages should be checked for libraries and renamed according to Debian library package naming.

The default value is “${PACKAGES}”, which causes the debian class to act on all packages that are explicitly generated by the recipe.

AUTO_SYSLINUXMENU 

Enables creating an automatic menu for the syslinux bootloader. You must set this variable in your recipe. The syslinux class checks this variable.

AUTOREV 

When SRCREV is set to the value of this variable, it specifies to use the latest source revision in the repository. Here is an example:

SRCREV = "${AUTOREV}"

If you use the previous statement to retrieve the latest version of software, you need to be sure PV contains ${SRCPV}. For example, suppose you have a kernel recipe that inherits the kernel class and you use the previous statement. In this example, ${SRCPV} does not automatically get into PV. Consequently, you need to change PV in your recipe so that it does contain ${SRCPV}.

For more information see the “Automatically Incrementing a Package Version Number” section in the Yocto Project Development Tasks Manual.

AVAILTUNES 

The list of defined CPU and Application Binary Interface (ABI) tunings (i.e. “tunes”) available for use by the OpenEmbedded build system.

The list simply presents the tunes that are available. Not all tunes may be compatible with a particular machine configuration, or with each other in a Multilib configuration.

To add a tune to the list, be sure to append it with spaces using the “+=” BitBake operator. Do not simply replace the list by using the “=” operator. See the “Basic Syntax” section in the BitBake User Manual for more information.

AZ_SAS 

Azure Storage Shared Access Signature, when using the Azure Storage fetcher (az://) This variable can be defined to be used by the fetcher to authenticate and gain access to non-public artifacts:

AZ_SAS = ""se=2021-01-01&sp=r&sv=2018-11-09&sr=c&skoid=<skoid>&sig=<signature>""

For more information see Microsoft’s Azure Storage documentation at https://docs.microsoft.com/en-us/azure/storage/common/storage-sas-overview

B 

The directory within the Build Directory in which the OpenEmbedded build system places generated objects during a recipe’s build process. By default, this directory is the same as the S directory, which is defined as:

S = "${WORKDIR}/${BP}"

You can separate the (S) directory and the directory pointed to by the B variable. Most Autotools-based recipes support separating these directories. The build system defaults to using separate directories for gcc and some kernel recipes.

BAD_RECOMMENDATIONS 

Lists “recommended-only” packages to not install. Recommended-only packages are packages installed only through the RRECOMMENDS variable. You can prevent any of these “recommended” packages from being installed by listing them with the BAD_RECOMMENDATIONS variable:

BAD_RECOMMENDATIONS = "package_name package_name package_name ..."

You can set this variable globally in your local.conf file or you can attach it to a specific image recipe by using the recipe name override:

BAD_RECOMMENDATIONS:pn-target_image = "package_name"

It is important to realize that if you choose to not install packages using this variable and some other packages are dependent on them (i.e. listed in a recipe’s RDEPENDS variable), the OpenEmbedded build system ignores your request and will install the packages to avoid dependency errors.

This variable is supported only when using the IPK and RPM packaging backends. DEB is not supported.

See the NO_RECOMMENDATIONS and the PACKAGE_EXCLUDE variables for related information.

BASE_LIB 

The library directory name for the CPU or Application Binary Interface (ABI) tune. The BASE_LIB applies only in the Multilib context. See the “Combining Multiple Versions of Library Files into One Image” section in the Yocto Project Development Tasks Manual for information on Multilib.

The BASE_LIB variable is defined in the machine include files in the Source Directory. If Multilib is not being used, the value defaults to “lib”.

BASE_WORKDIR 

Points to the base of the work directory for all recipes. The default value is “${TMPDIR}/work”.

BB_ALLOWED_NETWORKS 

Specifies a space-delimited list of hosts that the fetcher is allowed to use to obtain the required source code. Following are considerations surrounding this variable:

This host list is only used if BB_NO_NETWORK is either not set or set to “0”.
There is limited support for wildcard matching against the beginning of host names. For example, the following setting matches git.gnu.org, ftp.gnu.org, and foo.git.gnu.org:
```
BB_ALLOWED_NETWORKS = "*.gnu.org"
```
Note

The use of the “*” character only works at the beginning of a host name and it must be isolated from the remainder of the host name. You cannot use the wildcard character in any other location of the name or combined with the front part of the name.

For example, *.foo.bar is supported, while *aa.foo.bar is not.
Mirrors not in the host list are skipped and logged in debug.
Attempts to access networks not in the host list cause a failure.

Using BB_ALLOWED_NETWORKS in conjunction with PREMIRRORS is very useful. Adding the host you want to use to PREMIRRORS results in the source code being fetched from an allowed location and avoids raising an error when a host that is not allowed is in a SRC_URI statement. This is because the fetcher does not attempt to use the host listed in SRC_URI after a successful fetch from the PREMIRRORS occurs.

BB_BASEHASH_IGNORE_VARS 

See BB_BASEHASH_IGNORE_VARS in the BitBake manual.

BB_CACHEDIR 

See BB_CACHEDIR in the BitBake manual.

BB_CHECK_SSL_CERTS 

See BB_CHECK_SSL_CERTS in the BitBake manual.

BB_CONSOLELOG 

See BB_CONSOLELOG in the BitBake manual.

BB_CURRENTTASK 

See BB_CURRENTTASK in the BitBake manual.

BB_DANGLINGAPPENDS_WARNONLY 

Defines how BitBake handles situations where an append file (.bbappend) has no corresponding recipe file (.bb). This condition often occurs when layers get out of sync (e.g. oe-core bumps a recipe version and the old recipe no longer exists and the other layer has not been updated to the new version of the recipe yet).

The default fatal behavior is safest because it is the sane reaction given something is out of sync. It is important to realize when your changes are no longer being applied.

You can change the default behavior by setting this variable to “1”, “yes”, or “true” in your local.conf file, which is located in the Build Directory: Here is an example:

BB_DANGLINGAPPENDS_WARNONLY = "1"

BB_DEFAULT_TASK 

See BB_DEFAULT_TASK in the BitBake manual.

BB_DEFAULT_UMASK 

See BB_DEFAULT_UMASK in the BitBake manual.

BB_DISKMON_DIRS 

Monitors disk space and available inodes during the build and allows you to control the build based on these parameters.

Disk space monitoring is disabled by default. To enable monitoring, add the BB_DISKMON_DIRS variable to your conf/local.conf file found in the Build Directory. Use the following form:

BB_DISKMON_DIRS = "action,dir,threshold [...]"

where:

   action is:
      ABORT:     Immediately stop the build when
                 a threshold is broken.
      STOPTASKS: Stop the build after the currently
                 executing tasks have finished when
                 a threshold is broken.
      WARN:      Issue a warning but continue the
                 build when a threshold is broken.
                 Subsequent warnings are issued as
                 defined by the BB_DISKMON_WARNINTERVAL
                 variable, which must be defined in
                 the conf/local.conf file.

   dir is:
      Any directory you choose. You can specify one or
      more directories to monitor by separating the
      groupings with a space.  If two directories are
      on the same device, only the first directory
      is monitored.

   threshold is:
      Either the minimum available disk space,
      the minimum number of free inodes, or
      both.  You must specify at least one.  To
      omit one or the other, simply omit the value.
      Specify the threshold using G, M, K for Gbytes,
      Mbytes, and Kbytes, respectively. If you do
      not specify G, M, or K, Kbytes is assumed by
      default.  Do not use GB, MB, or KB.

Here are some examples:

BB_DISKMON_DIRS = "ABORT,${TMPDIR},1G,100K WARN,${SSTATE_DIR},1G,100K"
BB_DISKMON_DIRS = "STOPTASKS,${TMPDIR},1G"
BB_DISKMON_DIRS = "ABORT,${TMPDIR},,100K"

The first example works only if you also provide the BB_DISKMON_WARNINTERVAL variable in the conf/local.conf. This example causes the build system to immediately stop when either the disk space in ${TMPDIR} drops below 1 Gbyte or the available free inodes drops below 100 Kbytes. Because two directories are provided with the variable, the build system also issue a warning when the disk space in the ${SSTATE_DIR} directory drops below 1 Gbyte or the number of free inodes drops below 100 Kbytes. Subsequent warnings are issued during intervals as defined by the BB_DISKMON_WARNINTERVAL variable.

The second example stops the build after all currently executing tasks complete when the minimum disk space in the ${TMPDIR} directory drops below 1 Gbyte. No disk monitoring occurs for the free inodes in this case.

The final example immediately stops the build when the number of free inodes in the ${TMPDIR} directory drops below 100 Kbytes. No disk space monitoring for the directory itself occurs in this case.

BB_DISKMON_WARNINTERVAL 

Defines the disk space and free inode warning intervals. To set these intervals, define the variable in your conf/local.conf file in the Build Directory.

If you are going to use the BB_DISKMON_WARNINTERVAL variable, you must also use the BB_DISKMON_DIRS variable and define its action as “WARN”. During the build, subsequent warnings are issued each time disk space or number of free inodes further reduces by the respective interval.

If you do not provide a BB_DISKMON_WARNINTERVAL variable and you do use BB_DISKMON_DIRS with the “WARN” action, the disk monitoring interval defaults to the following:

BB_DISKMON_WARNINTERVAL = "50M,5K"

When specifying the variable in your configuration file, use the following form:

BB_DISKMON_WARNINTERVAL = "disk_space_interval,disk_inode_interval"

where:

   disk_space_interval is:
      An interval of memory expressed in either
      G, M, or K for Gbytes, Mbytes, or Kbytes,
      respectively. You cannot use GB, MB, or KB.

   disk_inode_interval is:
      An interval of free inodes expressed in either
      G, M, or K for Gbytes, Mbytes, or Kbytes,
      respectively. You cannot use GB, MB, or KB.

Here is an example:

BB_DISKMON_DIRS = "WARN,${SSTATE_DIR},1G,100K"
BB_DISKMON_WARNINTERVAL = "50M,5K"

These variables cause the OpenEmbedded build system to issue subsequent warnings each time the available disk space further reduces by 50 Mbytes or the number of free inodes further reduces by 5 Kbytes in the ${SSTATE_DIR} directory. Subsequent warnings based on the interval occur each time a respective interval is reached beyond the initial warning (i.e. 1 Gbytes and 100 Kbytes).

BB_ENV_PASSTHROUGH 

See BB_ENV_PASSTHROUGH in the BitBake manual.

BB_ENV_PASSTHROUGH_ADDITIONS 

See BB_ENV_PASSTHROUGH_ADDITIONS in the BitBake manual.

BB_FETCH_PREMIRRORONLY 

See BB_FETCH_PREMIRRORONLY in the BitBake manual.

BB_FILENAME 

See BB_FILENAME in the BitBake manual.

BB_GENERATE_MIRROR_TARBALLS 

Causes tarballs of the source control repositories (e.g. Git repositories), including metadata, to be placed in the DL_DIR directory.

For performance reasons, creating and placing tarballs of these repositories is not the default action by the OpenEmbedded build system:

BB_GENERATE_MIRROR_TARBALLS = "1"

Set this variable in your local.conf file in the Build Directory.

Once you have the tarballs containing your source files, you can clean up your DL_DIR directory by deleting any Git or other source control work directories.

BB_GENERATE_SHALLOW_TARBALLS 

See BB_GENERATE_SHALLOW_TARBALLS in the BitBake manual.

BB_GIT_SHALLOW 

See BB_GIT_SHALLOW in the BitBake manual.

BB_GIT_SHALLOW_DEPTH 

See BB_GIT_SHALLOW_DEPTH in the BitBake manual.

BB_HASHCHECK_FUNCTION 

See BB_HASHCHECK_FUNCTION in the BitBake manual.

BB_HASHCONFIG_IGNORE_VARS 

See BB_HASHCONFIG_IGNORE_VARS in the BitBake manual.

BB_HASHSERVE 

See BB_HASHSERVE in the BitBake manual.

BB_HASHSERVE_UPSTREAM 

See BB_HASHSERVE_UPSTREAM in the BitBake manual.

BB_INVALIDCONF 

See BB_INVALIDCONF in the BitBake manual.

BB_LOGCONFIG 

See BB_LOGCONFIG in the BitBake manual.

BB_LOGFMT 

See BB_LOGFMT in the BitBake manual.

BB_MULTI_PROVIDER_ALLOWED 

See BB_MULTI_PROVIDER_ALLOWED in the BitBake manual.

BB_NICE_LEVEL 

See BB_NICE_LEVEL in the BitBake manual.

BB_NO_NETWORK 

See BB_NO_NETWORK in the BitBake manual.

BB_NUMBER_PARSE_THREADS 

See BB_NUMBER_PARSE_THREADS in the BitBake manual.

BB_NUMBER_THREADS 

The maximum number of tasks BitBake should run in parallel at any one time. The OpenEmbedded build system automatically configures this variable to be equal to the number of cores on the build system. For example, a system with a dual core processor that also uses hyper-threading causes the BB_NUMBER_THREADS variable to default to “4”.

For single socket systems (i.e. one CPU), you should not have to override this variable to gain optimal parallelism during builds. However, if you have very large systems that employ multiple physical CPUs, you might want to make sure the BB_NUMBER_THREADS variable is not set higher than “20”.

For more information on speeding up builds, see the “Speeding Up a Build” section in the Yocto Project Development Tasks Manual.

On the other hand, if your goal is to limit the amount of system resources consumed by BitBake tasks, setting BB_NUMBER_THREADS to a number lower than the number of CPU threads in your machine won’t be sufficient. That’s because each package will still be built and installed through a number of parallel jobs specified by the PARALLEL_MAKE variable, which is by default the number of CPU threads in your system, and is not impacted by the BB_NUMBER_THREADS value.

So, if you set BB_NUMBER_THREADS to “1” but don’t set PARALLEL_MAKE, most of your system resources will be consumed anyway.

Therefore, if you intend to reduce the load of your build system by setting BB_NUMBER_THREADS to a relatively low value compared to the number of CPU threads on your system, you should also set PARALLEL_MAKE to a similarly low value.

An alternative to using BB_NUMBER_THREADS to keep the usage of build system resources under control is to use the smarter BB_PRESSURE_MAX_CPU, BB_PRESSURE_MAX_IO or BB_PRESSURE_MAX_MEMORY controls. They will prevent BitBake from starting new tasks as long as thresholds are exceeded. Anyway, as with BB_NUMBER_THREADS, such controls won’t prevent the tasks already being run from using all CPU threads on the system if PARALLEL_MAKE is not set to a low value.

BB_ORIGENV 

See BB_ORIGENV in the BitBake manual.

BB_PRESERVE_ENV 

See BB_PRESERVE_ENV in the BitBake manual.

BB_PRESSURE_MAX_CPU 

See BB_PRESSURE_MAX_CPU in the BitBake manual.

BB_PRESSURE_MAX_IO 

See BB_PRESSURE_MAX_IO in the BitBake manual.

BB_PRESSURE_MAX_MEMORY 

See BB_PRESSURE_MAX_MEMORY in the BitBake manual.

BB_RUNFMT 

See BB_RUNFMT in the BitBake manual.

BB_RUNTASK 

See BB_RUNTASK in the BitBake manual.

BB_SCHEDULER 

See BB_SCHEDULER in the BitBake manual.

BB_SCHEDULERS 

See BB_SCHEDULERS in the BitBake manual.

BB_SERVER_TIMEOUT 

Specifies the time (in seconds) after which to unload the BitBake server due to inactivity. Set BB_SERVER_TIMEOUT to determine how long the BitBake server stays resident between invocations.

For example, the following statement in your local.conf file instructs the server to be unloaded after 20 seconds of inactivity:

BB_SERVER_TIMEOUT = "20"

If you want the server to never be unloaded, set BB_SERVER_TIMEOUT to “-1”.

BB_SETSCENE_DEPVALID 

See BB_SETSCENE_DEPVALID in the BitBake manual.

BB_SIGNATURE_EXCLUDE_FLAGS 

See BB_SIGNATURE_EXCLUDE_FLAGS in the BitBake manual.

BB_SIGNATURE_HANDLER 

See BB_SIGNATURE_HANDLER in the BitBake manual.

BB_SRCREV_POLICY 

See BB_SRCREV_POLICY in the BitBake manual.

BB_STRICT_CHECKSUM 

See BB_STRICT_CHECKSUM in the BitBake manual.

BB_TASK_IONICE_LEVEL 

See BB_TASK_IONICE_LEVEL in the BitBake manual.

BB_TASK_NICE_LEVEL 

See BB_TASK_NICE_LEVEL in the BitBake manual.

BB_TASKHASH 

See BB_TASKHASH in the BitBake manual.

BB_VERBOSE_LOGS 

See BB_VERBOSE_LOGS in the BitBake manual.

BB_WORKERCONTEXT 

See BB_WORKERCONTEXT in the BitBake manual.

BBCLASSEXTEND 

Allows you to extend a recipe so that it builds variants of the software. There are common variants for recipes as “natives” like quilt-native, which is a copy of Quilt built to run on the build system; “crosses” such as gcc-cross, which is a compiler built to run on the build machine but produces binaries that run on the target MACHINE; “nativesdk”, which targets the SDK machine instead of MACHINE; and “mulitlibs” in the form “multilib:multilib_name”.

To build a different variant of the recipe with a minimal amount of code, it usually is as simple as adding the following to your recipe:

BBCLASSEXTEND =+ "native nativesdk"
BBCLASSEXTEND =+ "multilib:multilib_name"

Note

Internally, the BBCLASSEXTEND mechanism generates recipe variants by rewriting variable values and applying overrides such as :class-native. For example, to generate a native version of a recipe, a DEPENDS on “foo” is rewritten to a DEPENDS on “foo-native”.

Even when using BBCLASSEXTEND, the recipe is only parsed once. Parsing once adds some limitations. For example, it is not possible to include a different file depending on the variant, since include statements are processed when the recipe is parsed.

BBDEBUG 

See BBDEBUG in the BitBake manual.

BBFILE_COLLECTIONS 

Lists the names of configured layers. These names are used to find the other BBFILE_* variables. Typically, each layer will append its name to this variable in its conf/layer.conf file.

BBFILE_PATTERN 

Variable that expands to match files from BBFILES in a particular layer. This variable is used in the conf/layer.conf file and must be suffixed with the name of the specific layer (e.g. BBFILE_PATTERN_emenlow).

BBFILE_PRIORITY 

Assigns the priority for recipe files in each layer.

This variable is useful in situations where the same recipe appears in more than one layer. Setting this variable allows you to prioritize a layer against other layers that contain the same recipe — effectively letting you control the precedence for the multiple layers. The precedence established through this variable stands regardless of a recipe’s version (PV variable). For example, a layer that has a recipe with a higher PV value but for which the BBFILE_PRIORITY is set to have a lower precedence still has a lower precedence.

A larger value for the BBFILE_PRIORITY variable results in a higher precedence. For example, the value 6 has a higher precedence than the value 5. If not specified, the BBFILE_PRIORITY variable is set based on layer dependencies (see the LAYERDEPENDS variable for more information. The default priority, if unspecified for a layer with no dependencies, is the lowest defined priority + 1 (or 1 if no priorities are defined).

Tip

You can use the command bitbake-layers show-layers to list all configured layers along with their priorities.

BBFILES 

A space-separated list of recipe files BitBake uses to build software.

When specifying recipe files, you can pattern match using Python’s glob syntax. For details on the syntax, see the documentation by following the previous link.

BBFILES_DYNAMIC 

Activates content when identified layers are present. You identify the layers by the collections that the layers define.

Use the BBFILES_DYNAMIC variable to avoid .bbappend files whose corresponding .bb file is in a layer that attempts to modify other layers through .bbappend but does not want to introduce a hard dependency on those other layers.

Use the following form for BBFILES_DYNAMIC: collection_name:filename_pattern.

The following example identifies two collection names and two filename patterns:

BBFILES_DYNAMIC += " \
   clang-layer:${LAYERDIR}/bbappends/meta-clang/*/*/*.bbappend \
   core:${LAYERDIR}/bbappends/openembedded-core/meta/*/*/*.bbappend \
   "

This next example shows an error message that occurs because invalid entries are found, which cause parsing to fail:

ERROR: BBFILES_DYNAMIC entries must be of the form <collection name>:<filename pattern>, not:
    /work/my-layer/bbappends/meta-security-isafw/*/*/*.bbappend
    /work/my-layer/bbappends/openembedded-core/meta/*/*/*.bbappend

BBINCLUDED 

See BBINCLUDED in the BitBake manual.

BBINCLUDELOGS 

Variable that controls how BitBake displays logs on build failure.

BBINCLUDELOGS_LINES 

If BBINCLUDELOGS is set, specifies the maximum number of lines from the task log file to print when reporting a failed task. If you do not set BBINCLUDELOGS_LINES, the entire log is printed.

BBLAYERS 

Lists the layers to enable during the build. This variable is defined in the bblayers.conf configuration file in the Build Directory. Here is an example:

BBLAYERS = " \
    /home/scottrif/poky/meta \
    /home/scottrif/poky/meta-poky \
    /home/scottrif/poky/meta-yocto-bsp \
    /home/scottrif/poky/meta-mykernel \
    "

This example enables four layers, one of which is a custom, user-defined layer named meta-mykernel.

BBLAYERS_FETCH_DIR 

See BBLAYERS_FETCH_DIR in the BitBake manual.

BBMASK 

Prevents BitBake from processing recipes and recipe append files.

You can use the BBMASK variable to “hide” these .bb and .bbappend files. BitBake ignores any recipe or recipe append files that match any of the expressions. It is as if BitBake does not see them at all. Consequently, matching files are not parsed or otherwise used by BitBake.

The values you provide are passed to Python’s regular expression compiler. Consequently, the syntax follows Python’s Regular Expression (re) syntax. The expressions are compared against the full paths to the files. For complete syntax information, see Python’s documentation at https://docs.python.org/3/library/re.html#regular-expression-syntax.

The following example uses a complete regular expression to tell BitBake to ignore all recipe and recipe append files in the meta-ti/recipes-misc/ directory:

BBMASK = "meta-ti/recipes-misc/"

If you want to mask out multiple directories or recipes, you can specify multiple regular expression fragments. This next example masks out multiple directories and individual recipes:

BBMASK += "/meta-ti/recipes-misc/ meta-ti/recipes-ti/packagegroup/"
BBMASK += "/meta-oe/recipes-support/"
BBMASK += "/meta-foo/.*/openldap"
BBMASK += "opencv.*\.bbappend"
BBMASK += "lzma"

Note

When specifying a directory name, use the trailing slash character to ensure you match just that directory name.

BBMULTICONFIG 

Specifies each additional separate configuration when you are building targets with multiple configurations. Use this variable in your conf/local.conf configuration file. Specify a multiconfigname for each configuration file you are using. For example, the following line specifies three configuration files:

BBMULTICONFIG = "configA configB configC"

Each configuration file you use must reside in a multiconfig subdirectory of a configuration directory within a layer, or within the Build Directory (e.g. build_directory/conf/multiconfig/configA.conf or mylayer/conf/multiconfig/configB.conf).

For information on how to use BBMULTICONFIG in an environment that supports building targets with multiple configurations, see the “Building Images for Multiple Targets Using Multiple Configurations” section in the Yocto Project Development Tasks Manual.

BBPATH 

See BBPATH in the BitBake manual.

BBSERVER 

If defined in the BitBake environment, BBSERVER points to the BitBake remote server.

Use the following format to export the variable to the BitBake environment:

export BBSERVER=localhost:$port

By default, BBSERVER also appears in BB_BASEHASH_IGNORE_VARS. Consequently, BBSERVER is excluded from checksum and dependency data.

BBTARGETS 

See BBTARGETS in the BitBake manual.

BINCONFIG 

When inheriting the binconfig-disabled class, this variable specifies binary configuration scripts to disable in favor of using pkg-config to query the information. The binconfig-disabled class will modify the specified scripts to return an error so that calls to them can be easily found and replaced.

To add multiple scripts, separate them by spaces. Here is an example from the libpng recipe:

BINCONFIG = "${bindir}/libpng-config ${bindir}/libpng16-config"

BINCONFIG_GLOB 

When inheriting the binconfig class, this variable specifies a wildcard for configuration scripts that need editing. The scripts are edited to correct any paths that have been set up during compilation so that they are correct for use when installed into the sysroot and called by the build processes of other recipes.

Note

The BINCONFIG_GLOB variable uses shell globbing, which is recognition and expansion of wildcards during pattern matching. Shell globbing is very similar to fnmatch and glob.

For more information on how this variable works, see meta/classes-recipe/binconfig.bbclass in the Source Directory. You can also find general information on the class in the “binconfig” section.

BITBAKE_UI 

See BITBAKE_UI in the BitBake manual.

BP 

The base recipe name and version but without any special recipe name suffix (i.e. -native, lib64-, and so forth). BP is comprised of the following:

${BPN}-${PV}

BPN 

This variable is a version of the PN variable with common prefixes and suffixes removed, such as nativesdk-, -cross, -native, and multilib’s lib64- and lib32-. The exact lists of prefixes and suffixes removed are specified by the MLPREFIX and SPECIAL_PKGSUFFIX variables, respectively.

BUGTRACKER 

Specifies a URL for an upstream bug tracking website for a recipe. The OpenEmbedded build system does not use this variable. Rather, the variable is a useful pointer in case a bug in the software being built needs to be manually reported.

BUILD_ARCH 

Specifies the architecture of the build host (e.g. i686). The OpenEmbedded build system sets the value of BUILD_ARCH from the machine name reported by the uname command.

BUILD_AS_ARCH 

Specifies the architecture-specific assembler flags for the build host. By default, the value of BUILD_AS_ARCH is empty.

BUILD_CC_ARCH 

Specifies the architecture-specific C compiler flags for the build host. By default, the value of BUILD_CC_ARCH is empty.

BUILD_CCLD 

Specifies the linker command to be used for the build host when the C compiler is being used as the linker. By default, BUILD_CCLD points to GCC and passes as arguments the value of BUILD_CC_ARCH, assuming BUILD_CC_ARCH is set.

BUILD_CFLAGS 

Specifies the flags to pass to the C compiler when building for the build host. When building in the -native context, CFLAGS is set to the value of this variable by default.

BUILD_CPPFLAGS 

Specifies the flags to pass to the C preprocessor (i.e. to both the C and the C++ compilers) when building for the build host. When building in the -native context, CPPFLAGS is set to the value of this variable by default.

BUILD_CXXFLAGS 

Specifies the flags to pass to the C++ compiler when building for the build host. When building in the -native context, CXXFLAGS is set to the value of this variable by default.

BUILD_FC 

Specifies the Fortran compiler command for the build host. By default, BUILD_FC points to Gfortran and passes as arguments the value of BUILD_CC_ARCH, assuming BUILD_CC_ARCH is set.

BUILD_LD 

Specifies the linker command for the build host. By default, BUILD_LD points to the GNU linker (ld) and passes as arguments the value of BUILD_LD_ARCH, assuming BUILD_LD_ARCH is set.

BUILD_LD_ARCH 

Specifies architecture-specific linker flags for the build host. By default, the value of BUILD_LD_ARCH is empty.

BUILD_LDFLAGS 

Specifies the flags to pass to the linker when building for the build host. When building in the -native context, LDFLAGS is set to the value of this variable by default.

BUILD_OPTIMIZATION 

Specifies the optimization flags passed to the C compiler when building for the build host or the SDK. The flags are passed through the BUILD_CFLAGS and BUILDSDK_CFLAGS default values.

The default value of the BUILD_OPTIMIZATION variable is “-O2 -pipe”.

BUILD_OS 

Specifies the operating system in use on the build host (e.g. “linux”). The OpenEmbedded build system sets the value of BUILD_OS from the OS reported by the uname command — the first word, converted to lower-case characters.

BUILD_PREFIX 

The toolchain binary prefix used for native recipes. The OpenEmbedded build system uses the BUILD_PREFIX value to set the TARGET_PREFIX when building for native recipes.

BUILD_STRIP 

Specifies the command to be used to strip debugging symbols from binaries produced for the build host. By default, BUILD_STRIP points to ${BUILD_PREFIX}strip.

BUILD_SYS 

Specifies the system, including the architecture and the operating system, to use when building for the build host (i.e. when building native recipes).

The OpenEmbedded build system automatically sets this variable based on BUILD_ARCH, BUILD_VENDOR, and BUILD_OS. You do not need to set the BUILD_SYS variable yourself.

BUILD_VENDOR 

Specifies the vendor name to use when building for the build host. The default value is an empty string (“”).

BUILDDIR 

Points to the location of the Build Directory. You can define this directory indirectly through the oe-init-build-env script by passing in a Build Directory path when you run the script. If you run the script and do not provide a Build Directory path, the BUILDDIR defaults to build in the current directory.

BUILDHISTORY_COMMIT 

When inheriting the buildhistory class, this variable specifies whether or not to commit the build history output in a local Git repository. If set to “1”, this local repository will be maintained automatically by the buildhistory class and a commit will be created on every build for changes to each top-level subdirectory of the build history output (images, packages, and sdk). If you want to track changes to build history over time, you should set this value to “1”.

By default, the buildhistory class enables committing the buildhistory output in a local Git repository:

BUILDHISTORY_COMMIT ?= "1"

BUILDHISTORY_COMMIT_AUTHOR 

When inheriting the buildhistory class, this variable specifies the author to use for each Git commit. In order for the BUILDHISTORY_COMMIT_AUTHOR variable to work, the BUILDHISTORY_COMMIT variable must be set to “1”.

Git requires that the value you provide for the BUILDHISTORY_COMMIT_AUTHOR variable takes the form of “name email@host”. Providing an email address or host that is not valid does not produce an error.

By default, the buildhistory class sets the variable as follows:

BUILDHISTORY_COMMIT_AUTHOR ?= "buildhistory <buildhistory@${DISTRO}>"

BUILDHISTORY_DIR 

When inheriting the buildhistory class, this variable specifies the directory in which build history information is kept. For more information on how the variable works, see the buildhistory class.

By default, the buildhistory class sets the directory as follows:

BUILDHISTORY_DIR ?= "${TOPDIR}/buildhistory"

BUILDHISTORY_FEATURES 

When inheriting the buildhistory class, this variable specifies the build history features to be enabled. For more information on how build history works, see the “Maintaining Build Output Quality” section in the Yocto Project Development Tasks Manual.

You can specify these features in the form of a space-separated list:

image: Analysis of the contents of images, which includes the list of installed packages among other things.
package: Analysis of the contents of individual packages.
sdk: Analysis of the contents of the software development kit (SDK).
task: Save output file signatures for shared state (sstate) tasks. This saves one file per task and lists the SHA-256 checksums for each file staged (i.e. the output of the task).

By default, the buildhistory class enables the following features:

BUILDHISTORY_FEATURES ?= "image package sdk"

BUILDHISTORY_IMAGE_FILES 

When inheriting the buildhistory class, this variable specifies a list of paths to files copied from the image contents into the build history directory under an “image-files” directory in the directory for the image, so that you can track the contents of each file. The default is to copy /etc/passwd and /etc/group, which allows you to monitor for changes in user and group entries. You can modify the list to include any file. Specifying an invalid path does not produce an error. Consequently, you can include files that might not always be present.

By default, the buildhistory class provides paths to the following files:

BUILDHISTORY_IMAGE_FILES ?= "/etc/passwd /etc/group"

BUILDHISTORY_PATH_PREFIX_STRIP 

When inheriting the buildhistory class, this variable specifies a common path prefix that should be stripped off the beginning of paths in the task signature list when the task feature is active in BUILDHISTORY_FEATURES. This can be useful when build history is populated from multiple sources that may not all use the same top level directory.

By default, the buildhistory class sets the variable as follows:

BUILDHISTORY_PATH_PREFIX_STRIP ?= ""

In this case, no prefixes will be stripped.

BUILDHISTORY_PUSH_REPO 

When inheriting the buildhistory class, this variable optionally specifies a remote repository to which build history pushes Git changes. In order for BUILDHISTORY_PUSH_REPO to work, BUILDHISTORY_COMMIT must be set to “1”.

The repository should correspond to a remote address that specifies a repository as understood by Git, or alternatively to a remote name that you have set up manually using git remote within the local repository.

By default, the buildhistory class sets the variable as follows:

BUILDHISTORY_PUSH_REPO ?= ""

BUILDNAME 

See BUILDNAME in the BitBake manual.

BUILDSDK_CFLAGS 

Specifies the flags to pass to the C compiler when building for the SDK. When building in the nativesdk- context, CFLAGS is set to the value of this variable by default.

BUILDSDK_CPPFLAGS 

Specifies the flags to pass to the C pre-processor (i.e. to both the C and the C++ compilers) when building for the SDK. When building in the nativesdk- context, CPPFLAGS is set to the value of this variable by default.

BUILDSDK_CXXFLAGS 

Specifies the flags to pass to the C++ compiler when building for the SDK. When building in the nativesdk- context, CXXFLAGS is set to the value of this variable by default.

BUILDSDK_LDFLAGS 

Specifies the flags to pass to the linker when building for the SDK. When building in the nativesdk- context, LDFLAGS is set to the value of this variable by default.

BUILDSTATS_BASE 

Points to the location of the directory that holds build statistics when you use and enable the buildstats class. The BUILDSTATS_BASE directory defaults to ${TMPDIR}/buildstats/.

BUSYBOX_SPLIT_SUID 

For the BusyBox recipe, specifies whether to split the output executable file into two parts: one for features that require setuid root, and one for the remaining features (i.e. those that do not require setuid root).

The BUSYBOX_SPLIT_SUID variable defaults to “1”, which results in splitting the output executable file. Set the variable to “0” to get a single output executable file.

BZRDIR 

See BZRDIR in the BitBake manual.

CACHE 

Specifies the directory BitBake uses to store a cache of the Metadata so it does not need to be parsed every time BitBake is started.

CC 

The minimal command and arguments used to run the C compiler.

CFLAGS 

Specifies the flags to pass to the C compiler. This variable is exported to an environment variable and thus made visible to the software being built during the compilation step.

Default initialization for CFLAGS varies depending on what is being built:

TARGET_CFLAGS when building for the target
BUILD_CFLAGS when building for the build host (i.e. -native)
BUILDSDK_CFLAGS when building for an SDK (i.e. nativesdk-)

CLASSOVERRIDE 

An internal variable specifying the special class override that should currently apply (e.g. “class-target”, “class-native”, and so forth). The classes that use this variable (e.g. native, nativesdk, and so forth) set the variable to appropriate values.

Note

CLASSOVERRIDE gets its default “class-target” value from the bitbake.conf file.

As an example, the following override allows you to install extra files, but only when building for the target:

do_install:append:class-target() {
    install my-extra-file ${D}${sysconfdir}
}

Here is an example where FOO is set to “native” when building for the build host, and to “other” when not building for the build host:

FOO:class-native = "native"
FOO = "other"

The underlying mechanism behind CLASSOVERRIDE is simply that it is included in the default value of OVERRIDES.

CLEANBROKEN 

If set to “1” within a recipe, CLEANBROKEN specifies that the make clean command does not work for the software being built. Consequently, the OpenEmbedded build system will not try to run make clean during the do_configure task, which is the default behavior.

COMBINED_FEATURES 

Provides a list of hardware features that are enabled in both MACHINE_FEATURES and DISTRO_FEATURES. This select list of features contains features that make sense to be controlled both at the machine and distribution configuration level. For example, the “bluetooth” feature requires hardware support but should also be optional at the distribution level, in case the hardware supports Bluetooth but you do not ever intend to use it.

COMMERCIAL_AUDIO_PLUGINS 

This variable is specific to the GStreamer recipes. It allows to build the GStreamer “ugly” and “bad” audio plugins.

See the Other Variables Related to Commercial Licenses section for usage details.

COMMERCIAL_VIDEO_PLUGINS 

This variable is specific to the GStreamer recipes. It allows to build the GStreamer “ugly” and “bad” video plugins.

See the Other Variables Related to Commercial Licenses section for usage details.

COMMON_LICENSE_DIR 

Points to meta/files/common-licenses in the Source Directory, which is where generic license files reside.

COMPATIBLE_HOST 

A regular expression that resolves to one or more hosts (when the recipe is native) or one or more targets (when the recipe is non-native) with which a recipe is compatible. The regular expression is matched against HOST_SYS. You can use the variable to stop recipes from being built for classes of systems with which the recipes are not compatible. Stopping these builds is particularly useful with kernels. The variable also helps to increase parsing speed since the build system skips parsing recipes not compatible with the current system.

