sphinx: bitbake-user-manual: use builtin sphinx glossary

Sphinx has a glossary directive. From the documentation:
This directive must contain a reST definition list with terms and
definitions. The definitions will then be referencable with the 'term'
role.

So anywhere in *any* manual, we can do :term:`VAR` to refer to an item
from the glossary, and create a link.

An HTML anchor is created for each term in the glossary, and can be
accessed as:
<link>/ref-variables.html#term-<NAME>

To convert to a glossary, we needed proper indentation (e.g. added 3
spaces to each line)

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>

1 files changed, 1236 insertions, 1202 deletions

diff --git a/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst b/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst
index 41a77b3bc..efc496039 100644
--- a/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst
+++ b/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst
@@ -23,1213 +23,1247 @@ overview of their function and contents.
       not appear in the BitBake glossary. These other variables are
       variables used in systems that use BitBake.
 
-`A <#var-bb-ASSUME_PROVIDED>`__ `B <#var-bb-B>`__ `C <#var-bb-CACHE>`__
-`D <#var-bb-DEFAULT_PREFERENCE>`__ `E <#var-bb-EXCLUDE_FROM_WORLD>`__
-`F <#var-bb-FAKEROOT>`__ `G <#var-bb-GITDIR>`__ `H <#var-bb-HGDIR>`__
-`I <#var-bb-INHERIT>`__ `L <#var-bb-LAYERDEPENDS>`__
-`M <#var-bb-MIRRORS>`__ `O <#var-bb-OVERRIDES>`__ `P <#var-bb-P4DIR>`__
-`R <#var-bb-RDEPENDS>`__ `S <#var-bb-SECTION>`__ `T <#var-bb-T>`__
-
-ASSUME_PROVIDED
-   Lists recipe names (```PN`` <#var-bb-PN>`__ values) BitBake does not
-   attempt to build. Instead, BitBake assumes these recipes have already
-   been built.
-
-   In OpenEmbedded-Core, ``ASSUME_PROVIDED`` mostly specifies native
-   tools that should not be built. An example is ``git-native``, which
-   when specified allows for the Git binary from the host to be used
-   rather than building ``git-native``.
-
-B
-   The directory in which BitBake executes functions during a recipe's
-   build process.
-
-BB_ALLOWED_NETWORKS
-   Specifies a space-delimited list of hosts that the fetcher is allowed
-   to use to obtain the required source code. Following are
-   considerations surrounding this variable:
-
-   -  This host list is only used if
-      ```BB_NO_NETWORK`` <#var-bb-BB_NO_NETWORK>`__ is either not set or
-      set to "0".
-
-   -  Limited support for the "``*``" wildcard character for matching
-      against the beginning of host names exists. For example, the
-      following setting matches ``git.gnu.org``, ``ftp.gnu.org``, and
-      ``foo.git.gnu.org``. BB_ALLOWED_NETWORKS = "*.gnu.org"
+.. glossary::
+
+   ASSUME_PROVIDED
+      Lists recipe names (```PN`` <#var-bb-PN>`__ values) BitBake does not
+      attempt to build. Instead, BitBake assumes these recipes have already
+      been built.
+
+      In OpenEmbedded-Core, ``ASSUME_PROVIDED`` mostly specifies native
+      tools that should not be built. An example is ``git-native``, which
+      when specified allows for the Git binary from the host to be used
+      rather than building ``git-native``.
+
+   B
+      The directory in which BitBake executes functions during a recipe's
+      build process.
+
+   BB_ALLOWED_NETWORKS
+      Specifies a space-delimited list of hosts that the fetcher is allowed
+      to use to obtain the required source code. Following are
+      considerations surrounding this variable:
+
+      -  This host list is only used if
+         ```BB_NO_NETWORK`` <#var-bb-BB_NO_NETWORK>`__ is either not set or
+         set to "0".
+
+      -  Limited support for the "``*``" wildcard character for matching
+         against the beginning of host names exists. For example, the
+         following setting matches ``git.gnu.org``, ``ftp.gnu.org``, and
+         ``foo.git.gnu.org``. BB_ALLOWED_NETWORKS = "*.gnu.org"
+
+         .. note::
+
+            The use of the "``*``" character only works at the beginning of
+            a host name and it must be isolated from the remainder of the
+            host name. You cannot use the wildcard character in any other
+            location of the name or combined with the front part of the
+            name.
