# 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 H I K L M O P R S T U W

### A

ALLOW_EMPTY

  Specifies if an output package should still be produced 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 runtime hard-requirement on the existence of the package.

  Like all package-controlling variables, you must always use them in conjunction with a package name override. Here is an example:

           ALLOW_EMPTY_${PN} = "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 also exist as part of another package. For example, if the `busybox` package has four commands that also exist as part of another package, you identify them as follows:

           ALTERNATIVE_busybox = "sh sed test bracket"

  For more information on the alternatives system, see the "Alternatives - `update-alternatives.bbclass`" 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/`.

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

  For more information on the alternatives system, see the "Alternatives - `update-alternatives.bbclass`" 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 "Alternatives - `update-alternatives.bbclass`" 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>"

  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 "Alternatives - `update-alternatives.bbclass`" section.

AUTHOR

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

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}"

### B

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:

           B = "${WORKDIR}/${BPN}/{PV}/"

  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.

  Support for this variable exists only when using the IPK and RPM packaging backend. Support does not exist for DEB.

  See the `NO_RECOMMENDATIONS` and the `PACKAGE_EXCLUDE` variables for related information.

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" in the `local.conf` file in the Build Directory as follows:

           BB_DANGLINGAPPENDS_WARNONLY = "1"

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 abort 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 abort 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 aborts 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_GENERATE_MIRROR_TARBALLS

  Causes tarballs of the Git repositories to be placed in the `DL_DIR` directory. For performance reasons, creating and placing tarballs of the Git 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.
BB_NUMBER_THREADS

  The maximum number of tasks BitBake should run in parallel at any one time. If your host development system supports multiple cores a good rule of thumb is to set this variable to twice the number of cores.

BBCLASSEXTEND

  Allows you to extend a recipe so that it builds variants of the software. Common variants for recipes exist such 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>"

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).

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

BBFILES

  List of recipe files used by BitBake to build software.

BBINCLUDELOGS

  Variable that controls how BitBake displays logs on build failure.

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

           BBLAYERS_NON_REMOVABLE ?= " \
             /home/scottrif/poky/meta \
             /home/scottrif/poky/meta-yocto \
             "

  This example enables four layers, one of which is a custom, user-defined layer named `meta-mykernel`.
BBLAYERS_NON_REMOVABLE
  Core layer for images cannot be removed

  Lists core layers that cannot be removed from the `bblayers.conf` file. In order for BitBake to build your image, your `bblayers.conf` file must include the `meta` and `meta-yocto` core layers. Here is an example that shows these two layers listed in the `BBLAYERS_NON_REMOVABLE` statement:

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

           BBLAYERS_NON_REMOVABLE ?= " \
             /home/scottrif/poky/meta \
             /home/scottrif/poky/meta-yocto \
             "

BBMASK

  Prevents BitBake from processing recipes and recipe append files. Use the `BBMASK` variable from within the `conf/local.conf` file found in the Build Directory.

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

  The value you provide is passed to Python's regular expression compiler. The expression is compared against the full paths to the files. For complete syntax information, see Python's documentation at .

  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, use the vertical bar to separate the 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 .= "|.*openldap"
           BBMASK .= "|.*opencv"
           BBMASK .= "|.*lzma"

  Notice how the vertical bar is used to append the fragments.

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

BBPATH

  Used by BitBake to locate `.bbclass` and configuration files. This variable is analogous to the `PATH` variable.

  If you run BitBake from a directory outside of the Build Directory, you must be sure to set `BBPATH` to point to the Build Directory. Set the variable as you would any environment variable and then run BitBake:

           $ BBPATH = "<build_directory>"
           $ export BBPATH
           $ bitbake <target>

BBSERVER

  Points to the server that runs memory-resident BitBake. This variable is set by the `oe-init-build-env-memres` setup script and should not be hand-edited. The variable is only used when you employ memory-resident BitBake. The setup script exports the value as follows:

           export BBSERVER=localhost:$port

  For more information on how the `BBSERVER` is used, see the `oe-init-build-env-memres` script, which is located in the Source Directory.
BINCONFIG_GLOB

  When inheriting `binconfig.bbclass` from a recipe, 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.

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

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

  The bare name of the recipe. This variable is a version of the `PN` variable but removes common suffixes such as "-native" and "-cross" as well as removes common prefixes such as multilib's "lib64-" and "lib32-". The exact list of suffixes removed is specified by the `SPECIAL_PKGSUFFIX` variable. The exact list of prefixes removed is specified by the `MLPREFIX` variable. Prefixes are removed for `multilib` and `nativesdk` cases.

BUILDDIR

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

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 a single output executable file. Set the variable to "0" to split the output file.

### C

CFLAGS

  Flags passed to the C compiler for the target system. This variable evaluates to the same as `TARGET_CFLAGS`.

COMBINED_FEATURES

  A set of features common between `MACHINE_FEATURES` and `DISTRO_FEATURES`. See the glossary descriptions for these variables for more information.

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 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'

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"

  A relationship exists 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.

  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_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`.

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.

### D

D

  The destination directory.

DATETIME

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

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 -g".

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.

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

DEPENDS

  Lists a recipe's build-time dependencies (i.e. other recipe files). The system ensures that all the dependencies listed have been built and have their contents in the appropriate sysroots before the recipe's configure task is executed.

  Consider this simple example for two recipes named "a" and "b" that produce similarly named packages. In this example, the `DEPENDS` statement appears in the "a" recipe:

           DEPENDS = "b"

  Here, the dependency is such that the `do_configure` task for recipe "a" depends on the `do_populate_sysroot` task of recipe "b". This means anything that recipe "b" puts into sysroot is available when recipe "a" is configuring itself.