COMPATIBLE_MACHINE 

A regular expression that resolves to one or more target machines with which a recipe is compatible. The regular expression is matched against MACHINEOVERRIDES. You can use the variable to stop recipes from being built for machines with which the recipes are not compatible. Stopping these builds is particularly useful with kernels. The variable also helps to increase parsing speed since the build system skips parsing recipes not compatible with the current machine.

COMPLEMENTARY_GLOB 

Defines wildcards to match when installing a list of complementary packages for all the packages explicitly (or implicitly) installed in an image.

The COMPLEMENTARY_GLOB variable uses Unix filename pattern matching (fnmatch), which is similar to the Unix style pathname pattern expansion (glob).

The resulting list of complementary packages is associated with an item that can be added to IMAGE_FEATURES. An example usage of this is the “dev-pkgs” item that when added to IMAGE_FEATURES will install -dev packages (containing headers and other development files) for every package in the image.

To add a new feature item pointing to a wildcard, use a variable flag to specify the feature item name and use the value to specify the wildcard. Here is an example:

COMPLEMENTARY_GLOB[dev-pkgs] = '*-dev'

Note

When installing complementary packages, recommends relationships (set via RRECOMMENDS) are always ignored.

COMPONENTS_DIR 

Stores sysroot components for each recipe. The OpenEmbedded build system uses COMPONENTS_DIR when constructing recipe-specific sysroots for other recipes.

The default is “${STAGING_DIR}-components.” (i.e. “${TMPDIR}/sysroots-components”).

CONF_VERSION 

Tracks the version of the local configuration file (i.e. local.conf). The value for CONF_VERSION increments each time build/conf/ compatibility changes.

CONFFILES 

Identifies editable or configurable files that are part of a package. If the Package Management System (PMS) is being used to update packages on the target system, it is possible that configuration files you have changed after the original installation and that you now want to remain unchanged are overwritten. In other words, editable files might exist in the package that you do not want reset as part of the package update process. You can use the CONFFILES variable to list the files in the package that you wish to prevent the PMS from overwriting during this update process.

To use the CONFFILES variable, provide a package name override that identifies the resulting package. Then, provide a space-separated list of files. Here is an example:

CONFFILES:${PN} += "${sysconfdir}/file1 \
    ${sysconfdir}/file2 ${sysconfdir}/file3"

There is a relationship between the CONFFILES and FILES variables. The files listed within CONFFILES must be a subset of the files listed within FILES. Because the configuration files you provide with CONFFILES are simply being identified so that the PMS will not overwrite them, it makes sense that the files must already be included as part of the package through the FILES variable.

Note

When specifying paths as part of the CONFFILES variable, it is good practice to use appropriate path variables. For example, ${sysconfdir} rather than /etc or ${bindir} rather than /usr/bin. You can find a list of these variables at the top of the meta/conf/bitbake.conf file in the Source Directory.

CONFIG_INITRAMFS_SOURCE 

Identifies the initial RAM filesystem (Initramfs) source files. The OpenEmbedded build system receives and uses this kernel Kconfig variable as an environment variable. By default, the variable is set to null (“”).

The CONFIG_INITRAMFS_SOURCE can be either a single cpio archive with a .cpio suffix or a space-separated list of directories and files for building the Initramfs image. A cpio archive should contain a filesystem archive to be used as an Initramfs image. Directories should contain a filesystem layout to be included in the Initramfs image. Files should contain entries according to the format described by the usr/gen_init_cpio program in the kernel tree.

If you specify multiple directories and files, the Initramfs image will be the aggregate of all of them.

For information on creating an Initramfs, see the “Building an Initial RAM Filesystem (Initramfs) Image” section in the Yocto Project Development Tasks Manual.

CONFIG_SITE 

A list of files that contains autoconf test results relevant to the current build. This variable is used by the Autotools utilities when running configure.

CONFIGURE_FLAGS 

The minimal arguments for GNU configure.

CONFLICT_DISTRO_FEATURES 

When inheriting the features_check class, this variable identifies distribution features that would be in conflict should the recipe be built. In other words, if the CONFLICT_DISTRO_FEATURES variable lists a feature that also appears in DISTRO_FEATURES within the current configuration, then the recipe will be skipped, and if the build system attempts to build the recipe then an error will be triggered.

CONVERSION_CMD 

This variable is used for storing image conversion commands. Image conversion can convert an image into different objects like:

Compressed version of the image
Checksums for the image

An example of CONVERSION_CMD from image_types class is:

CONVERSION_CMD:lzo = "lzop -9 ${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${type}"

COPY_LIC_DIRS 

If set to “1” along with the COPY_LIC_MANIFEST variable, the OpenEmbedded build system copies into the image the license files, which are located in /usr/share/common-licenses, for each package. The license files are placed in directories within the image itself during build time.

Note

The COPY_LIC_DIRS does not offer a path for adding licenses for newly installed packages to an image, which might be most suitable for read-only filesystems that cannot be upgraded. See the LICENSE_CREATE_PACKAGE variable for additional information. You can also reference the “Providing License Text” section in the Yocto Project Development Tasks Manual for information on providing license text.

COPY_LIC_MANIFEST 

If set to “1”, the OpenEmbedded build system copies the license manifest for the image to /usr/share/common-licenses/license.manifest within the image itself during build time.

Note

The COPY_LIC_MANIFEST does not offer a path for adding licenses for newly installed packages to an image, which might be most suitable for read-only filesystems that cannot be upgraded. See the LICENSE_CREATE_PACKAGE variable for additional information. You can also reference the “Providing License Text” section in the Yocto Project Development Tasks Manual for information on providing license text.

COPYLEFT_LICENSE_EXCLUDE 

A space-separated list of licenses to exclude from the source archived by the archiver class. In other words, if a license in a recipe’s LICENSE value is in the value of COPYLEFT_LICENSE_EXCLUDE, then its source is not archived by the class.

Note

The COPYLEFT_LICENSE_EXCLUDE variable takes precedence over the COPYLEFT_LICENSE_INCLUDE variable.

The default value, which is “CLOSED Proprietary”, for COPYLEFT_LICENSE_EXCLUDE is set by the copyleft_filter class, which is inherited by the archiver class.

COPYLEFT_LICENSE_INCLUDE 

A space-separated list of licenses to include in the source archived by the archiver class. In other words, if a license in a recipe’s LICENSE value is in the value of COPYLEFT_LICENSE_INCLUDE, then its source is archived by the class.

The default value is set by the copyleft_filter class, which is inherited by the archiver class. The default value includes “GPL*”, “LGPL*”, and “AGPL*”.

COPYLEFT_PN_EXCLUDE 

A list of recipes to exclude in the source archived by the archiver class. The COPYLEFT_PN_EXCLUDE variable overrides the license inclusion and exclusion caused through the COPYLEFT_LICENSE_INCLUDE and COPYLEFT_LICENSE_EXCLUDE variables, respectively.

The default value, which is “” indicating to not explicitly exclude any recipes by name, for COPYLEFT_PN_EXCLUDE is set by the copyleft_filter class, which is inherited by the archiver class.

COPYLEFT_PN_INCLUDE 

A list of recipes to include in the source archived by the archiver class. The COPYLEFT_PN_INCLUDE variable overrides the license inclusion and exclusion caused through the COPYLEFT_LICENSE_INCLUDE and COPYLEFT_LICENSE_EXCLUDE variables, respectively.

The default value, which is “” indicating to not explicitly include any recipes by name, for COPYLEFT_PN_INCLUDE is set by the copyleft_filter class, which is inherited by the archiver class.

COPYLEFT_RECIPE_TYPES 

A space-separated list of recipe types to include in the source archived by the archiver class. Recipe types are target, native, nativesdk, cross, crosssdk, and cross-canadian.

The default value, which is “target*”, for COPYLEFT_RECIPE_TYPES is set by the copyleft_filter class, which is inherited by the archiver class.

CORE_IMAGE_EXTRA_INSTALL 

Specifies the list of packages to be added to the image. You should only set this variable in the local.conf configuration file found in the Build Directory.

This variable replaces POKY_EXTRA_INSTALL, which is no longer supported.

COREBASE 

Specifies the parent directory of the OpenEmbedded-Core Metadata layer (i.e. meta).

It is an important distinction that COREBASE points to the parent of this layer and not the layer itself. Consider an example where you have cloned the Poky Git repository and retained the poky name for your local copy of the repository. In this case, COREBASE points to the poky folder because it is the parent directory of the poky/meta layer.

COREBASE_FILES 

Lists files from the COREBASE directory that should be copied other than the layers listed in the bblayers.conf file. The COREBASE_FILES variable allows to copy metadata from the OpenEmbedded build system into the extensible SDK.

Explicitly listing files in COREBASE is needed because it typically contains build directories and other files that should not normally be copied into the extensible SDK. Consequently, the value of COREBASE_FILES is used in order to only copy the files that are actually needed.

CPP 

The minimal command and arguments used to run the C preprocessor.

CPPFLAGS 

Specifies the flags to pass to the C pre-processor (i.e. to both the C and the C++ compilers). This variable is exported to an environment variable and thus made visible to the software being built during the compilation step.

Default initialization for CPPFLAGS varies depending on what is being built:

TARGET_CPPFLAGS when building for the target
BUILD_CPPFLAGS when building for the build host (i.e. -native)
BUILDSDK_CPPFLAGS when building for an SDK (i.e. nativesdk-)

CROSS_COMPILE 

The toolchain binary prefix for the target tools. The CROSS_COMPILE variable is the same as the TARGET_PREFIX variable.

Note

The OpenEmbedded build system sets the CROSS_COMPILE variable only in certain contexts (e.g. when building for kernel and kernel module recipes).

CVE_CHECK_IGNORE 

The list of CVE IDs which are ignored. Here is an example from the Python3 recipe:

# This is windows only issue.
CVE_CHECK_IGNORE += "CVE-2020-15523"

CVE_CHECK_SHOW_WARNINGS 

Specifies whether or not the cve-check class should generate warning messages on the console when unpatched CVEs are found. The default is “1”, but you may wish to set it to “0” if you are already examining/processing the logs after the build has completed and thus do not need the warning messages.

CVE_CHECK_SKIP_RECIPE 

The list of package names (PN) for which CVEs (Common Vulnerabilities and Exposures) are ignored.

CVE_DB_UPDATE_INTERVAL 

Specifies the CVE database update interval in seconds, as used by cve-update-db-native. The default value is “86400” i.e. once a day (24*60*60). If the value is set to “0” then the update will be forced every time. Alternatively, a negative value e.g. “-1” will disable updates entirely.

CVE_PRODUCT 

In a recipe, defines the name used to match the recipe name against the name in the upstream NIST CVE database.

The default is ${BPN} (except for recipes that inherit the pypi class where it is set based upon PYPI_PACKAGE). If it does not match the name in the NIST CVE database or matches with multiple entries in the database, the default value needs to be changed.

Here is an example from the Berkeley DB recipe:

CVE_PRODUCT = "oracle_berkeley_db berkeley_db"

Sometimes the product name is not specific enough, for example “tar” has been matching CVEs for the GNU tar package and also the node-tar node.js extension. To avoid this problem, use the vendor name as a prefix. The syntax for this is:

CVE_PRODUCT = "vendor:package"

CVE_VERSION 

In a recipe, defines the version used to match the recipe version against the version in the NIST CVE database when usign cve-check.

The default is ${PV} but if recipes use custom version numbers which do not map to upstream software component release versions and the versions used in the CVE database, then this variable can be used to set the version number for cve-check. Example:

CVE_VERSION = "2.39"

CVSDIR 

The directory in which files checked out under the CVS system are stored.

CXX 

The minimal command and arguments used to run the C++ compiler.

CXXFLAGS 

Specifies the flags to pass to the C++ compiler. This variable is exported to an environment variable and thus made visible to the software being built during the compilation step.

Default initialization for CXXFLAGS varies depending on what is being built:

TARGET_CXXFLAGS when building for the target
BUILD_CXXFLAGS when building for the build host (i.e. -native)
BUILDSDK_CXXFLAGS when building for an SDK (i.e. nativesdk-)

D 

The destination directory. The location in the Build Directory where components are installed by the do_install task. This location defaults to:

${WORKDIR}/image

Note

Tasks that read from or write to this directory should run under fakeroot.

DATE 

The date the build was started. Dates appear using the year, month, and day (YMD) format (e.g. “20150209” for February 9th, 2015).

DATETIME 

The date and time on which the current build started. The format is suitable for timestamps.

DEBIAN_NOAUTONAME 

When the debian class is inherited, which is the default behavior, DEBIAN_NOAUTONAME specifies a particular package should not be renamed according to Debian library package naming. You must use the package name as an override when you set this variable. Here is an example from the fontconfig recipe:

DEBIAN_NOAUTONAME:fontconfig-utils = "1"

DEBIANNAME 

When the debian class is inherited, which is the default behavior, DEBIANNAME allows you to override the library name for an individual package. Overriding the library name in these cases is rare. You must use the package name as an override when you set this variable. Here is an example from the dbus recipe:

DEBIANNAME:${PN} = "dbus-1"

DEBUG_BUILD 

Specifies to build packages with debugging information. This influences the value of the SELECTED_OPTIMIZATION variable.

DEBUG_OPTIMIZATION 

The options to pass in TARGET_CFLAGS and CFLAGS when compiling a system for debugging. This variable defaults to “-O -fno-omit-frame-pointer ${DEBUG_FLAGS} -pipe”.

DEBUG_PREFIX_MAP 

Allows to set C compiler options, such as -fdebug-prefix-map, -fmacro-prefix-map, and -ffile-prefix-map, which allow to replace build-time paths by install-time ones in the debugging sections of binaries. This makes compiler output files location independent, at the cost of having to pass an extra command to tell the debugger where source files are.

This is used by the Yocto Project to guarantee Reproducible Builds even when the source code of a package uses the __FILE__ or assert() macros. See the reproducible-builds.org website for details.

This variable is set in the meta/conf/bitbake.conf file. It is not intended to be user-configurable.

DEFAULT_PREFERENCE 

Specifies a weak bias for recipe selection priority.

The most common usage of this is variable is to set it to “-1” within a recipe for a development version of a piece of software. Using the variable in this way causes the stable version of the recipe to build by default in the absence of PREFERRED_VERSION being used to build the development version.

Note

The bias provided by DEFAULT_PREFERENCE is weak and is overridden by BBFILE_PRIORITY if that variable is different between two layers that contain different versions of the same recipe.

DEFAULTTUNE 

The default CPU and Application Binary Interface (ABI) tunings (i.e. the “tune”) used by the OpenEmbedded build system. The DEFAULTTUNE helps define TUNE_FEATURES.

The default tune is either implicitly or explicitly set by the machine (MACHINE). However, you can override the setting using available tunes as defined with AVAILTUNES.

DEPENDS 

Lists a recipe’s build-time dependencies. These are dependencies on other recipes whose contents (e.g. headers and shared libraries) are needed by the recipe at build time.

As an example, consider a recipe foo that contains the following assignment:

DEPENDS = "bar"

The practical effect of the previous assignment is that all files installed by bar will be available in the appropriate staging sysroot, given by the STAGING_DIR* variables, by the time the do_configure task for foo runs. This mechanism is implemented by having do_configure depend on the do_populate_sysroot task of each recipe listed in DEPENDS, through a [deptask] declaration in the base class.

Note

It seldom is necessary to reference, for example, STAGING_DIR_HOST explicitly. The standard classes and build-related variables are configured to automatically use the appropriate staging sysroots.

As another example, DEPENDS can also be used to add utilities that run on the build machine during the build. For example, a recipe that makes use of a code generator built by the recipe codegen might have the following:

DEPENDS = "codegen-native"

For more information, see the native class and the EXTRANATIVEPATH variable.

Note

DEPENDS is a list of recipe names. Or, to be more precise, it is a list of PROVIDES names, which usually match recipe names. Putting a package name such as “foo-dev” in DEPENDS does not make sense. Use “foo” instead, as this will put files from all the packages that make up foo, which includes those from foo-dev, into the sysroot.
One recipe having another recipe in DEPENDS does not by itself add any runtime dependencies between the packages produced by the two recipes. However, as explained in the “Automatically Added Runtime Dependencies” section in the Yocto Project Overview and Concepts Manual, runtime dependencies will often be added automatically, meaning DEPENDS alone is sufficient for most recipes.
Counterintuitively, DEPENDS is often necessary even for recipes that install precompiled components. For example, if libfoo is a precompiled library that links against libbar, then linking against libfoo requires both libfoo and libbar to be available in the sysroot. Without a DEPENDS from the recipe that installs libfoo to the recipe that installs libbar, other recipes might fail to link against libfoo.

For information on runtime dependencies, see the RDEPENDS variable. You can also see the “Tasks” and “Dependencies” sections in the BitBake User Manual for additional information on tasks and dependencies.

DEPLOY_DIR 

Points to the general area that the OpenEmbedded build system uses to place images, packages, SDKs, and other output files that are ready to be used outside of the build system. By default, this directory resides within the Build Directory as ${TMPDIR}/deploy.

For more information on the structure of the Build Directory, see “The Build Directory — build/” section. For more detail on the contents of the deploy directory, see the “Images”, “Package Feeds”, and “Application Development SDK” sections all in the Yocto Project Overview and Concepts Manual.

DEPLOY_DIR_DEB 

Points to the area that the OpenEmbedded build system uses to place Debian packages that are ready to be used outside of the build system. This variable applies only when PACKAGE_CLASSES contains “package_deb”.

The BitBake configuration file initially defines the DEPLOY_DIR_DEB variable as a sub-folder of DEPLOY_DIR:

DEPLOY_DIR_DEB = "${DEPLOY_DIR}/deb"

The package_deb class uses the DEPLOY_DIR_DEB variable to make sure the do_package_write_deb task writes Debian packages into the appropriate folder. For more information on how packaging works, see the “Package Feeds” section in the Yocto Project Overview and Concepts Manual.

DEPLOY_DIR_IMAGE 

Points to the area that the OpenEmbedded build system uses to place images and other associated output files that are ready to be deployed onto the target machine. The directory is machine-specific as it contains the ${MACHINE} name. By default, this directory resides within the Build Directory as ${DEPLOY_DIR}/images/${MACHINE}/.

It must not be used directly in recipes when deploying files. Instead, it’s only useful when a recipe needs to “read” a file already deployed by a dependency. So, it should be filled with the contents of DEPLOYDIR by the deploy class or with the contents of IMGDEPLOYDIR by the image class.

For more information on the structure of the Build Directory, see “The Build Directory — build/” section. For more detail on the contents of the deploy directory, see the “Images” and “Application Development SDK” sections both in the Yocto Project Overview and Concepts Manual.

DEPLOY_DIR_IPK 

Points to the area that the OpenEmbedded build system uses to place IPK packages that are ready to be used outside of the build system. This variable applies only when PACKAGE_CLASSES contains “package_ipk”.

The BitBake configuration file initially defines this variable as a sub-folder of DEPLOY_DIR:

DEPLOY_DIR_IPK = "${DEPLOY_DIR}/ipk"

The package_ipk class uses the DEPLOY_DIR_IPK variable to make sure the do_package_write_ipk task writes IPK packages into the appropriate folder. For more information on how packaging works, see the “Package Feeds” section in the Yocto Project Overview and Concepts Manual.

DEPLOY_DIR_RPM 

Points to the area that the OpenEmbedded build system uses to place RPM packages that are ready to be used outside of the build system. This variable applies only when PACKAGE_CLASSES contains “package_rpm”.

The BitBake configuration file initially defines this variable as a sub-folder of DEPLOY_DIR:

DEPLOY_DIR_RPM = "${DEPLOY_DIR}/rpm"

The package_rpm class uses the DEPLOY_DIR_RPM variable to make sure the do_package_write_rpm task writes RPM packages into the appropriate folder. For more information on how packaging works, see the “Package Feeds” section in the Yocto Project Overview and Concepts Manual.

DEPLOYDIR 

When inheriting the deploy class, the DEPLOYDIR points to a temporary work area for deployed files that is set in the deploy class as follows:

DEPLOYDIR = "${WORKDIR}/deploy-${PN}"

Recipes inheriting the deploy class should copy files to be deployed into DEPLOYDIR, and the class will take care of copying them into DEPLOY_DIR_IMAGE afterwards.

DESCRIPTION 

The package description used by package managers. If not set, DESCRIPTION takes the value of the SUMMARY variable.

DEV_PKG_DEPENDENCY 

Provides an easy way for recipes to disable or adjust the runtime recommendation (RRECOMMENDS) of the ${PN}-dev package on the main (${PN}) package.

DISABLE_STATIC 

Used in order to disable static linking by default (in order to save space, since static libraries are often unused in embedded systems.) The default value is “ –disable-static”, however it can be set to “” in order to enable static linking if desired. Certain recipes do this individually, and also there is a meta/conf/distro/include/no-static-libs.inc include file that disables static linking for a number of recipes. Some software packages or build tools (such as CMake) have explicit support for enabling / disabling static linking, and in those cases DISABLE_STATIC is not used.

DISTRO 

The short name of the distribution. For information on the long name of the distribution, see the DISTRO_NAME variable.

The DISTRO variable corresponds to a distribution configuration file whose root name is the same as the variable’s argument and whose filename extension is .conf. For example, the distribution configuration file for the Poky distribution is named poky.conf and resides in the meta-poky/conf/distro directory of the Source Directory.

Within that poky.conf file, the DISTRO variable is set as follows:

DISTRO = "poky"

Distribution configuration files are located in a conf/distro directory within the Metadata that contains the distribution configuration. The value for DISTRO must not contain spaces, and is typically all lower-case.

Note

If the DISTRO variable is blank, a set of default configurations are used, which are specified within meta/conf/distro/defaultsetup.conf also in the Source Directory.

DISTRO_CODENAME 

Specifies a codename for the distribution being built.

DISTRO_EXTRA_RDEPENDS 

Specifies a list of distro-specific packages to add to all images. This variable takes effect through packagegroup-base so the variable only really applies to the more full-featured images that include packagegroup-base. You can use this variable to keep distro policy out of generic images. As with all other distro variables, you set this variable in the distro .conf file.

DISTRO_EXTRA_RRECOMMENDS 

Specifies a list of distro-specific packages to add to all images if the packages exist. The packages might not exist or be empty (e.g. kernel modules). The list of packages are automatically installed but you can remove them.

DISTRO_FEATURES 

The software support you want in your distribution for various features. You define your distribution features in the distribution configuration file.

In most cases, the presence or absence of a feature in DISTRO_FEATURES is translated to the appropriate option supplied to the configure script during the do_configure task for recipes that optionally support the feature. For example, specifying “x11” in DISTRO_FEATURES, causes every piece of software built for the target that can optionally support X11 to have its X11 support enabled.

Note

Just enabling DISTRO_FEATURES alone doesn’t enable feature support for packages. Mechanisms such as making PACKAGECONFIG track DISTRO_FEATURES are used to enable/disable package features.

Two more examples are Bluetooth and NFS support. For a more complete list of features that ships with the Yocto Project and that you can provide with this variable, see the “Distro Features” section.

DISTRO_FEATURES_BACKFILL 

A space-separated list of features to be added to DISTRO_FEATURES if not also present in DISTRO_FEATURES_BACKFILL_CONSIDERED.

This variable is set in the meta/conf/bitbake.conf file. It is not intended to be user-configurable. It is best to just reference the variable to see which distro features are being backfilled for all distro configurations.

DISTRO_FEATURES_BACKFILL_CONSIDERED 

A space-separated list of features from DISTRO_FEATURES_BACKFILL that should not be backfilled (i.e. added to DISTRO_FEATURES) during the build.

This corresponds to an opt-out mechanism. When new default distro features are introduced, distribution maintainers can review (consider) them and decide to exclude them from the backfilled features. Therefore, the combination of DISTRO_FEATURES_BACKFILL and DISTRO_FEATURES_BACKFILL_CONSIDERED makes it possible to add new default features without breaking existing distributions.

DISTRO_FEATURES_DEFAULT 

A convenience variable that gives you the default list of distro features with the exception of any features specific to the C library (libc).

When creating a custom distribution, you might find it useful to be able to reuse the default DISTRO_FEATURES options without the need to write out the full set. Here is an example that uses DISTRO_FEATURES_DEFAULT from a custom distro configuration file:

DISTRO_FEATURES ?= "${DISTRO_FEATURES_DEFAULT} myfeature"

DISTRO_FEATURES_FILTER_NATIVE 

Specifies a list of features that if present in the target DISTRO_FEATURES value should be included in DISTRO_FEATURES when building native recipes. This variable is used in addition to the features filtered using the DISTRO_FEATURES_NATIVE variable.

DISTRO_FEATURES_FILTER_NATIVESDK 

Specifies a list of features that if present in the target DISTRO_FEATURES value should be included in DISTRO_FEATURES when building nativesdk recipes. This variable is used in addition to the features filtered using the DISTRO_FEATURES_NATIVESDK variable.

DISTRO_FEATURES_NATIVE 

Specifies a list of features that should be included in DISTRO_FEATURES when building native recipes. This variable is used in addition to the features filtered using the DISTRO_FEATURES_FILTER_NATIVE variable.

DISTRO_FEATURES_NATIVESDK 

Specifies a list of features that should be included in DISTRO_FEATURES when building nativesdk recipes. This variable is used in addition to the features filtered using the DISTRO_FEATURES_FILTER_NATIVESDK variable.

DISTRO_NAME 

The long name of the distribution. For information on the short name of the distribution, see the DISTRO variable.

The DISTRO_NAME variable corresponds to a distribution configuration file whose root name is the same as the variable’s argument and whose filename extension is .conf. For example, the distribution configuration file for the Poky distribution is named poky.conf and resides in the meta-poky/conf/distro directory of the Source Directory.

Within that poky.conf file, the DISTRO_NAME variable is set as follows:

DISTRO_NAME = "Poky (Yocto Project Reference Distro)"

Distribution configuration files are located in a conf/distro directory within the Metadata that contains the distribution configuration.

Note

If the DISTRO_NAME variable is blank, a set of default configurations are used, which are specified within meta/conf/distro/defaultsetup.conf also in the Source Directory.

DISTRO_VERSION 

The version of the distribution.

DISTROOVERRIDES 

A colon-separated list of overrides specific to the current distribution. By default, this list includes the value of DISTRO.

You can extend DISTROOVERRIDES to add extra overrides that should apply to the distribution.

The underlying mechanism behind DISTROOVERRIDES is simply that it is included in the default value of OVERRIDES.

DL_DIR 

The central download directory used by the build process to store downloads. By default, DL_DIR gets files suitable for mirroring for everything except Git repositories. If you want tarballs of Git repositories, use the BB_GENERATE_MIRROR_TARBALLS variable.

You can set this directory by defining the DL_DIR variable in the conf/local.conf file. This directory is self-maintaining and you should not have to touch it. By default, the directory is downloads in the Build Directory:

#DL_DIR ?= "${TOPDIR}/downloads"

To specify a different download directory, simply remove the comment from the line and provide your directory.

During a first build, the system downloads many different source code tarballs from various upstream projects. Downloading can take a while, particularly if your network connection is slow. Tarballs are all stored in the directory defined by DL_DIR and the build system looks there first to find source tarballs.

Note

When wiping and rebuilding, you can preserve this directory to speed up this part of subsequent builds.

You can safely share this directory between multiple builds on the same development machine. For additional information on how the build process gets source files when working behind a firewall or proxy server, see this specific question in the “FAQ” chapter. You can also refer to the “Working Behind a Network Proxy” Wiki page.

DOC_COMPRESS 

When inheriting the compress_doc class, this variable sets the compression policy used when the OpenEmbedded build system compresses man pages and info pages. By default, the compression method used is gz (gzip). Other policies available are xz and bz2.

For information on policies and on how to use this variable, see the comments in the meta/classes-recipe/compress_doc.bbclass file.

EFI_PROVIDER 

When building bootable images (i.e. where hddimg, iso, or wic.vmdk is in IMAGE_FSTYPES), the EFI_PROVIDER variable specifies the EFI bootloader to use. The default is “grub-efi”, but “systemd-boot” can be used instead.

See the systemd-boot and image-live classes for more information.

ENABLE_BINARY_LOCALE_GENERATION 

Variable that controls which locales for glibc are generated during the build (useful if the target device has 64Mbytes of RAM or less).

ERR_REPORT_DIR 

When used with the report-error class, specifies the path used for storing the debug files created by the error reporting tool, which allows you to submit build errors you encounter to a central database. By default, the value of this variable is ${LOG_DIR}/error-report.

You can set ERR_REPORT_DIR to the path you want the error reporting tool to store the debug files as follows in your local.conf file:

ERR_REPORT_DIR = "path"

ERROR_QA 

Specifies the quality assurance checks whose failures are reported as errors by the OpenEmbedded build system. You set this variable in your distribution configuration file. For a list of the checks you can control with this variable, see the “insane” section.

ESDK_CLASS_INHERIT_DISABLE 

A list of classes to remove from the INHERIT value globally within the extensible SDK configuration. The populate-sdk-ext class sets the default value:

ESDK_CLASS_INHERIT_DISABLE ?= "buildhistory icecc"

Some classes are not generally applicable within the extensible SDK context. You can use this variable to disable those classes.

For additional information on how to customize the extensible SDK’s configuration, see the “Configuring the Extensible SDK” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

ESDK_LOCALCONF_ALLOW 

A list of variables allowed through from the OpenEmbedded build system configuration into the extensible SDK configuration. By default, the list of variables is empty and is set in the populate-sdk-ext class.

This list overrides the variables specified using the ESDK_LOCALCONF_REMOVE variable as well as other variables automatically added due to the “/” character being found at the start of the value, which is usually indicative of being a path and thus might not be valid on the system where the SDK is installed.

For additional information on how to customize the extensible SDK’s configuration, see the “Configuring the Extensible SDK” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

ESDK_LOCALCONF_REMOVE 

A list of variables not allowed through from the OpenEmbedded build system configuration into the extensible SDK configuration. Usually, these are variables that are specific to the machine on which the build system is running and thus would be potentially problematic within the extensible SDK.

By default, ESDK_LOCALCONF_REMOVE is set in the populate-sdk-ext class and excludes the following variables:

CONF_VERSION
BB_NUMBER_THREADS
BB_NUMBER_PARSE_THREADS
PARALLEL_MAKE
PRSERV_HOST
SSTATE_MIRRORS DL_DIR
SSTATE_DIR TMPDIR
BB_SERVER_TIMEOUT

For additional information on how to customize the extensible SDK’s configuration, see the “Configuring the Extensible SDK” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

EXCLUDE_FROM_SHLIBS 

Triggers the OpenEmbedded build system’s shared libraries resolver to exclude an entire package when scanning for shared libraries.

Note

The shared libraries resolver’s functionality results in part from the internal function package_do_shlibs, which is part of the do_package task. You should be aware that the shared libraries resolver might implicitly define some dependencies between packages.

The EXCLUDE_FROM_SHLIBS variable is similar to the PRIVATE_LIBS variable, which excludes a package’s particular libraries only and not the whole package.

Use the EXCLUDE_FROM_SHLIBS variable by setting it to “1” for a particular package:

EXCLUDE_FROM_SHLIBS = "1"

EXCLUDE_FROM_WORLD 

Directs BitBake to exclude a recipe from world builds (i.e. bitbake world). During world builds, BitBake locates, parses and builds all recipes found in every layer exposed in the bblayers.conf configuration file.

To exclude a recipe from a world build using this variable, set the variable to “1” in the recipe.

Note

Recipes added to EXCLUDE_FROM_WORLD may still be built during a world build in order to satisfy dependencies of other recipes. Adding a recipe to EXCLUDE_FROM_WORLD only ensures that the recipe is not explicitly added to the list of build targets in a world build.

EXTENDPE 

Used with file and pathnames to create a prefix for a recipe’s version based on the recipe’s PE value. If PE is set and greater than zero for a recipe, EXTENDPE becomes that value (e.g if PE is equal to “1” then EXTENDPE becomes “1”). If a recipe’s PE is not set (the default) or is equal to zero, EXTENDPE becomes “”.

See the STAMP variable for an example.

EXTENDPKGV 

The full package version specification as it appears on the final packages produced by a recipe. The variable’s value is normally used to fix a runtime dependency to the exact same version of another package in the same recipe:

RDEPENDS:${PN}-additional-module = "${PN} (= ${EXTENDPKGV})"

The dependency relationships are intended to force the package manager to upgrade these types of packages in lock-step.

EXTERNAL_KERNEL_TOOLS 

When set, the EXTERNAL_KERNEL_TOOLS variable indicates that these tools are not in the source tree.

When kernel tools are available in the tree, they are preferred over any externally installed tools. Setting the EXTERNAL_KERNEL_TOOLS variable tells the OpenEmbedded build system to prefer the installed external tools. See the kernel-yocto class in meta/classes-recipe to see how the variable is used.

EXTERNAL_TOOLCHAIN 

When you intend to use an external toolchain, this variable allows to specify the directory where this toolchain was installed.

EXTERNALSRC 

When inheriting the externalsrc class, this variable points to the source tree, which is outside of the OpenEmbedded build system. When set, this variable sets the S variable, which is what the OpenEmbedded build system uses to locate unpacked recipe source code.

See the “externalsrc” section for details. You can also find information on how to use this variable in the “Building Software from an External Source” section in the Yocto Project Development Tasks Manual.

EXTERNALSRC_BUILD 

When inheriting the externalsrc class, this variable points to the directory in which the recipe’s source code is built, which is outside of the OpenEmbedded build system. When set, this variable sets the B variable, which is what the OpenEmbedded build system uses to locate the Build Directory.

See the “externalsrc” section for details. You can also find information on how to use this variable in the “Building Software from an External Source” section in the Yocto Project Development Tasks Manual.

EXTRA_AUTORECONF 

For recipes inheriting the autotools* class, you can use EXTRA_AUTORECONF to specify extra options to pass to the autoreconf command that is executed during the do_configure task.

The default value is “–exclude=autopoint”.

EXTRA_IMAGE_FEATURES 

A list of additional features to include in an image. When listing more than one feature, separate them with a space.

Typically, you configure this variable in your local.conf file, which is found in the Build Directory. Although you can use this variable from within a recipe, best practices dictate that you do not.

Note

To enable primary features from within the image recipe, use the IMAGE_FEATURES variable.

Here are some examples of features you can add:

“dbg-pkgs” — adds -dbg packages for all installed packages including symbol information for debugging and profiling.

“debug-tweaks” — makes an image suitable for debugging. For example, allows root logins without passwords and enables post-installation logging. See the ‘allow-empty-password’ and ‘post-install-logging’ features in the “Image Features” section for more information.

“dev-pkgs” — adds -dev packages for all installed packages. This is useful if you want to develop against the libraries in the image.

“read-only-rootfs” — creates an image whose root filesystem is read-only. See the “Creating a Read-Only Root Filesystem” section in the Yocto Project Development Tasks Manual for more information

“tools-debug” — adds debugging tools such as gdb and strace.

“tools-sdk” — adds development tools such as gcc, make, pkgconfig and so forth.

“tools-testapps” — adds useful testing tools such as ts_print, aplay, arecord and so forth.

For a complete list of image features that ships with the Yocto Project, see the “Image Features” section.

For an example that shows how to customize your image by using this variable, see the “Customizing Images Using Custom IMAGE_FEATURES and EXTRA_IMAGE_FEATURES” section in the Yocto Project Development Tasks Manual.

EXTRA_IMAGECMD 

Specifies additional options for the image creation command that has been specified in IMAGE_CMD. When setting this variable, use an override for the associated image type. Here is an example:

EXTRA_IMAGECMD:ext3 ?= "-i 4096"

EXTRA_IMAGEDEPENDS 

A list of recipes to build that do not provide packages for installing into the root filesystem.

Sometimes a recipe is required to build the final image but is not needed in the root filesystem. You can use the EXTRA_IMAGEDEPENDS variable to list these recipes and thus specify the dependencies. A typical example is a required bootloader in a machine configuration.

Note

To add packages to the root filesystem, see the various RDEPENDS and RRECOMMENDS variables.

EXTRA_OECMAKE 

Additional CMake options. See the cmake class for additional information.

EXTRA_OECONF 

Additional configure script options. See PACKAGECONFIG_CONFARGS for additional information on passing configure script options.

EXTRA_OEMAKE 

Additional GNU make options.