+
+            For example, ``*.foo.bar`` is supported, while ``*aa.foo.bar``
+            is not.
+
+      -  Mirrors not in the host list are skipped and logged in debug.
+
+      -  Attempts to access networks not in the host list cause a failure.
+
+      Using ``BB_ALLOWED_NETWORKS`` in conjunction with
+      ```PREMIRRORS`` <#var-bb-PREMIRRORS>`__ is very useful. Adding the
+      host you want to use to ``PREMIRRORS`` results in the source code
+      being fetched from an allowed location and avoids raising an error
+      when a host that is not allowed is in a
+      ```SRC_URI`` <#var-bb-SRC_URI>`__ statement. This is because the
+      fetcher does not attempt to use the host listed in ``SRC_URI`` after
+      a successful fetch from the ``PREMIRRORS`` occurs.
+
+   BB_CONSOLELOG
+      Specifies the path to a log file into which BitBake's user interface
+      writes output during the build.
+
+   BB_CURRENTTASK
+      Contains the name of the currently running task. The name does not
+      include the ``do_`` prefix.
+
+   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.
+
+   BB_DEFAULT_TASK
+      The default task to use when none is specified (e.g. with the ``-c``
+      command line option). The task name specified should not include the
+      ``do_`` prefix.
+
+   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. When setting this
+      variable, 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 <#var-bb-BB_DISKMON_WARNINTERVAL>`__
+      variable, which must be defined. <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 set the
+      ```BB_DISKMON_WARNINTERVAL`` <#var-bb-BB_DISKMON_WARNINTERVAL>`__
+      variable. This example causes the build system to immediately abort
+      when either the disk space in ``${TMPDIR}`` drops below 1 Gbyte or
+      the available free inodes drops below 100 Kbytes. Because two
+      directories are provided with the variable, the build system also
+      issues a warning when the disk space in the ``${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.
+
+      If you are going to use the ``BB_DISKMON_WARNINTERVAL`` variable, you
+      must also use the ```BB_DISKMON_DIRS`` <#var-bb-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,${SSTATE_DIR},1G,100K"
+      BB_DISKMON_WARNINTERVAL = "50M,5K" These variables cause BitBake to
+      issue subsequent warnings each time the available disk space further
+      reduces by 50 Mbytes or the number of free inodes further reduces by
+      5 Kbytes in the ``${SSTATE_DIR}`` directory. Subsequent warnings
+      based on the interval occur each time a respective interval is
+      reached beyond the initial warning (i.e. 1 Gbytes and 100 Kbytes).
+
+   BB_ENV_WHITELIST
+      Specifies the internal whitelist of variables to allow through from
+      the external environment into BitBake's datastore. If the value of
+      this variable is not specified (which is the default), the following
+      list is used: ```BBPATH`` <#var-bb-BBPATH>`__,
+      ```BB_PRESERVE_ENV`` <#var-bb-BB_PRESERVE_ENV>`__,
+      ```BB_ENV_WHITELIST`` <#var-bb-BB_ENV_WHITELIST>`__, and
+      ```BB_ENV_EXTRAWHITE`` <#var-bb-BB_ENV_EXTRAWHITE>`__.
 
       .. note::
 
-         The use of the "``*``" character only works at the beginning of
-         a host name and it must be isolated from the remainder of the
-         host name. You cannot use the wildcard character in any other
-         location of the name or combined with the front part of the
-         name.
-
-         For example, ``*.foo.bar`` is supported, while ``*aa.foo.bar``
-         is not.
-
-   -  Mirrors not in the host list are skipped and logged in debug.
-
-   -  Attempts to access networks not in the host list cause a failure.
-
-   Using ``BB_ALLOWED_NETWORKS`` in conjunction with
-   ```PREMIRRORS`` <#var-bb-PREMIRRORS>`__ is very useful. Adding the
-   host you want to use to ``PREMIRRORS`` results in the source code
-   being fetched from an allowed location and avoids raising an error
-   when a host that is not allowed is in a
-   ```SRC_URI`` <#var-bb-SRC_URI>`__ statement. This is because the
-   fetcher does not attempt to use the host listed in ``SRC_URI`` after
-   a successful fetch from the ``PREMIRRORS`` occurs.