  For information on runtime dependencies, see the `RDEPENDS` variable.

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 `tmp/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" and "Application Development SDK" sections.

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 `${MACHINE}` name. By default, this directory resides within the Build Directory as `tmp/deploy/images/${MACHINE}/`.

  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.

DESCRIPTION

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

DISTRO

  The short name of the distribution. This variable corresponds to a file with the extension `.conf` located in a `conf/distro` directory within the Metadata that contains the distribution configuration. The value must not contain spaces, and is typically all lower-case.

  If the variable is blank, a set of default configuration will be used, which is specified within `meta/conf/distro/defaultsetup.conf`.

DISTRO_EXTRA_RDEPENDS

  Specifies a list of distro-specific packages to add to all images. This variable takes affect 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 features enabled for the distribution. For a list of supported features that ship with the Yocto Project, see the "Distro" section.

DISTRO_FEATURES_BACKFILL

  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. See the Feature backfilling section for more information.

DISTRO_FEATURES_BACKFILL_CONSIDERED

  Features from `DISTRO_FEATURES_BACKFILL` that should not be backfilled (i.e. added to `DISTRO_FEATURES`) during the build. See the "Feature Backfilling" section for more information.

DISTRO_NAME

  The long name of the distribution.

DISTRO_PN_ALIAS

  Alias names used for the recipe in various Linux distributions.

  See the "Handling a Package Name Alias" section in the Yocto Project Development Manual for more information.

DISTRO_VERSION

  the version of the distribution.

DISTROOVERRIDES

  This variable lists overrides specific to the current distribution. By default, the variable list includes the value of the `DISTRO` variable. You can extend the variable to apply any variable overrides you want as part of the distribution and are not already in `OVERRIDES` through some other means.

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.

  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.

### E

ENABLE_BINARY_LOCALE_GENERATION

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

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.bbclass`" section.

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.

  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.

EXTERNALSRC

  If `externalsrc.bbclass` is inherited, 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.

  For more information on `externalsrc.bbclass`, see the "`externalsrc.bbclass`" section. 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 Manual.

EXTERNALSRC_BUILD

  If `externalsrc.bbclass` is inherited, 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.

  For more information on `externalsrc.bbclass`, see the "`externalsrc.bbclass`" section. 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 Manual.

EXTRA_IMAGE_FEATURES

  The list of additional features to include in an image. 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.

  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 development.
                       For example, ssh root access has a blank
                       password.  You should remove this feature
                       before you produce a production image.

      "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 Manual for more
                           information

      "tools-debug" - Adds debugging tools such as gdb and
                      strace.

      "tools-profile" - Adds profiling tools such as oprofile,
                        exmap, lttng and valgrind (x86 only).

      "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 "Images" 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 Manual.

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.

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

EXTRA_OECMAKE

  Additional `cmake` options.

EXTRA_OECONF

  Additional `configure` script options.

EXTRA_OEMAKE

  Additional GNU `make` options.

### F

FILES

  The list of directories or files that are placed in packages.

  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 identifies the files you want included as part of the resulting package. Here is an example:

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

  When specifying paths as part of the `FILES` 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.

  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.

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.

  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.

  Here is a final example that specifically adds three paths:

           FILESEXTRAPATHS_prepend := "path_1:path_2:path_3:"

  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`. You can find more information on how overrides are handled in the BitBake Manual that is located at `bitbake/doc/manual` in the Source Directory.

  By default, the `FILESOVERRIDES` variable is defined as:

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

  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.

  The default value for the `FILESPATH` variable is defined in the `base.bbclass` class found in `meta/classes` in the Source Directory:

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

  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.
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 distros 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`.

FULL_OPTIMIZATION

  The options to pass in `TARGET_CFLAGS` and `CFLAGS` when compiling an optimized system. This variable defaults to "-fexpensive-optimizations -fomit-frame-pointer -frename-registers -O2".

### H

HOMEPAGE

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

HOST_SYS

  Specifies the system, including the architecture and the operating system, for with the build is occurring in the context of the current recipe. The OpenEmbedded build system automatically sets this variable. You do not need to set the variable yourself.

  Here are 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".

### I

IMAGE_BASENAME

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

IMAGE_CLASSES

  A list of classes that all images should inherit. You typically use this variable to specify the list of classes that register the different types of images the OpenEmbedded build system creates.

  The default value for `IMAGE_CLASSES` is `image_types`. You can set this variable in your `local.conf` or in a distribution configuration file.

  For more information, see `meta/classes/image_types.bbclass` in the Source Directory.

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.

  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 "Images" section.

  For 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 Manual.

IMAGE_FSTYPES

  Specifies the formats of the root filesystem created by the OpenEmbedded build system. Available formats are a subset of the supported images listed in `IMAGE_TYPES`.

IMAGE_INSTALL

  Specifies the packages to install into an image. The `IMAGE_INSTALL` variable is a mechanism for an image recipe and you should use it with care to avoid ordering issues.

  Image recipes set `IMAGE_INSTALL` to specify the packages to install into an image through `image.bbclass`. Additionally, "helper" classes exist, such as `core-image.bbclass`, that can take `IMAGE_FEATURES` lists and turn these into auto-generated entries in `IMAGE_INSTALL` in addition to its default contents.