Because the EXTRA_OEMAKE defaults to “”, you need to set the variable to specify any required GNU options.

PARALLEL_MAKE and PARALLEL_MAKEINST also make use of EXTRA_OEMAKE to pass the required flags.

EXTRA_OEMESON 

Additional Meson options. See the meson class for additional information.

In addition to standard Meson options, such options correspond to Meson build options defined in the meson_options.txt file in the sources to build. Here is an example:

EXTRA_OEMESON = "-Dpython=disabled -Dvalgrind=disabled"

Note that any custom value for the Meson --buildtype option should be set through the MESON_BUILDTYPE variable.

EXTRA_OESCONS 

When inheriting the scons class, this variable specifies additional configuration options you want to pass to the scons command line.

EXTRA_USERS_PARAMS 

When inheriting the extrausers class, this variable provides image level user and group operations. This is a more global method of providing user and group configuration as compared to using the useradd* class, which ties user and group configurations to a specific recipe.

The set list of commands you can configure using the EXTRA_USERS_PARAMS is shown in the extrausers class. These commands map to the normal Unix commands of the same names:

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

Hardcoded passwords are supported via the -p parameters for useradd or usermod, but only hashed.

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.

Additionally there is a special passwd-expire command that will cause the password for a user to be expired and thus force changing it on first login, for example:

EXTRA_USERS_PARAMS += " useradd myuser; passwd-expire myuser;"

Note

At present, passwd-expire may only work for remote logins when using OpenSSH and not dropbear as an SSH server.

EXTRANATIVEPATH 

A list of subdirectories of ${STAGING_BINDIR_NATIVE} added to the beginning of the environment variable PATH. As an example, the following prepends “${STAGING_BINDIR_NATIVE}/foo:${STAGING_BINDIR_NATIVE}/bar:” to PATH:

EXTRANATIVEPATH = "foo bar"

FAKEROOT 

See FAKEROOT in the BitBake manual.

FAKEROOTBASEENV 

See FAKEROOTBASEENV in the BitBake manual.

FAKEROOTCMD 

See FAKEROOTCMD in the BitBake manual.

FAKEROOTDIRS 

See FAKEROOTDIRS in the BitBake manual.

FAKEROOTENV 

See FAKEROOTENV in the BitBake manual.

FAKEROOTNOENV 

See FAKEROOTNOENV in the BitBake manual.

FEATURE_PACKAGES 

Defines one or more packages to include in an image when a specific item is included in IMAGE_FEATURES. When setting the value, FEATURE_PACKAGES should have the name of the feature item as an override. Here is an example:

FEATURE_PACKAGES_widget = "package1 package2"

In this example, if “widget” were added to IMAGE_FEATURES, package1 and package2 would be included in the image.

Note

Packages installed by features defined through FEATURE_PACKAGES are often package groups. While similarly named, you should not confuse the FEATURE_PACKAGES variable with package groups, which are discussed elsewhere in the documentation.

FEED_DEPLOYDIR_BASE_URI 

Points to the base URL of the server and location within the document-root that provides the metadata and packages required by OPKG to support runtime package management of IPK packages. You set this variable in your local.conf file.

Consider the following example:

FEED_DEPLOYDIR_BASE_URI = "http://192.168.7.1/BOARD-dir"

This example assumes you are serving your packages over HTTP and your databases are located in a directory named BOARD-dir, which is underneath your HTTP server’s document-root. In this case, the OpenEmbedded build system generates a set of configuration files for you in your target that work with the feed.

FETCHCMD 

See FETCHCMD in the BitBake manual.

FILE 

See FILE in the BitBake manual.

FILES 

The list of files and directories that are placed in a package. The PACKAGES variable lists the packages generated by a recipe.

To use the FILES variable, provide a package name override that identifies the resulting package. Then, provide a space-separated list of files or paths that identify the files you want included as part of the resulting package. Here is an example:

FILES:${PN} += "${bindir}/mydir1 ${bindir}/mydir2/myfile"

Note

When specifying files or paths, you can pattern match using Python’s glob syntax. For details on the syntax, see the documentation by following the previous link.
When specifying paths as part of the FILES variable, it is good practice to use appropriate path variables. For example, use ${sysconfdir} rather than /etc, or ${bindir} rather than /usr/bin. You can find a list of these variables at the top of the meta/conf/bitbake.conf file in the Source Directory. You will also find the default values of the various FILES:* variables in this file.

If some of the files you provide with the FILES variable are editable and you know they should not be overwritten during the package update process by the Package Management System (PMS), you can identify these files so that the PMS will not overwrite them. See the CONFFILES variable for information on how to identify these files to the PMS.

FILES_SOLIBSDEV 

Defines the file specification to match SOLIBSDEV. In other words, FILES_SOLIBSDEV defines the full path name of the development symbolic link (symlink) for shared libraries on the target platform.

The following statement from the bitbake.conf shows how it is set:

FILES_SOLIBSDEV ?= "${base_libdir}/lib*${SOLIBSDEV} ${libdir}/lib*${SOLIBSDEV}"

FILESEXTRAPATHS 

Extends the search path the OpenEmbedded build system uses when looking for files and patches as it processes recipes and append files. The default directories BitBake uses when it processes recipes are initially defined by the FILESPATH variable. You can extend FILESPATH variable by using FILESEXTRAPATHS.

Best practices dictate that you accomplish this by using FILESEXTRAPATHS from within a .bbappend file and that you prepend paths as follows:

FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:"

In the above example, the build system first looks for files in a directory that has the same name as the corresponding append file.

Note

When extending FILESEXTRAPATHS, be sure to use the immediate expansion (:=) operator. Immediate expansion makes sure that BitBake evaluates THISDIR at the time the directive is encountered rather than at some later time when expansion might result in a directory that does not contain the files you need.

Also, include the trailing separating colon character if you are prepending. The trailing colon character is necessary because you are directing BitBake to extend the path by prepending directories to the search path.

Here is another common use:

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"

In this example, the build system extends the FILESPATH variable to include a directory named files that is in the same directory as the corresponding append file.

This next example specifically adds three paths:

FILESEXTRAPATHS:prepend := "path_1:path_2:path_3:"

A final example shows how you can extend the search path and include a MACHINE-specific override, which is useful in a BSP layer:

FILESEXTRAPATHS:prepend:intel-x86-common := "${THISDIR}/${PN}:"

The previous statement appears in the linux-yocto-dev.bbappend file, which is found in the Yocto Project Source Repositories in meta-intel/common/recipes-kernel/linux. Here, the machine override is a special PACKAGE_ARCH definition for multiple meta-intel machines.

Note

For a layer that supports a single BSP, the override could just be the value of MACHINE.

By prepending paths in .bbappend files, you allow multiple append files that reside in different layers but are used for the same recipe to correctly extend the path.

FILESOVERRIDES 

A subset of OVERRIDES used by the OpenEmbedded build system for creating FILESPATH. The FILESOVERRIDES variable uses overrides to automatically extend the FILESPATH variable. For an example of how that works, see the FILESPATH variable description. Additionally, you find more information on how overrides are handled in the “Conditional Syntax (Overrides)” section of the BitBake User Manual.

By default, the FILESOVERRIDES variable is defined as:

FILESOVERRIDES = "${TRANSLATED_TARGET_ARCH}:${MACHINEOVERRIDES}:${DISTROOVERRIDES}"

Note

Do not hand-edit the FILESOVERRIDES variable. The values match up with expected overrides and are used in an expected manner by the build system.

FILESPATH 

The default set of directories the OpenEmbedded build system uses when searching for patches and files.

During the build process, BitBake searches each directory in FILESPATH in the specified order when looking for files and patches specified by each file:// URI in a recipe’s SRC_URI statements.

The default value for the FILESPATH variable is defined in the base class found in meta/classes-global in the Source Directory:

FILESPATH = "${@base_set_filespath(["${FILE_DIRNAME}/${BP}", \
    "${FILE_DIRNAME}/${BPN}", "${FILE_DIRNAME}/files"], d)}"

The FILESPATH variable is automatically extended using the overrides from the FILESOVERRIDES variable.

Note

Do not hand-edit the FILESPATH variable. If you want the build system to look in directories other than the defaults, extend the FILESPATH variable by using the FILESEXTRAPATHS variable.
Be aware that the default FILESPATH directories do not map to directories in custom layers where append files (.bbappend) are used. If you want the build system to find patches or files that reside with your append files, you need to extend the FILESPATH variable by using the FILESEXTRAPATHS variable.

You can take advantage of this searching behavior in useful ways. For example, consider a case where there is the following directory structure for general and machine-specific configurations:

files/defconfig
files/MACHINEA/defconfig
files/MACHINEB/defconfig

Also in the example, the SRC_URI statement contains “file://defconfig”. Given this scenario, you can set MACHINE to “MACHINEA” and cause the build system to use files from files/MACHINEA. Set MACHINE to “MACHINEB” and the build system uses files from files/MACHINEB. Finally, for any machine other than “MACHINEA” and “MACHINEB”, the build system uses files from files/defconfig.

You can find out more about the patching process in the “Patching” section in the Yocto Project Overview and Concepts Manual and the “Patching Code” section in the Yocto Project Development Tasks Manual. See the do_patch task as well.

FILESYSTEM_PERMS_TABLES 

Allows you to define your own file permissions settings table as part of your configuration for the packaging process. For example, suppose you need a consistent set of custom permissions for a set of groups and users across an entire work project. It is best to do this in the packages themselves but this is not always possible.

By default, the OpenEmbedded build system uses the fs-perms.txt, which is located in the meta/files folder in the Source Directory. If you create your own file permissions setting table, you should place it in your layer or the distro’s layer.

You define the FILESYSTEM_PERMS_TABLES variable in the conf/local.conf file, which is found in the Build Directory, to point to your custom fs-perms.txt. You can specify more than a single file permissions setting table. The paths you specify to these files must be defined within the BBPATH variable.

For guidance on how to create your own file permissions settings table file, examine the existing fs-perms.txt.

FIT_CONF_DEFAULT_DTB 

Specifies the default device tree binary (dtb) file for a fitImage when multiple are provided.

FIT_DESC 

Specifies the description string encoded into a fitImage. The default value is set by the kernel-fitimage class as follows:

FIT_DESC ?= "U-Boot fitImage for ${DISTRO_NAME}/${PV}/${MACHINE}"

FIT_GENERATE_KEYS 

Decides whether to generate the keys for signing fitImage if they don’t already exist. The keys are created in UBOOT_SIGN_KEYDIR. The default value is 0.

FIT_HASH_ALG 

Specifies the hash algorithm used in creating the FIT Image. For e.g. sha256.

FIT_KERNEL_COMP_ALG 

Compression algorithm to use for the kernel image inside the FIT Image. At present, the only supported values are “gzip” (default), “lzo” or “none”. If you set this variable to anything other than “none” you may also need to set FIT_KERNEL_COMP_ALG_EXTENSION.

FIT_KERNEL_COMP_ALG_EXTENSION 

File extension corresponding to FIT_KERNEL_COMP_ALG. The default value is “.gz”. If you set FIT_KERNEL_COMP_ALG to “lzo”, you may want to set this variable to “.lzo”.

FIT_KEY_GENRSA_ARGS 

Arguments to openssl genrsa for generating RSA private key for signing fitImage. The default value is “-F4”. i.e. the public exponent 65537 to use.

FIT_KEY_REQ_ARGS 

Arguments to openssl req for generating certificate for signing fitImage. The default value is “-batch -new”. batch for non interactive mode and new for generating new keys.

FIT_KEY_SIGN_PKCS 

Format for public key certificate used in signing fitImage. The default value is “x509”.

FIT_PAD_ALG 

Specifies the padding algorithm used in creating the FIT Image. The default value is “pkcs-1.5”.

FIT_SIGN_ALG 

Specifies the signature algorithm used in creating the FIT Image. For e.g. rsa2048.

FIT_SIGN_INDIVIDUAL 

If set to “1”, then the kernel-fitimage class will sign the kernel, dtb and ramdisk images individually in addition to signing the fitImage itself. This could be useful if you are intending to verify signatures in another context than booting via U-Boot.

FIT_SIGN_NUMBITS 

Size of private key in number of bits used in fitImage. The default value is “2048”.

FONT_EXTRA_RDEPENDS 

When inheriting the fontcache class, this variable specifies the runtime dependencies for font packages. By default, the FONT_EXTRA_RDEPENDS is set to “fontconfig-utils”.

FONT_PACKAGES 

When inheriting the fontcache class, this variable identifies packages containing font files that need to be cached by Fontconfig. By default, the fontcache class assumes that fonts are in the recipe’s main package (i.e. ${PN}). Use this variable if fonts you need are in a package other than that main package.

FORCE_RO_REMOVE 

Forces the removal of the packages listed in ROOTFS_RO_UNNEEDED during the generation of the root filesystem.

Set the variable to “1” to force the removal of these packages.

FULL_OPTIMIZATION 

The options to pass in TARGET_CFLAGS and CFLAGS when compiling an optimized system. This variable defaults to “-O2 -pipe ${DEBUG_FLAGS}”.

GCCPIE 

Enables Position Independent Executables (PIE) within the GNU C Compiler (GCC). Enabling PIE in the GCC makes Return Oriented Programming (ROP) attacks much more difficult to execute.

By default the security_flags.inc file enables PIE by setting the variable as follows:

GCCPIE ?= "--enable-default-pie"

GCCVERSION 

Specifies the default version of the GNU C Compiler (GCC) used for compilation. By default, GCCVERSION is set to “8.x” in the meta/conf/distro/include/tcmode-default.inc include file:

GCCVERSION ?= "8.%"

You can override this value by setting it in a configuration file such as the local.conf.

GDB 

The minimal command and arguments to run the GNU Debugger.

GIR_EXTRA_LIBS_PATH 

Allows to specify an extra search path for .so files in GLib related recipes using GObject introspection, and which do not compile without this setting. See the “Enabling GObject Introspection Support” section for details.

GITDIR 

The directory in which a local copy of a Git repository is stored when it is cloned.

GITHUB_BASE_URI 

When inheriting the github-releases class, specifies the base URL for fetching releases for the github project you wish to fetch sources from. The default value is as follows:

GITHUB_BASE_URI ?= "https://github.com/${BPN}/${BPN}/releases/"

GLIBC_GENERATE_LOCALES 

Specifies the list of GLIBC locales to generate should you not wish to generate all LIBC locals, which can be time consuming.

Note

If you specifically remove the locale en_US.UTF-8, you must set IMAGE_LINGUAS appropriately.

You can set GLIBC_GENERATE_LOCALES in your local.conf file. By default, all locales are generated:

GLIBC_GENERATE_LOCALES = "en_GB.UTF-8 en_US.UTF-8"

GO_IMPORT 

When inheriting the go class, this mandatory variable sets the import path for the Go package that will be created for the code to build. If you have a go.mod file in the source directory, this typically matches the path in the module line in this file.

Other Go programs importing this package will use this path.

Here is an example setting from the go-helloworld_0.1.bb recipe:

GO_IMPORT = "golang.org/x/example"

GO_INSTALL 

When inheriting the go class, this optional variable specifies which packages in the sources should be compiled and installed in the Go build space by the go install command.

Here is an example setting from the crucible recipe:

GO_INSTALL = "\
    ${GO_IMPORT}/cmd/crucible \
    ${GO_IMPORT}/cmd/habtool \
"

By default, GO_INSTALL is defined as:

GO_INSTALL ?= "${GO_IMPORT}/..."

The ... wildcard means that it will catch all packages found in the sources.

See the GO_INSTALL_FILTEROUT variable for filtering out unwanted packages from the ones found from the GO_INSTALL value.

GO_INSTALL_FILTEROUT 

When using the Go “vendor” mechanism to bring in dependencies for a Go package, the default GO_INSTALL setting, which uses the ... wildcard, will include the vendored packages in the build, which produces incorrect results.

There are also some Go packages that are structured poorly, so that the ... wildcard results in building example or test code that should not be included in the build, or could fail to build.

This optional variable allows for filtering out a subset of the sources. It defaults to excluding everything under the vendor subdirectory under package’s main directory. This is the normal location for vendored packages, but it can be overridden by a recipe to filter out other subdirectories if needed.

GO_WORKDIR 

When using Go Modules, the current working directory must be the directory containing the go.mod file, or one of its subdirectories. When the go tool is used, it will automatically look for the go.mod file in the Go working directory or in any parent directory, but not in subdirectories.

When using the go-mod class to use Go modules, the optional GO_WORKDIR variable, defaulting to the value of GO_IMPORT, allows to specify a different Go working directory.

GROUPADD_PARAM 

When inheriting the useradd* class, this variable specifies for a package what parameters should be passed to the groupadd command if you wish to add a group to the system when the package is installed.

Here is an example from the dbus recipe:

GROUPADD_PARAM:${PN} = "-r netdev"

For information on the standard Linux shell command groupadd, see https://linux.die.net/man/8/groupadd.

GROUPMEMS_PARAM 

When inheriting the useradd* class, this variable specifies for a package what parameters should be passed to the groupmems command if you wish to modify the members of a group when the package is installed.

For information on the standard Linux shell command groupmems, see https://linux.die.net/man/8/groupmems.

GRUB_GFXSERIAL 

Configures the GNU GRand Unified Bootloader (GRUB) to have graphics and serial in the boot menu. Set this variable to “1” in your local.conf or distribution configuration file to enable graphics and serial in the menu.

See the grub-efi class for more information on how this variable is used.

GRUB_OPTS 

Additional options to add to the GNU GRand Unified Bootloader (GRUB) configuration. Use a semi-colon character (;) to separate multiple options.

The GRUB_OPTS variable is optional. See the grub-efi class for more information on how this variable is used.

GRUB_TIMEOUT 

Specifies the timeout before executing the default LABEL in the GNU GRand Unified Bootloader (GRUB).

The GRUB_TIMEOUT variable is optional. See the grub-efi class for more information on how this variable is used.

GTKIMMODULES_PACKAGES 

When inheriting the gtk-immodules-cache class, this variable specifies the packages that contain the GTK+ input method modules being installed when the modules are in packages other than the main package.

HGDIR 

See HGDIR in the BitBake manual.

HOMEPAGE 

Website where more information about the software the recipe is building can be found.

HOST_ARCH 

The name of the target architecture, which is normally the same as TARGET_ARCH. The OpenEmbedded build system supports many architectures. Here is an example list of architectures supported. This list is by no means complete as the architecture is configurable:

arm
i586
x86_64
powerpc
powerpc64
mips
mipsel

HOST_CC_ARCH 

Specifies architecture-specific compiler flags that are passed to the C compiler.

Default initialization for HOST_CC_ARCH varies depending on what is being built:

TARGET_CC_ARCH when building for the target
BUILD_CC_ARCH when building for the build host (i.e. -native)
BUILDSDK_CC_ARCH when building for an SDK (i.e. nativesdk-)

HOST_OS 

Specifies the name of the target operating system, which is normally the same as the TARGET_OS. The variable can be set to “linux” for glibc-based systems and to “linux-musl” for musl. For ARM/EABI targets, there are also “linux-gnueabi” and “linux-musleabi” values possible.

HOST_PREFIX 

Specifies the prefix for the cross-compile toolchain. HOST_PREFIX is normally the same as TARGET_PREFIX.

HOST_SYS 

Specifies the system, including the architecture and the operating system, for which the build is occurring in the context of the current recipe.

The OpenEmbedded build system automatically sets this variable based on HOST_ARCH, HOST_VENDOR, and HOST_OS variables.

Note

You do not need to set the variable yourself.

Consider these two examples:

Given a native recipe on a 32-bit x86 machine running Linux, the value is “i686-linux”.
Given a recipe being built for a little-endian MIPS target running Linux, the value might be “mipsel-linux”.

HOST_VENDOR 

Specifies the name of the vendor. HOST_VENDOR is normally the same as TARGET_VENDOR.

HOSTTOOLS 

A space-separated list (filter) of tools on the build host that should be allowed to be called from within build tasks. Using this filter helps reduce the possibility of host contamination. If a tool specified in the value of HOSTTOOLS is not found on the build host, the OpenEmbedded build system produces an error and the build is not started.

For additional information, see HOSTTOOLS_NONFATAL.

HOSTTOOLS_NONFATAL 

A space-separated list (filter) of tools on the build host that should be allowed to be called from within build tasks. Using this filter helps reduce the possibility of host contamination. Unlike HOSTTOOLS, the OpenEmbedded build system does not produce an error if a tool specified in the value of HOSTTOOLS_NONFATAL is not found on the build host. Thus, you can use HOSTTOOLS_NONFATAL to filter optional host tools.

ICECC_CLASS_DISABLE 

Identifies user classes that you do not want the Icecream distributed compile support to consider. This variable is used by the icecc class. You set this variable in your local.conf file.

When you list classes using this variable, the recipes inheriting those classes will not benefit from distributed compilation across remote hosts. Instead they will be built locally.

ICECC_DISABLED 

Disables or enables the icecc (Icecream) function. For more information on this function and best practices for using this variable, see the “icecc” section.

Setting this variable to “1” in your local.conf disables the function:

ICECC_DISABLED ??= "1"

To enable the function, set the variable as follows:

ICECC_DISABLED = ""

ICECC_ENV_EXEC 

Points to the icecc-create-env script that you provide. This variable is used by the icecc class. You set this variable in your local.conf file.

If you do not point to a script that you provide, the OpenEmbedded build system uses the default script provided by the icecc-create-env_0.1.bb recipe, which is a modified version and not the one that comes with icecream.

ICECC_PARALLEL_MAKE 

Extra options passed to the make command during the do_compile task that specify parallel compilation. This variable usually takes the form of “-j x”, where x represents the maximum number of parallel threads make can run.

Note

The options passed affect builds on all enabled machines on the network, which are machines running the iceccd daemon.

If your enabled machines support multiple cores, coming up with the maximum number of parallel threads that gives you the best performance could take some experimentation since machine speed, network lag, available memory, and existing machine loads can all affect build time. Consequently, unlike the PARALLEL_MAKE variable, there is no rule-of-thumb for setting ICECC_PARALLEL_MAKE to achieve optimal performance.

If you do not set ICECC_PARALLEL_MAKE, the build system does not use it (i.e. the system does not detect and assign the number of cores as is done with PARALLEL_MAKE).

ICECC_PATH 

The location of the icecc binary. You can set this variable in your local.conf file. If your local.conf file does not define this variable, the icecc class attempts to define it by locating icecc using which.

ICECC_RECIPE_DISABLE 

Identifies user recipes that you do not want the Icecream distributed compile support to consider. This variable is used by the icecc class. You set this variable in your local.conf file.

When you list recipes using this variable, you are excluding them from distributed compilation across remote hosts. Instead they will be built locally.

ICECC_RECIPE_ENABLE 

Identifies user recipes that use an empty PARALLEL_MAKE variable that you want to force remote distributed compilation on using the Icecream distributed compile support. This variable is used by the icecc class. You set this variable in your local.conf file.

IMAGE_BASENAME 

The base name of image output files. This variable defaults to the recipe name (${PN}).

IMAGE_BOOT_FILES 

A space-separated list of files installed into the boot partition when preparing an image using the Wic tool with the bootimg-partition source plugin. By default, the files are installed under the same name as the source files. To change the installed name, separate it from the original name with a semi-colon (;). Source files need to be located in DEPLOY_DIR_IMAGE. Here are two examples:

IMAGE_BOOT_FILES = "u-boot.img uImage;kernel"
IMAGE_BOOT_FILES = "u-boot.${UBOOT_SUFFIX} ${KERNEL_IMAGETYPE}"

Alternatively, source files can be picked up using a glob pattern. In this case, the destination file must have the same name as the base name of the source file path. To install files into a directory within the target location, pass its name after a semi-colon (;). Here are two examples:

IMAGE_BOOT_FILES = "bcm2835-bootfiles/*"
IMAGE_BOOT_FILES = "bcm2835-bootfiles/*;boot/"

The first example installs all files from ${DEPLOY_DIR_IMAGE}/bcm2835-bootfiles into the root of the target partition. The second example installs the same files into a boot directory within the target partition.

You can find information on how to use the Wic tool in the “Creating Partitioned Images Using Wic” section of the Yocto Project Development Tasks Manual. Reference material for Wic is located in the “OpenEmbedded Kickstart (.wks) Reference” chapter.

IMAGE_BUILDINFO_FILE 

When using the image-buildinfo class, specifies the file in the image to write the build information into. The default value is “${sysconfdir}/buildinfo”.

IMAGE_BUILDINFO_VARS 

When using the image-buildinfo class, specifies the list of variables to include in the Build Configuration section of the output file (as a space-separated list). Defaults to “DISTRO DISTRO_VERSION”.

IMAGE_CLASSES 

A list of classes that all images should inherit. This is typically used to enable functionality across all image recipes.

Classes specified in IMAGE_CLASSES must be located in the classes-recipe/ or classes/ subdirectories.

IMAGE_CMD 

Specifies the command to create the image file for a specific image type, which corresponds to the value set in IMAGE_FSTYPES, (e.g. ext3, btrfs, and so forth). When setting this variable, you should use an override for the associated type. Here is an example:

IMAGE_CMD:jffs2 = "mkfs.jffs2 --root=${IMAGE_ROOTFS} --faketime \
    --output=${IMGDEPLOYDIR}/${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.jffs2 \
    ${EXTRA_IMAGECMD}"

You typically do not need to set this variable unless you are adding support for a new image type. For more examples on how to set this variable, see the image_types class file, which is meta/classes-recipe/image_types.bbclass.

IMAGE_DEVICE_TABLES 

Specifies one or more files that contain custom device tables that are passed to the makedevs command as part of creating an image. These files list basic device nodes that should be created under /dev within the image. If IMAGE_DEVICE_TABLES is not set, files/device_table-minimal.txt is used, which is located by BBPATH. For details on how you should write device table files, see meta/files/device_table-minimal.txt as an example.

IMAGE_EFI_BOOT_FILES 

A space-separated list of files installed into the boot partition when preparing an image using the Wic tool with the bootimg-efi source plugin. By default, the files are installed under the same name as the source files. To change the installed name, separate it from the original name with a semi-colon (;). Source files need to be located in DEPLOY_DIR_IMAGE. Here are two examples:

IMAGE_EFI_BOOT_FILES = "${KERNEL_IMAGETYPE};bz2"
IMAGE_EFI_BOOT_FILES = "${KERNEL_IMAGETYPE} microcode.cpio"

Alternatively, source files can be picked up using a glob pattern. In this case, the destination file must have the same name as the base name of the source file path. To install files into a directory within the target location, pass its name after a semi-colon (;). Here are two examples:

IMAGE_EFI_BOOT_FILES = "boot/loader/*"
IMAGE_EFI_BOOT_FILES = "boot/loader/*;boot/"

The first example installs all files from ${DEPLOY_DIR_IMAGE}/boot/loader/ into the root of the target partition. The second example installs the same files into a boot directory within the target partition.

You can find information on how to use the Wic tool in the “Creating Partitioned Images Using Wic” section of the Yocto Project Development Tasks Manual. Reference material for Wic is located in the “OpenEmbedded Kickstart (.wks) Reference” chapter.

IMAGE_FEATURES 

The primary list of features to include in an image. Typically, you configure this variable in an image recipe. Although you can use this variable from your local.conf file, which is found in the Build Directory, best practices dictate that you do not.

Note

To enable extra features from outside the image recipe, use the EXTRA_IMAGE_FEATURES variable.

For a list of image features that ships with the Yocto Project, see the “Image Features” section.

For an example that shows how to customize your image by using this variable, see the “Customizing Images Using Custom IMAGE_FEATURES and EXTRA_IMAGE_FEATURES” section in the Yocto Project Development Tasks Manual.

IMAGE_FSTYPES 

Specifies the formats the OpenEmbedded build system uses during the build when creating the root filesystem. For example, setting IMAGE_FSTYPES as follows causes the build system to create root filesystems using two formats: .ext3 and .tar.bz2:

IMAGE_FSTYPES = "ext3 tar.bz2"

For the complete list of supported image formats from which you can choose, see IMAGE_TYPES.

Note

If an image recipe uses the “inherit image” line and you are setting IMAGE_FSTYPES inside the recipe, you must set IMAGE_FSTYPES prior to using the “inherit image” line.
Due to the way the OpenEmbedded build system processes this variable, you cannot update its contents by using :append or :prepend. You must use the += operator to add one or more options to the IMAGE_FSTYPES variable.

IMAGE_INSTALL 

Used by recipes to specify the packages to install into an image through the image class. Use the IMAGE_INSTALL variable with care to avoid ordering issues.

Image recipes set IMAGE_INSTALL to specify the packages to install into an image through image. Additionally, there are “helper” classes such as the core-image class which can take lists used with IMAGE_FEATURES and turn them into auto-generated entries in IMAGE_INSTALL in addition to its default contents.

When you use this variable, it is best to use it as follows:

IMAGE_INSTALL:append = " package-name"

Be sure to include the space between the quotation character and the start of the package name or names.

Note

When working with a core-image-minimal-initramfs image, do not use the IMAGE_INSTALL variable to specify packages for installation. Instead, use the PACKAGE_INSTALL variable, which allows the initial RAM filesystem (Initramfs) recipe to use a fixed set of packages and not be affected by IMAGE_INSTALL. For information on creating an Initramfs, see the “Building an Initial RAM Filesystem (Initramfs) Image” section in the Yocto Project Development Tasks Manual.
Using IMAGE_INSTALL with the += BitBake operator within the /conf/local.conf file or from within an image recipe is not recommended. Use of this operator in these ways can cause ordering issues. Since core-image sets IMAGE_INSTALL to a default value using the ?= operator, using a += operation against IMAGE_INSTALL results in unexpected behavior when used within conf/local.conf. Furthermore, the same operation from within an image recipe may or may not succeed depending on the specific situation. In both these cases, the behavior is contrary to how most users expect the += operator to work.

IMAGE_LINGUAS 

Specifies the list of locales to install into the image during the root filesystem construction process. The OpenEmbedded build system automatically splits locale files, which are used for localization, into separate packages. Setting the IMAGE_LINGUAS variable ensures that any locale packages that correspond to packages already selected for installation into the image are also installed. Here is an example:

IMAGE_LINGUAS = "pt-br de-de"

In this example, the build system ensures any Brazilian Portuguese and German locale files that correspond to packages in the image are installed (i.e. *-locale-pt-br and *-locale-de-de as well as *-locale-pt and *-locale-de, since some software packages only provide locale files by language and not by country-specific language).

See the GLIBC_GENERATE_LOCALES variable for information on generating GLIBC locales.

IMAGE_LINK_NAME 

The name of the output image symlink (which does not include the version part as IMAGE_NAME does). The default value is derived using the IMAGE_BASENAME and IMAGE_MACHINE_SUFFIX variables:

IMAGE_LINK_NAME ?= "${IMAGE_BASENAME}${IMAGE_MACHINE_SUFFIX}"

Note

It is possible to set this to “” to disable symlink creation, however, you also need to set IMAGE_NAME to still have a reasonable value e.g.:

IMAGE_LINK_NAME = ""
IMAGE_NAME = "${IMAGE_BASENAME}${IMAGE_MACHINE_SUFFIX}${IMAGE_VERSION_SUFFIX}"

IMAGE_MACHINE_SUFFIX 

Specifies the by default machine-specific suffix for image file names (before the extension). The default value is set as follows:

IMAGE_MACHINE_SUFFIX ??= "-${MACHINE}"

The default DEPLOY_DIR_IMAGE already has a MACHINE subdirectory, so you may find it unnecessary to also include this suffix in the name of every image file. If you prefer to remove the suffix you can set this variable to an empty string:

IMAGE_MACHINE_SUFFIX = ""

(Not to be confused with IMAGE_NAME_SUFFIX.)

IMAGE_MANIFEST 

The manifest file for the image. This file lists all the installed packages that make up the image. The file contains package information on a line-per-package basis as follows:

packagename packagearch version

The rootfs-postcommands class defines the manifest file as follows:

IMAGE_MANIFEST ="${IMGDEPLOYDIR}/${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.manifest"

The location is derived using the IMGDEPLOYDIR and IMAGE_NAME variables. You can find information on how the image is created in the “Image Generation” section in the Yocto Project Overview and Concepts Manual.

IMAGE_NAME 

The name of the output image files minus the extension. By default this variable is set using the IMAGE_LINK_NAME, and IMAGE_VERSION_SUFFIX variables:

IMAGE_NAME ?= "${IMAGE_LINK_NAME}${IMAGE_VERSION_SUFFIX}"

IMAGE_NAME_SUFFIX 

Suffix used for the image output filename — defaults to ".rootfs" to distinguish the image file from other files created during image building; however if this suffix is redundant or not desired you can clear the value of this variable (set the value to “”). For example, this is typically cleared in Initramfs image recipes.

IMAGE_OVERHEAD_FACTOR 

Defines a multiplier that the build system applies to the initial image size for cases when the multiplier times the returned disk usage value for the image is greater than the sum of IMAGE_ROOTFS_SIZE and IMAGE_ROOTFS_EXTRA_SPACE. The result of the multiplier applied to the initial image size creates free disk space in the image as overhead. By default, the build process uses a multiplier of 1.3 for this variable. This default value results in 30% free disk space added to the image when this method is used to determine the final generated image size. You should be aware that post install scripts and the package management system uses disk space inside this overhead area. Consequently, the multiplier does not produce an image with all the theoretical free disk space. See IMAGE_ROOTFS_SIZE for information on how the build system determines the overall image size.

The default 30% free disk space typically gives the image enough room to boot and allows for basic post installs while still leaving a small amount of free disk space. If 30% free space is inadequate, you can increase the default value. For example, the following setting gives you 50% free space added to the image:

IMAGE_OVERHEAD_FACTOR = "1.5"

Alternatively, you can ensure a specific amount of free disk space is added to the image by using the IMAGE_ROOTFS_EXTRA_SPACE variable.

IMAGE_PKGTYPE 

Defines the package type (i.e. DEB, RPM, IPK, or TAR) used by the OpenEmbedded build system. The variable is defined appropriately by the package_deb, package_rpm, or package_ipk class.

The populate_sdk_* and image classes use the IMAGE_PKGTYPE for packaging up images and SDKs.

You should not set the IMAGE_PKGTYPE manually. Rather, the variable is set indirectly through the appropriate package_* class using the PACKAGE_CLASSES variable. The OpenEmbedded build system uses the first package type (e.g. DEB, RPM, or IPK) that appears with the variable

Note

Files using the .tar format are never used as a substitute packaging format for DEB, RPM, and IPK formatted files for your image or SDK.

IMAGE_POSTPROCESS_COMMAND 

Specifies a list of functions to call once the OpenEmbedded build system creates the final image output files. You can specify functions separated by semicolons:

IMAGE_POSTPROCESS_COMMAND += "function; ... "

If you need to pass the root filesystem path to a command within the function, you can use ${IMAGE_ROOTFS}, which points to the directory that becomes the root filesystem image. See the IMAGE_ROOTFS variable for more information.

IMAGE_PREPROCESS_COMMAND 

Specifies a list of functions to call before the OpenEmbedded build system creates the final image output files. You can specify functions separated by semicolons:

IMAGE_PREPROCESS_COMMAND += "function; ... "

If you need to pass the root filesystem path to a command within the function, you can use ${IMAGE_ROOTFS}, which points to the directory that becomes the root filesystem image. See the IMAGE_ROOTFS variable for more information.

IMAGE_ROOTFS 

The location of the root filesystem while it is under construction (i.e. during the do_rootfs task). This variable is not configurable. Do not change it.

IMAGE_ROOTFS_ALIGNMENT 

Specifies the alignment for the output image file in Kbytes. If the size of the image is not a multiple of this value, then the size is rounded up to the nearest multiple of the value. The default value is “1”. See IMAGE_ROOTFS_SIZE for additional information.

IMAGE_ROOTFS_EXTRA_SPACE 

Defines additional free disk space created in the image in Kbytes. By default, this variable is set to “0”. This free disk space is added to the image after the build system determines the image size as described in IMAGE_ROOTFS_SIZE.