-
-BB_CONSOLELOG
-   Specifies the path to a log file into which BitBake's user interface
-   writes output during the build.
-
-BB_CURRENTTASK
-   Contains the name of the currently running task. The name does not
-   include the ``do_`` prefix.
-
-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.
-
-BB_DEFAULT_TASK
-   The default task to use when none is specified (e.g. with the ``-c``
-   command line option). The task name specified should not include the
-   ``do_`` prefix.
-
-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. When setting this
-   variable, 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 <#var-bb-BB_DISKMON_WARNINTERVAL>`__
-   variable, which must be defined. <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 set the
-   ```BB_DISKMON_WARNINTERVAL`` <#var-bb-BB_DISKMON_WARNINTERVAL>`__
-   variable. This example causes the build system to immediately abort
-   when either the disk space in ``${TMPDIR}`` drops below 1 Gbyte or
-   the available free inodes drops below 100 Kbytes. Because two
-   directories are provided with the variable, the build system also
-   issues a warning when the disk space in the ``${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.
-
-   If you are going to use the ``BB_DISKMON_WARNINTERVAL`` variable, you
-   must also use the ```BB_DISKMON_DIRS`` <#var-bb-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,${SSTATE_DIR},1G,100K"
-   BB_DISKMON_WARNINTERVAL = "50M,5K" These variables cause BitBake to
-   issue subsequent warnings each time the available disk space further
-   reduces by 50 Mbytes or the number of free inodes further reduces by
-   5 Kbytes in the ``${SSTATE_DIR}`` directory. Subsequent warnings
-   based on the interval occur each time a respective interval is
-   reached beyond the initial warning (i.e. 1 Gbytes and 100 Kbytes).
-
-BB_ENV_WHITELIST
-   Specifies the internal whitelist of variables to allow through from
-   the external environment into BitBake's datastore. If the value of
-   this variable is not specified (which is the default), the following
-   list is used: ```BBPATH`` <#var-bb-BBPATH>`__,
-   ```BB_PRESERVE_ENV`` <#var-bb-BB_PRESERVE_ENV>`__,
-   ```BB_ENV_WHITELIST`` <#var-bb-BB_ENV_WHITELIST>`__, and
-   ```BB_ENV_EXTRAWHITE`` <#var-bb-BB_ENV_EXTRAWHITE>`__.
-
-   .. note::
-
-      You must set this variable in the external environment in order
-      for it to work.
-
-BB_ENV_EXTRAWHITE
-   Specifies an additional set of variables to allow through (whitelist)
-   from the external environment into BitBake's datastore. This list of
-   variables are on top of the internal list set in
-   ```BB_ENV_WHITELIST`` <#var-bb-BB_ENV_WHITELIST>`__.
-
-   .. note::
-
-      You must set this variable in the external environment in order
-      for it to work.
-
-BB_FETCH_PREMIRRORONLY
-   When set to "1", causes BitBake's fetcher module to only search
-   ```PREMIRRORS`` <#var-bb-PREMIRRORS>`__ for files. BitBake will not
-   search the main ```SRC_URI`` <#var-bb-SRC_URI>`__ or
-   ```MIRRORS`` <#var-bb-MIRRORS>`__.
-
-BB_FILENAME
-   Contains the filename of the recipe that owns the currently running
-   task. For example, if the ``do_fetch`` task that resides in the
-   ``my-recipe.bb`` is executing, the ``BB_FILENAME`` variable contains
-   "/foo/path/my-recipe.bb".
-
-BB_GENERATE_MIRROR_TARBALLS
-   Causes tarballs of the Git repositories, including the Git metadata,
-   to be placed in the ```DL_DIR`` <#var-bb-DL_DIR>`__ directory. Anyone
-   wishing to create a source mirror would want to enable this variable.
-
-   For performance reasons, creating and placing tarballs of the Git
-   repositories is not the default action by BitBake.
-   BB_GENERATE_MIRROR_TARBALLS = "1"
-
-BB_HASHCONFIG_WHITELIST
-   Lists variables that are excluded from base configuration checksum,
-   which is used to determine if the cache can be reused.