  Using `IMAGE_INSTALL` with the `+=` operator from the `/conf/local.conf` file or from within an image recipe is not recommended as it can cause ordering issues. Since `core-image.bbclass` sets `IMAGE_INSTALL` to a default value using the `?=` operator, using a `+=` operation against `IMAGE_INSTALL` will result in unexpected behavior when used in `/conf/local.conf`. Furthermore, the same operation from with 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.

  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.
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).
IMAGE_NAME

  The name of the output image files minus the extension. This variable is derived using the `IMAGE_BASENAME`, `MACHINE`, and `DATETIME` variables:

           IMAGE_NAME = "${IMAGE_BASENAME}-${MACHINE}-${DATETIME}"

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 `IMAGE_ROOTFS_EXTRA_SPACE` the variable.

IMAGE_POSTPROCESS_COMMAND

  Added by classes to run post processing commands once the OpenEmbedded build system has created the image. You can specify shell commands separated by semicolons:

           IMAGE_POSTPROCESS_COMMAND += "<shell_command>; ... "

  If you need to pass the path to the root filesystem within the command, you can use `${IMAGE_ROOTFS}`, which points to the root filesystem image.
IMAGE_ROOTFS

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

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"

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_TYPES

  Specifies the complete list of supported image types by default:

           jffs2
           sum.jffs2
           cramfs
           ext2
           ext2.gz
           ext2.bz2
           ext3
           ext3.gz
           ext2.lzma
           btrfs
           live
           squashfs
           squashfs-xz
           ubi
           ubifs
           tar
           tar.gz
           tar.bz2
           tar.xz
           cpio
           cpio.gz
           cpio.xz
           cpio.lzma
           vmdk
           elf

  For more information on how these types of images, see `meta/classes/image_types*.bbclass` in the Source Directory.
INC_PR

  Helps define the recipe revision for recipes that share a common `include` file. You can think of this variable as part of the recipe revision as set from within an include file.

  Suppose, for example, you have a set of recipes that are used across several projects. And, within each of those recipes the revision (its `PR` value) is set accordingly. In this case, when the revision of those recipes changes, the burden is on you to find all those recipes and be sure that they get changed to reflect the updated version of the recipe. In this scenario, it can get complicated when recipes that are used in many places and provide common functionality are upgraded to a new revision.

  A more efficient way of dealing with this situation is to set the `INC_PR` variable inside the `include` files that the recipes share and then expand the `INC_PR` variable within the recipes to help define the recipe revision.

  The following provides an example that shows how to use the `INC_PR` variable given a common `include` file that defines the variable. Once the variable is defined in the `include` file, you can use the variable to set the `PR` values in each recipe. You will notice that when you set a recipe's `PR` you can provide more granular revisioning by appending values to the `INC_PR` variable:

      recipes-graphics/xorg-font/xorg-font-common.inc:INC_PR = "r2"
      recipes-graphics/xorg-font/encodings_1.0.4.bb:PR = "${INC_PR}.1"
      recipes-graphics/xorg-font/font-util_1.3.0.bb:PR = "${INC_PR}.0"
      recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"

  The first line of the example establishes the baseline revision to be used for all recipes that use the `include` file. The remaining lines in the example are from individual recipes and show how the `PR` value is set.
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.

  This functionality is only regularly tested using the following setting:

           INCOMPATIBLE_LICENSE = "GPLv3"

  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.
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_STRIP

  If set to "1", causes the build to not strip binaries in resulting packages.

INHERIT

  Causes the named class to be inherited at this point during parsing. The variable is only valid in configuration files.

INITRAMFS_FSTYPES

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

INITSCRIPT_NAME

  The filename of the initscript as installed to `${etcdir}/init.d`.

  This variable is used in recipes when using `update-rc.d.bbclass`. 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.bbclass`. 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 is mandatory and is used in recipes when using `update-rc.d.bbclass`.

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.bbclass`" section for a list of the valid QA checks you can specify using this variable.

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.

### K

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. The `KBRANCH` variable is optional. You can use it to trigger checks 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 Yocto Project kernel that is based on the Linux 3.4 kernel, the kernel recipe file is the `meta/recipes-kernel/linux/linux-yocto_3.4.bb` file. Following is the default value for `KBRANCH` and the default override for the architectures the Yocto Project supports:

           KBRANCH_DEFAULT = "standard/base"
           KBRANCH = "${KBRANCH_DEFAULT}"

  This branch exists in the `linux-yocto-3.4` kernel Git repository .

  This variable is also used from the kernel's append file to identify the kernel branch specific to a particular machine or target hardware. The kernel's append file is located in the BSP layer for a given machine. For example, the kernel append file for the Crown Bay BSP is in the `meta-intel` Git repository and is named `meta-crownbay/recipes-kernel/linux/linux-yocto_3.4.bbappend`. Here are the related statements from the append file:

           COMPATIBLE_MACHINE_crownbay = "crownbay"
           KMACHINE_crownbay  = "crownbay"
           KBRANCH_crownbay  = "standard/crownbay"

           COMPATIBLE_MACHINE_crownbay-noemgd = "crownbay-noemgd"
           KMACHINE_crownbay-noemgd  = "crownbay"
           KBRANCH_crownbay-noemgd  = "standard/crownbay"

  The `KBRANCH_*` statements identify the kernel branch to use when building for the Crown Bay BSP. In this case there are two identical statements: one for each type of Crown Bay machine.
KBRANCH_DEFAULT

  Defines the Linux kernel source repository's default branch used to build the Linux kernel. The `KBRANCH_DEFAULT` value is the default value for `KBRANCH`. Unless you specify otherwise, `KBRANCH_DEFAULT` initializes to "master".