This variable is particularly useful when you want to ensure that a specific amount of free disk space is available on a device after an image is installed and running. For example, to be sure 5 Gbytes of free disk space is available, set the variable as follows:

IMAGE_ROOTFS_EXTRA_SPACE = "5242880"

For example, the Yocto Project Build Appliance specifically requests 40 Gbytes of extra space with the line:

IMAGE_ROOTFS_EXTRA_SPACE = "41943040"

IMAGE_ROOTFS_SIZE 

Defines the size in Kbytes for the generated image. The OpenEmbedded build system determines the final size for the generated image using an algorithm that takes into account the initial disk space used for the generated image, a requested size for the image, and requested additional free disk space to be added to the image. Programatically, the build system determines the final size of the generated image as follows:

if (image-du * overhead) < rootfs-size:
    internal-rootfs-size = rootfs-size + xspace
else:
    internal-rootfs-size = (image-du * overhead) + xspace
where:
    image-du = Returned value of the du command on the image.
    overhead = IMAGE_OVERHEAD_FACTOR
    rootfs-size = IMAGE_ROOTFS_SIZE
    internal-rootfs-size = Initial root filesystem size before any modifications.
    xspace = IMAGE_ROOTFS_EXTRA_SPACE

See the IMAGE_OVERHEAD_FACTOR and IMAGE_ROOTFS_EXTRA_SPACE variables for related information.

IMAGE_TYPEDEP 

Specifies a dependency from one image type on another. Here is an example from the image-live class:

IMAGE_TYPEDEP:live = "ext3"

In the previous example, the variable ensures that when “live” is listed with the IMAGE_FSTYPES variable, the OpenEmbedded build system produces an ext3 image first since one of the components of the live image is an ext3 formatted partition containing the root filesystem.

IMAGE_TYPES 

Specifies the complete list of supported image types by default:

btrfs
container
cpio
cpio.gz
cpio.lz4
cpio.lzma
cpio.xz
cramfs
erofs
erofs-lz4
erofs-lz4hc
ext2
ext2.bz2
ext2.gz
ext2.lzma
ext3
ext3.gz
ext4
ext4.gz
f2fs
hddimg
iso
jffs2
jffs2.sum
multiubi
squashfs
squashfs-lz4
squashfs-lzo
squashfs-xz
tar
tar.bz2
tar.gz
tar.lz4
tar.xz
tar.zst
ubi
ubifs
wic
wic.bz2
wic.gz
wic.lzma

For more information about these types of images, see meta/classes-recipe/image_types*.bbclass in the Source Directory.

IMAGE_VERSION_SUFFIX 

Version suffix that is part of the default IMAGE_NAME and KERNEL_ARTIFACT_NAME values. Defaults to "-${DATETIME}", however you could set this to a version string that comes from your external build environment if desired, and this suffix would then be used consistently across the build artifacts.

IMGDEPLOYDIR 

When inheriting the image class directly or through the core-image class, the IMGDEPLOYDIR points to a temporary work area for deployed files that is set in the image class as follows:

IMGDEPLOYDIR = "${WORKDIR}/deploy-${PN}-image-complete"

Recipes inheriting the image class should copy files to be deployed into IMGDEPLOYDIR, and the class will take care of copying them into DEPLOY_DIR_IMAGE afterwards.

INCOMPATIBLE_LICENSE 

Specifies a space-separated list of license names (as they would appear in LICENSE) that should be excluded from the build. Recipes that provide no alternatives to listed incompatible licenses are not built. Packages that are individually licensed with the specified incompatible licenses will be deleted.

There is some support for wildcards in this variable’s value, however it is restricted to specific licenses. Currently only these wildcards are allowed and expand as follows:

AGPL-3.0*": AGPL-3.0-only, AGPL-3.0-or-later
GPL-3.0*: GPL-3.0-only, GPL-3.0-or-later
LGPL-3.0*: LGPL-3.0-only, LGPL-3.0-or-later

Note

This functionality is only regularly tested using the following setting:

INCOMPATIBLE_LICENSE = "GPL-3.0* LGPL-3.0* AGPL-3.0*"

Although you can use other settings, you might be required to remove dependencies on (or provide alternatives to) components that are required to produce a functional system image.

INCOMPATIBLE_LICENSE_EXCEPTIONS 

Specifies a space-separated list of package and license pairs that are allowed to be used even if the license is specified in INCOMPATIBLE_LICENSE. The package and license pairs are separated using a colon. Example:

INCOMPATIBLE_LICENSE_EXCEPTIONS = "gdbserver:GPL-3.0-only gdbserver:LGPL-3.0-only"

INHERIT 

Causes the named class or classes to be inherited globally. Anonymous functions in the class or classes are not executed for the base configuration and in each individual recipe. The OpenEmbedded build system ignores changes to INHERIT in individual recipes. Classes inherited using INHERIT must be located in the classes-global/ or classes/ subdirectories.

For more information on INHERIT, see the INHERIT Configuration Directive” section in the BitBake User Manual.

INHERIT_DISTRO 

Lists classes that will be inherited at the distribution level. It is unlikely that you want to edit this variable.

Classes specified in INHERIT_DISTRO must be located in the classes-global/ or classes/ subdirectories.

The default value of the variable is set as follows in the meta/conf/distro/defaultsetup.conf file:

INHERIT_DISTRO ?= "debian devshell sstate license"

INHIBIT_DEFAULT_DEPS 

Prevents the default dependencies, namely the C compiler and standard C library (libc), from being added to DEPENDS. This variable is usually used within recipes that do not require any compilation using the C compiler.

Set the variable to “1” to prevent the default dependencies from being added.

INHIBIT_PACKAGE_DEBUG_SPLIT 

Prevents the OpenEmbedded build system from splitting out debug information during packaging. By default, the build system splits out debugging information during the do_package task. For more information on how debug information is split out, see the PACKAGE_DEBUG_SPLIT_STYLE variable.

To prevent the build system from splitting out debug information during packaging, set the INHIBIT_PACKAGE_DEBUG_SPLIT variable as follows:

INHIBIT_PACKAGE_DEBUG_SPLIT = "1"

INHIBIT_PACKAGE_STRIP 

If set to “1”, causes the build to not strip binaries in resulting packages and prevents the -dbg package from containing the source files.

By default, the OpenEmbedded build system strips binaries and puts the debugging symbols into ${PN}-dbg. Consequently, you should not set INHIBIT_PACKAGE_STRIP when you plan to debug in general.

INHIBIT_SYSROOT_STRIP 

If set to “1”, causes the build to not strip binaries in the resulting sysroot.

By default, the OpenEmbedded build system strips binaries in the resulting sysroot. When you specifically set the INHIBIT_SYSROOT_STRIP variable to “1” in your recipe, you inhibit this stripping.

If you want to use this variable, include the staging class. This class uses a sys_strip() function to test for the variable and acts accordingly.

Note

Use of the INHIBIT_SYSROOT_STRIP variable occurs in rare and special circumstances. For example, suppose you are building bare-metal firmware by using an external GCC toolchain. Furthermore, even if the toolchain’s binaries are strippable, there are other files needed for the build that are not strippable.

INIT_MANAGER 

Specifies the system init manager to use. Available options are:

sysvinit
systemd
mdev-busybox

With sysvinit, the init manager is set to SysVinit, the traditional UNIX init system. This is the default choice in the Poky distribution, together with the Udev device manager (see the “Selecting a Device Manager” section).

With systemd, the init manager becomes systemd, which comes with the udev device manager.

With mdev-busybox, the init manager becomes the much simpler BusyBox init, together with the BusyBox mdev device manager. This is the simplest and lightest solution, and probably the best choice for low-end systems with a rather slow CPU and a limited amount of RAM.

More concretely, this is used to include conf/distro/include/init-manager-${INIT_MANAGER}.inc into the global configuration. You can have a look at the meta/conf/distro/include/init-manager-*.inc files for more information, and also the “Selecting an Initialization Manager” section in the Yocto Project Development Tasks Manual.

INITRAMFS_DEPLOY_DIR_IMAGE 

Indicates the deploy directory used by do_bundle_initramfs where the INITRAMFS_IMAGE will be fetched from. This variable is set by default to ${DEPLOY_DIR_IMAGE} in the kernel class and it’s only meant to be changed when building an Initramfs image from a separate multiconfig via INITRAMFS_MULTICONFIG.

INITRAMFS_FSTYPES 

Defines the format for the output image of an initial RAM filesystem (Initramfs), which is used during boot. Supported formats are the same as those supported by the IMAGE_FSTYPES variable.

The default value of this variable, which is set in the meta/conf/bitbake.conf configuration file in the Source Directory, is “cpio.gz”. The Linux kernel’s Initramfs mechanism, as opposed to the initial RAM filesystem initrd mechanism, expects an optionally compressed cpio archive.

INITRAMFS_IMAGE 

Specifies the PROVIDES name of an image recipe that is used to build an initial RAM filesystem (Initramfs) image. In other words, the INITRAMFS_IMAGE variable causes an additional recipe to be built as a dependency to whatever root filesystem recipe you might be using (e.g. core-image-sato). The Initramfs image recipe you provide should set IMAGE_FSTYPES to INITRAMFS_FSTYPES.

An Initramfs image provides a temporary root filesystem used for early system initialization (e.g. loading of modules needed to locate and mount the “real” root filesystem).

Note

See the meta/recipes-core/images/core-image-minimal-initramfs.bb recipe in the Source Directory for an example Initramfs recipe. To select this sample recipe as the one built to provide the Initramfs image, set INITRAMFS_IMAGE to “core-image-minimal-initramfs”.

You can also find more information by referencing the meta-poky/conf/templates/default/local.conf.sample.extended configuration file in the Source Directory, the image class, and the kernel class to see how to use the INITRAMFS_IMAGE variable.

If INITRAMFS_IMAGE is empty, which is the default, then no Initramfs image is built.

For more information, you can also see the INITRAMFS_IMAGE_BUNDLE variable, which allows the generated image to be bundled inside the kernel image. Additionally, for information on creating an Initramfs image, see the “Building an Initial RAM Filesystem (Initramfs) Image” section in the Yocto Project Development Tasks Manual.

INITRAMFS_IMAGE_BUNDLE 

Controls whether or not the image recipe specified by INITRAMFS_IMAGE is run through an extra pass (do_bundle_initramfs) during kernel compilation in order to build a single binary that contains both the kernel image and the initial RAM filesystem (Initramfs) image. This makes use of the CONFIG_INITRAMFS_SOURCE kernel feature.

Note

Bundling the Initramfs with the kernel conflates the code in the Initramfs with the GPLv2 licensed Linux kernel binary. Thus only GPLv2 compatible software may be part of a bundled Initramfs.

Note

Using an extra compilation pass to bundle the Initramfs avoids a circular dependency between the kernel recipe and the Initramfs recipe should the Initramfs include kernel modules. Should that be the case, the Initramfs recipe depends on the kernel for the kernel modules, and the kernel depends on the Initramfs recipe since the Initramfs is bundled inside the kernel image.

The combined binary is deposited into the tmp/deploy directory, which is part of the Build Directory.

Setting the variable to “1” in a configuration file causes the OpenEmbedded build system to generate a kernel image with the Initramfs specified in INITRAMFS_IMAGE bundled within:

INITRAMFS_IMAGE_BUNDLE = "1"

By default, the kernel class sets this variable to a null string as follows:

INITRAMFS_IMAGE_BUNDLE ?= ""

Note

You must set the INITRAMFS_IMAGE_BUNDLE variable in a configuration file. You cannot set the variable in a recipe file.

See the local.conf.sample.extended file for additional information. Also, for information on creating an Initramfs, see the “Building an Initial RAM Filesystem (Initramfs) Image” section in the Yocto Project Development Tasks Manual.

INITRAMFS_IMAGE_NAME 

This value needs to stay in sync with IMAGE_LINK_NAME, but with INITRAMFS_IMAGE instead of IMAGE_BASENAME. The default value is set as follows:

INITRAMFS_IMAGE_NAME ?= “${@[‘${INITRAMFS_IMAGE}${IMAGE_MACHINE_SUFFIX}’, ‘’][d.getVar(‘INITRAMFS_IMAGE’) == ‘’]}”

That is, if INITRAMFS_IMAGE is set, the value of INITRAMFS_IMAGE_NAME will be set based upon INITRAMFS_IMAGE and IMAGE_MACHINE_SUFFIX.

INITRAMFS_LINK_NAME 

The link name of the initial RAM filesystem image. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

INITRAMFS_LINK_NAME ?= "initramfs-${KERNEL_ARTIFACT_LINK_NAME}"

The value of the KERNEL_ARTIFACT_LINK_NAME variable, which is set in the same file, has the following value:

KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"

See the MACHINE variable for additional information.

INITRAMFS_MULTICONFIG 

Defines the multiconfig to create a multiconfig dependency to be used by the kernel class.

This allows the kernel to bundle an INITRAMFS_IMAGE coming from a separate multiconfig, this is meant to be used in addition to INITRAMFS_DEPLOY_DIR_IMAGE.

For more information on how to bundle an Initramfs image from a separate multiconfig see the “Bundling an Initramfs Image From a Separate Multiconfig” section in the Yocto Project Development Tasks Manual.

INITRAMFS_NAME 

The base name of the initial RAM filesystem image. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

INITRAMFS_NAME ?= "initramfs-${KERNEL_ARTIFACT_NAME}"

See KERNEL_ARTIFACT_NAME for additional information.

INITRD 

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

The INITRD variable is an optional variable used with the image-live class.

INITRD_IMAGE 

When building a “live” bootable image (i.e. when IMAGE_FSTYPES contains “live”), INITRD_IMAGE specifies the image recipe that should be built to provide the initial RAM disk image. The default value is “core-image-minimal-initramfs”.

See the image-live class for more information.

INITSCRIPT_NAME 

The filename of the initialization script as installed to ${sysconfdir}/init.d.

This variable is used in recipes when using update-rc.d. The variable is mandatory.

INITSCRIPT_PACKAGES 

A list of the packages that contain initscripts. If multiple packages are specified, you need to append the package name to the other INITSCRIPT_* as an override.

This variable is used in recipes when using update-rc.d. The variable is optional and defaults to the PN variable.

INITSCRIPT_PARAMS 

Specifies the options to pass to update-rc.d. Here is an example:

INITSCRIPT_PARAMS = "start 99 5 2 . stop 20 0 1 6 ."

In this example, the script has a runlevel of 99, starts the script in initlevels 2 and 5, and stops the script in levels 0, 1 and 6.

The variable’s default value is “defaults”, which is set in the update-rc.d class.

The value in INITSCRIPT_PARAMS is passed through to the update-rc.d command. For more information on valid parameters, please see the update-rc.d manual page at https://manpages.debian.org/buster/init-system-helpers/update-rc.d.8.en.html

INSANE_SKIP 

Specifies the QA checks to skip for a specific package within a recipe. For example, to skip the check for symbolic link .so files in the main package of a recipe, add the following to the recipe. The package name override must be used, which in this example is ${PN}:

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

See the “insane” section for a list of the valid QA checks you can specify using this variable.

INSTALL_TIMEZONE_FILE 

By default, the tzdata recipe packages an /etc/timezone file. Set the INSTALL_TIMEZONE_FILE variable to “0” at the configuration level to disable this behavior.

IPK_FEED_URIS 

When the IPK backend is in use and package management is enabled on the target, you can use this variable to set up opkg in the target image to point to package feeds on a nominated server. Once the feed is established, you can perform installations or upgrades using the package manager at runtime.

KARCH 

Defines the kernel architecture used when assembling the configuration. Architectures supported for this release are:

powerpc
i386
x86_64
arm
qemu
mips

You define the KARCH variable in the BSP Descriptions.

KBRANCH 

A regular expression used by the build process to explicitly identify the kernel branch that is validated, patched, and configured during a build. You must set this variable to ensure the exact kernel branch you want is being used by the build process.

Values for this variable are set in the kernel’s recipe file and the kernel’s append file. For example, if you are using the linux-yocto_4.12 kernel, the kernel recipe file is the meta/recipes-kernel/linux/linux-yocto_4.12.bb file. KBRANCH is set as follows in that kernel recipe file:

KBRANCH ?= "standard/base"

This variable is also used from the kernel’s append file to identify the kernel branch specific to a particular machine or target hardware. Continuing with the previous kernel example, the kernel’s append file (i.e. linux-yocto_4.12.bbappend) is located in the BSP layer for a given machine. For example, the append file for the Beaglebone, EdgeRouter, and generic versions of both 32 and 64-bit IA machines (meta-yocto-bsp) is named meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.12.bbappend. Here are the related statements from that append file:

KBRANCH:genericx86 = "standard/base"
KBRANCH:genericx86-64 = "standard/base"
KBRANCH:edgerouter = "standard/edgerouter"
KBRANCH:beaglebone = "standard/beaglebone"

The KBRANCH statements identify the kernel branch to use when building for each supported BSP.

KBUILD_DEFCONFIG 

When used with the kernel-yocto class, specifies an “in-tree” kernel configuration file for use during a kernel build.

Typically, when using a defconfig to configure a kernel during a build, you place the file in your layer in the same manner as you would place patch files and configuration fragment files (i.e. “out-of-tree”). However, if you want to use a defconfig file that is part of the kernel tree (i.e. “in-tree”), you can use the KBUILD_DEFCONFIG variable and append the KMACHINE variable to point to the defconfig file.

To use the variable, set it in the append file for your kernel recipe using the following form:

KBUILD_DEFCONFIG:<machine> ?= "defconfig_file"

Here is an example from a “raspberrypi2” MACHINE build that uses a defconfig file named “bcm2709_defconfig”:

KBUILD_DEFCONFIG:raspberrypi2 = "bcm2709_defconfig"

As an alternative, you can use the following within your append file:

KBUILD_DEFCONFIG:pn-linux-yocto ?= "defconfig_file"

For more information on how to use the KBUILD_DEFCONFIG variable, see the “Using an “In-Tree” defconfig File” section in the Yocto Project Linux Kernel Development Manual.

KCONFIG_MODE 

When used with the kernel-yocto class, specifies the kernel configuration values to use for options not specified in the provided defconfig file. Valid options are:

KCONFIG_MODE = "alldefconfig"
KCONFIG_MODE = "allnoconfig"

In alldefconfig mode the options not explicitly specified will be assigned their Kconfig default value. In allnoconfig mode the options not explicitly specified will be disabled in the kernel config.

In case KCONFIG_MODE is not set the behaviour will depend on where the defconfig file is coming from. An “in-tree” defconfig file will be handled in alldefconfig mode, a defconfig file placed in ${WORKDIR} through a meta-layer will be handled in allnoconfig mode.

An “in-tree” defconfig file can be selected via the KBUILD_DEFCONFIG variable. KCONFIG_MODE does not need to be explicitly set.

A defconfig file compatible with allnoconfig mode can be generated by copying the .config file from a working Linux kernel build, renaming it to defconfig and placing it into the Linux kernel ${WORKDIR} through your meta-layer. KCONFIG_MODE does not need to be explicitly set.

A defconfig file compatible with alldefconfig mode can be generated using the do_savedefconfig task and placed into the Linux kernel ${WORKDIR} through your meta-layer. Explicitely set KCONFIG_MODE:

KCONFIG_MODE = "alldefconfig"

KERNEL_ALT_IMAGETYPE 

Specifies an alternate kernel image type for creation in addition to the kernel image type specified using the KERNEL_IMAGETYPE and KERNEL_IMAGETYPES variables.

KERNEL_ARTIFACT_NAME 

Specifies the name of all of the build artifacts. You can change the name of the artifacts by changing the KERNEL_ARTIFACT_NAME variable.

The value of KERNEL_ARTIFACT_NAME, which is set in the meta/classes-recipe/kernel-artifact-names.bbclass file, has the following default value:

KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}${IMAGE_MACHINE_SUFFIX}${IMAGE_VERSION_SUFFIX}"

See the PKGE, PKGV, PKGR, IMAGE_MACHINE_SUFFIX and IMAGE_VERSION_SUFFIX variables for additional information.

KERNEL_CLASSES 

A list of classes defining kernel image types that the kernel class should inherit. You typically append this variable to enable extended image types. An example is “kernel-fitimage”, which enables fitImage support and resides in meta/classes-recipe/kernel-fitimage.bbclass. You can register custom kernel image types with the kernel class using this variable.

KERNEL_DANGLING_FEATURES_WARN_ONLY 

When kernel configuration fragments are missing for some KERNEL_FEATURES specified by layers or BSPs, building and configuring the kernel stops with an error.

You can turn these errors into warnings by setting the following in conf/local.conf:

KERNEL_DANGLING_FEATURES_WARN_ONLY = "1"

You will still be warned that runtime issues may occur, but at least the kernel configuration and build process will be allowed to continue.

KERNEL_DEBUG_TIMESTAMPS 

If set to “1”, enables timestamping functionality during building the kernel. The default is “0” to disable this for reproducibility reasons.

KERNEL_DEPLOY_DEPEND 

Provides a means of controlling the dependency of an image recipe on the kernel. The default value is “virtual/kernel:do_deploy”, however for a small initramfs image or other images that do not need the kernel, this can be set to “” in the image recipe.

KERNEL_DEVICETREE 

Specifies the name of the generated Linux kernel device tree (i.e. the .dtb) file.

Note

There is legacy support for specifying the full path to the device tree. However, providing just the .dtb file is preferred.

In order to use this variable, the kernel-devicetree class must be inherited.

KERNEL_DTB_LINK_NAME 

The link name of the kernel device tree binary (DTB). This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

KERNEL_DTB_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"

The value of the KERNEL_ARTIFACT_LINK_NAME variable, which is set in the same file, has the following value:

KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"

See the MACHINE variable for additional information.

KERNEL_DTB_NAME 

The base name of the kernel device tree binary (DTB). This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

KERNEL_DTB_NAME ?= "${KERNEL_ARTIFACT_NAME}"

See KERNEL_ARTIFACT_NAME for additional information.

KERNEL_DTC_FLAGS 

Specifies the dtc flags that are passed to the Linux kernel build system when generating the device trees (via DTC_FLAGS environment variable).

In order to use this variable, the kernel-devicetree class must be inherited.

KERNEL_EXTRA_ARGS 

Specifies additional make command-line arguments the OpenEmbedded build system passes on when compiling the kernel.

KERNEL_FEATURES 

Includes additional kernel metadata. In the OpenEmbedded build system, the default Board Support Packages (BSPs) Metadata is provided through the KMACHINE and KBRANCH variables. You can use the KERNEL_FEATURES variable from within the kernel recipe or kernel append file to further add metadata for all BSPs or specific BSPs.

The metadata you add through this variable includes config fragments and features descriptions, which usually includes patches as well as config fragments. You typically override the KERNEL_FEATURES variable for a specific machine. In this way, you can provide validated, but optional, sets of kernel configurations and features.

For example, the following example from the linux-yocto-rt_4.12 kernel recipe adds “netfilter” and “taskstats” features to all BSPs as well as “virtio” configurations to all QEMU machines. The last two statements add specific configurations to targeted machine types:

KERNEL_EXTRA_FEATURES ?= "features/netfilter/netfilter.scc features/taskstats/taskstats.scc"
KERNEL_FEATURES:append = " ${KERNEL_EXTRA_FEATURES}"
KERNEL_FEATURES:append:qemuall = " cfg/virtio.scc"
KERNEL_FEATURES:append:qemux86 = "  cfg/sound.scc cfg/paravirt_kvm.scc"
KERNEL_FEATURES:append:qemux86-64 = " cfg/sound.scc"

KERNEL_FIT_LINK_NAME 

The link name of the kernel flattened image tree (FIT) image. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

KERNEL_FIT_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"

The value of the KERNEL_ARTIFACT_LINK_NAME variable, which is set in the same file, has the following value:

KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"

See the MACHINE variable for additional information.

KERNEL_FIT_NAME 

The base name of the kernel flattened image tree (FIT) image. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

KERNEL_FIT_NAME ?= "${KERNEL_ARTIFACT_NAME}"

See KERNEL_ARTIFACT_NAME for additional information.

KERNEL_IMAGE_LINK_NAME 

The link name for the kernel image. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

KERNEL_IMAGE_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"

The value of the KERNEL_ARTIFACT_LINK_NAME variable, which is set in the same file, has the following value:

KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"

See the MACHINE variable for additional information.

KERNEL_IMAGE_MAXSIZE 

Specifies the maximum size of the kernel image file in kilobytes. If KERNEL_IMAGE_MAXSIZE is set, the size of the kernel image file is checked against the set value during the do_sizecheck task. The task fails if the kernel image file is larger than the setting.

KERNEL_IMAGE_MAXSIZE is useful for target devices that have a limited amount of space in which the kernel image must be stored.

By default, this variable is not set, which means the size of the kernel image is not checked.

KERNEL_IMAGE_NAME 

The base name of the kernel image. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

KERNEL_IMAGE_NAME ?= "${KERNEL_ARTIFACT_NAME}"

See KERNEL_ARTIFACT_NAME for additional information.

KERNEL_IMAGETYPE 

The type of kernel to build for a device, usually set by the machine configuration files and defaults to “zImage”. This variable is used when building the kernel and is passed to make as the target to build.

To build additional kernel image types, use KERNEL_IMAGETYPES.

KERNEL_IMAGETYPES 

Lists additional types of kernel images to build for a device in addition to image type specified in KERNEL_IMAGETYPE. Usually set by the machine configuration files.

KERNEL_MODULE_AUTOLOAD 

Lists kernel modules that need to be auto-loaded during boot.

Note

This variable replaces the deprecated module_autoload variable.

You can use the KERNEL_MODULE_AUTOLOAD variable anywhere that it can be recognized by the kernel recipe or by an out-of-tree kernel module recipe (e.g. a machine configuration file, a distribution configuration file, an append file for the recipe, or the recipe itself).

Specify it as follows:

KERNEL_MODULE_AUTOLOAD += "module_name1 module_name2 module_name3"

Including KERNEL_MODULE_AUTOLOAD causes the OpenEmbedded build system to populate the /etc/modules-load.d/modname.conf file with the list of modules to be auto-loaded on boot. The modules appear one-per-line in the file. Here is an example of the most common use case:

KERNEL_MODULE_AUTOLOAD += "module_name"

For information on how to populate the modname.conf file with modprobe.d syntax lines, see the KERNEL_MODULE_PROBECONF variable.

KERNEL_MODULE_PROBECONF 

Provides a list of modules for which the OpenEmbedded build system expects to find module_conf_modname values that specify configuration for each of the modules. For information on how to provide those module configurations, see the module_conf_* variable.

KERNEL_PATH 

The location of the kernel sources. This variable is set to the value of the STAGING_KERNEL_DIR within the module class. For information on how this variable is used, see the “Incorporating Out-of-Tree Modules” section in the Yocto Project Linux Kernel Development Manual.

To help maximize compatibility with out-of-tree drivers used to build modules, the OpenEmbedded build system also recognizes and uses the KERNEL_SRC variable, which is identical to the KERNEL_PATH variable. Both variables are common variables used by external Makefiles to point to the kernel source directory.

KERNEL_SRC 

The location of the kernel sources. This variable is set to the value of the STAGING_KERNEL_DIR within the module class. For information on how this variable is used, see the “Incorporating Out-of-Tree Modules” section in the Yocto Project Linux Kernel Development Manual.

To help maximize compatibility with out-of-tree drivers used to build modules, the OpenEmbedded build system also recognizes and uses the KERNEL_PATH variable, which is identical to the KERNEL_SRC variable. Both variables are common variables used by external Makefiles to point to the kernel source directory.

KERNEL_VERSION 

Specifies the version of the kernel as extracted from version.h or utsrelease.h within the kernel sources. Effects of setting this variable do not take effect until the kernel has been configured. Consequently, attempting to refer to this variable in contexts prior to configuration will not work.

KERNELDEPMODDEPEND 

Specifies whether the data referenced through PKGDATA_DIR is needed or not. KERNELDEPMODDEPEND does not control whether or not that data exists, but simply whether or not it is used. If you do not need to use the data, set the KERNELDEPMODDEPEND variable in your Initramfs recipe. Setting the variable there when the data is not needed avoids a potential dependency loop.

KFEATURE_DESCRIPTION 

Provides a short description of a configuration fragment. You use this variable in the .scc file that describes a configuration fragment file. Here is the variable used in a file named smp.scc to describe SMP being enabled:

define KFEATURE_DESCRIPTION "Enable SMP"

KMACHINE 

The machine as known by the kernel. Sometimes the machine name used by the kernel does not match the machine name used by the OpenEmbedded build system. For example, the machine name that the OpenEmbedded build system understands as core2-32-intel-common goes by a different name in the Linux Yocto kernel. The kernel understands that machine as intel-core2-32. For cases like these, the KMACHINE variable maps the kernel machine name to the OpenEmbedded build system machine name.

These mappings between different names occur in the Yocto Linux Kernel’s meta branch. As an example take a look in the common/recipes-kernel/linux/linux-yocto_3.19.bbappend file:

LINUX_VERSION:core2-32-intel-common = "3.19.0"
COMPATIBLE_MACHINE:core2-32-intel-common = "${MACHINE}"
SRCREV_meta:core2-32-intel-common = "8897ef68b30e7426bc1d39895e71fb155d694974"
SRCREV_machine:core2-32-intel-common = "43b9eced9ba8a57add36af07736344dcc383f711"
KMACHINE:core2-32-intel-common = "intel-core2-32"
KBRANCH:core2-32-intel-common = "standard/base"
KERNEL_FEATURES:append:core2-32-intel-common = " ${KERNEL_FEATURES_INTEL_COMMON}"

The KMACHINE statement says that the kernel understands the machine name as “intel-core2-32”. However, the OpenEmbedded build system understands the machine as “core2-32-intel-common”.

KTYPE 

Defines the kernel type to be used in assembling the configuration. The linux-yocto recipes define “standard”, “tiny”, and “preempt-rt” kernel types. See the “Kernel Types” section in the Yocto Project Linux Kernel Development Manual for more information on kernel types.

You define the KTYPE variable in the BSP Descriptions. The value you use must match the value used for the LINUX_KERNEL_TYPE value used by the kernel recipe.

LABELS 

Provides a list of targets for automatic configuration.

See the grub-efi class for more information on how this variable is used.

LAYERDEPENDS 

Lists the layers, separated by spaces, on which this recipe depends. Optionally, you can specify a specific layer version for a dependency by adding it to the end of the layer name. Here is an example:

LAYERDEPENDS_mylayer = "anotherlayer (=3)"

In this previous example, version 3 of “anotherlayer” is compared against LAYERVERSION_anotherlayer.

An error is produced if any dependency is missing or the version numbers (if specified) do not match exactly. This variable is used in the conf/layer.conf file and must be suffixed with the name of the specific layer (e.g. LAYERDEPENDS_mylayer).

LAYERDIR 

When used inside the layer.conf configuration file, this variable provides the path of the current layer. This variable is not available outside of layer.conf and references are expanded immediately when parsing of the file completes.

LAYERDIR_RE 

See LAYERDIR_RE in the BitBake manual.

LAYERRECOMMENDS 

Lists the layers, separated by spaces, recommended for use with this layer.

Optionally, you can specify a specific layer version for a recommendation by adding the version to the end of the layer name. Here is an example:

LAYERRECOMMENDS_mylayer = "anotherlayer (=3)"

In this previous example, version 3 of “anotherlayer” is compared against LAYERVERSION_anotherlayer.

This variable is used in the conf/layer.conf file and must be suffixed with the name of the specific layer (e.g. LAYERRECOMMENDS_mylayer).

LAYERSERIES_COMPAT 

See LAYERSERIES_COMPAT in the BitBake manual.

LAYERVERSION 

Optionally specifies the version of a layer as a single number. You can use this within LAYERDEPENDS for another layer in order to depend on a specific version of the layer. This variable is used in the conf/layer.conf file and must be suffixed with the name of the specific layer (e.g. LAYERVERSION_mylayer).

LD 

The minimal command and arguments used to run the linker.

LDFLAGS 

Specifies the flags to pass to the linker. This variable is exported to an environment variable and thus made visible to the software being built during the compilation step.

Default initialization for LDFLAGS varies depending on what is being built:

TARGET_LDFLAGS when building for the target
BUILD_LDFLAGS when building for the build host (i.e. -native)
BUILDSDK_LDFLAGS when building for an SDK (i.e. nativesdk-)

LEAD_SONAME 

Specifies the lead (or primary) compiled library file (i.e. .so) that the debian class applies its naming policy to given a recipe that packages multiple libraries.

This variable works in conjunction with the debian class.

LIC_FILES_CHKSUM 

Checksums of the license text in the recipe source code.

This variable tracks changes in license text of the source code files. If the license text is changed, it will trigger a build failure, which gives the developer an opportunity to review any license change.

This variable must be defined for all recipes (unless LICENSE is set to “CLOSED”).

For more information, see the “Tracking License Changes” section in the Yocto Project Development Tasks Manual.

LICENSE 

The list of source licenses for the recipe. Follow these rules:

Do not use spaces within individual license names.
Separate license names using | (pipe) when there is a choice between licenses.
Separate license names using & (ampersand) when there are multiple licenses for different parts of the source.
You can use spaces between license names.
For standard licenses, use the names of the files in meta/files/common-licenses/ or the SPDXLICENSEMAP flag names defined in meta/conf/licenses.conf.

Here are some examples:

LICENSE = "LGPL-2.1-only | GPL-3.0-only"
LICENSE = "MPL-1.0 & LGPL-2.1-only"
LICENSE = "GPL-2.0-or-later"

The first example is from the recipes for Qt, which the user may choose to distribute under either the LGPL version 2.1 or GPL version 3. The second example is from Cairo where two licenses cover different parts of the source code. The final example is from sysstat, which presents a single license.

You can also specify licenses on a per-package basis to handle situations where components of the output have different licenses. For example, a piece of software whose code is licensed under GPLv2 but has accompanying documentation licensed under the GNU Free Documentation License 1.2 could be specified as follows:

LICENSE = "GFDL-1.2 & GPL-2.0-only"
LICENSE:${PN} = "GPL-2.0.only"
LICENSE:${PN}-doc = "GFDL-1.2"

LICENSE_CREATE_PACKAGE 

Setting LICENSE_CREATE_PACKAGE to “1” causes the OpenEmbedded build system to create an extra package (i.e. ${PN}-lic) for each recipe and to add those packages to the RRECOMMENDS:${PN}.

The ${PN}-lic package installs a directory in /usr/share/licenses named ${PN}, which is the recipe’s base name, and installs files in that directory that contain license and copyright information (i.e. copies of the appropriate license files from meta/common-licenses that match the licenses specified in the LICENSE variable of the recipe metadata and copies of files marked in LIC_FILES_CHKSUM as containing license text).

For related information on providing license text, see the COPY_LIC_DIRS variable, the COPY_LIC_MANIFEST variable, and the “Providing License Text” section in the Yocto Project Development Tasks Manual.

LICENSE_FLAGS 

Specifies additional flags for a recipe you must allow through LICENSE_FLAGS_ACCEPTED in order for the recipe to be built. When providing multiple flags, separate them with spaces.

This value is independent of LICENSE and is typically used to mark recipes that might require additional licenses in order to be used in a commercial product. For more information, see the “Enabling Commercially Licensed Recipes” section in the Yocto Project Development Tasks Manual.

LICENSE_FLAGS_ACCEPTED 

Lists license flags that when specified in LICENSE_FLAGS within a recipe should not prevent that recipe from being built. For more information, see the “Enabling Commercially Licensed Recipes” section in the Yocto Project Development Tasks Manual.

LICENSE_PATH 

Path to additional licenses used during the build. By default, the OpenEmbedded build system uses COMMON_LICENSE_DIR to define the directory that holds common license text used during the build. The LICENSE_PATH variable allows you to extend that location to other areas that have additional licenses:

LICENSE_PATH += "path-to-additional-common-licenses"

LINUX_KERNEL_TYPE 

Defines the kernel type to be used in assembling the configuration. The linux-yocto recipes define “standard”, “tiny”, and “preempt-rt” kernel types. See the “Kernel Types” section in the Yocto Project Linux Kernel Development Manual for more information on kernel types.

If you do not specify a LINUX_KERNEL_TYPE, it defaults to “standard”. Together with KMACHINE, the LINUX_KERNEL_TYPE variable defines the search arguments used by the kernel tools to find the appropriate description within the kernel Metadata with which to build out the sources and configuration.