-
-   One of the ways BitBake determines whether to re-parse the main
-   metadata is through checksums of the variables in the datastore of
-   the base configuration data. There are variables that you typically
-   want to exclude when checking whether or not to re-parse and thus
-   rebuild the cache. As an example, you would usually exclude ``TIME``
-   and ``DATE`` because these variables are always changing. If you did
-   not exclude them, BitBake would never reuse the cache.
-
-BB_HASHBASE_WHITELIST
-   Lists variables that are excluded from checksum and dependency data.
-   Variables that are excluded can therefore change without affecting
-   the checksum mechanism. A common example would be the variable for
-   the path of the build. BitBake's output should not (and usually does
-   not) depend on the directory in which it was built.
-
-BB_HASHCHECK_FUNCTION
-   Specifies the name of the function to call during the "setscene" part
-   of the task's execution in order to validate the list of task hashes.
-   The function returns the list of setscene tasks that should be
-   executed.
-
-   At this point in the execution of the code, the objective is to
-   quickly verify if a given setscene function is likely to work or not.
-   It's easier to check the list of setscene functions in one pass than
-   to call many individual tasks. The returned list need not be
-   completely accurate. A given setscene task can still later fail.
-   However, the more accurate the data returned, the more efficient the
-   build will be.
-
-BB_INVALIDCONF
-   Used in combination with the ``ConfigParsed`` event to trigger
-   re-parsing the base metadata (i.e. all the recipes). The
-   ``ConfigParsed`` event can set the variable to trigger the re-parse.
-   You must be careful to avoid recursive loops with this functionality.
-
-BB_LOGCONFIG
-   Specifies the name of a config file that contains the user logging
-   configuration. See `Logging <#logging>`__ for additional information
-
-BB_LOGFMT
-   Specifies the name of the log files saved into
-   ``${``\ ```T`` <#var-bb-T>`__\ ``}``. By default, the ``BB_LOGFMT``
-   variable is undefined and the log file names get created using the
-   following form: log.{task}.{pid} If you want to force log files to
-   take a specific name, you can set this variable in a configuration
-   file.
-
-BB_NICE_LEVEL
-   Allows BitBake to run at a specific priority (i.e. nice level).
-   System permissions usually mean that BitBake can reduce its priority
-   but not raise it again. See
-   ```BB_TASK_NICE_LEVEL`` <#var-bb-BB_TASK_NICE_LEVEL>`__ for
-   additional information.
-
-BB_NO_NETWORK
-   Disables network access in the BitBake fetcher modules. With this
-   access disabled, any command that attempts to access the network
-   becomes an error.
-
-   Disabling network access is useful for testing source mirrors,
-   running builds when not connected to the Internet, and when operating
-   in certain kinds of firewall environments.
-
-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.
-
-BB_NUMBER_PARSE_THREADS
-   Sets the number of threads BitBake uses when parsing. By default, the
-   number of threads is equal to the number of cores on the system.
-
-BB_ORIGENV
-   Contains a copy of the original external environment in which BitBake
-   was run. The copy is taken before any whitelisted variable values are
-   filtered into BitBake's datastore.
-
-   .. note::
-
-      The contents of this variable is a datastore object that can be
-      queried using the normal datastore operations.
-
-BB_PRESERVE_ENV
-   Disables whitelisting and instead allows all variables through from
-   the external environment into BitBake's datastore.
-
-   .. note::
-
-      You must set this variable in the external environment in order
-      for it to work.
-
-BB_RUNFMT
-   Specifies the name of the executable script files (i.e. run files)
-   saved into ``${``\ ```T`` <#var-bb-T>`__\ ``}``. By default, the
-   ``BB_RUNFMT`` variable is undefined and the run file names get
-   created using the following form: run.{task}.{pid} If you want to
-   force run files to take a specific name, you can set this variable in
-   a configuration file.
-
-BB_RUNTASK
-   Contains the name of the currently executing task. The value includes
-   the "do_" prefix. For example, if the currently executing task is
-   ``do_config``, the value is "do_config".
-
-BB_SCHEDULER
-   Selects the name of the scheduler to use for the scheduling of
-   BitBake tasks. Three options exist:
-
-   -  *basic* - The basic framework from which everything derives. Using
-      this option causes tasks to be ordered numerically as they are
-      parsed.
-
-   -  *speed* - Executes tasks first that have more tasks depending on
-      them. The "speed" option is the default.