KERNEL_EXTRA_ARGS

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

KERNEL_FEATURES

  Includes additional metadata from the Yocto Project kernel Git repository. 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 to further add metadata for all 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 adds `netfilter` to all the Yocto Project kernels and adds sound support to the `qemux86` machine:

           # Add netfilter to all linux-yocto kernels
           KERNEL_FEATURES="features/netfilter"

           # Add sound support to the qemux86 machine
           KERNEL_FEATURES_append_qemux86=" cfg/sound"

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.

KERNEL_PATH

  The location of the kernel sources. This variable is set to the value of the `STAGING_KERNEL_DIR` within the `module.bbclass` class. For information on how this variable is used, see the "Incorporating Out-of-Tree Modules" section.

  The `KERNEL_SRC` variable is identical to the `KERNEL_PATH` variable.

KERNEL_SRC

  The location of the kernel sources. This variable is set to the value of the `STAGING_KERNEL_DIR` within the `module.bbclass` class. For information on how this variable is used, see the "Incorporating Out-of-Tree Modules" section.

  The `KERNEL_PATH` variable is identical to the `KERNEL_SRC` variable.

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 `qemuarm` goes by a different name in the Linux Yocto kernel. The kernel understands that machine as `arm_versatile926ejs`. For cases like these, the `KMACHINE` variable maps the kernel machine name to the OpenEmbedded build system machine name.

  Kernel machine names are initially defined in the Yocto Linux Kernel's `meta` branch. From the `meta` branch, look in the `meta/cfg/kernel-cache/bsp/<bsp_name>/<bsp-name>-<kernel-type>.scc` file. For example, from the `meta` branch in the `linux-yocto-3.0` kernel, the `meta/cfg/kernel-cache/bsp/cedartrail/cedartrail-standard.scc` file has the following:

           define KMACHINE cedartrail
           define KTYPE standard
           define KARCH i386

           include ktypes/standard
           branch cedartrail

           include cedartrail.scc

  You can see that the kernel understands the machine name for the Cedar Trail Board Support Package (BSP) as `cedartrail`.

  If you look in the Cedar Trail BSP layer in the `meta-intel` Source Repositories at `meta-cedartrail/recipes-kernel/linux/linux-yocto_3.0.bbappend`, you will find the following statements among others:

           COMPATIBLE_MACHINE_cedartrail = "cedartrail"
           KMACHINE_cedartrail  = "cedartrail"
           KBRANCH_cedartrail  = "yocto/standard/cedartrail"
           KERNEL_FEATURES_append_cedartrail += "bsp/cedartrail/cedartrail-pvr-merge.scc"
           KERNEL_FEATURES_append_cedartrail += "cfg/efi-ext.scc"

           COMPATIBLE_MACHINE_cedartrail-nopvr = "cedartrail"
           KMACHINE_cedartrail-nopvr  = "cedartrail"
           KBRANCH_cedartrail-nopvr  = "yocto/standard/cedartrail"
           KERNEL_FEATURES_append_cedartrail-nopvr += " cfg/smp.scc"

  The `KMACHINE` statements in the kernel's append file make sure that the OpenEmbedded build system and the Yocto Linux kernel understand the same machine names.

  This append file uses two `KMACHINE` statements. The first is not really necessary but does ensure that the machine known to the OpenEmbedded build system as `cedartrail` maps to the machine in the kernel also known as `cedartrail`:

           KMACHINE_cedartrail  = "cedartrail"

  The second statement is a good example of why the `KMACHINE` variable is needed. In this example, the OpenEmbedded build system uses the `cedartrail-nopvr` machine name to refer to the Cedar Trail BSP that does not support the proprietary PowerVR driver. The kernel, however, uses the machine name `cedartrail`. Thus, the append file must map the `cedartrail-nopvr` machine name to the kernel's `cedartrail` name:

           KMACHINE_cedartrail-nopvr  = "cedartrail"

  BSPs that ship with the Yocto Project release provide all mappings between the Yocto Project kernel machine names and the OpenEmbedded machine names. Be sure to use the `KMACHINE` if you create a BSP and the machine name you use is different than that used in the kernel.

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.

### L

LAYERDEPENDS

  Lists the layers that this recipe depends upon, separated by spaces. Optionally, you can specify a specific layer version for a dependency by adding it to the end of the layer name with a colon, (e.g. "anotherlayer:3" to be compared against `LAYERVERSION``_anotherlayer` in this case). An error will be produced if any dependency is missing or the version numbers do not match exactly (if specified). 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.

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`).

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

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 multiple licenses exist that cover different parts of the source.

  - You can use spaces between license names.

  Here are some examples:

           LICENSE = "LGPLv2.1 | GPLv3"
           LICENSE = "MPL-1 & LGPLv2.1"
           LICENSE = "GPLv2+"

  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 & GPLv2"
           LICENSE_${PN} = "GPLv2"
           LICENSE_${PN}-doc = "GFDL-1.2"

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.

### M

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" there exists the corresponding `qemux86.conf` machine configuration file, which 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 ?= "qemumips"
           MACHINE ?= "qemuppc"
           MACHINE ?= "qemux86"
           MACHINE ?= "qemux86-64"
           MACHINE ?= "genericx86"
           MACHINE ?= "beagleboard"
           MACHINE ?= "mpc8315e-rdb"
           MACHINE ?= "routerstationpro"

  The last four are Yocto Project reference hardware boards, which are provided in the `meta-yocto-bsp` layer.