LINUX_VERSION 

The Linux version from kernel.org on which the Linux kernel image being built using the OpenEmbedded build system is based. You define this variable in the kernel recipe. For example, the linux-yocto-3.4.bb kernel recipe found in meta/recipes-kernel/linux defines the variables as follows:

LINUX_VERSION ?= "3.4.24"

The LINUX_VERSION variable is used to define PV for the recipe:

PV = "${LINUX_VERSION}+git${SRCPV}"

LINUX_VERSION_EXTENSION 

A string extension compiled into the version string of the Linux kernel built with the OpenEmbedded build system. You define this variable in the kernel recipe. For example, the linux-yocto kernel recipes all define the variable as follows:

LINUX_VERSION_EXTENSION ?= "-yocto-${LINUX_KERNEL_TYPE}"

Defining this variable essentially sets the Linux kernel configuration item CONFIG_LOCALVERSION, which is visible through the uname command. Here is an example that shows the extension assuming it was set as previously shown:

$ uname -r
3.7.0-rc8-custom

LOG_DIR 

Specifies the directory to which the OpenEmbedded build system writes overall log files. The default directory is ${TMPDIR}/log.

For the directory containing logs specific to each task, see the T variable.

MACHINE 

Specifies the target device for which the image is built. You define MACHINE in the local.conf file found in the Build Directory. By default, MACHINE is set to “qemux86”, which is an x86-based architecture machine to be emulated using QEMU:

MACHINE ?= "qemux86"

The variable corresponds to a machine configuration file of the same name, through which machine-specific configurations are set. Thus, when MACHINE is set to “qemux86”, the corresponding qemux86.conf machine configuration file can be found in the Source Directory in meta/conf/machine.

The list of machines supported by the Yocto Project as shipped include the following:

MACHINE ?= "qemuarm"
MACHINE ?= "qemuarm64"
MACHINE ?= "qemumips"
MACHINE ?= "qemumips64"
MACHINE ?= "qemuppc"
MACHINE ?= "qemux86"
MACHINE ?= "qemux86-64"
MACHINE ?= "genericx86"
MACHINE ?= "genericx86-64"
MACHINE ?= "beaglebone"
MACHINE ?= "edgerouter"

The last five are Yocto Project reference hardware boards, which are provided in the meta-yocto-bsp layer.

Note

Adding additional Board Support Package (BSP) layers to your configuration adds new possible settings for MACHINE.

MACHINE_ARCH 

Specifies the name of the machine-specific architecture. This variable is set automatically from MACHINE or TUNE_PKGARCH. You should not hand-edit the MACHINE_ARCH variable.

MACHINE_ESSENTIAL_EXTRA_RDEPENDS 

A list of required machine-specific packages to install as part of the image being built. The build process depends on these packages being present. Furthermore, because this is a “machine-essential” variable, the list of packages are essential for the machine to boot. The impact of this variable affects images based on packagegroup-core-boot, including the core-image-minimal image.

This variable is similar to the MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS variable with the exception that the image being built has a build dependency on the variable’s list of packages. In other words, the image will not build if a file in this list is not found.

As an example, suppose the machine for which you are building requires example-init to be run during boot to initialize the hardware. In this case, you would use the following in the machine’s .conf configuration file:

MACHINE_ESSENTIAL_EXTRA_RDEPENDS += "example-init"

MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS 

A list of recommended machine-specific packages to install as part of the image being built. The build process does not depend on these packages being present. However, because this is a “machine-essential” variable, the list of packages are essential for the machine to boot. The impact of this variable affects images based on packagegroup-core-boot, including the core-image-minimal image.

This variable is similar to the MACHINE_ESSENTIAL_EXTRA_RDEPENDS variable with the exception that the image being built does not have a build dependency on the variable’s list of packages. In other words, the image will still build if a package in this list is not found. Typically, this variable is used to handle essential kernel modules, whose functionality may be selected to be built into the kernel rather than as a module, in which case a package will not be produced.

Consider an example where you have a custom kernel where a specific touchscreen driver is required for the machine to be usable. However, the driver can be built as a module or into the kernel depending on the kernel configuration. If the driver is built as a module, you want it to be installed. But, when the driver is built into the kernel, you still want the build to succeed. This variable sets up a “recommends” relationship so that in the latter case, the build will not fail due to the missing package. To accomplish this, assuming the package for the module was called kernel-module-ab123, you would use the following in the machine’s .conf configuration file:

MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-module-ab123"

Note

In this example, the kernel-module-ab123 recipe needs to explicitly set its PACKAGES variable to ensure that BitBake does not use the kernel recipe’s PACKAGES_DYNAMIC variable to satisfy the dependency.

Some examples of these machine essentials are flash, screen, keyboard, mouse, or touchscreen drivers (depending on the machine).

MACHINE_EXTRA_RDEPENDS 

A list of machine-specific packages to install as part of the image being built that are not essential for the machine to boot. However, the build process for more fully-featured images depends on the packages being present.

This variable affects all images based on packagegroup-base, which does not include the core-image-minimal or core-image-full-cmdline images.

The variable is similar to the MACHINE_EXTRA_RRECOMMENDS variable with the exception that the image being built has a build dependency on the variable’s list of packages. In other words, the image will not build if a file in this list is not found.

An example is a machine that has WiFi capability but is not essential for the machine to boot the image. However, if you are building a more fully-featured image, you want to enable the WiFi. The package containing the firmware for the WiFi hardware is always expected to exist, so it is acceptable for the build process to depend upon finding the package. In this case, assuming the package for the firmware was called wifidriver-firmware, you would use the following in the .conf file for the machine:

MACHINE_EXTRA_RDEPENDS += "wifidriver-firmware"

MACHINE_EXTRA_RRECOMMENDS 

A list of machine-specific packages to install as part of the image being built that are not essential for booting the machine. The image being built has no build dependency on this list of packages.

This variable affects only images based on packagegroup-base, which does not include the core-image-minimal or core-image-full-cmdline images.

This variable is similar to the MACHINE_EXTRA_RDEPENDS variable with the exception that the image being built does not have a build dependency on the variable’s list of packages. In other words, the image will build if a file in this list is not found.

An example is a machine that has WiFi capability but is not essential For the machine to boot the image. However, if you are building a more fully-featured image, you want to enable WiFi. In this case, the package containing the WiFi kernel module will not be produced if the WiFi driver is built into the kernel, in which case you still want the build to succeed instead of failing as a result of the package not being found. To accomplish this, assuming the package for the module was called kernel-module-examplewifi, you would use the following in the .conf file for the machine:

MACHINE_EXTRA_RRECOMMENDS += "kernel-module-examplewifi"

MACHINE_FEATURES 

Specifies the list of hardware features the MACHINE is capable of supporting. For related information on enabling features, see the DISTRO_FEATURES, COMBINED_FEATURES, and IMAGE_FEATURES variables.

For a list of hardware features supported by the Yocto Project as shipped, see the “Machine Features” section.

MACHINE_FEATURES_BACKFILL 

A list of space-separated features to be added to MACHINE_FEATURES if not also present in MACHINE_FEATURES_BACKFILL_CONSIDERED.

This variable is set in the meta/conf/bitbake.conf file. It is not intended to be user-configurable. It is best to just reference the variable to see which machine features are being backfilled for all machine configurations.

MACHINE_FEATURES_BACKFILL_CONSIDERED 

A list of space-separated features from MACHINE_FEATURES_BACKFILL that should not be backfilled (i.e. added to MACHINE_FEATURES) during the build.

This corresponds to an opt-out mechanism. When new default machine features are introduced, machine definition maintainers can review (consider) them and decide to exclude them from the backfilled features. Therefore, the combination of MACHINE_FEATURES_BACKFILL and MACHINE_FEATURES_BACKFILL_CONSIDERED makes it possible to add new default features without breaking existing machine definitions.

MACHINEOVERRIDES 

A colon-separated list of overrides that apply to the current machine. By default, this list includes the value of MACHINE.

You can extend MACHINEOVERRIDES to add extra overrides that should apply to a machine. For example, all machines emulated in QEMU (e.g. qemuarm, qemux86, and so forth) include a file named meta/conf/machine/include/qemu.inc that prepends the following override to MACHINEOVERRIDES:

MACHINEOVERRIDES =. "qemuall:"

This override allows variables to be overridden for all machines emulated in QEMU, like in the following example from the connman-conf recipe:

SRC_URI:append:qemuall = " file://wired.config \
    file://wired-setup \
    "

The underlying mechanism behind MACHINEOVERRIDES is simply that it is included in the default value of OVERRIDES.

MAINTAINER 

The email address of the distribution maintainer.

MESON_BUILDTYPE 

Value of the Meson --buildtype argument used by the meson class. It defaults to debug if DEBUG_BUILD is set to “1”, and plain otherwise.

See Meson build options for the values you could set in a recipe. Values such as plain, debug, debugoptimized, release and minsize allow you to specify the inclusion of debugging symbols and the compiler optimizations (none, performance or size).

METADATA_BRANCH 

The branch currently checked out for the OpenEmbedded-Core layer (path determined by COREBASE).

METADATA_REVISION 

The revision currently checked out for the OpenEmbedded-Core layer (path determined by COREBASE).

MIME_XDG_PACKAGES 

The current implementation of the mime-xdg class cannot detect .desktop files installed through absolute symbolic links. Use this setting to make the class create post-install and post-remove scripts for these packages anyway, to invoke the update-destop-database command.

MIRRORS 

Specifies additional paths from which the OpenEmbedded build system gets source code. When the build system searches for source code, it first tries the local download directory. If that location fails, the build system tries locations defined by PREMIRRORS, the upstream source, and then locations specified by MIRRORS in that order.

Assuming your distribution (DISTRO) is “poky”, the default value for MIRRORS is defined in the conf/distro/poky.conf file in the meta-poky Git repository.

MLPREFIX 

Specifies a prefix has been added to PN to create a special version of a recipe or package (i.e. a Multilib version). The variable is used in places where the prefix needs to be added to or removed from a name (e.g. the BPN variable). MLPREFIX gets set when a prefix has been added to PN.

Note

The “ML” in MLPREFIX stands for “MultiLib”. This representation is historical and comes from a time when “nativesdk” was a suffix rather than a prefix on the recipe name. When “nativesdk” was turned into a prefix, it made sense to set MLPREFIX for it as well.

To help understand when MLPREFIX might be needed, consider when BBCLASSEXTEND is used to provide a nativesdk version of a recipe in addition to the target version. If that recipe declares build-time dependencies on tasks in other recipes by using DEPENDS, then a dependency on “foo” will automatically get rewritten to a dependency on “nativesdk-foo”. However, dependencies like the following will not get rewritten automatically:

do_foo[depends] += "recipe:do_foo"

If you want such a dependency to also get transformed, you can do the following:

do_foo[depends] += "${MLPREFIX}recipe:do_foo"

module_autoload 

This variable has been replaced by the KERNEL_MODULE_AUTOLOAD variable. You should replace all occurrences of module_autoload with additions to KERNEL_MODULE_AUTOLOAD, for example:

module_autoload_rfcomm = "rfcomm"

should now be replaced with:

KERNEL_MODULE_AUTOLOAD += "rfcomm"

See the KERNEL_MODULE_AUTOLOAD variable for more information.

module_conf 

Specifies modprobe.d syntax lines for inclusion in the /etc/modprobe.d/modname.conf file.

You can use this variable anywhere that it can be recognized by the kernel recipe or out-of-tree kernel module recipe (e.g. a machine configuration file, a distribution configuration file, an append file for the recipe, or the recipe itself). If you use this variable, you must also be sure to list the module name in the KERNEL_MODULE_PROBECONF variable.

Here is the general syntax:

module_conf_module_name = "modprobe.d-syntax"

You must use the kernel module name override.

Run man modprobe.d in the shell to find out more information on the exact syntax you want to provide with module_conf.

Including module_conf causes the OpenEmbedded build system to populate the /etc/modprobe.d/modname.conf file with modprobe.d syntax lines. Here is an example that adds the options arg1 and arg2 to a module named mymodule:

module_conf_mymodule = "options mymodule arg1=val1 arg2=val2"

For information on how to specify kernel modules to auto-load on boot, see the KERNEL_MODULE_AUTOLOAD variable.

MODULE_TARBALL_DEPLOY 

Controls creation of the modules-*.tgz file. Set this variable to “0” to disable creation of this file, which contains all of the kernel modules resulting from a kernel build.

MODULE_TARBALL_LINK_NAME 

The link name of the kernel module tarball. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

MODULE_TARBALL_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"

The value of the KERNEL_ARTIFACT_LINK_NAME variable, which is set in the same file, has the following value:

KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"

See the MACHINE variable for additional information.

MODULE_TARBALL_NAME 

The base name of the kernel module tarball. This variable is set in the meta/classes-recipe/kernel-artifact-names.bbclass file as follows:

MODULE_TARBALL_NAME ?= "${KERNEL_ARTIFACT_NAME}"

See KERNEL_ARTIFACT_NAME for additional information.

MOUNT_BASE 

On non-systemd systems (where udev-extraconf is being used), specifies the base directory for auto-mounting filesystems. The default value is “/run/media”.

MULTIMACH_TARGET_SYS 

Uniquely identifies the type of the target system for which packages are being built. This variable allows output for different types of target systems to be put into different subdirectories of the same output directory.

The default value of this variable is:

${PACKAGE_ARCH}${TARGET_VENDOR}-${TARGET_OS}

Some classes (e.g. cross-canadian) modify the MULTIMACH_TARGET_SYS value.

See the STAMP variable for an example. See the STAGING_DIR_TARGET variable for more information.

NATIVELSBSTRING 

A string identifying the host distribution. Strings consist of the host distributor ID followed by the release, as reported by the lsb_release tool or as read from /etc/lsb-release. For example, when running a build on Ubuntu 12.10, the value is “Ubuntu-12.10”. If this information is unable to be determined, the value resolves to “Unknown”.

This variable is used by default to isolate native shared state packages for different distributions (e.g. to avoid problems with glibc version incompatibilities). Additionally, the variable is checked against SANITY_TESTED_DISTROS if that variable is set.

NM 

The minimal command and arguments to run nm.

NO_GENERIC_LICENSE 

Avoids QA errors when you use a non-common, non-CLOSED license in a recipe. There are packages, such as the linux-firmware package, with many licenses that are not in any way common. Also, new licenses are added occasionally to avoid introducing a lot of common license files, which are only applicable to a specific package. NO_GENERIC_LICENSE is used to allow copying a license that does not exist in common licenses.

The following example shows how to add NO_GENERIC_LICENSE to a recipe:

NO_GENERIC_LICENSE[license_name] = "license_file_in_fetched_source"

Here is an example that uses the LICENSE.Abilis.txt file as the license from the fetched source:

NO_GENERIC_LICENSE[Firmware-Abilis] = "LICENSE.Abilis.txt"

NO_RECOMMENDATIONS 

Prevents installation of all “recommended-only” packages. Recommended-only packages are packages installed only through the RRECOMMENDS variable). Setting the NO_RECOMMENDATIONS variable to “1” turns this feature on:

NO_RECOMMENDATIONS = "1"

You can set this variable globally in your local.conf file or you can attach it to a specific image recipe by using the recipe name override:

NO_RECOMMENDATIONS:pn-target_image = "1"

It is important to realize that if you choose to not install packages using this variable and some other packages are dependent on them (i.e. listed in a recipe’s RDEPENDS variable), the OpenEmbedded build system ignores your request and will install the packages to avoid dependency errors.

Note

Some recommended packages might be required for certain system functionality, such as kernel modules. It is up to you to add packages with the IMAGE_INSTALL variable.

This variable is only supported when using the IPK and RPM packaging backends. DEB is not supported.

See the BAD_RECOMMENDATIONS and the PACKAGE_EXCLUDE variables for related information.

NOAUTOPACKAGEDEBUG 

Disables auto package from splitting .debug files. If a recipe requires FILES:${PN}-dbg to be set manually, the NOAUTOPACKAGEDEBUG can be defined allowing you to define the content of the debug package. For example:

NOAUTOPACKAGEDEBUG = "1"
FILES:${PN}-dev = "${includedir}/${QT_DIR_NAME}/Qt/*"
FILES:${PN}-dbg = "/usr/src/debug/"
FILES:${QT_BASE_NAME}-demos-doc = "${docdir}/${QT_DIR_NAME}/qch/qt.qch"

NON_MULTILIB_RECIPES 

A list of recipes that should not be built for multilib. OE-Core’s multilib.conf file defines a reasonable starting point for this list with:

NON_MULTILIB_RECIPES = "grub grub-efi make-mod-scripts ovmf u-boot"

OBJCOPY 

The minimal command and arguments to run objcopy.

OBJDUMP 

The minimal command and arguments to run objdump.

OE_BINCONFIG_EXTRA_MANGLE 

When inheriting the binconfig class, this variable specifies additional arguments passed to the “sed” command. The sed command alters any paths in configuration scripts that have been set up during compilation. 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 will use the correct directories for the cross compiling layout.

See the meta/classes-recipe/binconfig.bbclass in the Source Directory for details on how this class applies these additional sed command arguments.

OE_IMPORTS 

An internal variable used to tell the OpenEmbedded build system what Python modules to import for every Python function run by the system.

Note

Do not set this variable. It is for internal use only.

OE_INIT_ENV_SCRIPT 

The name of the build environment setup script for the purposes of setting up the environment within the extensible SDK. The default value is “oe-init-build-env”.

If you use a custom script to set up your build environment, set the OE_INIT_ENV_SCRIPT variable to its name.

OE_TERMINAL 

Controls how the OpenEmbedded build system spawns interactive terminals on the host development system (e.g. using the BitBake command with the -c devshell command-line option). For more information, see the “Using a Development Shell” section in the Yocto Project Development Tasks Manual.

You can use the following values for the OE_TERMINAL variable:

auto
gnome
xfce
rxvt
screen
konsole
none

OECMAKE_GENERATOR 

A variable for the cmake class, allowing to choose which back-end will be generated by CMake to build an application.

By default, this variable is set to Ninja, which is faster than GNU make, but if building is broken with Ninja, a recipe can use this variable to use GNU make instead:

OECMAKE_GENERATOR = "Unix Makefiles"

OEROOT 

The directory from which the top-level build environment setup script is sourced. The Yocto Project provides a top-level build environment setup script: oe-init-build-env. When you run this script, the OEROOT variable resolves to the directory that contains the script.

For additional information on how this variable is used, see the initialization script.

OLDEST_KERNEL 

Declares the oldest version of the Linux kernel that the produced binaries must support. This variable is passed into the build of the Embedded GNU C Library (glibc).

The default for this variable comes from the meta/conf/bitbake.conf configuration file. You can override this default by setting the variable in a custom distribution configuration file.

OVERLAYFS_ETC_DEVICE 

When the overlayfs-etc class is inherited, specifies the device to be mounted for the read/write layer of /etc. There is no default, so you must set this if you wish to enable overlayfs-etc, for example, assuming /dev/mmcblk0p2 was the desired device:

OVERLAYFS_ETC_DEVICE = "/dev/mmcblk0p2"

OVERLAYFS_ETC_EXPOSE_LOWER 

When the overlayfs-etc class is inherited, if set to “1” then a read-only access to the original /etc content will be provided as a lower/ subdirectory of OVERLAYFS_ETC_MOUNT_POINT. The default value is “0”.

OVERLAYFS_ETC_FSTYPE 

When the overlayfs-etc class is inherited, specifies the file system type for the read/write layer of /etc. There is no default, so you must set this if you wish to enable overlayfs-etc, for example, assuming the file system is ext4:

OVERLAYFS_ETC_FSTYPE = "ext4"

OVERLAYFS_ETC_MOUNT_OPTIONS 

When the overlayfs-etc class is inherited, specifies the mount options for the read-write layer. The default value is “defaults”.

OVERLAYFS_ETC_MOUNT_POINT 

When the overlayfs-etc class is inherited, specifies the parent mount path for the filesystem layers. There is no default, so you must set this if you wish to enable overlayfs-etc, for example if the desired path is “/data”:

OVERLAYFS_ETC_MOUNT_POINT = "/data"

OVERLAYFS_ETC_USE_ORIG_INIT_NAME 

When the overlayfs-etc class is inherited, controls how the generated init will be named. For more information, see the overlayfs-etc class documentation. The default value is “1”.

OVERLAYFS_MOUNT_POINT 

When inheriting the overlayfs class, specifies mount point(s) to be used. For example:

OVERLAYFS_MOUNT_POINT[data] = "/data"

The assumes you have a data.mount systemd unit defined elsewhere in your BSP (e.g. in systemd-machine-units recipe) and it is installed into the image. For more information see overlayfs.

Note

Although the overlayfs class is inherited by individual recipes, OVERLAYFS_MOUNT_POINT should be set in your machine configuration.

OVERLAYFS_QA_SKIP 

When inheriting the overlayfs class, provides the ability to disable QA checks for particular overlayfs mounts. For example:

OVERLAYFS_QA_SKIP[data] = "mount-configured"

Note

Although the overlayfs class is inherited by individual recipes, OVERLAYFS_QA_SKIP should be set in your machine configuration.

OVERLAYFS_WRITABLE_PATHS 

When inheriting the overlayfs class, specifies writable paths used at runtime for the recipe. For example:

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

OVERRIDES 

A colon-separated list of overrides that currently apply. Overrides are a BitBake mechanism that allows variables to be selectively overridden at the end of parsing. The set of overrides in OVERRIDES represents the “state” during building, which includes the current recipe being built, the machine for which it is being built, and so forth.

As an example, if the string “an-override” appears as an element in the colon-separated list in OVERRIDES, then the following assignment will override FOO with the value “overridden” at the end of parsing:

FOO:an-override = "overridden"

See the “Conditional Syntax (Overrides)” section in the BitBake User Manual for more information on the overrides mechanism.

The default value of OVERRIDES includes the values of the CLASSOVERRIDE, MACHINEOVERRIDES, and DISTROOVERRIDES variables. Another important override included by default is pn-${PN}. This override allows variables to be set for a single recipe within configuration (.conf) files. Here is an example:

FOO:pn-myrecipe = "myrecipe-specific value"

Note

An easy way to see what overrides apply is to search for OVERRIDES in the output of the bitbake -e command. See the “Viewing Variable Values” section in the Yocto Project Development Tasks Manual for more information.

P 

The recipe name and version. P is comprised of the following:

${PN}-${PV}

P4DIR 

See P4DIR in the BitBake manual.

PACKAGE_ADD_METADATA 

This variable defines additional metadata to add to packages.

You may find you need to inject additional metadata into packages. This variable allows you to do that by setting the injected data as the value. Multiple fields can be added by splitting the content with the literal separator “n”.

The suffixes ‘_IPK’, ‘_DEB’, or ‘_RPM’ can be applied to the variable to do package type specific settings. It can also be made package specific by using the package name as a suffix.

You can find out more about applying this variable in the “Adding custom metadata to packages” section in the Yocto Project Development Tasks Manual.

PACKAGE_ARCH 

The architecture of the resulting package or packages.

By default, the value of this variable is set to TUNE_PKGARCH when building for the target, BUILD_ARCH when building for the build host, and “${SDK_ARCH}-${SDKPKGSUFFIX}” when building for the SDK.

Note

See SDK_ARCH for more information.

However, if your recipe’s output packages are built specific to the target machine rather than generally for the architecture of the machine, you should set PACKAGE_ARCH to the value of MACHINE_ARCH in the recipe as follows:

PACKAGE_ARCH = "${MACHINE_ARCH}"

PACKAGE_ARCHS 

Specifies a list of architectures compatible with the target machine. This variable is set automatically and should not normally be hand-edited. Entries are separated using spaces and listed in order of priority. The default value for PACKAGE_ARCHS is “all any noarch ${PACKAGE_EXTRA_ARCHS} ${MACHINE_ARCH}”.

PACKAGE_BEFORE_PN 

Enables easily adding packages to PACKAGES before ${PN} so that those added packages can pick up files that would normally be included in the default package.

PACKAGE_CLASSES 

This variable, which is set in the local.conf configuration file found in the conf folder of the Build Directory, specifies the package manager the OpenEmbedded build system uses when packaging data.

You can provide one or more of the following arguments for the variable:

PACKAGE_CLASSES ?= "package_rpm package_deb package_ipk"

The build system uses only the first argument in the list as the package manager when creating your image or SDK. However, packages will be created using any additional packaging classes you specify. For example, if you use the following in your local.conf file:

PACKAGE_CLASSES ?= "package_ipk"

The OpenEmbedded build system uses the IPK package manager to create your image or SDK.

For information on packaging and build performance effects as a result of the package manager in use, see the “package” section.

PACKAGE_DEBUG_SPLIT_STYLE 

Determines how to split up and package debug and source information when creating debugging packages to be used with the GNU Project Debugger (GDB). In general, based on the value of this variable, you can combine the source and debug info in a single package, you can break out the source into a separate package that can be installed independently, or you can choose to not have the source packaged at all.

The possible values of PACKAGE_DEBUG_SPLIT_STYLE variable:

“.debug”: All debugging and source info is placed in a single *-dbg package; debug symbol files are placed next to the binary in a .debug directory so that, if a binary is installed into /bin, the corresponding debug symbol file is installed in /bin/.debug. Source files are installed in the same *-dbg package under /usr/src/debug.
“debug-file-directory”: As above, all debugging and source info is placed in a single *-dbg package; debug symbol files are placed entirely under the directory /usr/lib/debug and separated by the path from where the binary is installed, so that if a binary is installed in /bin, the corresponding debug symbols are installed in /usr/lib/debug/bin, and so on. As above, source is installed in the same package under /usr/src/debug.
“debug-with-srcpkg”: Debugging info is placed in the standard *-dbg package as with the .debug value, while source is placed in a separate *-src package, which can be installed independently. This is the default setting for this variable, as defined in Poky’s bitbake.conf file.
“debug-without-src”: The same behavior as with the .debug setting, but no source is packaged at all.

Note

Much of the above package splitting can be overridden via use of the INHIBIT_PACKAGE_DEBUG_SPLIT variable.

You can find out more about debugging using GDB by reading the “Debugging With the GNU Project Debugger (GDB) Remotely” section in the Yocto Project Development Tasks Manual.

PACKAGE_EXCLUDE 

Lists packages that should not be installed into an image. For example:

PACKAGE_EXCLUDE = "package_name package_name package_name ..."

You can set this variable globally in your local.conf file or you can attach it to a specific image recipe by using the recipe name override:

PACKAGE_EXCLUDE:pn-target_image = "package_name"

If you choose to not install a package using this variable and some other package is dependent on it (i.e. listed in a recipe’s RDEPENDS variable), the OpenEmbedded build system generates a fatal installation error. Because the build system halts the process with a fatal error, you can use the variable with an iterative development process to remove specific components from a system.

This variable is supported only when using the IPK and RPM packaging backends. DEB is not supported.

See the NO_RECOMMENDATIONS and the BAD_RECOMMENDATIONS variables for related information.

PACKAGE_EXCLUDE_COMPLEMENTARY 

Prevents specific packages from being installed when you are installing complementary packages.

You might find that you want to prevent installing certain packages when you are installing complementary packages. For example, if you are using IMAGE_FEATURES to install dev-pkgs, you might not want to install all packages from a particular multilib. If you find yourself in this situation, you can use the PACKAGE_EXCLUDE_COMPLEMENTARY variable to specify regular expressions to match the packages you want to exclude.

PACKAGE_EXTRA_ARCHS 

Specifies the list of architectures compatible with the device CPU. This variable is useful when you build for several different devices that use miscellaneous processors such as XScale and ARM926-EJS.

PACKAGE_FEED_ARCHS 

Optionally specifies the package architectures used as part of the package feed URIs during the build. When used, the PACKAGE_FEED_ARCHS variable is appended to the final package feed URI, which is constructed using the PACKAGE_FEED_URIS and PACKAGE_FEED_BASE_PATHS variables.

Note

You can use the PACKAGE_FEED_ARCHS variable to allow specific package architectures. If you do not need to allow specific architectures, which is a common case, you can omit this variable. Omitting the variable results in all available architectures for the current machine being included into remote package feeds.

Consider the following example where the PACKAGE_FEED_URIS, PACKAGE_FEED_BASE_PATHS, and PACKAGE_FEED_ARCHS variables are defined in your local.conf file:

PACKAGE_FEED_URIS = "https://example.com/packagerepos/release \
                     https://example.com/packagerepos/updates"
PACKAGE_FEED_BASE_PATHS = "rpm rpm-dev"
PACKAGE_FEED_ARCHS = "all core2-64"

Given these settings, the resulting package feeds are as follows:

https://example.com/packagerepos/release/rpm/all
https://example.com/packagerepos/release/rpm/core2-64
https://example.com/packagerepos/release/rpm-dev/all
https://example.com/packagerepos/release/rpm-dev/core2-64
https://example.com/packagerepos/updates/rpm/all
https://example.com/packagerepos/updates/rpm/core2-64
https://example.com/packagerepos/updates/rpm-dev/all
https://example.com/packagerepos/updates/rpm-dev/core2-64

PACKAGE_FEED_BASE_PATHS 

Specifies the base path used when constructing package feed URIs. The PACKAGE_FEED_BASE_PATHS variable makes up the middle portion of a package feed URI used by the OpenEmbedded build system. The base path lies between the PACKAGE_FEED_URIS and PACKAGE_FEED_ARCHS variables.

Consider the following example where the PACKAGE_FEED_URIS, PACKAGE_FEED_BASE_PATHS, and PACKAGE_FEED_ARCHS variables are defined in your local.conf file:

PACKAGE_FEED_URIS = "https://example.com/packagerepos/release \
                     https://example.com/packagerepos/updates"
PACKAGE_FEED_BASE_PATHS = "rpm rpm-dev"
PACKAGE_FEED_ARCHS = "all core2-64"

Given these settings, the resulting package feeds are as follows:

https://example.com/packagerepos/release/rpm/all
https://example.com/packagerepos/release/rpm/core2-64
https://example.com/packagerepos/release/rpm-dev/all
https://example.com/packagerepos/release/rpm-dev/core2-64
https://example.com/packagerepos/updates/rpm/all
https://example.com/packagerepos/updates/rpm/core2-64
https://example.com/packagerepos/updates/rpm-dev/all
https://example.com/packagerepos/updates/rpm-dev/core2-64

PACKAGE_FEED_URIS 

Specifies the front portion of the package feed URI used by the OpenEmbedded build system. Each final package feed URI is comprised of PACKAGE_FEED_URIS, PACKAGE_FEED_BASE_PATHS, and PACKAGE_FEED_ARCHS variables.

Consider the following example where the PACKAGE_FEED_URIS, PACKAGE_FEED_BASE_PATHS, and PACKAGE_FEED_ARCHS variables are defined in your local.conf file:

PACKAGE_FEED_URIS = "https://example.com/packagerepos/release \
                     https://example.com/packagerepos/updates"
PACKAGE_FEED_BASE_PATHS = "rpm rpm-dev"
PACKAGE_FEED_ARCHS = "all core2-64"

Given these settings, the resulting package feeds are as follows:

https://example.com/packagerepos/release/rpm/all
https://example.com/packagerepos/release/rpm/core2-64
https://example.com/packagerepos/release/rpm-dev/all
https://example.com/packagerepos/release/rpm-dev/core2-64
https://example.com/packagerepos/updates/rpm/all
https://example.com/packagerepos/updates/rpm/core2-64
https://example.com/packagerepos/updates/rpm-dev/all
https://example.com/packagerepos/updates/rpm-dev/core2-64

PACKAGE_INSTALL 

The final list of packages passed to the package manager for installation into the image.

Because the package manager controls actual installation of all packages, the list of packages passed using PACKAGE_INSTALL is not the final list of packages that are actually installed. This variable is internal to the image construction code. Consequently, in general, you should use the IMAGE_INSTALL variable to specify packages for installation. The exception to this is when working with the core-image-minimal-initramfs image. When working with an initial RAM filesystem (Initramfs) image, use the PACKAGE_INSTALL variable. For information on creating an Initramfs, see the “Building an Initial RAM Filesystem (Initramfs) Image” section in the Yocto Project Development Tasks Manual.

PACKAGE_INSTALL_ATTEMPTONLY 

Specifies a list of packages the OpenEmbedded build system attempts to install when creating an image. If a listed package fails to install, the build system does not generate an error. This variable is generally not user-defined.

PACKAGE_PREPROCESS_FUNCS 

Specifies a list of functions run to pre-process the PKGD directory prior to splitting the files out to individual packages.

PACKAGE_WRITE_DEPS 

Specifies a list of dependencies for post-installation and pre-installation scripts on native/cross tools. If your post-installation or pre-installation script can execute at root filesystem creation time rather than on the target but depends on a native tool in order to execute, you need to list the tools in PACKAGE_WRITE_DEPS.

For information on running post-installation scripts, see the “Post-Installation Scripts” section in the Yocto Project Development Tasks Manual.

PACKAGECONFIG 

This variable provides a means of enabling or disabling features of a recipe on a per-recipe basis. PACKAGECONFIG blocks are defined in recipes when you specify features and then arguments that define feature behaviors. Here is the basic block structure (broken over multiple lines for readability):

PACKAGECONFIG ??= "f1 f2 f3 ..."
PACKAGECONFIG[f1] = "\
    --with-f1, \
    --without-f1, \
    build-deps-for-f1, \
    runtime-deps-for-f1, \
    runtime-recommends-for-f1, \
    packageconfig-conflicts-for-f1"
PACKAGECONFIG[f2] = "\
     ... and so on and so on ...

The PACKAGECONFIG variable itself specifies a space-separated list of the features to enable. Following the features, you can determine the behavior of each feature by providing up to six order-dependent arguments, which are separated by commas. You can omit any argument you like but must retain the separating commas. The order is important and specifies the following:

Extra arguments that should be added to the configure script argument list (EXTRA_OECONF or PACKAGECONFIG_CONFARGS) if the feature is enabled.
Extra arguments that should be added to EXTRA_OECONF or PACKAGECONFIG_CONFARGS if the feature is disabled.
Additional build dependencies (DEPENDS) that should be added if the feature is enabled.
Additional runtime dependencies (RDEPENDS) that should be added if the feature is enabled.
Additional runtime recommendations (RRECOMMENDS) that should be added if the feature is enabled.
Any conflicting (that is, mutually exclusive) PACKAGECONFIG settings for this feature.

Consider the following PACKAGECONFIG block taken from the librsvg recipe. In this example the feature is gtk, which has three arguments that determine the feature’s behavior:

PACKAGECONFIG[gtk] = "--with-gtk3,--without-gtk3,gtk+3"

The --with-gtk3 and gtk+3 arguments apply only if the feature is enabled. In this case, --with-gtk3 is added to the configure script argument list and gtk+3 is added to DEPENDS. On the other hand, if the feature is disabled say through a .bbappend file in another layer, then the second argument --without-gtk3 is added to the configure script instead.

The basic PACKAGECONFIG structure previously described holds true regardless of whether you are creating a block or changing a block. When creating a block, use the structure inside your recipe.

If you want to change an existing PACKAGECONFIG block, you can do so one of two ways:

Append file: Create an append file named recipename.bbappend in your layer and override the value of PACKAGECONFIG. You can either completely override the variable:
```
PACKAGECONFIG = "f4 f5"
```
Or, you can just append the variable:
```
PACKAGECONFIG:append = " f4"
```
Configuration file: This method is identical to changing the block through an append file except you edit your local.conf or mydistro.conf file. As with append files previously described, you can either completely override the variable:
```
PACKAGECONFIG:pn-recipename = "f4 f5"
```
Or, you can just amend the variable:
```
PACKAGECONFIG:append:pn-recipename = " f4"
```

PACKAGECONFIG_CONFARGS 

A space-separated list of configuration options generated from the PACKAGECONFIG setting.

Classes such as autotools* and cmake use PACKAGECONFIG_CONFARGS to pass PACKAGECONFIG options to configure and cmake, respectively. If you are using PACKAGECONFIG but not a class that handles the do_configure task, then you need to use PACKAGECONFIG_CONFARGS appropriately.

PACKAGEGROUP_DISABLE_COMPLEMENTARY 

For recipes inheriting the packagegroup class, setting PACKAGEGROUP_DISABLE_COMPLEMENTARY to “1” specifies that the normal complementary packages (i.e. -dev, -dbg, and so forth) should not be automatically created by the packagegroup recipe, which is the default behavior.

PACKAGES 

The list of packages the recipe creates. The default value is the following:

${PN}-src ${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKAGE_BEFORE_PN} ${PN}

During packaging, the do_package task goes through PACKAGES and uses the FILES variable corresponding to each package to assign files to the package. If a file matches the FILES variable for more than one package in PACKAGES, it will be assigned to the earliest (leftmost) package.