-
-   -  *completion* - Causes the scheduler to try to complete a given
-      recipe once its build has started.
-
-BB_SCHEDULERS
-   Defines custom schedulers to import. Custom schedulers need to be
-   derived from the ``RunQueueScheduler`` class.
-
-   For information how to select a scheduler, see the
-   ```BB_SCHEDULER`` <#var-bb-BB_SCHEDULER>`__ variable.
-
-BB_SETSCENE_DEPVALID
-   Specifies a function BitBake calls that determines whether BitBake
-   requires a setscene dependency to be met.
-
-   When running a setscene task, BitBake needs to know which
-   dependencies of that setscene task also need to be run. Whether
-   dependencies also need to be run is highly dependent on the metadata.
-   The function specified by this variable returns a "True" or "False"
-   depending on whether the dependency needs to be met.
-
-BB_SETSCENE_VERIFY_FUNCTION2
-   Specifies a function to call that verifies the list of planned task
-   execution before the main task execution happens. The function is
-   called once BitBake has a list of setscene tasks that have run and
-   either succeeded or failed.
-
-   The function allows for a task list check to see if they make sense.
-   Even if BitBake was planning to skip a task, the returned value of
-   the function can force BitBake to run the task, which is necessary
-   under certain metadata defined circumstances.
-
-BB_SIGNATURE_EXCLUDE_FLAGS
-   Lists variable flags (varflags) that can be safely excluded from
-   checksum and dependency data for keys in the datastore. When
-   generating checksum or dependency data for keys in the datastore, the
-   flags set against that key are normally included in the checksum.
-
-   For more information on varflags, see the "`Variable
-   Flags <#variable-flags>`__" section.
-
-BB_SIGNATURE_HANDLER
-   Defines the name of the signature handler BitBake uses. The signature
-   handler defines the way stamp files are created and handled, if and
-   how the signature is incorporated into the stamps, and how the
-   signature itself is generated.
-
-   A new signature handler can be added by injecting a class derived
-   from the ``SignatureGenerator`` class into the global namespace.
-
-BB_SRCREV_POLICY
-   Defines the behavior of the fetcher when it interacts with source
-   control systems and dynamic source revisions. The
-   ``BB_SRCREV_POLICY`` variable is useful when working without a
-   network.
-
-   The variable can be set using one of two policies:
-
-   -  *cache* - Retains the value the system obtained previously rather
-      than querying the source control system each time.
-
-   -  *clear* - Queries the source controls system every time. With this
-      policy, there is no cache. The "clear" policy is the default.
-
-BB_STAMP_POLICY
-   Defines the mode used for how timestamps of stamp files are compared.
-   You can set the variable to one of the following modes:
-
-   -  *perfile* - Timestamp comparisons are only made between timestamps
-      of a specific recipe. This is the default mode.
-
-   -  *full* - Timestamp comparisons are made for all dependencies.
-
-   -  *whitelist* - Identical to "full" mode except timestamp
-      comparisons are made for recipes listed in the
-      ```BB_STAMP_WHITELIST`` <#var-bb-BB_STAMP_WHITELIST>`__ variable.
-
-   .. note::
-
-      Stamp policies are largely obsolete with the introduction of
-      setscene tasks.
-
-BB_STAMP_WHITELIST
-   Lists files whose stamp file timestamps are compared when the stamp
-   policy mode is set to "whitelist". For information on stamp policies,
-   see the ```BB_STAMP_POLICY`` <#var-bb-BB_STAMP_POLICY>`__ variable.
-
-BB_STRICT_CHECKSUM
-   Sets a more strict checksum mechanism for non-local URLs. Setting
-   this variable to a value causes BitBake to report an error if it
-   encounters a non-local URL that does not have at least one checksum
-   specified.
-
-BB_TASK_IONICE_LEVEL
-   Allows adjustment of a task's Input/Output priority. During
-   Autobuilder testing, random failures can occur for tasks due to I/O
-   starvation. These failures occur during various QEMU runtime
-   timeouts. You can use the ``BB_TASK_IONICE_LEVEL`` variable to adjust
-   the I/O priority of these tasks.
-
-   .. note::
-
-      This variable works similarly to the
-      BB_TASK_NICE_LEVEL
-      variable except with a task's I/O priorities.