  Adding additional Board Support Package (BSP) layers to your configuration adds new possible settings for `MACHINE`.

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"

  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-basic` 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-basic` 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 supports. For example, including the "bluetooth" feature causes the `bluez` bluetooth daemon to be built and added to the image. It also causes the `connman` recipe to look at `MACHINE_FEATURES` and when it finds "bluetooth" there it enables the bluetooth support in ConnMan.

  For a list of features supported by the Yocto Project as shipped, see the "Machine" section.

MACHINE_FEATURES_BACKFILL

  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. See the "Feature backfilling" section for more information.

MACHINE_FEATURES_BACKFILL_CONSIDERED

  Features from `MACHINE_FEATURES_BACKFILL` that should not be backfilled (i.e. added to `MACHINE_FEATURES`) during the build. See the "Feature backfilling" section for more information.

MACHINEOVERRIDES

  Lists overrides specific to the current machine. By default, this list includes the value of `MACHINE`. You can extend the list to apply variable overrides for classes of machines. For example, all QEMU emulated machines (e.g. qemuarm, qemux86, and so forth) include a common file named `meta/conf/machine/include/qemu.inc` that prepends `MACHINEOVERRIDES` with the following variable override:

          MACHINEOVERRIDES =. "qemuall:"

  Applying an override like `qemuall` affects all QEMU emulated machines elsewhere. Here is an example from the `connman-conf` recipe:

          SRC_URI_append_qemuall = "file://wired.config \
                                    file://wired-setup \
                                   "

MAINTAINER

  The email address of the distribution maintainer.

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-yocto` Git repository.

MLPREFIX

  Specifies a prefix has been added to `PN` to create a special version of a recipe or package, such as a Multilib version. The variable is used in places where the prefix needs to be added to or removed from a the name (e.g. the `BPN` variable). `MLPREFIX` gets set when a prefix has been added to `PN`.

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.

MULTIMACH_TARGET_SYS

  Separates files for different machines such that you can build for multiple target machines using the same output directories. See the `STAMP` variable for an example.

### N

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.

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> = "<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.

  Some recommended packages might be required for certain system functionality, such as kernel modules. It is up to you to add packages with `IMAGE_INSTALL` variable.

  Support for this variable exists only when using the IPK and RPM packaging backend. Support does not exist for DEB.

  See the `BAD_RECOMMENDATIONS` and the `PACKAGE_EXCLUDE` variables for related information.

### O

OE_BINCONFIG_EXTRA_MANGLE

  When a recipe inherits the `binconfig.bbclass` 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/binconfig.bbclass` in the Source Directory for details on how this class applies these additional sed command arguments. For general information on the `binconfig.bbclass` class, see the "Binary Configuration Scripts - `binconfig.bbclass`" section.

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.

  Do not set this variable. It is for internal use only.

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 Manual.

  You can use the following values for the `OE_TERMINAL` variable:

           auto
           gnome
           xfce
           rxvt
           screen
           konsole
           none

  Konsole support only works for KDE 3.x. Also, "auto" is the default behavior for `OE_TERMINAL`

OEROOT

  The directory from which the top-level build environment setup script is sourced. The Yocto Project makes two top-level build environment setup scripts available: `&OE_INIT_FILE;` and `oe-init-build-env-memres`. When you run one of these scripts, the `OEROOT` variable resolves to the directory that holds the script.

  For additional information on how this variable is used, see the initialization scripts.

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 (`eglibc`).

  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.

OVERRIDES

  BitBake uses `OVERRIDES` to control what variables are overridden after BitBake parses recipes and configuration files. You can find more information on how overrides are handled in the BitBake Manual that is located at `bitbake/doc/manual` in the Source Directory.

### P

P

  The recipe name and version. `P` is comprised of the following:

           ${PN}-${PV}

PACKAGE_ARCH

  The architecture of the resulting package or packages.

PACKAGE_BEFORE_PN

  Enables easily adding packages to `PACKAGES` before `${PN}` so that the 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 Source Directory, specifies the package manager to use when packaging data. You can provide one or more arguments for the variable with the first argument being the package manager used to create images:

           PACKAGE_CLASSES ?= "package_rpm package_deb package_ipk"

  For information on build performance effects as a result of the package manager use, see Packaging - `package*.bbclass` in this 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.

  Support for this variable exists only when using the IPK and RPM packaging backend. Support does not exist for DEB.

  See the `NO_RECOMMENDATIONS` and the `BAD_RECOMMENDATIONS` variables for related information.

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_GROUP

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

           PACKAGE_GROUP_widget = "package1 package2"

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

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

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. Use the `IMAGE_INSTALL` variable to specify packages for installation.

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:

           PACKAGECONFIG ??= "f1 f2 f3 ..."
           PACKAGECONFIG[f1] = "--with-f1,--without-f1,build-deps-f1,rt-deps-f1"
           PACKAGECONFIG[f2] = "--with-f2,--without-f2,build-deps-f2,rt-deps-f2"
           PACKAGECONFIG[f3] = "--with-f3,--without-f3,build-deps-f3,rt-deps-f3"

  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 four 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:

  1. Extra arguments that should be added to the configure script argument list (`EXTRA_OECONF`) if the feature is enabled.

  2. Extra arguments that should be added to `EXTRA_OECONF` if the feature is disabled.

  3. Additional build dependencies (`DEPENDS`) that should be added if the feature is enabled.

  4. Additional runtime dependencies (`RDEPENDS`) that should be added if the feature is enabled.

  Consider the following `PACKAGECONFIG` block taken from the `librsvg` recipe. In this example the feature is `croco`, which has three arguments that determine the feature's behavior.