Packages in the variable’s list that are empty (i.e. where none of the patterns in FILES:pkg match any files installed by the do_install task) are not generated, unless generation is forced through the ALLOW_EMPTY variable.

PACKAGES_DYNAMIC 

A promise that your recipe satisfies runtime dependencies for optional modules that are found in other recipes. PACKAGES_DYNAMIC does not actually satisfy the dependencies, it only states that they should be satisfied. For example, if a hard, runtime dependency (RDEPENDS) of another package is satisfied at build time through the PACKAGES_DYNAMIC variable, but a package with the module name is never actually produced, then the other package will be broken. Thus, if you attempt to include that package in an image, you will get a dependency failure from the packaging system during the do_rootfs task.

Typically, if there is a chance that such a situation can occur and the package that is not created is valid without the dependency being satisfied, then you should use RRECOMMENDS (a soft runtime dependency) instead of RDEPENDS.

For an example of how to use the PACKAGES_DYNAMIC variable when you are splitting packages, see the “Handling Optional Module Packaging” section in the Yocto Project Development Tasks Manual.

PACKAGESPLITFUNCS 

Specifies a list of functions run to perform additional splitting of files into individual packages. Recipes can either prepend to this variable or prepend to the populate_packages function in order to perform additional package splitting. In either case, the function should set PACKAGES, FILES, RDEPENDS and other packaging variables appropriately in order to perform the desired splitting.

PARALLEL_MAKE 

Extra options passed to the build tool command (make, ninja or more specific build engines, like the Go language one) during the do_compile task, to specify parallel compilation on the local build host. This variable is usually in the form “-j x”, where x represents the maximum number of parallel threads such engines can run.

Note

For software compiled by make, in order for PARALLEL_MAKE to be effective, make must be called with ${EXTRA_OEMAKE}. An easy way to ensure this is to use the oe_runmake function.

By default, the OpenEmbedded build system automatically sets this variable to be equal to the number of cores the build system uses.

Note

If the software being built experiences dependency issues during the do_compile task that result in race conditions, you can clear the PARALLEL_MAKE variable within the recipe as a workaround. For information on addressing race conditions, see the “Debugging Parallel Make Races” section in the Yocto Project Development Tasks Manual.

For single socket systems (i.e. one CPU), you should not have to override this variable to gain optimal parallelism during builds. However, if you have very large systems that employ multiple physical CPUs, you might want to make sure the PARALLEL_MAKE variable is not set higher than “-j 20”.

For more information on speeding up builds, see the “Speeding Up a Build” section in the Yocto Project Development Tasks Manual.

PARALLEL_MAKEINST 

Extra options passed to the build tool install command (make install, ninja install or more specific ones) during the do_install task in order to specify parallel installation. This variable defaults to the value of PARALLEL_MAKE.

Note

For software compiled by make, in order for PARALLEL_MAKEINST to be effective, make must be called with ${EXTRA_OEMAKE}. An easy way to ensure this is to use the oe_runmake function.

If the software being built experiences dependency issues during the do_install task that result in race conditions, you can clear the PARALLEL_MAKEINST variable within the recipe as a workaround. For information on addressing race conditions, see the “Debugging Parallel Make Races” section in the Yocto Project Development Tasks Manual.

PATCHRESOLVE 

Determines the action to take when a patch fails. You can set this variable to one of two values: “noop” and “user”.

The default value of “noop” causes the build to simply fail when the OpenEmbedded build system cannot successfully apply a patch. Setting the value to “user” causes the build system to launch a shell and places you in the right location so that you can manually resolve the conflicts.

Set this variable in your local.conf file.

PATCHTOOL 

Specifies the utility used to apply patches for a recipe during the do_patch task. You can specify one of three utilities: “patch”, “quilt”, or “git”. The default utility used is “quilt” except for the quilt-native recipe itself. Because the quilt tool is not available at the time quilt-native is being patched, it uses “patch”.

If you wish to use an alternative patching tool, set the variable in the recipe using one of the following:

PATCHTOOL = "patch"
PATCHTOOL = "quilt"
PATCHTOOL = "git"

PE 

The epoch of the recipe. By default, this variable is unset. The variable is used to make upgrades possible when the versioning scheme changes in some backwards incompatible way.

PE is the default value of the PKGE variable.

PEP517_WHEEL_PATH 

When used by recipes that inherit the python_pep517 class, denotes the path to dist/ (short for distribution) where the binary archive wheel is built.

PERSISTENT_DIR 

See PERSISTENT_DIR in the BitBake manual.

PF 

Specifies the recipe or package name and includes all version and revision numbers (i.e. glibc-2.13-r20+svnr15508/ and bash-4.2-r1/). This variable is comprised of the following: ${PN}-${EXTENDPE}${PV}-${PR}

PIXBUF_PACKAGES 

When inheriting the pixbufcache class, this variable identifies packages that contain the pixbuf loaders used with gdk-pixbuf. By default, the pixbufcache class assumes that the loaders are in the recipe’s main package (i.e. ${PN}). Use this variable if the loaders you need are in a package other than that main package.

PKG 

The name of the resulting package created by the OpenEmbedded build system.

Note

When using the PKG variable, you must use a package name override.

For example, when the debian class renames the output package, it does so by setting PKG:packagename.

PKG_CONFIG_PATH 

The path to pkg-config files for the current build context. pkg-config reads this variable from the environment.

PKGD 

Points to the destination directory for files to be packaged before they are split into individual packages. This directory defaults to the following:

${WORKDIR}/package

Do not change this default.

PKGDATA_DIR 

Points to a shared, global-state directory that holds data generated during the packaging process. During the packaging process, the do_packagedata task packages data for each recipe and installs it into this temporary, shared area. This directory defaults to the following, which you should not change:

${STAGING_DIR_HOST}/pkgdata

For examples of how this data is used, see the “Automatically Added Runtime Dependencies” section in the Yocto Project Overview and Concepts Manual and the “Viewing Package Information with oe-pkgdata-util” section in the Yocto Project Development Tasks Manual. For more information on the shared, global-state directory, see STAGING_DIR_HOST.

PKGDEST 

Points to the parent directory for files to be packaged after they have been split into individual packages. This directory defaults to the following:

${WORKDIR}/packages-split

Under this directory, the build system creates directories for each package specified in PACKAGES. Do not change this default.

PKGDESTWORK 

Points to a temporary work area where the do_package task saves package metadata. The PKGDESTWORK location defaults to the following:

${WORKDIR}/pkgdata

Do not change this default.

The do_packagedata task copies the package metadata from PKGDESTWORK to PKGDATA_DIR to make it available globally.

PKGE 

The epoch of the package(s) built by the recipe. By default, PKGE is set to PE.

PKGR 

The revision of the package(s) built by the recipe. By default, PKGR is set to PR.

PKGV 

The version of the package(s) built by the recipe. By default, PKGV is set to PV.

PN 

This variable can have two separate functions depending on the context: a recipe name or a resulting package name.

PN refers to a recipe name in the context of a file used by the OpenEmbedded build system as input to create a package. The name is normally extracted from the recipe file name. For example, if the recipe is named expat_2.0.1.bb, then the default value of PN will be “expat”.

The variable refers to a package name in the context of a file created or produced by the OpenEmbedded build system.

If applicable, the PN variable also contains any special suffix or prefix. For example, using bash to build packages for the native machine, PN is bash-native. Using bash to build packages for the target and for Multilib, PN would be bash and lib64-bash, respectively.

POPULATE_SDK_POST_HOST_COMMAND 

Specifies a list of functions to call once the OpenEmbedded build system has created the host part of the SDK. You can specify functions separated by semicolons:

POPULATE_SDK_POST_HOST_COMMAND += "function; ... "

If you need to pass the SDK path to a command within a function, you can use ${SDK_DIR}, which points to the parent directory used by the OpenEmbedded build system when creating SDK output. See the SDK_DIR variable for more information.

POPULATE_SDK_POST_TARGET_COMMAND 

Specifies a list of functions to call once the OpenEmbedded build system has created the target part of the SDK. You can specify functions separated by semicolons:

POPULATE_SDK_POST_TARGET_COMMAND += "function; ... "

If you need to pass the SDK path to a command within a function, you can use ${SDK_DIR}, which points to the parent directory used by the OpenEmbedded build system when creating SDK output. See the SDK_DIR variable for more information.

PR 

The revision of the recipe. The default value for this variable is “r0”. Subsequent revisions of the recipe conventionally have the values “r1”, “r2”, and so forth. When PV increases, PR is conventionally reset to “r0”.

Note

The OpenEmbedded build system does not need the aid of PR to know when to rebuild a recipe. The build system uses the task input checksums along with the stamp and Shared State Cache mechanisms.

The PR variable primarily becomes significant when a package manager dynamically installs packages on an already built image. In this case, PR, which is the default value of PKGR, helps the package manager distinguish which package is the most recent one in cases where many packages have the same PV (i.e. PKGV). A component having many packages with the same PV usually means that the packages all install the same upstream version, but with later (PR) version packages including packaging fixes.

Note

PR does not need to be increased for changes that do not change the package contents or metadata.

Because manually managing PR can be cumbersome and error-prone, an automated solution exists. See the “Working With a PR Service” section in the Yocto Project Development Tasks Manual for more information.

PREFERRED_PROVIDER 

If multiple recipes provide the same item, this variable determines which recipe is preferred and thus provides the item (i.e. the preferred provider). You should always suffix this variable with the name of the provided item. And, you should define the variable using the preferred recipe’s name (PN). Here is a common example:

PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"

In the previous example, multiple recipes are providing “virtual/kernel”. The PREFERRED_PROVIDER variable is set with the name (PN) of the recipe you prefer to provide “virtual/kernel”.

Following are more examples:

PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"
PREFERRED_PROVIDER_virtual/libgl ?= "mesa"

For more information, see the “Using Virtual Providers” section in the Yocto Project Development Tasks Manual.

Note

If you use a virtual/\* item with PREFERRED_PROVIDER, then any recipe that PROVIDES that item but is not selected (defined) by PREFERRED_PROVIDER is prevented from building, which is usually desirable since this mechanism is designed to select between mutually exclusive alternative providers.

PREFERRED_PROVIDERS 

See PREFERRED_PROVIDERS in the BitBake manual.

PREFERRED_VERSION 

If there are multiple versions of a recipe available, this variable determines which version should be given preference. You must always suffix the variable with the PN you want to select (python in the first example below), and you should specify the PV accordingly (3.4.0 in the example).

The PREFERRED_VERSION variable supports limited wildcard use through the “%” character. You can use the character to match any number of characters, which can be useful when specifying versions that contain long revision numbers that potentially change. Here are two examples:

PREFERRED_VERSION_python = "3.4.0"
PREFERRED_VERSION_linux-yocto = "5.0%"

Note

The use of the “%” character is limited in that it only works at the end of the string. You cannot use the wildcard character in any other location of the string.

The specified version is matched against PV, which does not necessarily match the version part of the recipe’s filename. For example, consider two recipes foo_1.2.bb and foo_git.bb where foo_git.bb contains the following assignment:

PV = "1.1+git${SRCPV}"

In this case, the correct way to select foo_git.bb is by using an assignment such as the following:

PREFERRED_VERSION_foo = "1.1+git%"

Compare that previous example against the following incorrect example, which does not work:

PREFERRED_VERSION_foo = "git"

Sometimes the PREFERRED_VERSION variable can be set by configuration files in a way that is hard to change. You can use OVERRIDES to set a machine-specific override. Here is an example:

PREFERRED_VERSION_linux-yocto:qemux86 = "5.0%"

Although not recommended, worst case, you can also use the “forcevariable” override, which is the strongest override possible. Here is an example:

PREFERRED_VERSION_linux-yocto:forcevariable = "5.0%"

Note

The :forcevariable override is not handled specially. This override only works because the default value of OVERRIDES includes “forcevariable”.

If a recipe with the specified version is not available, a warning message will be shown. See REQUIRED_VERSION if you want this to be an error instead.

PREMIRRORS 

Specifies additional paths from which the OpenEmbedded build system gets source code. When the build system searches for source code, it first tries the local download directory. If that location fails, the build system tries locations defined by PREMIRRORS, the upstream source, and then locations specified by MIRRORS in that order.

Assuming your distribution (DISTRO) is “poky”, the default value for PREMIRRORS is defined in the conf/distro/poky.conf file in the meta-poky Git repository.

Typically, you could add a specific server for the build system to attempt before any others by adding something like the following to the local.conf configuration file in the Build Directory:

PREMIRRORS:prepend = "\
    git://.*/.* https://downloads.yoctoproject.org/mirror/sources/ \
    ftp://.*/.* https://downloads.yoctoproject.org/mirror/sources/ \
    http://.*/.* https://downloads.yoctoproject.org/mirror/sources/ \
    https://.*/.* https://downloads.yoctoproject.org/mirror/sources/"

These changes cause the build system to intercept Git, FTP, HTTP, and HTTPS requests and direct them to the http:// sources mirror. You can use file:// URLs to point to local directories or network shares as well.

PRIORITY 

Indicates the importance of a package.

PRIORITY is considered to be part of the distribution policy because the importance of any given recipe depends on the purpose for which the distribution is being produced. Thus, PRIORITY is not normally set within recipes.

You can set PRIORITY to “required”, “standard”, “extra”, and “optional”, which is the default.

PRIVATE_LIBS 

Specifies libraries installed within a recipe that should be ignored by the OpenEmbedded build system’s shared library resolver. This variable is typically used when software being built by a recipe has its own private versions of a library normally provided by another recipe. In this case, you would not want the package containing the private libraries to be set as a dependency on other unrelated packages that should instead depend on the package providing the standard version of the library.

Libraries specified in this variable should be specified by their file name. For example, from the Firefox recipe in meta-browser:

PRIVATE_LIBS = "libmozjs.so \
                libxpcom.so \
                libnspr4.so \
                libxul.so \
                libmozalloc.so \
                libplc4.so \
                libplds4.so"

For more information, see the “Automatically Added Runtime Dependencies” section in the Yocto Project Overview and Concepts Manual.

PROVIDES 

A list of aliases by which a particular recipe can be known. By default, a recipe’s own PN is implicitly already in its PROVIDES list and therefore does not need to mention that it provides itself. If a recipe uses PROVIDES, the additional aliases are synonyms for the recipe and can be useful for satisfying dependencies of other recipes during the build as specified by DEPENDS.

Consider the following example PROVIDES statement from the recipe file eudev_3.2.9.bb:

PROVIDES += "udev"

The PROVIDES statement results in the “eudev” recipe also being available as simply “udev”.

Note

A recipe’s own recipe name (PN) is always implicitly prepended to PROVIDES, so while using “+=” in the above example may not be strictly necessary it is recommended to avoid confusion.

In addition to providing recipes under alternate names, the PROVIDES mechanism is also used to implement virtual targets. A virtual target is a name that corresponds to some particular functionality (e.g. a Linux kernel). Recipes that provide the functionality in question list the virtual target in PROVIDES. Recipes that depend on the functionality in question can include the virtual target in DEPENDS to leave the choice of provider open.

Conventionally, virtual targets have names on the form “virtual/function” (e.g. “virtual/kernel”). The slash is simply part of the name and has no syntactical significance.

The PREFERRED_PROVIDER variable is used to select which particular recipe provides a virtual target.

Note

A corresponding mechanism for virtual runtime dependencies (packages) exists. However, the mechanism does not depend on any special functionality beyond ordinary variable assignments. For example, VIRTUAL-RUNTIME_dev_manager refers to the package of the component that manages the /dev directory.

Setting the “preferred provider” for runtime dependencies is as simple as using the following assignment in a configuration file:

VIRTUAL-RUNTIME_dev_manager = "udev"

PRSERV_HOST 

The network based PR service host and port.

The conf/templates/default/local.conf.sample.extended configuration file in the Source Directory shows how the PRSERV_HOST variable is set:

PRSERV_HOST = "localhost:0"

You must set the variable if you want to automatically start a local PR service. You can set PRSERV_HOST to other values to use a remote PR service.

PSEUDO_IGNORE_PATHS 

A comma-separated (without spaces) list of path prefixes that should be ignored by pseudo when monitoring and recording file operations, in order to avoid problems with files being written to outside of the pseudo context and reduce pseudo’s overhead. A path is ignored if it matches any prefix in the list and can include partial directory (or file) names.

PTEST_ENABLED 

Specifies whether or not Package Test (ptest) functionality is enabled when building a recipe. You should not set this variable directly. Enabling and disabling building Package Tests at build time should be done by adding “ptest” to (or removing it from) DISTRO_FEATURES.

PV 

The version of the recipe. The version is normally extracted from the recipe filename. For example, if the recipe is named expat_2.0.1.bb, then the default value of PV will be “2.0.1”. PV is generally not overridden within a recipe unless it is building an unstable (i.e. development) version from a source code repository (e.g. Git or Subversion).

PV is the default value of the PKGV variable.

PYPI_PACKAGE 

When inheriting the pypi class, specifies the PyPI package name to be built. The default value is set based upon BPN (stripping any “python-” or “python3-” prefix off if present), however for some packages it will need to be set explicitly if that will not match the package name (e.g. where the package name has a prefix, underscores, uppercase letters etc.)

PYTHON_ABI 

When used by recipes that inherit the setuptools3 class, denotes the Application Binary Interface (ABI) currently in use for Python. By default, the ABI is “m”. You do not have to set this variable as the OpenEmbedded build system sets it for you.

The OpenEmbedded build system uses the ABI to construct directory names used when installing the Python headers and libraries in sysroot (e.g. .../python3.3m/...).

PYTHON_PN 

When used by recipes that inherit the setuptools3 class, specifies the major Python version being built. For Python 3.x, PYTHON_PN would be “python3”. You do not have to set this variable as the OpenEmbedded build system automatically sets it for you.

The variable allows recipes to use common infrastructure such as the following:

DEPENDS += "${PYTHON_PN}-native"

In the previous example, the version of the dependency is PYTHON_PN.

QA_EMPTY_DIRS 

Specifies a list of directories that are expected to be empty when packaging; if empty-dirs appears in ERROR_QA or WARN_QA these will be checked and an error or warning (respectively) will be produced.

The default QA_EMPTY_DIRS value is set in insane.bbclass.

QA_EMPTY_DIRS_RECOMMENDATION 

Specifies a recommendation for why a directory must be empty, which will be included in the error message if a specific directory is found to contain files. Must be overridden with the directory path to match on.

If no recommendation is specified for a directory, then the default “but it is expected to be empty” will be used.

An example message shows if files were present in ‘/dev’:

QA_EMPTY_DIRS_RECOMMENDATION:/dev = "but all devices must be created at runtime"

RANLIB 

The minimal command and arguments to run ranlib.

RCONFLICTS 

The list of packages that conflict with packages. Note that packages will not be installed if conflicting packages are not first removed.

Like all package-controlling variables, you must always use them in conjunction with a package name override. Here is an example:

RCONFLICTS:${PN} = "another_conflicting_package_name"

BitBake, which the OpenEmbedded build system uses, supports specifying versioned dependencies. Although the syntax varies depending on the packaging format, BitBake hides these differences from you. Here is the general syntax to specify versions with the RCONFLICTS variable:

RCONFLICTS:${PN} = "package (operator version)"

For operator, you can specify the following:

=
<
>
<=
>=

For example, the following sets up a dependency on version 1.2 or greater of the package foo:

RCONFLICTS:${PN} = "foo (>= 1.2)"

RDEPENDS 

Lists runtime dependencies of a package. These dependencies are other packages that must be installed in order for the package to function correctly. As an example, the following assignment declares that the package foo needs the packages bar and baz to be installed:

RDEPENDS:foo = "bar baz"

The most common types of package runtime dependencies are automatically detected and added. Therefore, most recipes do not need to set RDEPENDS. For more information, see the “Automatically Added Runtime Dependencies” section in the Yocto Project Overview and Concepts Manual.

The practical effect of the above RDEPENDS assignment is that bar and baz will be declared as dependencies inside the package foo when it is written out by one of the do_package_write_* tasks. Exactly how this is done depends on which package format is used, which is determined by PACKAGE_CLASSES. When the corresponding package manager installs the package, it will know to also install the packages on which it depends.

To ensure that the packages bar and baz get built, the previous RDEPENDS assignment also causes a task dependency to be added. This dependency is from the recipe’s do_build (not to be confused with do_compile) task to the do_package_write_* task of the recipes that build bar and baz.

The names of the packages you list within RDEPENDS must be the names of other packages — they cannot be recipe names. Although package names and recipe names usually match, the important point here is that you are providing package names within the RDEPENDS variable. For an example of the default list of packages created from a recipe, see the PACKAGES variable.

Because the RDEPENDS variable applies to packages being built, you should always use the variable in a form with an attached package name (remember that a single recipe can build multiple packages). For example, suppose you are building a development package that depends on the perl package. In this case, you would use the following RDEPENDS statement:

RDEPENDS:${PN}-dev += "perl"

In the example, the development package depends on the perl package. Thus, the RDEPENDS variable has the ${PN}-dev package name as part of the variable.

Note

RDEPENDS:${PN}-dev includes ${PN} by default. This default is set in the BitBake configuration file (meta/conf/bitbake.conf). Be careful not to accidentally remove ${PN} when modifying RDEPENDS:${PN}-dev. Use the “+=” operator rather than the “=” operator.

The package names you use with RDEPENDS must appear as they would in the PACKAGES variable. The PKG variable allows a different name to be used for the final package (e.g. the debian class uses this to rename packages), but this final package name cannot be used with RDEPENDS, which makes sense as RDEPENDS is meant to be independent of the package format used.

BitBake, which the OpenEmbedded build system uses, supports specifying versioned dependencies. Although the syntax varies depending on the packaging format, BitBake hides these differences from you. Here is the general syntax to specify versions with the RDEPENDS variable:

RDEPENDS:${PN} = "package (operator version)"

For operator, you can specify the following:

=
<
>
<=
>=

For version, provide the version number.

Note

You can use EXTENDPKGV to provide a full package version specification.

For example, the following sets up a dependency on version 1.2 or greater of the package foo:

RDEPENDS:${PN} = "foo (>= 1.2)"

For information on build-time dependencies, see the DEPENDS variable. You can also see the “Tasks” and “Dependencies” sections in the BitBake User Manual for additional information on tasks and dependencies.

RECIPE_NO_UPDATE_REASON 

If a recipe should not be replaced by a more recent upstream version, putting the reason why in this variable in a recipe allows devtool check-upgrade-status command to display it, as explained in the “Checking on the Upgrade Status of a Recipe” section.

REPODIR 

See REPODIR in the BitBake manual.

REQUIRED_DISTRO_FEATURES 

When inheriting the features_check class, this variable identifies distribution features that must exist in the current configuration in order for the OpenEmbedded build system to build the recipe. In other words, if the REQUIRED_DISTRO_FEATURES variable lists a feature that does not appear in DISTRO_FEATURES within the current configuration, then the recipe will be skipped, and if the build system attempts to build the recipe then an error will be triggered.

REQUIRED_VERSION 

If there are multiple versions of a recipe available, this variable determines which version should be given preference. REQUIRED_VERSION works in exactly the same manner as PREFERRED_VERSION, except that if the specified version is not available then an error message is shown and the build fails immediately.

If both REQUIRED_VERSION and PREFERRED_VERSION are set for the same recipe, the REQUIRED_VERSION value applies.

RM_WORK_EXCLUDE 

With rm_work enabled, this variable specifies a list of recipes whose work directories should not be removed. See the “rm_work” section for more details.

ROOT_HOME 

Defines the root home directory. By default, this directory is set as follows in the BitBake configuration file:

ROOT_HOME ??= "/home/root"

Note

This default value is likely used because some embedded solutions prefer to have a read-only root filesystem and prefer to keep writeable data in one place.

You can override the default by setting the variable in any layer or in the local.conf file. Because the default is set using a “weak” assignment (i.e. “??=”), you can use either of the following forms to define your override:

ROOT_HOME = "/root"
ROOT_HOME ?= "/root"

These override examples use /root, which is probably the most commonly used override.

ROOTFS 

Indicates a filesystem image to include as the root filesystem.

The ROOTFS variable is an optional variable used with the image-live class.

ROOTFS_POSTINSTALL_COMMAND 

Specifies a list of functions to call after the OpenEmbedded build system has installed packages. You can specify functions separated by semicolons:

ROOTFS_POSTINSTALL_COMMAND += "function; ... "

If you need to pass the root filesystem path to a command within a function, you can use ${IMAGE_ROOTFS}, which points to the directory that becomes the root filesystem image. See the IMAGE_ROOTFS variable for more information.

ROOTFS_POSTPROCESS_COMMAND 

Specifies a list of functions to call once the OpenEmbedded build system has created the root filesystem. You can specify functions separated by semicolons:

ROOTFS_POSTPROCESS_COMMAND += "function; ... "

If you need to pass the root filesystem path to a command within a function, you can use ${IMAGE_ROOTFS}, which points to the directory that becomes the root filesystem image. See the IMAGE_ROOTFS variable for more information.

ROOTFS_POSTUNINSTALL_COMMAND 

Specifies a list of functions to call after the OpenEmbedded build system has removed unnecessary packages. When runtime package management is disabled in the image, several packages are removed including base-passwd, shadow, and update-alternatives. You can specify functions separated by semicolons:

ROOTFS_POSTUNINSTALL_COMMAND += "function; ... "

If you need to pass the root filesystem path to a command within a function, you can use ${IMAGE_ROOTFS}, which points to the directory that becomes the root filesystem image. See the IMAGE_ROOTFS variable for more information.

ROOTFS_PREPROCESS_COMMAND 

Specifies a list of functions to call before the OpenEmbedded build system has created the root filesystem. You can specify functions separated by semicolons:

ROOTFS_PREPROCESS_COMMAND += "function; ... "

If you need to pass the root filesystem path to a command within a function, you can use ${IMAGE_ROOTFS}, which points to the directory that becomes the root filesystem image. See the IMAGE_ROOTFS variable for more information.

RPROVIDES 

A list of package name aliases that a package also provides. These aliases are useful for satisfying runtime dependencies of other packages both during the build and on the target (as specified by RDEPENDS).

Note

A package’s own name is implicitly already in its RPROVIDES list.

As with all package-controlling variables, you must always use the variable in conjunction with a package name override. Here is an example:

RPROVIDES:${PN} = "widget-abi-2"

RRECOMMENDS 

A list of packages that extends the usability of a package being built. The package being built does not depend on this list of packages in order to successfully build, but rather uses them for extended usability. To specify runtime dependencies for packages, see the RDEPENDS variable.

The package manager will automatically install the RRECOMMENDS list of packages when installing the built package. However, you can prevent listed packages from being installed by using the BAD_RECOMMENDATIONS, NO_RECOMMENDATIONS, and PACKAGE_EXCLUDE variables.

Packages specified in RRECOMMENDS need not actually be produced. However, there must be a recipe providing each package, either through the PACKAGES or PACKAGES_DYNAMIC variables or the RPROVIDES variable, or an error will occur during the build. If such a recipe does exist and the package is not produced, the build continues without error.

Because the RRECOMMENDS variable applies to packages being built, you should always attach an override to the variable to specify the particular package whose usability is being extended. For example, suppose you are building a development package that is extended to support wireless functionality. In this case, you would use the following:

RRECOMMENDS:${PN}-dev += "wireless_package_name"

In the example, the package name (${PN}-dev) must appear as it would in the PACKAGES namespace before any renaming of the output package by classes such as debian.

BitBake, which the OpenEmbedded build system uses, supports specifying versioned recommends. Although the syntax varies depending on the packaging format, BitBake hides these differences from you. Here is the general syntax to specify versions with the RRECOMMENDS variable:

RRECOMMENDS:${PN} = "package (operator version)"

For operator, you can specify the following:

=
<
>
<=
>=

For example, the following sets up a recommend on version 1.2 or greater of the package foo:

RRECOMMENDS:${PN} = "foo (>= 1.2)"

RREPLACES 

A list of packages replaced by a package. The package manager uses this variable to determine which package should be installed to replace other package(s) during an upgrade. In order to also have the other package(s) removed at the same time, you must add the name of the other package to the RCONFLICTS variable.

As with all package-controlling variables, you must use this variable in conjunction with a package name override. Here is an example:

RREPLACES:${PN} = "other_package_being_replaced"

BitBake, which the OpenEmbedded build system uses, supports specifying versioned replacements. Although the syntax varies depending on the packaging format, BitBake hides these differences from you. Here is the general syntax to specify versions with the RREPLACES variable:

RREPLACES:${PN} = "package (operator version)"

For operator, you can specify the following:

=
<
>
<=
>=

For example, the following sets up a replacement using version 1.2 or greater of the package foo:

RREPLACES:${PN} = "foo (>= 1.2)"

RSUGGESTS 

A list of additional packages that you can suggest for installation by the package manager at the time a package is installed. Not all package managers support this functionality.

As with all package-controlling variables, you must always use this variable in conjunction with a package name override. Here is an example:

RSUGGESTS:${PN} = "useful_package another_package"

RUST_CHANNEL 

Specifies which version of Rust to build - “stable”, “beta” or “nightly”. The default value is “stable”. Set this at your own risk, as values other than “stable” are not guaranteed to work at a given time.

S 

The location in the Build Directory where unpacked recipe source code resides. By default, this directory is ${WORKDIR}/${BPN}-${PV}, where ${BPN} is the base recipe name and ${PV} is the recipe version. If the source tarball extracts the code to a directory named anything other than ${BPN}-${PV}, or if the source code is fetched from an SCM such as Git or Subversion, then you must set S in the recipe so that the OpenEmbedded build system knows where to find the unpacked source.

As an example, assume a Source Directory top-level folder named poky and a default Build Directory at poky/build. In this case, the work directory the build system uses to keep the unpacked recipe for db is the following:

poky/build/tmp/work/qemux86-poky-linux/db/5.1.19-r3/db-5.1.19

The unpacked source code resides in the db-5.1.19 folder.

This next example assumes a Git repository. By default, Git repositories are cloned to ${WORKDIR}/git during do_fetch. Since this path is different from the default value of S, you must set it specifically so the source can be located:

SRC_URI = "git://path/to/repo.git;branch=main"
S = "${WORKDIR}/git"

SANITY_REQUIRED_UTILITIES 

Specifies a list of command-line utilities that should be checked for during the initial sanity checking process when running BitBake. If any of the utilities are not installed on the build host, then BitBake immediately exits with an error.

SANITY_TESTED_DISTROS 

A list of the host distribution identifiers that the build system has been tested against. Identifiers consist of the host distributor ID followed by the release, as reported by the lsb_release tool or as read from /etc/lsb-release. Separate the list items with explicit newline characters (\n). If SANITY_TESTED_DISTROS is not empty and the current value of NATIVELSBSTRING does not appear in the list, then the build system reports a warning that indicates the current host distribution has not been tested as a build host.

SDK_ARCH 

The target architecture for the SDK. Typically, you do not directly set this variable. Instead, use SDKMACHINE.

SDK_ARCHIVE_TYPE 

Specifies the type of archive to create for the SDK. Valid values:

tar.xz (default)
zip

Only one archive type can be specified.

SDK_BUILDINFO_FILE 

When using the image-buildinfo class, specifies the file in the SDK to write the build information into. The default value is “/buildinfo”.

SDK_CUSTOM_TEMPLATECONF 

When building the extensible SDK, if SDK_CUSTOM_TEMPLATECONF is set to “1” and a conf/templateconf.cfg file exists in the Build Directory (TOPDIR) then this will be copied into the SDK.

SDK_DEPLOY 

The directory set up and used by the populate_sdk_base class to which the SDK is deployed. The populate_sdk_base class defines SDK_DEPLOY as follows:

SDK_DEPLOY = "${TMPDIR}/deploy/sdk"

SDK_DIR 

The parent directory used by the OpenEmbedded build system when creating SDK output. The populate_sdk_base class defines the variable as follows:

SDK_DIR = "${WORKDIR}/sdk"

Note

The SDK_DIR directory is a temporary directory as it is part of WORKDIR. The final output directory is SDK_DEPLOY.

SDK_EXT_TYPE 

Controls whether or not shared state artifacts are copied into the extensible SDK. The default value of “full” copies all of the required shared state artifacts into the extensible SDK. The value “minimal” leaves these artifacts out of the SDK.

Note

If you set the variable to “minimal”, you need to ensure SSTATE_MIRRORS is set in the SDK’s configuration to enable the artifacts to be fetched as needed.

SDK_HOST_MANIFEST 

The manifest file for the host part of the SDK. This file lists all the installed packages that make up the host part of the SDK. The file contains package information on a line-per-package basis as follows:

packagename packagearch version

The populate_sdk_base class defines the manifest file as follows:

SDK_HOST_MANIFEST = "${SDK_DEPLOY}/${TOOLCHAIN_OUTPUTNAME}.host.manifest"

The location is derived using the SDK_DEPLOY and TOOLCHAIN_OUTPUTNAME variables.

SDK_INCLUDE_PKGDATA 

When set to “1”, specifies to include the packagedata for all recipes in the “world” target in the extensible SDK. Including this data allows the devtool search command to find these recipes in search results, as well as allows the devtool add command to map dependencies more effectively.

Note

Enabling the SDK_INCLUDE_PKGDATA variable significantly increases build time because all of world needs to be built. Enabling the variable also slightly increases the size of the extensible SDK.

SDK_INCLUDE_TOOLCHAIN 

When set to “1”, specifies to include the toolchain in the extensible SDK. Including the toolchain is useful particularly when SDK_EXT_TYPE is set to “minimal” to keep the SDK reasonably small but you still want to provide a usable toolchain. For example, suppose you want to use the toolchain from an IDE or from other tools and you do not want to perform additional steps to install the toolchain.

The SDK_INCLUDE_TOOLCHAIN variable defaults to “0” if SDK_EXT_TYPE is set to “minimal”, and defaults to “1” if SDK_EXT_TYPE is set to “full”.

SDK_NAME 

The base name for SDK output files. The name is derived from the DISTRO, TCLIBC, SDK_ARCH, IMAGE_BASENAME, and TUNE_PKGARCH variables:

SDK_NAME = "${DISTRO}-${TCLIBC}-${SDK_ARCH}-${IMAGE_BASENAME}-${TUNE_PKGARCH}"

SDK_OS 

Specifies the operating system for which the SDK will be built. The default value is the value of BUILD_OS.

SDK_OUTPUT 

The location used by the OpenEmbedded build system when creating SDK output. The populate_sdk_base class defines the variable as follows:

SDK_DIR = "${WORKDIR}/sdk"
SDK_OUTPUT = "${SDK_DIR}/image"
SDK_DEPLOY = "${DEPLOY_DIR}/sdk"

Note

The SDK_OUTPUT directory is a temporary directory as it is part of WORKDIR by way of SDK_DIR. The final output directory is SDK_DEPLOY.

SDK_PACKAGE_ARCHS 

Specifies a list of architectures compatible with the SDK machine. This variable is set automatically and should not normally be hand-edited. Entries are separated using spaces and listed in order of priority. The default value for SDK_PACKAGE_ARCHS is “all any noarch ${SDK_ARCH}-${SDKPKGSUFFIX}”.

SDK_POSTPROCESS_COMMAND 

Specifies a list of functions to call once the OpenEmbedded build system creates the SDK. You can specify functions separated by semicolons: SDK_POSTPROCESS_COMMAND += “function; … “

If you need to pass an SDK path to a command within a function, you can use ${SDK_DIR}, which points to the parent directory used by the OpenEmbedded build system when creating SDK output. See the SDK_DIR variable for more information.

SDK_PREFIX 

The toolchain binary prefix used for nativesdk recipes. The OpenEmbedded build system uses the SDK_PREFIX value to set the TARGET_PREFIX when building nativesdk recipes. The default value is “${SDK_SYS}-“.

SDK_RECRDEP_TASKS 

A list of shared state tasks added to the extensible SDK. By default, the following tasks are added:

Despite the default value of “” for the SDK_RECRDEP_TASKS variable, the above four tasks are always added to the SDK. To specify tasks beyond these four, you need to use the SDK_RECRDEP_TASKS variable (e.g. you are defining additional tasks that are needed in order to build SDK_TARGETS).

SDK_SYS 

Specifies the system, including the architecture and the operating system, for which the SDK will be built.