-
-   Set the variable as follows: BB_TASK_IONICE_LEVEL = "class.prio" For
-   class, the default value is "2", which is a best effort. You can use
-   "1" for realtime and "3" for idle. If you want to use realtime, you
-   must have superuser privileges.
-
-   For prio, you can use any value from "0", which is the highest
-   priority, to "7", which is the lowest. The default value is "4". You
-   do not need any special privileges to use this range of priority
-   values.
-
-   .. note::
-
-      In order for your I/O priority settings to take effect, you need
-      the Completely Fair Queuing (CFQ) Scheduler selected for the
-      backing block device. To select the scheduler, use the following
-      command form where
-      device
-      is the device (e.g. sda, sdb, and so forth):
-      ::
-
-               $ sudo sh -c “echo cfq > /sys/block/device/queu/scheduler
-                                 
-
-BB_TASK_NICE_LEVEL
-   Allows specific tasks to change their priority (i.e. nice level).
-
-   You can use this variable in combination with task overrides to raise
-   or lower priorities of specific tasks. For example, on the `Yocto
-   Project <http://www.yoctoproject.org>`__ autobuilder, QEMU emulation
-   in images is given a higher priority as compared to build tasks to
-   ensure that images do not suffer timeouts on loaded systems.
-
-BB_TASKHASH
-   Within an executing task, this variable holds the hash of the task as
-   returned by the currently enabled signature generator.
-
-BB_VERBOSE_LOGS
-   Controls how verbose BitBake is during builds. If set, shell scripts
-   echo commands and shell script output appears on standard out
-   (stdout).
-
-BB_WORKERCONTEXT
-   Specifies if the current context is executing a task. BitBake sets
-   this variable to "1" when a task is being executed. The value is not
-   set when the task is in server context during parsing or event
-   handling.
-
-BBCLASSEXTEND
-   Allows you to extend a recipe so that it builds variants of the
-   software. Some examples of these variants for recipes from the
-   OpenEmbedded-Core metadata are "natives" such as ``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 variable to your recipe.
-   Here are two examples. The "native" variants are from the
-   OpenEmbedded-Core metadata: BBCLASSEXTEND =+ "native nativesdk"
-   BBCLASSEXTEND =+ "multilib:multilib_name"
-
-   .. note::
-
-      Internally, the ``BBCLASSEXTEND`` mechanism generates recipe
-      variants by rewriting variable values and applying overrides such
-      as ``_class-native``. For example, to generate a native version of
-      a recipe, a ```DEPENDS`` <#var-bb-DEPENDS>`__ on "foo" is
-      rewritten to a ``DEPENDS`` on "foo-native".
-
-      Even when using ``BBCLASSEXTEND``, the recipe is only parsed once.
-      Parsing once adds some limitations. For example, it is not
-      possible to include a different file depending on the variant,
-      since ``include`` statements are processed when the recipe is
-      parsed.
-
-BBDEBUG
-   Sets the BitBake debug output level to a specific value as
-   incremented by the ``-D`` command line option.
-
-   .. note::
-
-      You must set this variable in the external environment in order
-      for it to work.
-
-BBFILE_COLLECTIONS
-   Lists the names of configured layers. These names are used to find
-   the other ``BBFILE_*`` variables. Typically, each layer appends its
-   name to this variable in its ``conf/layer.conf`` file.
-
-BBFILE_PATTERN
-   Variable that expands to match files from
-   ```BBFILES`` <#var-bb-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`` <#var-bb-PV>`__ variable).
-   For example, a layer that has a recipe with a higher ``PV`` value but
-   for which the ``BBFILE_PRIORITY`` is set to have a lower precedence
-   still has a lower precedence.
-
-   A larger value for the ``BBFILE_PRIORITY`` variable results in a
-   higher precedence. For example, the value 6 has a higher precedence
-   than the value 5. If not specified, the ``BBFILE_PRIORITY`` variable
-   is set based on layer dependencies (see the ``LAYERDEPENDS`` variable
-   for more information. The default priority, if unspecified for a
-   layer with no dependencies, is the lowest defined priority + 1 (or 1
-   if no priorities are defined).
-
-   .. tip::
-
-      You can use the command
-      bitbake-layers show-layers
-      to list all configured layers along with their priorities.
-
-BBFILES
-   A space-separated list of recipe files BitBake uses to build
-   software.