           PACKAGECONFIG ??= "croco"
           PACKAGECONFIG[croco] = "--with-croco,--without-croco,libcroco"

  The `--with-croco` and `libcroco` arguments apply only if the feature is enabled. In this case, `--with-croco` is added to the configure script argument list and `libcroco` 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-croco` is added to the configure script rather than `--with-croco`.

  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 amended 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 amended the variable:

             PACKAGECONFIG_append_pn-<recipename> = " f4"

PACKAGES

  The list of packages to be created from the recipe. The default value is the following:

           ${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKAGE_BEFORE_PN} ${PN}

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 `do_rootfs`.

  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 Manual.

PARALLEL_MAKE

  Extra options that are passed to the `make` command during the `do_compile` task in order to specify parallel compilation. This variable is usually in the form `-j 4`, where the number represents the maximum number of parallel threads make can run. If you development host supports multiple cores a good rule of thumb is to set this variable to twice the number of cores on the host.

  Individual recipes might clear out this variable if the software being built has problems running its `make` process in parallel.

PARALLEL_MAKEINST

  Extra options passed to the `make install` command during the `do_install` task in order to specify parallel installation. This variable defaults to the value of `PARALLEL_MAKE`.

  Individual recipes might clear out this variable if the software being built has problems running its `make install` process in parallel.

PARALLEL_MAKEINST with the description ".

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 `do_patch`. 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 field is used to make upgrades possible when the versioning scheme changes in some backwards incompatible way.

PF

  Specifies the recipe or package name and includes all version and revision numbers (i.e. `eglibc-2.13-r20+svnr15508/` and `bash-4.2-r1/`). This variable is comprised of the following:

           ${PN}-${EXTENDPE}${PV}-${PR}

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.

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 used by the `do_package` task to write output from the `do_packagedata` task. The `PKGDESTWORK` location defaults to the following:

           ${WORKDIR}/pkgdata

  The `do_packagedata` task then packages the data in the temporary work area and installs it into a shared directory pointed to by `PKGDATA_DIR`.

  Do not change this default.

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.

PR

  The revision of the recipe. The default value for this variable is "r0".

PREFERRED_PROVIDER

  If multiple recipes provide an item, this variable determines which recipe should be given preference. You should always suffix the variable with the name of the provided item, and you should set it to the `PN` of the recipe to which you want to give precedence. Here is an example:

           PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"

PREFERRED_VERSION

  If there are multiple versions of recipes available, this variable determines which recipe should be given preference. You must always suffix the variable with the `PN` you want to select, and you should set to the `PV` accordingly for precedence. You can use the "`%`" character as a wildcard to match any number of characters, which can be useful when specifying versions that contain long revision numbers that could potentially change. Here are two examples:

           PREFERRED_VERSION_python = "2.6.6"
           PREFERRED_VERSION_linux-yocto = "3.0+git%"

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-yocto` 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://.*/.* http://www.yoctoproject.org/sources/ \n \
           ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
           http://.*/.* http://www.yoctoproject.org/sources/ \n \
           https://.*/.* http://www.yoctoproject.org/sources/ \n"

  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.
PRINC

  Causes the `PR` variable of `.bbappend` files to dynamically increment. This increment minimizes the impact of layer ordering.

  In order to ensure multiple `.bbappend` files can co-exist, `PRINC` should be self referencing. This variable defaults to 0.

  Following is an example that increments `PR` by two:

           PRINC := "${@int(PRINC) + 2}"

  It is advisable not to use strings such as ".= '.1'" with the variable because this usage is very sensitive to layer ordering. You should avoid explicit assignments as they cannot adequately represent multiple `.bbappend` files.
PROVIDES

  A list of aliases that a recipe also provides. These aliases are useful for satisfying dependencies of other recipes during the build (as specified by `DEPENDS`).

  A recipe's own `PN` is implicitly already in its `PROVIDES` list.

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).

### R

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 a package's runtime dependencies (i.e. other packages) that must be installed in order for the built package to run correctly. If a package in this list cannot be found during the build, you will get a build error.

  When you use the `RDEPENDS` variable in a recipe, you are essentially stating that the recipe's `do_build` task depends on the existence of a specific package. Consider this simple example for two recipes named "a" and "b" that produce similarly named packages. In this example, the `RDEPENDS` statement appears in the "a" recipe:

           RDEPENDS_${PN} = "b"

  Here, the dependency is such that the `do_build` task for recipe "a" depends on the `do_package_write` task of recipe "b". This means the package file for "b" must be available when the output for recipe "a" has been completely built. More importantly, package "a" will be marked as depending on package "b" in a manner that is understood by the package manager in use (i.e. rpm, opkg, or dpkg).

  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. 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.

  The package name you attach to the `RDEPENDS` variable must appear as it would in the `PACKAGES` namespace before any renaming of the output package by classes like `debian.bbclass`.

  In many cases you do not need to explicitly add runtime dependencies using `RDEPENDS` since some automatic handling occurs:

  - `shlibdeps`: If a runtime package contains a shared library (`.so`), the build processes the library in order to determine other libraries to which it is dynamically linked. The build process adds these libraries to `RDEPENDS` when creating the runtime package.

  - `pcdeps`: If the package ships a `pkg-config` information file, the build process uses this file to add items to the `RDEPENDS` variable to create the runtime packages.

  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 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.