The OpenEmbedded build system automatically sets this variable based on SDK_ARCH, SDK_VENDOR, and SDK_OS. You do not need to set the SDK_SYS variable yourself.

SDK_TARGET_MANIFEST 

The manifest file for the target part of the SDK. This file lists all the installed packages that make up the target part of the SDK. The file contains package information on a line-per-package basis as follows:

packagename packagearch version

The populate_sdk_base class defines the manifest file as follows:

SDK_TARGET_MANIFEST = "${SDK_DEPLOY}/${TOOLCHAIN_OUTPUTNAME}.target.manifest"

The location is derived using the SDK_DEPLOY and TOOLCHAIN_OUTPUTNAME variables.

SDK_TARGETS 

A list of targets to install from shared state as part of the standard or extensible SDK installation. The default value is “${PN}” (i.e. the image from which the SDK is built).

The SDK_TARGETS variable is an internal variable and typically would not be changed.

SDK_TITLE 

The title to be printed when running the SDK installer. By default, this title is based on the DISTRO_NAME or DISTRO variable and is set in the populate_sdk_base class as follows:

SDK_TITLE ??= "${@d.getVar('DISTRO_NAME') or d.getVar('DISTRO')} SDK"

For the default distribution “poky”, SDK_TITLE is set to “Poky (Yocto Project Reference Distro)”.

For information on how to change this default title, see the “Changing the Extensible SDK Installer Title” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

SDK_TOOLCHAIN_LANGS 

Specifies programming languages to support in the SDK, as a space-separated list. Currently supported items are rust and go.

SDK_UPDATE_URL 

An optional URL for an update server for the extensible SDK. If set, the value is used as the default update server when running devtool sdk-update within the extensible SDK.

SDK_VENDOR 

Specifies the name of the SDK vendor.

SDK_VERSION 

Specifies the version of the SDK. The Poky distribution configuration file (/meta-poky/conf/distro/poky.conf) sets the default SDK_VERSION as follows:

SDK_VERSION = "${@d.getVar('DISTRO_VERSION').replace('snapshot-${METADATA_REVISION}', 'snapshot')}"

For additional information, see the DISTRO_VERSION and METADATA_REVISION variables.

SDK_ZIP_OPTIONS 

Specifies extra options to pass to the zip command when zipping the SDK (i.e. when SDK_ARCHIVE_TYPE is set to “zip”). The default value is “-y”.

SDKEXTPATH 

The default installation directory for the Extensible SDK. By default, this directory is based on the DISTRO variable and is set in the populate_sdk_base class as follows:

SDKEXTPATH ??= "~/${@d.getVar('DISTRO')}_sdk"

For the default distribution “poky”, the SDKEXTPATH is set to “poky_sdk”.

For information on how to change this default directory, see the “Changing the Default SDK Installation Directory” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

SDKIMAGE_FEATURES 

Equivalent to IMAGE_FEATURES. However, this variable applies to the SDK generated from an image using the following command:

$ bitbake -c populate_sdk imagename

SDKMACHINE 

The machine for which the SDK is built. In other words, the SDK is built such that it runs on the target you specify with the SDKMACHINE value. The value points to a corresponding .conf file under conf/machine-sdk/ in the enabled layers, for example aarch64, i586, i686, ppc64, ppc64le, and x86_64 are available in OpenEmbedded-Core.

The variable defaults to BUILD_ARCH so that SDKs are built for the architecture of the build machine.

Note

You cannot set the SDKMACHINE variable in your distribution configuration file. If you do, the configuration will not take effect.

SDKPATH 

Defines the path offered to the user for installation of the SDK that is generated by the OpenEmbedded build system. The path appears as the default location for installing the SDK when you run the SDK’s installation script. You can override the offered path when you run the script.

SDKTARGETSYSROOT 

The full path to the sysroot used for cross-compilation within an SDK as it will be when installed into the default SDKPATH.

SECTION 

The section in which packages should be categorized. Package management utilities can make use of this variable.

SELECTED_OPTIMIZATION 

Specifies the optimization flags passed to the C compiler when building for the target. The flags are passed through the default value of the TARGET_CFLAGS variable.

The SELECTED_OPTIMIZATION variable takes the value of FULL_OPTIMIZATION unless DEBUG_BUILD = “1”, in which case the value of DEBUG_OPTIMIZATION is used.

SERIAL_CONSOLES 

Defines a serial console (TTY) to enable using getty. Provide a value that specifies the baud rate followed by the TTY device name separated by a semicolon. Use spaces to separate multiple devices:

SERIAL_CONSOLES = "115200;ttyS0 115200;ttyS1"

SERIAL_CONSOLES_CHECK 

Specifies serial consoles, which must be listed in SERIAL_CONSOLES, to check against /proc/console before enabling them using getty. This variable allows aliasing in the format: <device>:<alias>. If a device was listed as “sclp_line0” in /dev/ and “ttyS0” was listed in /proc/console, you would do the following:

SERIAL_CONSOLES_CHECK = "slcp_line0:ttyS0"

This variable is currently only supported with SysVinit (i.e. not with systemd). Note that SERIAL_CONSOLES_CHECK also requires /etc/inittab to be writable when used with SysVinit. This makes it incompatible with customizations such as the following:

EXTRA_IMAGE_FEATURES += "read-only-rootfs"

SETUPTOOLS_BUILD_ARGS 

When used by recipes that inherit the setuptools3 class, this variable can be used to specify additional arguments to be passed to setup.py build in the setuptools3_do_compile() task.

SETUPTOOLS_INSTALL_ARGS 

When used by recipes that inherit the setuptools3 class, this variable can be used to specify additional arguments to be passed to setup.py install in the setuptools3_do_install() task.

SETUPTOOLS_SETUP_PATH 

When used by recipes that inherit the setuptools3 class, this variable should be used to specify the directory in which the setup.py file is located if it is not at the root of the source tree (as specified by S). For example, in a recipe where the sources are fetched from a Git repository and setup.py is in a python/pythonmodule subdirectory, you would have this:

S = "${WORKDIR}/git"
SETUPTOOLS_SETUP_PATH = "${S}/python/pythonmodule"

SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS 

A list of recipe dependencies that should not be used to determine signatures of tasks from one recipe when they depend on tasks from another recipe. For example:

SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS += "intone->mplayer2"

In the previous example, intone depends on mplayer2.

You can use the special token "*" on the left-hand side of the dependency to match all recipes except the one on the right-hand side. Here is an example:

SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS += "*->quilt-native"

In the previous example, all recipes except quilt-native ignore task signatures from the quilt-native recipe when determining their task signatures.

Use of this variable is one mechanism to remove dependencies that affect task signatures and thus force rebuilds when a recipe changes.

Note

If you add an inappropriate dependency for a recipe relationship, the software might break during runtime if the interface of the second recipe was changed after the first recipe had been built.

SIGGEN_EXCLUDERECIPES_ABISAFE 

A list of recipes that are completely stable and will never change. The ABI for the recipes in the list are presented by output from the tasks run to build the recipe. Use of this variable is one way to remove dependencies from one recipe on another that affect task signatures and thus force rebuilds when the recipe changes.

Note

If you add an inappropriate variable to this list, the software might break at runtime if the interface of the recipe was changed after the other had been built.

SITEINFO_BITS 

Specifies the number of bits for the target system CPU. The value should be either “32” or “64”.

SITEINFO_ENDIANNESS 

Specifies the endian byte order of the target system. The value should be either “le” for little-endian or “be” for big-endian.

SKIP_FILEDEPS 

Enables removal of all files from the “Provides” section of an RPM package. Removal of these files is required for packages containing prebuilt binaries and libraries such as libstdc++ and glibc.

To enable file removal, set the variable to “1” in your conf/local.conf configuration file in your: Build Directory:

SKIP_FILEDEPS = "1"

SKIP_RECIPE 

Used to prevent the OpenEmbedded build system from building a given recipe. Specify the PN value as a variable flag (varflag) and provide a reason, which will be reported when attempting to build the recipe.

To prevent a recipe from being built, use the SKIP_RECIPE variable in your local.conf file or distribution configuration. Here is an example which prevents myrecipe from being built:

SKIP_RECIPE[myrecipe] = "Not supported by our organization."

SOC_FAMILY 

Groups together machines based upon the same family of SOC (System On Chip). You typically set this variable in a common .inc file that you include in the configuration files of all the machines.

Note

You must include conf/machine/include/soc-family.inc for this variable to appear in MACHINEOVERRIDES.

SOLIBS 

Defines the suffix for shared libraries used on the target platform. By default, this suffix is “.so.*” for all Linux-based systems and is defined in the meta/conf/bitbake.conf configuration file.

You will see this variable referenced in the default values of FILES:${PN}.

SOLIBSDEV 

Defines the suffix for the development symbolic link (symlink) for shared libraries on the target platform. By default, this suffix is “.so” for Linux-based systems and is defined in the meta/conf/bitbake.conf configuration file.

You will see this variable referenced in the default values of FILES:${PN}-dev.

SOURCE_DATE_EPOCH 

This defines a date expressed in number of seconds since the UNIX EPOCH (01 Jan 1970 00:00:00 UTC), which is used by multiple build systems to force a timestamp in built binaries. Many upstream projects already support this variable.

You will find more details in the official specifications.

A value for each recipe is computed from the sources by meta/lib/oe/reproducible.py.

If a recipe wishes to override the default behavior, it should set its own SOURCE_DATE_EPOCH value:

SOURCE_DATE_EPOCH = "1613559011"

SOURCE_MIRROR_FETCH 

When you are fetching files to create a mirror of sources (i.e. creating a source mirror), setting SOURCE_MIRROR_FETCH to “1” in your local.conf configuration file ensures the source for all recipes are fetched regardless of whether or not a recipe is compatible with the configuration. A recipe is considered incompatible with the currently configured machine when either or both the COMPATIBLE_MACHINE variable and COMPATIBLE_HOST variables specify compatibility with a machine other than that of the current machine or host.

Note

Do not set the SOURCE_MIRROR_FETCH variable unless you are creating a source mirror. In other words, do not set the variable during a normal build.

SOURCE_MIRROR_URL 

Defines your own PREMIRRORS from which to first fetch source before attempting to fetch from the upstream specified in SRC_URI.

To use this variable, you must globally inherit the own-mirrors class and then provide the URL to your mirrors. Here is the general syntax:

INHERIT += "own-mirrors"
SOURCE_MIRROR_URL = "http://example.com/my_source_mirror"

Note

You can specify only a single URL in SOURCE_MIRROR_URL.

SPDX_ARCHIVE_PACKAGED 

This option allows to add to SPDX output compressed archives of the files in the generated target packages.

Such archives are available in tmp/deploy/spdx/MACHINE/packages/packagename.tar.zst under the Build Directory.

Enable this option as follows:

SPDX_ARCHIVE_PACKAGED = "1"

According to our tests on release 4.1 “langdale”, building core-image-minimal for the qemux86-64 machine, enabling this option multiplied the size of the tmp/deploy/spdx directory by a factor of 13 (+1.6 GiB for this image), compared to just using the create-spdx class with no option.

Note that this option doesn’t increase the size of SPDX files in tmp/deploy/images/MACHINE.

SPDX_ARCHIVE_SOURCES 

This option allows to add to SPDX output compressed archives of the sources for packages installed on the target. It currently only works when SPDX_INCLUDE_SOURCES is set.

This is one way of fulfilling “source code access” license requirements.

Such source archives are available in tmp/deploy/spdx/MACHINE/recipes/recipe-packagename.tar.zst under the Build Directory.

Enable this option as follows:

SPDX_INCLUDE_SOURCES = "1"
SPDX_ARCHIVE_SOURCES = "1"

According to our tests on release 4.1 “langdale”, building core-image-minimal for the qemux86-64 machine, enabling these options multiplied the size of the tmp/deploy/spdx directory by a factor of 11 (+1.4 GiB for this image), compared to just using the create-spdx class with no option.

Note that using this option only marginally increases the size of the SPDX output in tmp/deploy/images/MACHINE/ (+ 0.07% with the tested image), compared to just enabling SPDX_INCLUDE_SOURCES.

SPDX_CUSTOM_ANNOTATION_VARS 

This option allows to associate SPDX annotations to a recipe, using the values of variables in the recipe:

ANNOTATION1 = "First annotation for recipe"
ANNOTATION2 = "Second annotation for recipe"
SPDX_CUSTOM_ANNOTATION_VARS = "ANNOTATION1 ANNOTATION2"

This will add a new block to the recipe .sdpx.json output:

"annotations": [
  {
    "annotationDate": "2023-04-18T08:32:12Z",
    "annotationType": "OTHER",
    "annotator": "Tool: oe-spdx-creator - 1.0",
    "comment": "ANNOTATION1=First annotation for recipe"
  },
  {
    "annotationDate": "2023-04-18T08:32:12Z",
    "annotationType": "OTHER",
    "annotator": "Tool: oe-spdx-creator - 1.0",
    "comment": "ANNOTATION2=Second annotation for recipe"
  }
],

SPDX_INCLUDE_SOURCES 

This option allows to add a description of the source files used to build the host tools and the target packages, to the spdx.json files in tmp/deploy/spdx/MACHINE/recipes/ under the Build Directory. As a consequence, the spdx.json files under the by-namespace and packages subdirectories in tmp/deploy/spdx/MACHINE are also modified to include references to such source file descriptions.

Enable this option as follows:

SPDX_INCLUDE_SOURCES = "1"

According to our tests on release 4.1 “langdale”, building core-image-minimal for the qemux86-64 machine, enabling this option multiplied the total size of the tmp/deploy/spdx directory by a factor of 3 (+291 MiB for this image), and the size of the IMAGE-MACHINE.spdx.tar.zst in tmp/deploy/images/MACHINE by a factor of 130 (+15 MiB for this image), compared to just using the create-spdx class with no option.

SPDX_PRETTY 

This option makes the SPDX output more human-readable, using identation and newlines, instead of the default output in a single line:

SPDX_PRETTY = "1"

The generated SPDX files are approximately 20% bigger, but this option is recommended if you want to inspect the SPDX output files with a text editor.

SPDXLICENSEMAP 

Maps commonly used license names to their SPDX counterparts found in meta/files/common-licenses/. For the default SPDXLICENSEMAP mappings, see the meta/conf/licenses.conf file.

For additional information, see the LICENSE variable.

SPECIAL_PKGSUFFIX 

A list of prefixes for PN used by the OpenEmbedded build system to create variants of recipes or packages. The list specifies the prefixes to strip off during certain circumstances such as the generation of the BPN variable.

SPL_BINARY 

The file type for the Secondary Program Loader (SPL). Some devices use an SPL from which to boot (e.g. the BeagleBone development board). For such cases, you can declare the file type of the SPL binary in the u-boot.inc include file, which is used in the U-Boot recipe.

The SPL file type is set to “null” by default in the u-boot.inc file as follows:

# Some versions of u-boot build an SPL (Second Program Loader) image that
# should be packaged along with the u-boot binary as well as placed in the
# deploy directory. For those versions they can set the following variables
# to allow packaging the SPL.
SPL_BINARY ?= ""
SPL_BINARYNAME ?= "${@os.path.basename(d.getVar("SPL_BINARY"))}"
SPL_IMAGE ?= "${SPL_BINARYNAME}-${MACHINE}-${PV}-${PR}"
SPL_SYMLINK ?= "${SPL_BINARYNAME}-${MACHINE}"

The SPL_BINARY variable helps form various SPL_* variables used by the OpenEmbedded build system.

See the BeagleBone machine configuration example in the “Adding a Layer Using the bitbake-layers Script” section in the Yocto Project Board Support Package Developer’s Guide for additional information.

SRC_URI 

See the BitBake manual for the initial description for this variable: SRC_URI.

The following features are added by OpenEmbedded and the Yocto Project.

There are standard and recipe-specific options. Here are standard ones:

apply — whether to apply the patch or not. The default action is to apply the patch.
striplevel — which striplevel to use when applying the patch. The default level is 1.
patchdir — specifies the directory in which the patch should be applied. The default is ${S}.

Here are options specific to recipes building code from a revision control system:

mindate — apply the patch only if SRCDATE is equal to or greater than mindate.
maxdate — apply the patch only if SRCDATE is not later than maxdate.
minrev — apply the patch only if SRCREV is equal to or greater than minrev.
maxrev — apply the patch only if SRCREV is not later than maxrev.
rev — apply the patch only if SRCREV is equal to rev.
notrev — apply the patch only if SRCREV is not equal to rev.

Note

If you want the build system to pick up files specified through a SRC_URI statement from your append file, you need to be sure to extend the FILESPATH variable by also using the FILESEXTRAPATHS variable from within your append file.

SRC_URI_OVERRIDES_PACKAGE_ARCH 

By default, the OpenEmbedded build system automatically detects whether SRC_URI contains files that are machine-specific. If so, the build system automatically changes PACKAGE_ARCH. Setting this variable to “0” disables this behavior.

SRCDATE 

The date of the source code used to build the package. This variable applies only if the source was fetched from a Source Code Manager (SCM).

SRCPV 

Returns the version string of the current package. This string is used to help define the value of PV.

The SRCPV variable is defined in the meta/conf/bitbake.conf configuration file in the Source Directory as follows:

SRCPV = "${@bb.fetch2.get_srcrev(d)}"

Recipes that need to define PV do so with the help of the SRCPV. For example, the ofono recipe (ofono_git.bb) located in meta/recipes-connectivity in the Source Directory defines PV as follows:

PV = "0.12-git${SRCPV}"

SRCREV 

The revision of the source code used to build the package. This variable applies to Subversion, Git, Mercurial, and Bazaar only. Note that if you want to build a fixed revision and you want to avoid performing a query on the remote repository every time BitBake parses your recipe, you should specify a SRCREV that is a full revision identifier and not just a tag.

Note

For information on limitations when inheriting the latest revision of software using SRCREV, see the AUTOREV variable description and the “Automatically Incrementing a Package Version Number” section, which is in the Yocto Project Development Tasks Manual.

SRCREV_FORMAT 

See SRCREV_FORMAT in the BitBake manual.

SRCTREECOVEREDTASKS 

A list of tasks that are typically not relevant (and therefore skipped) when building using the externalsrc class. The default value as set in that class file is the set of tasks that are rarely needed when using external source:

SRCTREECOVEREDTASKS ?= "do_patch do_unpack do_fetch"

The notable exception is when processing external kernel source as defined in the kernel-yocto class file (formatted for aesthetics):

SRCTREECOVEREDTASKS += "\
  do_validate_branches \
  do_kernel_configcheck \
  do_kernel_checkout \
  do_fetch \
  do_unpack \
  do_patch \
"

See the associated EXTERNALSRC and EXTERNALSRC_BUILD variables for more information.

SSTATE_DIR 

The directory for the shared state cache.

SSTATE_EXCLUDEDEPS_SYSROOT 

This variable allows to specify indirect dependencies to exclude from sysroots, for example to avoid the situations when a dependency on any -native recipe will pull in all dependencies of that recipe in the recipe sysroot. This behaviour might not always be wanted, for example when that -native recipe depends on build tools that are not relevant for the current recipe.

This way, irrelevant dependencies are ignored, which could have prevented the reuse of prebuilt artifacts stored in the Shared State Cache.

SSTATE_EXCLUDEDEPS_SYSROOT is evaluated as two regular expressions of recipe and dependency to ignore. An example is the rule in meta/conf/layer.conf:

# Nothing needs to depend on libc-initial
# base-passwd/shadow-sysroot don't need their dependencies
SSTATE_EXCLUDEDEPS_SYSROOT += "\
    .*->.*-initial.* \
    .*(base-passwd|shadow-sysroot)->.* \
"

The -> substring represents the dependency between the two regular expressions.

SSTATE_MIRROR_ALLOW_NETWORK 

If set to “1”, allows fetches from mirrors that are specified in SSTATE_MIRRORS to work even when fetching from the network is disabled by setting BB_NO_NETWORK to “1”. Using the SSTATE_MIRROR_ALLOW_NETWORK variable is useful if you have set SSTATE_MIRRORS to point to an internal server for your shared state cache, but you want to disable any other fetching from the network.

SSTATE_MIRRORS 

Configures the OpenEmbedded build system to search other mirror locations for prebuilt cache data objects before building out the data. This variable works like fetcher MIRRORS and PREMIRRORS and points to the cache locations to check for the shared state (sstate) objects.

You can specify a filesystem directory or a remote URL such as HTTP or FTP. The locations you specify need to contain the shared state cache (sstate-cache) results from previous builds. The sstate-cache you point to can also be from builds on other machines.

When pointing to sstate build artifacts on another machine that uses a different GCC version for native builds, you must configure SSTATE_MIRRORS with a regular expression that maps local search paths to server paths. The paths need to take into account NATIVELSBSTRING set by the uninative class. For example, the following maps the local search path universal-4.9 to the server-provided path server_url_sstate_path:

SSTATE_MIRRORS ?= "file://universal-4.9/(.*) https://server_url_sstate_path/universal-4.8/\1"

If a mirror uses the same structure as SSTATE_DIR, you need to add “PATH” at the end as shown in the examples below. The build system substitutes the correct path within the directory structure:

SSTATE_MIRRORS ?= "\
    file://.* https://someserver.tld/share/sstate/PATH;downloadfilename=PATH \
    file://.* file:///some-local-dir/sstate/PATH"

SSTATE_SCAN_FILES 

Controls the list of files the OpenEmbedded build system scans for hardcoded installation paths. The variable uses a space-separated list of filenames (not paths) with standard wildcard characters allowed.

During a build, the OpenEmbedded build system creates a shared state (sstate) object during the first stage of preparing the sysroots. That object is scanned for hardcoded paths for original installation locations. The list of files that are scanned for paths is controlled by the SSTATE_SCAN_FILES variable. Typically, recipes add files they want to be scanned to the value of SSTATE_SCAN_FILES rather than the variable being comprehensively set. The sstate class specifies the default list of files.

For details on the process, see the staging class.

STAGING_BASE_LIBDIR_NATIVE 

Specifies the path to the /lib subdirectory of the sysroot directory for the build host.

STAGING_BASELIBDIR 

Specifies the path to the /lib subdirectory of the sysroot directory for the target for which the current recipe is being built (STAGING_DIR_HOST).

STAGING_BINDIR 

Specifies the path to the /usr/bin subdirectory of the sysroot directory for the target for which the current recipe is being built (STAGING_DIR_HOST).

STAGING_BINDIR_CROSS 

Specifies the path to the directory containing binary configuration scripts. These scripts provide configuration information for other software that wants to make use of libraries or include files provided by the software associated with the script.

Note

This style of build configuration has been largely replaced by pkg-config. Consequently, if pkg-config is supported by the library to which you are linking, it is recommended you use pkg-config instead of a provided configuration script.

STAGING_BINDIR_NATIVE 

Specifies the path to the /usr/bin subdirectory of the sysroot directory for the build host.

STAGING_DATADIR 

Specifies the path to the /usr/share subdirectory of the sysroot directory for the target for which the current recipe is being built (STAGING_DIR_HOST).

STAGING_DATADIR_NATIVE 

Specifies the path to the /usr/share subdirectory of the sysroot directory for the build host.

STAGING_DIR 

Helps construct the recipe-sysroots directory, which is used during packaging.

For information on how staging for recipe-specific sysroots occurs, see the do_populate_sysroot task, the “Sharing Files Between Recipes” section in the Yocto Project Development Tasks Manual, the “Configuration, Compilation, and Staging” section in the Yocto Project Overview and Concepts Manual, and the SYSROOT_DIRS variable.

Note

Recipes should never write files directly under the STAGING_DIR directory because the OpenEmbedded build system manages the directory automatically. Instead, files should be installed to ${D} within your recipe’s do_install task and then the OpenEmbedded build system will stage a subset of those files into the sysroot.

STAGING_DIR_HOST 

Specifies the path to the sysroot directory for the system on which the component is built to run (the system that hosts the component). For most recipes, this sysroot is the one in which that recipe’s do_populate_sysroot task copies files. Exceptions include -native recipes, where the do_populate_sysroot task instead uses STAGING_DIR_NATIVE. Depending on the type of recipe and the build target, STAGING_DIR_HOST can have the following values:

For recipes building for the target machine, the value is “${STAGING_DIR}/${MACHINE}”.
For native recipes building for the build host, the value is empty given the assumption that when building for the build host, the build host’s own directories should be used.

Note

-native recipes are not installed into host paths like such as /usr. Rather, these recipes are installed into STAGING_DIR_NATIVE. When compiling -native recipes, standard build environment variables such as CPPFLAGS and CFLAGS are set up so that both host paths and STAGING_DIR_NATIVE are searched for libraries and headers using, for example, GCC’s -isystem option.

Thus, the emphasis is that the STAGING_DIR* variables should be viewed as input variables by tasks such as do_configure, do_compile, and do_install. Having the real system root correspond to STAGING_DIR_HOST makes conceptual sense for -native recipes, as they make use of host headers and libraries.

STAGING_DIR_NATIVE 

Specifies the path to the sysroot directory used when building components that run on the build host itself.

STAGING_DIR_TARGET 

Specifies the path to the sysroot used for the system for which the component generates code. For components that do not generate code, which is the majority, STAGING_DIR_TARGET is set to match STAGING_DIR_HOST.

Some recipes build binaries that can run on the target system but those binaries in turn generate code for another different system (e.g. cross-canadian recipes). Using terminology from GNU, the primary system is referred to as the “HOST” and the secondary, or different, system is referred to as the “TARGET”. Thus, the binaries run on the “HOST” system and generate binaries for the “TARGET” system. The STAGING_DIR_HOST variable points to the sysroot used for the “HOST” system, while STAGING_DIR_TARGET points to the sysroot used for the “TARGET” system.

STAGING_ETCDIR_NATIVE 

Specifies the path to the /etc subdirectory of the sysroot directory for the build host.

STAGING_EXECPREFIXDIR 

Specifies the path to the /usr subdirectory of the sysroot directory for the target for which the current recipe is being built (STAGING_DIR_HOST).

STAGING_INCDIR 

Specifies the path to the /usr/include subdirectory of the sysroot directory for the target for which the current recipe being built (STAGING_DIR_HOST).

STAGING_INCDIR_NATIVE 

Specifies the path to the /usr/include subdirectory of the sysroot directory for the build host.

STAGING_KERNEL_BUILDDIR 

Points to the directory containing the kernel build artifacts. Recipes building software that needs to access kernel build artifacts (e.g. systemtap-uprobes) can look in the directory specified with the STAGING_KERNEL_BUILDDIR variable to find these artifacts after the kernel has been built.

STAGING_KERNEL_DIR 

The directory with kernel headers that are required to build out-of-tree modules.

STAGING_LIBDIR 

Specifies the path to the /usr/lib subdirectory of the sysroot directory for the target for which the current recipe is being built (STAGING_DIR_HOST).

STAGING_LIBDIR_NATIVE 

Specifies the path to the /usr/lib subdirectory of the sysroot directory for the build host.

STAMP 

Specifies the base path used to create recipe stamp files. The path to an actual stamp file is constructed by evaluating this string and then appending additional information. Currently, the default assignment for STAMP as set in the meta/conf/bitbake.conf file is:

STAMP = "${STAMPS_DIR}/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}"

For information on how BitBake uses stamp files to determine if a task should be rerun, see the “Stamp Files and the Rerunning of Tasks” section in the Yocto Project Overview and Concepts Manual.

See STAMPS_DIR, MULTIMACH_TARGET_SYS, PN, EXTENDPE, PV, and PR for related variable information.

STAMPCLEAN 

See STAMPCLEAN in the BitBake manual.

STAMPS_DIR 

Specifies the base directory in which the OpenEmbedded build system places stamps. The default directory is ${TMPDIR}/stamps.

STRIP 

The minimal command and arguments to run strip, which is used to strip symbols.

SUMMARY 

The short (72 characters or less) summary of the binary package for packaging systems such as opkg, rpm, or dpkg. By default, SUMMARY is used to define the DESCRIPTION variable if DESCRIPTION is not set in the recipe.

SVNDIR 

The directory in which files checked out of a Subversion system are stored.

SYSLINUX_DEFAULT_CONSOLE 

Specifies the kernel boot default console. If you want to use a console other than the default, set this variable in your recipe as follows where “X” is the console number you want to use:

SYSLINUX_DEFAULT_CONSOLE = "console=ttyX"

The syslinux class initially sets this variable to null but then checks for a value later.

SYSLINUX_OPTS 

Lists additional options to add to the syslinux file. You need to set this variable in your recipe. If you want to list multiple options, separate the options with a semicolon character (;).

The syslinux class uses this variable to create a set of options.

SYSLINUX_SERIAL 

Specifies the alternate serial port or turns it off. To turn off serial, set this variable to an empty string in your recipe. The variable’s default value is set in the syslinux class as follows:

SYSLINUX_SERIAL ?= "0 115200"

The class checks for and uses the variable as needed.

SYSLINUX_SERIAL_TTY 

Specifies the alternate console=tty… kernel boot argument. The variable’s default value is set in the syslinux class as follows:

SYSLINUX_SERIAL_TTY ?= "console=ttyS0,115200"

The class checks for and uses the variable as needed.

SYSLINUX_SPLASH 

An .LSS file used as the background for the VGA boot menu when you use the boot menu. You need to set this variable in your recipe.

The syslinux class checks for this variable and if found, the OpenEmbedded build system installs the splash screen.

SYSROOT_DESTDIR 

Points to the temporary directory under the work directory (default “${WORKDIR}/sysroot-destdir”) where the files populated into the sysroot are assembled during the do_populate_sysroot task.

SYSROOT_DIRS 

Directories that are staged into the sysroot by the do_populate_sysroot task. By default, the following directories are staged:

SYSROOT_DIRS = " \
    ${includedir} \
    ${libdir} \
    ${base_libdir} \
    ${nonarch_base_libdir} \
    ${datadir} \
    /sysroot-only \
    "

SYSROOT_DIRS_IGNORE 

Directories that are not staged into the sysroot by the do_populate_sysroot task. You can use this variable to exclude certain subdirectories of directories listed in SYSROOT_DIRS from staging. By default, the following directories are not staged:

SYSROOT_DIRS_IGNORE = " \
    ${mandir} \
    ${docdir} \
    ${infodir} \
    ${datadir}/X11/locale \
    ${datadir}/applications \
    ${datadir}/bash-completion \
    ${datadir}/fonts \
    ${datadir}/gtk-doc/html \
    ${datadir}/installed-tests \
    ${datadir}/locale \
    ${datadir}/pixmaps \
    ${datadir}/terminfo \
    ${libdir}/${BPN}/ptest \
    "

SYSROOT_DIRS_NATIVE 

Extra directories staged into the sysroot by the do_populate_sysroot task for -native recipes, in addition to those specified in SYSROOT_DIRS. By default, the following extra directories are staged:

SYSROOT_DIRS_NATIVE = " \
    ${bindir} \
    ${sbindir} \
    ${base_bindir} \
    ${base_sbindir} \
    ${libexecdir} \
    ${sysconfdir} \
    ${localstatedir} \
    "

Note

Programs built by -native recipes run directly from the sysroot (STAGING_DIR_NATIVE), which is why additional directories containing program executables and supporting files need to be staged.

SYSROOT_PREPROCESS_FUNCS 

A list of functions to execute after files are staged into the sysroot. These functions are usually used to apply additional processing on the staged files, or to stage additional files.

SYSTEMD_AUTO_ENABLE 

When inheriting the systemd class, this variable specifies whether the specified service in SYSTEMD_SERVICE should start automatically or not. By default, the service is enabled to automatically start at boot time. The default setting is in the systemd class as follows:

SYSTEMD_AUTO_ENABLE ??= "enable"

You can disable the service by setting the variable to “disable”.

SYSTEMD_BOOT_CFG 

When EFI_PROVIDER is set to “systemd-boot”, the SYSTEMD_BOOT_CFG variable specifies the configuration file that should be used. By default, the systemd-boot class sets the SYSTEMD_BOOT_CFG as follows:

SYSTEMD_BOOT_CFG ?= "${S}/loader.conf"

For information on Systemd-boot, see the Systemd-boot documentation.

SYSTEMD_BOOT_ENTRIES 

When EFI_PROVIDER is set to “systemd-boot”, the SYSTEMD_BOOT_ENTRIES variable specifies a list of entry files (*.conf) to install that contain one boot entry per file. By default, the systemd-boot class sets the SYSTEMD_BOOT_ENTRIES as follows:

SYSTEMD_BOOT_ENTRIES ?= ""

For information on Systemd-boot, see the Systemd-boot documentation.

SYSTEMD_BOOT_TIMEOUT 

When EFI_PROVIDER is set to “systemd-boot”, the SYSTEMD_BOOT_TIMEOUT variable specifies the boot menu timeout in seconds. By default, the systemd-boot class sets the SYSTEMD_BOOT_TIMEOUT as follows:

SYSTEMD_BOOT_TIMEOUT ?= "10"

For information on Systemd-boot, see the Systemd-boot documentation.

SYSTEMD_DEFAULT_TARGET 

This variable allows to set the default unit that systemd starts at bootup. Usually, this is either multi-user.target or graphical.target. This works by creating a default.target symbolic link to the chosen systemd target file.

See systemd’s documentation for details.

For example, this variable is used in the core-image-minimal-xfce.bb recipe:

SYSTEMD_DEFAULT_TARGET = "graphical.target"

SYSTEMD_PACKAGES 

When inheriting the systemd class, this variable locates the systemd unit files when they are not found in the main recipe’s package. By default, the SYSTEMD_PACKAGES variable is set such that the systemd unit files are assumed to reside in the recipes main package:

SYSTEMD_PACKAGES ?= "${PN}"

If these unit files are not in this recipe’s main package, you need to use SYSTEMD_PACKAGES to list the package or packages in which the build system can find the systemd unit files.

SYSTEMD_SERVICE 

When inheriting the systemd class, this variable specifies the systemd service name for a package.

Multiple services can be specified, each one separated by a space.

When you specify this file in your recipe, use a package name override to indicate the package to which the value applies. Here is an example from the connman recipe:

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

The package overrides that can be specified are directly related to the value of SYSTEMD_PACKAGES. Overrides not included in SYSTEMD_PACKAGES will be silently ignored.

SYSVINIT_ENABLED_GETTYS 

When using SysVinit, specifies a space-separated list of the virtual terminals that should run a getty (allowing login), assuming USE_VT is not set to “0”.

The default value for SYSVINIT_ENABLED_GETTYS is “1” (i.e. only run a getty on the first virtual terminal).

T 

This variable points to a directory were BitBake places temporary files, which consist mostly of task logs and scripts, when building a particular recipe. The variable is typically set as follows:

T = "${WORKDIR}/temp"

The WORKDIR is the directory into which BitBake unpacks and builds the recipe. The default bitbake.conf file sets this variable.

The T variable is not to be confused with the TMPDIR variable, which points to the root of the directory tree where BitBake places the output of an entire build.

TARGET_ARCH 

The target machine’s architecture. The OpenEmbedded build system supports many architectures. Here is an example list of architectures supported. This list is by no means complete as the architecture is configurable:

arm
i586
x86_64
powerpc
powerpc64
mips
mipsel

For additional information on machine architectures, see the TUNE_ARCH variable.

TARGET_AS_ARCH 

Specifies architecture-specific assembler flags for the target system. TARGET_AS_ARCH is initialized from TUNE_ASARGS by default in the BitBake configuration file (meta/conf/bitbake.conf):

TARGET_AS_ARCH = "${TUNE_ASARGS}"

TARGET_CC_ARCH 

Specifies architecture-specific C compiler flags for the target system. TARGET_CC_ARCH is initialized from TUNE_CCARGS by default.

Note

It is a common workaround to append LDFLAGS to TARGET_CC_ARCH in recipes that build software for the target that would not otherwise respect the exported LDFLAGS variable.

TARGET_CC_KERNEL_ARCH 

This is a specific kernel compiler flag for a CPU or Application Binary Interface (ABI) tune. The flag is used rarely and only for cases where a userspace TUNE_CCARGS is not compatible with the kernel compilation. The TARGET_CC_KERNEL_ARCH variable allows the kernel (and associated modules) to use a different configuration. See the meta/conf/machine/include/arm/feature-arm-thumb.inc file in the Source Directory for an example.

TARGET_CFLAGS 

Specifies the flags to pass to the C compiler when building for the target. When building in the target context, CFLAGS is set to the value of this variable by default.