-
-   When specifying recipe files, you can pattern match using Python's
-   ```glob`` <https://docs.python.org/3/library/glob.html>`__ syntax.
-   For details on the syntax, see the documentation by following the
-   previous link.
-
-BBINCLUDED
-   Contains a space-separated list of all of all files that BitBake's
-   parser included during parsing of the current file.
-
-BBINCLUDELOGS
-   If set to a value, enables printing the task log when reporting a
-   failed task.
-
-BBINCLUDELOGS_LINES
-   If ```BBINCLUDELOGS`` <#var-bb-BBINCLUDELOGS>`__ is set, specifies
-   the maximum number of lines from the task log file to print when
-   reporting a failed task. If you do not set ``BBINCLUDELOGS_LINES``,
-   the entire log is printed.
-
-BBLAYERS
-   Lists the layers to enable during the build. This variable is defined
-   in the ``bblayers.conf`` configuration file in the build directory.
-   Here is an example: BBLAYERS = " \\ /home/scottrif/poky/meta \\
-   /home/scottrif/poky/meta-yocto \\ /home/scottrif/poky/meta-yocto-bsp
-   \\ /home/scottrif/poky/meta-mykernel \\ " This example enables four
-   layers, one of which is a custom, user-defined layer named
-   ``meta-mykernel``.
-
-BBLAYERS_FETCH_DIR
-   Sets the base location where layers are stored. This setting is used
-   in conjunction with ``bitbake-layers layerindex-fetch`` and tells
-   ``bitbake-layers`` where to place the fetched layers.
-
-BBMASK
-   Prevents BitBake from processing recipes and recipe append files.
-
-   You can use the ``BBMASK`` variable to "hide" these ``.bb`` and
-   ``.bbappend`` files. BitBake ignores any recipe or recipe append
-   files that match any of the expressions. It is as if BitBake does not
-   see them at all. Consequently, matching files are not parsed or
-   otherwise used by BitBake.
-
-   The values you provide are passed to Python's regular expression
-   compiler. Consequently, the syntax follows Python's Regular
-   Expression (re) syntax. The expressions are compared against the full
-   paths to the files. For complete syntax information, see Python's
-   documentation at ` <http://docs.python.org/3/library/re.html#re>`__.
-
-   The following example uses a complete regular expression to tell
-   BitBake to ignore all recipe and recipe append files in the
-   ``meta-ti/recipes-misc/`` directory: BBMASK = "meta-ti/recipes-misc/"
-   If you want to mask out multiple directories or recipes, you can
-   specify multiple regular expression fragments. This next example
-   masks out multiple directories and individual recipes: BBMASK +=
-   "/meta-ti/recipes-misc/ meta-ti/recipes-ti/packagegroup/" BBMASK +=
-   "/meta-oe/recipes-support/" BBMASK += "/meta-foo/.*/openldap" BBMASK
-   += "opencv.*\.bbappend" BBMASK += "lzma"
-
-   .. note::
-
-      When specifying a directory name, use the trailing slash character
-      to ensure you match just that directory name.
-
-BBMULTICONFIG
-   Enables BitBake to perform multiple configuration builds and lists
-   each separate configuration (multiconfig). You can use this variable
-   to cause BitBake to build multiple targets where each target has a
-   separate configuration. Define ``BBMULTICONFIG`` in your
-   ``conf/local.conf`` configuration file.
-
-   As an example, the following line specifies three multiconfigs, each
-   having a separate configuration file: BBMULTIFONFIG = "configA
-   configB configC" Each configuration file you use must reside in the
-   build directory within a directory named ``conf/multiconfig`` (e.g.
-   build_directory\ ``/conf/multiconfig/configA.conf``).
-
-   For information on how to use ``BBMULTICONFIG`` in an environment
-   that supports building targets with multiple configurations, see the
-   "`Executing a Multiple Configuration
-   Build <#executing-a-multiple-configuration-build>`__" section.
-
-BBPATH
-   Used by BitBake to locate class (``.bbclass``) and configuration
-   (``.conf``) 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. The variable
-   is only used when you employ memory-resident BitBake.
-
-BBTARGETS
-   Allows you to use a configuration file to add to the list of
-   command-line target recipes you want to build.