RM_OLD_IMAGE

  Reclaims disk space by removing previously built versions of the same image from the `images` directory pointed to by the `DEPLOY_DIR` variable.

  Set this variable to "1" in your `local.conf` file to remove these images.

RM_WORK_EXCLUDE

  With `rm_work` enabled, this variable specifies a list of recipes whose work directories should not be removed. See the "Removing Work Files During the Build - `rm_work.bbclass`" section for more details.

ROOTFS_POSTPROCESS_COMMAND

  Added by classes to run post processing commands once the OpenEmbedded build system has created the root filesystem. You can specify shell commands separated by semicolons:

           ROOTFS_POSTPROCESS_COMMAND += "<shell_command>; ... "

  If you need to pass the path to the root filesystem within the command, you can use `${IMAGE_ROOTFS}`, which points to the root filesystem image.
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`).

  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 needs them for the extended usability. To specify runtime dependencies for packages, see the `RDEPENDS` variable.

  The OpenEmbedded build process automatically installs the list of packages as part of the built package. However, you can remove these packages later if you want. If, during the build, a package from the `RRECOMMENDS` list cannot be found, the build process continues without an error.

  You can also prevent packages in the list from being installed by using several variables. See the `BAD_RECOMMENDATIONS`, `NO_RECOMMENDATIONS`, and `PACKAGE_EXCLUDE` variables for more information.

  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.bbclass`.

  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"

### S

S

  The location in the Build Directory where unpacked recipe source code resides. This location is within the working directory (`WORKDIR`), which is not static. The unpacked source location depends on the recipe name (`PN`) and recipe version (`PV`) as follows:

       ${WORKDIR}/${PN}-${PV}

  As an example, assume a Source Directory top-level folder named `poky` and a default Build Directory at `poky/build`. In this case, the working 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

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_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}"

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 architecture of the machine that runs Application Development Toolkit (ADT) items. In other words, packages are built so that they will run on the target you specify with the argument. This implies that you can build out ADT/SDK items that run on an architecture other than that of your build host. For example, you can use an x86_64-based build host to create packages that will run on an i686-based SDK Machine.

  You can use "i686" and "x86_64" as possible values for this variable. The variable defaults to "i686" and is set in the `local.conf` file in the Build Directory.

           SDKMACHINE ?= "i686"

SECTION

  The section in which packages should be categorized. Package management utilities can make use of this variable.

SELECTED_OPTIMIZATION

  The variable takes the value of `FULL_OPTIMIZATION` unless `DEBUG_BUILD` = "1". In this case the value of `DEBUG_OPTIMIZATION` is used.

SERIAL_CONSOLE

  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 space. You cannot specify more than one TTY device:

           SERIAL_CONSOLE = "115200 ttyS0"

  The `SERIAL_CONSOLE` variable is deprecated. Please use the `SERIAL_CONSOLES` variable.

SERIAL_CONSOLES

  Defines the serial consoles (TTYs) 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

  Similar to `SERIAL_CONSOLES` except the device is checked for existence before attempting to enable it. This variable is currently only supported with SysVinit (i.e. not with systemd).

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 this example, `intone` depends on `mplayer2`.

  Use of this variable is one mechanism to remove dependencies that affect task signatures and thus force rebuilds when a recipe changes.

  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.

  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.

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.

  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`.

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.

SRC_URI

  The list of source files - local or remote. This variable tells the OpenEmbedded build system which bits to pull in for the build and how to pull them in. For example, if the recipe or append file only needs to fetch a tarball from the Internet, the recipe or append file uses a single `SRC_URI` entry. On the other hand, if the recipe or append file needs to fetch a tarball, apply two patches, and include a custom file, the recipe or append file would include four instances of the variable.

  The following list explains the available URI protocols:

  - `file://` - Fetches files, which are usually files shipped with the Metadata, from the local machine. The path is relative to the `FILESPATH` variable. Thus, the build system searches, in order, from the following directories, which are assumed to be a subdirectories of the directory in which the recipe file (`.bb`) or append file (`.bbappend`) resides:

    - `${BPN}` - The base recipe name without any special suffix or version numbers.

    - `${BP}` - `${BPN}-${PV}`. The base recipe name and version but without any special package name suffix.

    - files - Files within a directory, which is named `files` and is also alongside the recipe or append file.

    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.

  - `bzr://` - Fetches files from a Bazaar revision control repository.

  - `git://` - Fetches files from a Git revision control repository.

  - `osc://` - Fetches files from an OSC (OpenSUSE Build service) revision control repository.

  - `repo://` - Fetches files from a repo (Git) repository.

  - `svk://` - Fetches files from an SVK revision control repository.

  - `http://` - Fetches files from the Internet using `http`.

  - `https://` - Fetches files from the Internet using `https`.

  - `ftp://` - Fetches files from the Internet using `ftp`.

  - `cvs://` - Fetches files from a CVS revision control repository.

  - `hg://` - Fetches files from a Mercurial (`hg`) revision control repository.

  - `p4://` - Fetches files from a Perforce (`p4`) revision control repository.

  - `ssh://` - Fetches files from a secure shell.

  - `svn://` - Fetches files from a Subversion (`svn`) revision control repository.

  Standard and recipe-specific options for `SRC_URI` exist. Here are standard options:

  - `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 `mindate`.

  - `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`.

  Here are some additional options worth mentioning:

  - `unpack` - Controls whether or not to unpack the file if it is an archive. The default action is to unpack the file.

  - `subdir` - Places the file (or extracts its contents) into the specified subdirectory of `WORKDIR`. This option is useful for unusual tarballs or other archives that do not have their files already in a subdirectory within the archive.