Additionally, the SDK’s environment setup script sets the CFLAGS variable in the environment to the TARGET_CFLAGS value so that executables built using the SDK also have the flags applied.

TARGET_CPPFLAGS 

Specifies the flags to pass to the C pre-processor (i.e. to both the C and the C++ compilers) when building for the target. When building in the target context, CPPFLAGS is set to the value of this variable by default.

Additionally, the SDK’s environment setup script sets the CPPFLAGS variable in the environment to the TARGET_CPPFLAGS value so that executables built using the SDK also have the flags applied.

TARGET_CXXFLAGS 

Specifies the flags to pass to the C++ compiler when building for the target. When building in the target context, CXXFLAGS is set to the value of this variable by default.

Additionally, the SDK’s environment setup script sets the CXXFLAGS variable in the environment to the TARGET_CXXFLAGS value so that executables built using the SDK also have the flags applied.

TARGET_FPU 

Specifies the method for handling FPU code. For FPU-less targets, which include most ARM CPUs, the variable must be set to “soft”. If not, the kernel emulation gets used, which results in a performance penalty.

TARGET_LD_ARCH 

Specifies architecture-specific linker flags for the target system. TARGET_LD_ARCH is initialized from TUNE_LDARGS by default in the BitBake configuration file (meta/conf/bitbake.conf):

TARGET_LD_ARCH = "${TUNE_LDARGS}"

TARGET_LDFLAGS 

Specifies the flags to pass to the linker when building for the target. When building in the target context, LDFLAGS is set to the value of this variable by default.

Additionally, the SDK’s environment setup script sets the LDFLAGS variable in the environment to the TARGET_LDFLAGS value so that executables built using the SDK also have the flags applied.

TARGET_OS 

Specifies the target’s operating system. The variable can be set to “linux” for glibc-based systems (GNU C Library) and to “linux-musl” for musl libc. For ARM/EABI targets, the possible values are “linux-gnueabi” and “linux-musleabi”.

TARGET_PREFIX 

Specifies the prefix used for the toolchain binary target tools.

Depending on the type of recipe and the build target, TARGET_PREFIX is set as follows:

For recipes building for the target machine, the value is “${TARGET_SYS}-“.
For native recipes, the build system sets the variable to the value of BUILD_PREFIX.
For native SDK recipes (nativesdk), the build system sets the variable to the value of SDK_PREFIX.

TARGET_SYS 

Specifies the system, including the architecture and the operating system, for which the build is occurring in the context of the current recipe.

The OpenEmbedded build system automatically sets this variable based on TARGET_ARCH, TARGET_VENDOR, and TARGET_OS variables.

Note

You do not need to set the TARGET_SYS variable yourself.

Consider these two examples:

Given a native recipe on a 32-bit, x86 machine running Linux, the value is “i686-linux”.
Given a recipe being built for a little-endian, MIPS target running Linux, the value might be “mipsel-linux”.

TARGET_VENDOR 

Specifies the name of the target vendor.

TC_CXX_RUNTIME 

Specifies the C/C++ STL and runtime variant to use during the build process. Default value is ‘gnu’

You can select “gnu”, “llvm”, or “android”.

TCLIBC 

Specifies the GNU standard C library (libc) variant to use during the build process.

You can select “glibc”, “musl”, “newlib”, or “baremetal”.

TCLIBCAPPEND 

Specifies a suffix to be appended onto the TMPDIR value. The suffix identifies the libc variant for building. When you are building for multiple variants with the same Build Directory, this mechanism ensures that output for different libc variants is kept separate to avoid potential conflicts.

In the defaultsetup.conf file, the default value of TCLIBCAPPEND is “-${TCLIBC}”. However, distros such as poky, which normally only support one libc variant, set TCLIBCAPPEND to “” in their distro configuration file resulting in no suffix being applied.

TCMODE 

Specifies the toolchain selector. TCMODE controls the characteristics of the generated packages and images by telling the OpenEmbedded build system which toolchain profile to use. By default, the OpenEmbedded build system builds its own internal toolchain. The variable’s default value is “default”, which uses that internal toolchain.

Note

If TCMODE is set to a value other than “default”, then it is your responsibility to ensure that the toolchain is compatible with the default toolchain. Using older or newer versions of these components might cause build problems. See Release Information for your version of the Yocto Project, to find the specific components with which the toolchain must be compatible.

The TCMODE variable is similar to TCLIBC, which controls the variant of the GNU standard C library (libc) used during the build process: glibc or musl.

With additional layers, it is possible to use a pre-compiled external toolchain. One example is the Sourcery G++ Toolchain. The support for this toolchain resides in the separate Mentor Graphics meta-sourcery layer at https://github.com/MentorEmbedded/meta-sourcery/.

The layer’s README file contains information on how to use the Sourcery G++ Toolchain as an external toolchain. You will have to add the layer to your bblayers.conf file and then set the EXTERNAL_TOOLCHAIN variable in your local.conf file to the location of the toolchain.

The fundamentals used for this example apply to any external toolchain. You can use meta-sourcery as a template for adding support for other external toolchains.

In addition to toolchain configuration, you will also need a corresponding toolchain recipe file. This recipe file needs to package up any pre-built objects in the toolchain such as libgcc, libstdcc++, any locales, and libc.

TEMPLATECONF 

Specifies the directory used by the build system to find templates from which to build the bblayers.conf and local.conf files. Use this variable if you wish to customize such files, and the default BitBake targets shown when sourcing the oe-init-build-env script.

For details, see the Creating a Custom Template Configuration Directory section in the Yocto Project Development Tasks manual.

Note

You must set this variable in the external environment in order for it to work.

TEST_EXPORT_DIR 

The location the OpenEmbedded build system uses to export tests when the TEST_EXPORT_ONLY variable is set to “1”.

The TEST_EXPORT_DIR variable defaults to "${TMPDIR}/testimage/${PN}".

TEST_EXPORT_ONLY 

Specifies to export the tests only. Set this variable to “1” if you do not want to run the tests but you want them to be exported in a manner that you to run them outside of the build system.

TEST_LOG_DIR 

Holds the SSH log and the boot log for QEMU machines. The TEST_LOG_DIR variable defaults to "${WORKDIR}/testimage".

Note

Actual test results reside in the task log (log.do_testimage), which is in the ${WORKDIR}/temp/ directory.

TEST_POWERCONTROL_CMD 

For automated hardware testing, specifies the command to use to control the power of the target machine under test. Typically, this command would point to a script that performs the appropriate action (e.g. interacting with a web-enabled power strip). The specified command should expect to receive as the last argument “off”, “on” or “cycle” specifying to power off, on, or cycle (power off and then power on) the device, respectively.

TEST_POWERCONTROL_EXTRA_ARGS 

For automated hardware testing, specifies additional arguments to pass through to the command specified in TEST_POWERCONTROL_CMD. Setting TEST_POWERCONTROL_EXTRA_ARGS is optional. You can use it if you wish, for example, to separate the machine-specific and non-machine-specific parts of the arguments.

TEST_QEMUBOOT_TIMEOUT 

The time in seconds allowed for an image to boot before automated runtime tests begin to run against an image. The default timeout period to allow the boot process to reach the login prompt is 500 seconds. You can specify a different value in the local.conf file.

For more information on testing images, see the “Performing Automated Runtime Testing” section in the Yocto Project Development Tasks Manual.

TEST_SERIALCONTROL_CMD 

For automated hardware testing, specifies the command to use to connect to the serial console of the target machine under test. This command simply needs to connect to the serial console and forward that connection to standard input and output as any normal terminal program does.

For example, to use the Picocom terminal program on serial device /dev/ttyUSB0 at 115200bps, you would set the variable as follows:

TEST_SERIALCONTROL_CMD = "picocom /dev/ttyUSB0 -b 115200"

TEST_SERIALCONTROL_EXTRA_ARGS 

For automated hardware testing, specifies additional arguments to pass through to the command specified in TEST_SERIALCONTROL_CMD. Setting TEST_SERIALCONTROL_EXTRA_ARGS is optional. You can use it if you wish, for example, to separate the machine-specific and non-machine-specific parts of the command.

TEST_SERVER_IP 

The IP address of the build machine (host machine). This IP address is usually automatically detected. However, if detection fails, this variable needs to be set to the IP address of the build machine (i.e. where the build is taking place).

Note

The TEST_SERVER_IP variable is only used for a small number of tests such as the “dnf” test suite, which needs to download packages from WORKDIR/oe-rootfs-repo.

TEST_SUITES 

An ordered list of tests (modules) to run against an image when performing automated runtime testing.

The OpenEmbedded build system provides a core set of tests that can be used against images.

Note

Currently, there is only support for running these tests under QEMU.

Tests include ping, ssh, df among others. You can add your own tests to the list of tests by appending TEST_SUITES as follows:

TEST_SUITES:append = " mytest"

Alternatively, you can provide the “auto” option to have all applicable tests run against the image:

TEST_SUITES:append = " auto"

Using this option causes the build system to automatically run tests that are applicable to the image. Tests that are not applicable are skipped.

The order in which tests are run is important. Tests that depend on another test must appear later in the list than the test on which they depend. For example, if you append the list of tests with two tests (test_A and test_B) where test_B is dependent on test_A, then you must order the tests as follows:

TEST_SUITES = "test_A test_B"

For more information on testing images, see the “Performing Automated Runtime Testing” section in the Yocto Project Development Tasks Manual.

TEST_TARGET 

Specifies the target controller to use when running tests against a test image. The default controller to use is “qemu”:

TEST_TARGET = "qemu"

A target controller is a class that defines how an image gets deployed on a target and how a target is started. A layer can extend the controllers by adding a module in the layer’s /lib/oeqa/controllers directory and by inheriting the BaseTarget class, which is an abstract class that cannot be used as a value of TEST_TARGET.

You can provide the following arguments with TEST_TARGET:

“qemu”: Boots a QEMU image and runs the tests. See the “Enabling Runtime Tests on QEMU” section in the Yocto Project Development Tasks Manual for more information.
“simpleremote”: Runs the tests on target hardware that is already up and running. The hardware can be on the network or it can be a device running an image on QEMU. You must also set TEST_TARGET_IP when you use “simpleremote”.

Note

This argument is defined in meta/lib/oeqa/controllers/simpleremote.py.

For information on running tests on hardware, see the “Enabling Runtime Tests on Hardware” section in the Yocto Project Development Tasks Manual.

TEST_TARGET_IP 

The IP address of your hardware under test. The TEST_TARGET_IP variable has no effect when TEST_TARGET is set to “qemu”.

When you specify the IP address, you can also include a port. Here is an example:

TEST_TARGET_IP = "192.168.1.4:2201"

Specifying a port is useful when SSH is started on a non-standard port or in cases when your hardware under test is behind a firewall or network that is not directly accessible from your host and you need to do port address translation.

TESTIMAGE_AUTO 

Automatically runs the series of automated tests for images when an image is successfully built. Setting TESTIMAGE_AUTO to “1” causes any image that successfully builds to automatically boot under QEMU. Using the variable also adds in dependencies so that any SDK for which testing is requested is automatically built first.

These tests are written in Python making use of the unittest module, and the majority of them run commands on the target system over ssh. You can set this variable to “1” in your local.conf file in the Build Directory to have the OpenEmbedded build system automatically run these tests after an image successfully builds:

TESTIMAGE_AUTO = “1”

For more information on enabling, running, and writing these tests, see the “Performing Automated Runtime Testing” section in the Yocto Project Development Tasks Manual and the “testimage” section.

THISDIR 

The directory in which the file BitBake is currently parsing is located. Do not manually set this variable.

TIME 

The time the build was started. Times appear using the hour, minute, and second (HMS) format (e.g. “140159” for one minute and fifty-nine seconds past 1400 hours).

TMPDIR 

This variable is the base directory the OpenEmbedded build system uses for all build output and intermediate files (other than the shared state cache). By default, the TMPDIR variable points to tmp within the Build Directory.

If you want to establish this directory in a location other than the default, you can uncomment and edit the following statement in the conf/local.conf file in the Source Directory:

#TMPDIR = "${TOPDIR}/tmp"

An example use for this scenario is to set TMPDIR to a local disk, which does not use NFS, while having the Build Directory use NFS.

The filesystem used by TMPDIR must have standard filesystem semantics (i.e. mixed-case files are unique, POSIX file locking, and persistent inodes). Due to various issues with NFS and bugs in some implementations, NFS does not meet this minimum requirement. Consequently, TMPDIR cannot be on NFS.

TOOLCHAIN_HOST_TASK 

This variable lists packages the OpenEmbedded build system uses when building an SDK, which contains a cross-development environment. The packages specified by this variable are part of the toolchain set that runs on the SDKMACHINE, and each package should usually have the prefix nativesdk-. For example, consider the following command when building an SDK:

$ bitbake -c populate_sdk imagename

In this case, a default list of packages is set in this variable, but you can add additional packages to the list. See the “Adding Individual Packages to the Standard SDK” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual for more information.

For background information on cross-development toolchains in the Yocto Project development environment, see the “The Cross-Development Toolchain” section in the Yocto Project Overview and Concepts Manual. For information on setting up a cross-development environment, see the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

Note that this variable applies to building an SDK, not an eSDK, in which case the TOOLCHAIN_HOST_TASK_ESDK setting should be used instead.

TOOLCHAIN_HOST_TASK_ESDK 

This variable allows to extend what is installed in the host portion of an eSDK. This is similar to TOOLCHAIN_HOST_TASK applying to SDKs.

TOOLCHAIN_OUTPUTNAME 

This variable defines the name used for the toolchain output. The populate_sdk_base class sets the TOOLCHAIN_OUTPUTNAME variable as follows:

TOOLCHAIN_OUTPUTNAME ?= "${SDK_NAME}-toolchain-${SDK_VERSION}"

See the SDK_NAME and SDK_VERSION variables for additional information.

TOOLCHAIN_TARGET_TASK 

This variable lists packages the OpenEmbedded build system uses when it creates the target part of an SDK (i.e. the part built for the target hardware), which includes libraries and headers. Use this variable to add individual packages to the part of the SDK that runs on the target. See the “Adding Individual Packages to the Standard SDK” section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual for more information.

For background information on cross-development toolchains in the Yocto Project development environment, see the “The Cross-Development Toolchain” section in the Yocto Project Overview and Concepts Manual. For information on setting up a cross-development environment, see the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

TOPDIR 

See TOPDIR in the BitBake manual.

TRANSLATED_TARGET_ARCH 

A sanitized version of TARGET_ARCH. This variable is used where the architecture is needed in a value where underscores are not allowed, for example within package filenames. In this case, dash characters replace any underscore characters used in TARGET_ARCH.

Do not edit this variable.

TUNE_ARCH 

The GNU canonical architecture for a specific architecture (i.e. arm, armeb, mips, mips64, and so forth). BitBake uses this value to setup configuration.

TUNE_ARCH definitions are specific to a given architecture. The definitions can be a single static definition, or can be dynamically adjusted. You can see details for a given CPU family by looking at the architecture’s README file. For example, the meta/conf/machine/include/mips/README file in the Source Directory provides information for TUNE_ARCH specific to the mips architecture.

TUNE_ARCH is tied closely to TARGET_ARCH, which defines the target machine’s architecture. The BitBake configuration file (meta/conf/bitbake.conf) sets TARGET_ARCH as follows:

TARGET_ARCH = "${TUNE_ARCH}"

The following list, which is by no means complete since architectures are configurable, shows supported machine architectures:

arm
i586
x86_64
powerpc
powerpc64
mips
mipsel

TUNE_ASARGS 

Specifies architecture-specific assembler flags for the target system. The set of flags is based on the selected tune features. TUNE_ASARGS is set using the tune include files, which are typically under meta/conf/machine/include/ and are influenced through TUNE_FEATURES. For example, the meta/conf/machine/include/x86/arch-x86.inc file defines the flags for the x86 architecture as follows:

TUNE_ASARGS += "${@bb.utils.contains("TUNE_FEATURES", "mx32", "-x32", "", d)}"

Note

Board Support Packages (BSPs) select the tune. The selected tune, in turn, affects the tune variables themselves (i.e. the tune can supply its own set of flags).

TUNE_CCARGS 

Specifies architecture-specific C compiler flags for the target system. The set of flags is based on the selected tune features. TUNE_CCARGS is set using the tune include files, which are typically under meta/conf/machine/include/ and are influenced through TUNE_FEATURES.

Note

Board Support Packages (BSPs) select the tune. The selected tune, in turn, affects the tune variables themselves (i.e. the tune can supply its own set of flags).

TUNE_FEATURES 

Features used to “tune” a compiler for optimal use given a specific processor. The features are defined within the tune files and allow arguments (i.e. TUNE_*ARGS) to be dynamically generated based on the features.

The OpenEmbedded build system verifies the features to be sure they are not conflicting and that they are supported.

The BitBake configuration file (meta/conf/bitbake.conf) defines TUNE_FEATURES as follows:

TUNE_FEATURES ??= "${TUNE_FEATURES:tune-${DEFAULTTUNE}}"

See the DEFAULTTUNE variable for more information.

TUNE_LDARGS 

Specifies architecture-specific linker flags for the target system. The set of flags is based on the selected tune features. TUNE_LDARGS is set using the tune include files, which are typically under meta/conf/machine/include/ and are influenced through TUNE_FEATURES. For example, the meta/conf/machine/include/x86/arch-x86.inc file defines the flags for the x86 architecture as follows:

TUNE_LDARGS += "${@bb.utils.contains("TUNE_FEATURES", "mx32", "-m elf32_x86_64", "", d)}"

Note

Board Support Packages (BSPs) select the tune. The selected tune, in turn, affects the tune variables themselves (i.e. the tune can supply its own set of flags).

TUNE_PKGARCH 

The package architecture understood by the packaging system to define the architecture, ABI, and tuning of output packages. The specific tune is defined using the “_tune” override as follows:

TUNE_PKGARCH:tune-tune = "tune"

These tune-specific package architectures are defined in the machine include files. Here is an example of the “core2-32” tuning as used in the meta/conf/machine/include/x86/tune-core2.inc file:

TUNE_PKGARCH:tune-core2-32 = "core2-32"

TUNECONFLICTS[feature]

Specifies CPU or Application Binary Interface (ABI) tuning features that conflict with feature.

Known tuning conflicts are specified in the machine include files in the Source Directory. Here is an example from the meta/conf/machine/include/mips/arch-mips.inc include file that lists the “o32” and “n64” features as conflicting with the “n32” feature:

TUNECONFLICTS[n32] = "o32 n64"

TUNEVALID[feature]

Specifies a valid CPU or Application Binary Interface (ABI) tuning feature. The specified feature is stored as a flag. Valid features are specified in the machine include files (e.g. meta/conf/machine/include/arm/arch-arm.inc). Here is an example from that file:

TUNEVALID[bigendian] = "Enable big-endian mode."

See the machine include files in the Source Directory for these features.

UBOOT_CONFIG 

Configures the UBOOT_MACHINE and can also define IMAGE_FSTYPES for individual cases.

Following is an example from the meta-fsl-arm layer.

UBOOT_CONFIG ??= "sd"
UBOOT_CONFIG[sd] = "mx6qsabreauto_config,sdcard"
UBOOT_CONFIG[eimnor] = "mx6qsabreauto_eimnor_config"
UBOOT_CONFIG[nand] = "mx6qsabreauto_nand_config,ubifs"
UBOOT_CONFIG[spinor] = "mx6qsabreauto_spinor_config"

In this example, “sd” is selected as the configuration of the possible four for the UBOOT_MACHINE. The “sd” configuration defines “mx6qsabreauto_config” as the value for UBOOT_MACHINE, while the “sdcard” specifies the IMAGE_FSTYPES to use for the U-Boot image.

For more information on how the UBOOT_CONFIG is handled, see the uboot-config class.

UBOOT_DTB_LOADADDRESS 

Specifies the load address for the dtb image used by U-Boot. During FIT image creation, the UBOOT_DTB_LOADADDRESS variable is used in kernel-fitimage class to specify the load address to be used in creating the dtb sections of Image Tree Source for the FIT image.

UBOOT_DTBO_LOADADDRESS 

Specifies the load address for the dtbo image used by U-Boot. During FIT image creation, the UBOOT_DTBO_LOADADDRESS variable is used in kernel-fitimage class to specify the load address to be used in creating the dtbo sections of Image Tree Source for the FIT image.

UBOOT_ENTRYPOINT 

Specifies the entry point for the U-Boot image. During U-Boot image creation, the UBOOT_ENTRYPOINT variable is passed as a command-line parameter to the uboot-mkimage utility.

UBOOT_LOADADDRESS 

Specifies the load address for the U-Boot image. During U-Boot image creation, the UBOOT_LOADADDRESS variable is passed as a command-line parameter to the uboot-mkimage utility.

UBOOT_LOCALVERSION 

Appends a string to the name of the local version of the U-Boot image. For example, assuming the version of the U-Boot image built was “2013.10”, the full version string reported by U-Boot would be “2013.10-yocto” given the following statement:

UBOOT_LOCALVERSION = "-yocto"

UBOOT_MACHINE 

Specifies the value passed on the make command line when building a U-Boot image. The value indicates the target platform configuration. You typically set this variable from the machine configuration file (i.e. conf/machine/machine_name.conf).

Please see the “Selection of Processor Architecture and Board Type” section in the U-Boot README for valid values for this variable.

UBOOT_MAKE_TARGET 

Specifies the target called in the Makefile. The default target is “all”.

UBOOT_MKIMAGE 

Specifies the name of the mkimage command as used by the kernel-fitimage class to assemble the FIT image. This can be used to substitute an alternative command, wrapper script or function if desired. The default is “uboot-mkimage”.

UBOOT_MKIMAGE_DTCOPTS 

Options for the device tree compiler passed to mkimage ‘-D’ feature while creating FIT image in kernel-fitimage class. If UBOOT_MKIMAGE_DTCOPTS is not set then kernel-fitimage will not pass the -D option to mkimage.

UBOOT_MKIMAGE_KERNEL_TYPE 

Specifies the type argument for the kernel as passed to uboot-mkimage. The default value is “kernel”.

UBOOT_MKIMAGE_SIGN 

Specifies the name of the mkimage command as used by the kernel-fitimage class to sign the FIT image after it has been assembled (if enabled). This can be used to substitute an alternative command, wrapper script or function if desired. The default is “${UBOOT_MKIMAGE}”.

UBOOT_MKIMAGE_SIGN_ARGS 

Optionally specifies additional arguments for the kernel-fitimage class to pass to the mkimage command when signing the FIT image.

UBOOT_RD_ENTRYPOINT 

Specifies the entrypoint for the RAM disk image. During FIT image creation, the UBOOT_RD_ENTRYPOINT variable is used in kernel-fitimage class to specify the entrypoint to be used in creating the Image Tree Source for the FIT image.

UBOOT_RD_LOADADDRESS 

Specifies the load address for the RAM disk image. During FIT image creation, the UBOOT_RD_LOADADDRESS variable is used in kernel-fitimage class to specify the load address to be used in creating the Image Tree Source for the FIT image.

UBOOT_SIGN_ENABLE 

Enable signing of FIT image. The default value is “0”.

UBOOT_SIGN_KEYDIR 

Location of the directory containing the RSA key and certificate used for signing FIT image.

UBOOT_SIGN_KEYNAME 

The name of keys used for signing U-Boot FIT image stored in UBOOT_SIGN_KEYDIR directory. For e.g. dev.key key and dev.crt certificate stored in UBOOT_SIGN_KEYDIR directory will have UBOOT_SIGN_KEYNAME set to “dev”.

UBOOT_SUFFIX 

Points to the generated U-Boot extension. For example, u-boot.sb has a .sb extension.

The default U-Boot extension is .bin

UBOOT_TARGET 

Specifies the target used for building U-Boot. The target is passed directly as part of the “make” command (e.g. SPL and AIS). If you do not specifically set this variable, the OpenEmbedded build process passes and uses “all” for the target during the U-Boot building process.

UNKNOWN_CONFIGURE_OPT_IGNORE 

Specifies a list of options that, if reported by the configure script as being invalid, should not generate a warning during the do_configure task. Normally, invalid configure options are simply not passed to the configure script (e.g. should be removed from EXTRA_OECONF or PACKAGECONFIG_CONFARGS). However, there are common options that are passed to all configure scripts at a class level, but might not be valid for some configure scripts. Therefore warnings about these options are useless. For these cases, the options are added to UNKNOWN_CONFIGURE_OPT_IGNORE.

The configure arguments check that uses UNKNOWN_CONFIGURE_OPT_IGNORE is part of the insane class and is only enabled if the recipe inherits the autotools* class.

UPDATERCPN 

For recipes inheriting the update-rc.d class, UPDATERCPN specifies the package that contains the initscript that is enabled.

The default value is “${PN}”. Given that almost all recipes that install initscripts package them in the main package for the recipe, you rarely need to set this variable in individual recipes.

UPSTREAM_CHECK_COMMITS 

You can perform a per-recipe check for what the latest upstream source code version is by calling devtool latest-version recipe. If the recipe source code is provided from Git repositories, but releases are not identified by Git tags, set UPSTREAM_CHECK_COMMITS to 1 in the recipe, and the OpenEmbedded build system will compare the latest commit with the one currently specified by the recipe (SRCREV):

UPSTREAM_CHECK_COMMITS = "1"

UPSTREAM_CHECK_GITTAGREGEX 

You can perform a per-recipe check for what the latest upstream source code version is by calling devtool latest-version recipe. If the recipe source code is provided from Git repositories, the OpenEmbedded build system determines the latest upstream version by picking the latest tag from the list of all repository tags.

You can use the UPSTREAM_CHECK_GITTAGREGEX variable to provide a regular expression to filter only the relevant tags should the default filter not work correctly:

UPSTREAM_CHECK_GITTAGREGEX = "git_tag_regex"

UPSTREAM_CHECK_REGEX 

Use the UPSTREAM_CHECK_REGEX variable to specify a different regular expression instead of the default one when the package checking system is parsing the page found using UPSTREAM_CHECK_URI:

UPSTREAM_CHECK_REGEX = "package_regex"

UPSTREAM_CHECK_URI 

You can perform a per-recipe check for what the latest upstream source code version is by calling devtool latest-version recipe. If the source code is provided from tarballs, the latest version is determined by fetching the directory listing where the tarball is and attempting to find a later tarball. When this approach does not work, you can use UPSTREAM_CHECK_URI to provide a different URI that contains the link to the latest tarball:

UPSTREAM_CHECK_URI = "recipe_url"

UPSTREAM_VERSION_UNKNOWN 

You can perform a per-recipe check for what the latest upstream source code version is by calling devtool latest-version recipe. If no combination of the UPSTREAM_CHECK_URI, UPSTREAM_CHECK_REGEX, UPSTREAM_CHECK_GITTAGREGEX and UPSTREAM_CHECK_COMMITS variables in the recipe allows to determine what the latest upstream version is, you can set UPSTREAM_VERSION_UNKNOWN to 1 in the recipe to acknowledge that the check cannot be performed:

UPSTREAM_VERSION_UNKNOWN = "1"

USE_DEVFS 

Determines if devtmpfs is used for /dev population. The default value used for USE_DEVFS is “1” when no value is specifically set. Typically, you would set USE_DEVFS to “0” for a statically populated /dev directory.

See the “Selecting a Device Manager” section in the Yocto Project Development Tasks Manual for information on how to use this variable.

USE_VT 

When using SysVinit, determines whether or not to run a getty on any virtual terminals in order to enable logging in through those terminals.

The default value used for USE_VT is “1” when no default value is specifically set. Typically, you would set USE_VT to “0” in the machine configuration file for machines that do not have a graphical display attached and therefore do not need virtual terminal functionality.

USER_CLASSES 

A list of classes to globally inherit. These classes are used by the OpenEmbedded build system to enable extra features.

Classes inherited using USER_CLASSES must be located in the classes-global/ or classes/ subdirectories.

The default list is set in your local.conf file:

USER_CLASSES ?= "buildstats"

For more information, see meta-poky/conf/templates/default/local.conf.sample in the Source Directory.

USERADD_ERROR_DYNAMIC 

If set to error, forces the OpenEmbedded build system to produce an error if the user identification (uid) and group identification (gid) values are not defined in any of the files listed in USERADD_UID_TABLES and USERADD_GID_TABLES. If set to warn, a warning will be issued instead.

The default behavior for the build system is to dynamically apply uid and gid values. Consequently, the USERADD_ERROR_DYNAMIC variable is by default not set. If you plan on using statically assigned gid and uid values, you should set the USERADD_ERROR_DYNAMIC variable in your local.conf file as follows:

USERADD_ERROR_DYNAMIC = "error"

Overriding the default behavior implies you are going to also take steps to set static uid and gid values through use of the USERADDEXTENSION, USERADD_UID_TABLES, and USERADD_GID_TABLES variables.

Note

There is a difference in behavior between setting USERADD_ERROR_DYNAMIC to error and setting it to warn. When it is set to warn, the build system will report a warning for every undefined uid and gid in any recipe. But when it is set to error, it will only report errors for recipes that are actually built. This saves you from having to add static IDs for recipes that you know will never be built.

USERADD_GID_TABLES 

Specifies a password file to use for obtaining static group identification (gid) values when the OpenEmbedded build system adds a group to the system during package installation.

When applying static group identification (gid) values, the OpenEmbedded build system looks in BBPATH for a files/group file and then applies those uid values. Set the variable as follows in your local.conf file:

USERADD_GID_TABLES = "files/group"

Note

Setting the USERADDEXTENSION variable to “useradd-staticids” causes the build system to use static gid values.

USERADD_PACKAGES 

When inheriting the useradd* class, this variable specifies the individual packages within the recipe that require users and/or groups to be added.

You must set this variable if the recipe inherits the class. For example, the following enables adding a user for the main package in a recipe:

USERADD_PACKAGES = "${PN}"

Note

It follows that if you are going to use the USERADD_PACKAGES variable, you need to set one or more of the USERADD_PARAM, GROUPADD_PARAM, or GROUPMEMS_PARAM variables.

USERADD_PARAM 

When inheriting the useradd* class, this variable specifies for a package what parameters should pass to the useradd command if you add a user to the system when the package is installed.

Here is an example from the dbus recipe:

USERADD_PARAM:${PN} = "--system --home ${localstatedir}/lib/dbus \
                       --no-create-home --shell /bin/false \
                       --user-group messagebus"

For information on the standard Linux shell command useradd, see https://linux.die.net/man/8/useradd.

USERADD_UID_TABLES 

Specifies a password file to use for obtaining static user identification (uid) values when the OpenEmbedded build system adds a user to the system during package installation.

When applying static user identification (uid) values, the OpenEmbedded build system looks in BBPATH for a files/passwd file and then applies those uid values. Set the variable as follows in your local.conf file:

USERADD_UID_TABLES = "files/passwd"

Note

Setting the USERADDEXTENSION variable to “useradd-staticids” causes the build system to use static uid values.

USERADDEXTENSION 

When set to “useradd-staticids”, causes the OpenEmbedded build system to base all user and group additions on a static passwd and group files found in BBPATH.

To use static user identification (uid) and group identification (gid) values, set the variable as follows in your local.conf file: USERADDEXTENSION = “useradd-staticids”

Note

Setting this variable to use static uid and gid values causes the OpenEmbedded build system to employ the useradd* class.

If you use static uid and gid information, you must also specify the files/passwd and files/group files by setting the USERADD_UID_TABLES and USERADD_GID_TABLES variables. Additionally, you should also set the USERADD_ERROR_DYNAMIC variable.

VOLATILE_LOG_DIR 

Specifies the persistence of the target’s /var/log directory, which is used to house postinstall target log files.

By default, VOLATILE_LOG_DIR is set to “yes”, which means the file is not persistent. You can override this setting by setting the variable to “no” to make the log directory persistent.

VOLATILE_TMP_DIR 

Specifies the persistence of the target’s /tmp directory.

By default, VOLATILE_TMP_DIR is set to “yes”, in which case /tmp links to a directory which resides in RAM in a tmpfs filesystem.

If instead, you want the /tmp directory to be persistent, set the variable to “no” to make it a regular directory in the root filesystem.

This supports both sysvinit and systemd based systems.

WARN_QA 

Specifies the quality assurance checks whose failures are reported as warnings by the OpenEmbedded build system. You set this variable in your distribution configuration file. For a list of the checks you can control with this variable, see the “insane” section.

WATCHDOG_TIMEOUT 

Specifies the timeout in seconds used by the watchdog recipe and also by systemd during reboot. The default is 60 seconds.

WIRELESS_DAEMON 

For connman and packagegroup-base, specifies the wireless daemon to use. The default is “wpa-supplicant” (note that the value uses a dash and not an underscore).

WKS_FILE 

Specifies the location of the Wic kickstart file that is used by the OpenEmbedded build system to create a partitioned image (image.wic). For information on how to create a partitioned image, see the “Creating Partitioned Images Using Wic” section in the Yocto Project Development Tasks Manual. For details on the kickstart file format, see the “OpenEmbedded Kickstart (.wks) Reference” Chapter.

WKS_FILE_DEPENDS 

When placed in the recipe that builds your image, this variable lists build-time dependencies. The WKS_FILE_DEPENDS variable is only applicable when Wic images are active (i.e. when IMAGE_FSTYPES contains entries related to Wic). If your recipe does not create Wic images, the variable has no effect.

The WKS_FILE_DEPENDS variable is similar to the DEPENDS variable. When you use the variable in your recipe that builds the Wic image, dependencies you list in the WKS_FILE_DEPENDS variable are added to the DEPENDS variable.

With the WKS_FILE_DEPENDS variable, you have the possibility to specify a list of additional dependencies (e.g. native tools, bootloaders, and so forth), that are required to build Wic images. Following is an example:

WKS_FILE_DEPENDS = "some-native-tool"

In the previous example, some-native-tool would be replaced with an actual native tool on which the build would depend.

WKS_FILES 

Specifies a list of candidate Wic kickstart files to be used by the OpenEmbedded build system to create a partitioned image. Only the first one that is found, from left to right, will be used.

This is only useful when there are multiple .wks files that can be used to produce an image. A typical case is when multiple layers are used for different hardware platforms, each supplying a different .wks file. In this case, you specify all possible ones through WKS_FILES.

If only one .wks file is used, set WKS_FILE instead.

WORKDIR 

The pathname of the work directory in which the OpenEmbedded build system builds a recipe. This directory is located within the TMPDIR directory structure and is specific to the recipe being built and the system for which it is being built.

The WORKDIR directory is defined as follows:

${TMPDIR}/work/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}

The actual directory depends on several things:

TMPDIR: The top-level build output directory
MULTIMACH_TARGET_SYS: The target system identifier
PN: The recipe name
EXTENDPE: The epoch — if PE is not specified, which is usually the case for most recipes, then EXTENDPE is blank.
PV: The recipe version
PR: The recipe revision

As an example, assume a Source Directory top-level folder name poky, a default Build Directory at poky/build, and a qemux86-poky-linux machine target system. Furthermore, suppose your recipe is named foo_1.3.0-r0.bb. In this case, the work directory the build system uses to build the package would be as follows:

poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0

XSERVER 

Specifies the packages that should be installed to provide an X server and drivers for the current machine, assuming your image directly includes packagegroup-core-x11-xserver or, perhaps indirectly, includes “x11-base” in IMAGE_FEATURES.

The default value of XSERVER, if not specified in the machine configuration, is “xserver-xorg xf86-video-fbdev xf86-input-evdev”.

XZ_MEMLIMIT 

Specifies the maximum memory the xz compression should use as a percentage of system memory. If unconstrained the xz compressor can use large amounts of memory and become problematic with parallelism elsewhere in the build. “50%” has been found to be a good value.

XZ_THREADS 

Specifies the number of parallel threads that should be used when using xz compression.

By default this scales with core count, but is never set less than 2 to ensure that multi-threaded mode is always used so that the output file contents are deterministic. Builds will work with a value of 1 but the output will differ compared to the output from the compression generated when more than one thread is used.

On systems where many tasks run in parallel, setting a limit to this can be helpful in controlling system resource usage.

ZSTD_THREADS 

Specifies the number of parallel threads that should be used when using ZStandard compression.

By default this scales with core count, but is never set less than 2 to ensure that multi-threaded mode is always used so that the output file contents are deterministic. Builds will work with a value of 1 but the output will differ compared to the output from the compression generated when more than one thread is used.

On systems where many tasks run in parallel, setting a limit to this can be helpful in controlling system resource usage.