  - `name` - Specifies a name to be used for association with `SRC_URI` checksums when you have more than one file specified in `SRC_URI`.

  - `downloadfilename` - Specifies the filename used when storing the downloaded 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 = "1.5.0+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 wish to build a fixed revision and you wish 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.

SSTATE_DIR

  The directory for the shared state cache.

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 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.

  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://.* http://someserver.tld/share/sstate/PATH \n \
           file://.* file:///some/local/dir/sstate/PATH"

STAGING_KERNEL_DIR

  The directory with kernel headers that are required to build out-of-tree modules.

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}"

  See `STAMPS_DIR`, `MULTIMACH_TARGET_SYS`, `PN`, `EXTENDPE`, `PV`, and `PR` for related variable information.
STAMPS_DIR

  Specifies the base directory in which the OpenEmbedded build system places stamps. The default directory is `${TMPDIR}/stamps`.

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.

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.

### T

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

TARGET_CFLAGS

  Flags passed to the C compiler for the target system. This variable evaluates to the same as `CFLAGS`.

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_OS

  Specifies the target's operating system. The variable can be set to "linux" for `eglibc`-based systems and to "linux-uclibc" for `uclibc`. For ARM/EABI targets, there are also "linux-gnueabi" and "linux-uclibc-gnueabi" values possible.

TCLIBC

  Specifies which variant of the GNU standard C library (`libc`) to use during the build process. This variable replaces `POKYLIBC`, which is no longer supported.

  You can select `eglibc` or `uclibc`.

  This release of the Yocto Project does not support the `glibc` implementation of `libc`.

TCMODE

  The toolchain selector. This variable replaces `POKYMODE`, which is no longer supported.

  The `TCMODE` variable selects the external toolchain built using the OpenEmbedded build system or a few supported combinations of the upstream GCC or CodeSourcery Labs toolchain. The variable identifies the `tcmode-*` files used in the `meta/conf/distro/include` directory, which is found in the Source Directory.

  By default, `TCMODE` is set to "default", which chooses the `tcmode-default.inc` file. The variable is similar to `TCLIBC`, which controls the variant of the GNU standard C library (`libc`) used during the build process: `eglibc` or `uclibc`.

TEST_IMAGE

  Automatically runs the series of automated tests for images when an image is successfully built.

  Currently, there is only support for running these tests under QEMU.

  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:

           TEST_IMAGE = "1"

  For more information on enabling, running, and writing these tests, see the "Performing Automated Runtime Testing" section in the Yocto Project Development Manual and the "`testimage.bbclass`" section.
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 Manual.

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.

  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 Manual.

THISDIR

  The directory in which the file BitBake is currently parsing is located. Do not manually set this variable.

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"

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-". When building an SDK using `bitbake -c populate_sdk <imagename>`, a default list of packages is set in this variable, but you can add additional packages to the list.

  For background information on cross-development toolchains in the Yocto Project development environment, see the "Cross-Development Toolchain Generation" section. For information on setting up a cross-development environment, see the "Installing the ADT and Toolchains" section in the Yocto Project Application Developer's Guide.

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.

  For background information on cross-development toolchains in the Yocto Project development environment, see the "Cross-Development Toolchain Generation" section. For information on setting up a cross-development environment, see the "Installing the ADT and Toolchains" section in the Yocto Project Application Developer's Guide.

TOPDIR

  This variable points to the Build Directory. BitBake automatically sets this variable.

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_PKGARCH

  The package architecture understood by the packaging system to define the architecture, ABI, and tuning of output packages.

### U

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_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`).

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.

USER_CLASSES

  A list of classes to globally inherit. These classes are used by the OpenEmbedded build system to enable extra features (e.g. `buildstats`, `image-mklibs`, and so forth).

  The default list is set in your `local.conf` file:

           USER_CLASSES ?= "buildstats image-mklibs image-prelink"

  For more information, see `meta-yocto/conf/local.conf.sample` in the Source Directory.

### W

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.bbclass`" section.

WORKDIR

  The pathname of the working directory in which the OpenEmbedded build system builds a recipe. This directory is located within the `TMPDIR` directory structure and changes as different packages are built.

  The actual `WORKDIR` directory depends on several things:

  - The temporary directory - `TMPDIR`
  - The package architecture - `PACKAGE_ARCH`
  - The target machine - `MACHINE`
  - The target operating system - `TARGET_OS`
  - The recipe name - `PN`
  - The recipe version - `PV`
  - The recipe revision - `PR`

  For packages that are not dependent on a particular machine, `WORKDIR` is defined as follows:

       ${TMPDIR}/work/${PACKAGE_ARCH}-poky-${TARGET_OS}/${PN}/${PV}-${PR}

  As an example, assume a Source Directory top-level folder name `poky` and a default Build Directory at `poky/build`. In this case, the working directory the build system uses to build the `v86d` package is the following:

           ~/poky/build/tmp/work/qemux86-poky-linux/v86d/01.9-r0

  For packages that are dependent on a particular machine, `WORKDIR` is defined slightly different:

       ${TMPDIR}/work/${MACHINE}-poky-${TARGET_OS}/${PN}/${PV}-${PR}

  As an example, again assume a Source Directory top-level folder named `poky` and a default Build Directory at `poky/build`. In this case, the working directory the build system uses to build the `acl` recipe, which is being built for a MIPS-based device, is the following:

           ~/poky/build/tmp/work/mips-poky-linux/acl/2.2.51-r2