-
-BBVERSIONS
-   Allows a single recipe to build multiple versions of a project from a
-   single recipe file. You also able to specify conditional metadata
-   using the ```OVERRIDES`` <#var-bb-OVERRIDES>`__ mechanism for a
-   single version or for an optionally named range of versions.
-
-   For more information on ``BBVERSIONS``, see the "`Variants - Class
-   Extension Mechanism <#variants-class-extension-mechanism>`__"
-   section.
-
-BITBAKE_UI
-   Used to specify the UI module to use when running BitBake. Using this
-   variable is equivalent to using the ``-u`` command-line option.
-
-   .. note::
-
-      You must set this variable in the external environment in order
-      for it to work.
-
-BUILDNAME
-   A name assigned to the build. The name defaults to a datetime stamp
-   of when the build was started but can be defined by the metadata.
-
-BZRDIR
-   The directory in which files checked out of a Bazaar system are
-   stored.
-
-CACHE
-   Specifies the directory BitBake uses to store a cache of the metadata
-   so it does not need to be parsed every time BitBake is started.
-
-CVSDIR
-   The directory in which files checked out under the CVS system are
-   stored.
-
-DEFAULT_PREFERENCE
-   Specifies a weak bias for recipe selection priority.
-
-   The most common usage of this is variable is to set it to "-1" within
-   a recipe for a development version of a piece of software. Using the
-   variable in this way causes the stable version of the recipe to build
-   by default in the absence of ``PREFERRED_VERSION`` being used to
-   build the development version.
-
-   .. note::
-
-      The bias provided by
-      DEFAULT_PREFERENCE
-      is weak and is overridden by
-      BBFILE_PRIORITY
-      if that variable is different between two layers that contain
-      different versions of the same recipe.
-
-DEPENDS
-   Lists a recipe's build-time dependencies (i.e. other recipe files).
-
-   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`` <#var-bb-RDEPENDS>`__ variable.
-
-DESCRIPTION
-   A long description for the recipe.
-
-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`` <#var-bb-BB_GENERATE_MIRROR_TARBALLS>`__
-   variable.
-
-EXCLUDE_FROM_WORLD
-   Directs BitBake to exclude a recipe from world builds (i.e.
-   ``bitbake world``). During world builds, BitBake locates, parses and
-   builds all recipes found in every layer exposed in the
-   ``bblayers.conf`` configuration file.
-
-   To exclude a recipe from a world build using this variable, set the
-   variable to "1" in the recipe.
-
-   .. note::
-
-      Recipes added to
-      EXCLUDE_FROM_WORLD
-      may still be built during a world build in order to satisfy
-      dependencies of other recipes. Adding a recipe to
-      EXCLUDE_FROM_WORLD
-      only ensures that the recipe is not explicitly added to the list
-      of build targets in a world build.
-
-FAKEROOT
-   Contains the command to use when running a shell script in a fakeroot
-   environment. The ``FAKEROOT`` variable is obsolete and has been
-   replaced by the other ``FAKEROOT*`` variables. See these entries in
-   the glossary for more information.
-
-FAKEROOTBASEENV
-   Lists environment variables to set when executing the command defined
-   by ```FAKEROOTCMD`` <#var-bb-FAKEROOTCMD>`__ that starts the
-   bitbake-worker process in the fakeroot environment.
-
-FAKEROOTCMD
-   Contains the command that starts the bitbake-worker process in the
-   fakeroot environment.
-
-FAKEROOTDIRS
-   Lists directories to create before running a task in the fakeroot
-   environment.
-
-FAKEROOTENV
-   Lists environment variables to set when running a task in the
-   fakeroot environment. For additional information on environment
-   variables and the fakeroot environment, see the
-   ```FAKEROOTBASEENV`` <#var-bb-FAKEROOTBASEENV>`__ variable.
-
-FAKEROOTNOENV
-   Lists environment variables to set when running a task that is not in
-   the fakeroot environment. For additional information on environment
-   variables and the fakeroot environment, see the
-   ```FAKEROOTENV`` <#var-bb-FAKEROOTENV>`__ variable.
-
-FETCHCMD
-   Defines the command the BitBake fetcher module executes when running
-   fetch operations. You need to use an override suffix when you use the
-   variable (e.g. ``FETCHCMD_git`` or ``FETCHCMD_svn``).
-
-FILE
-   Points at the current file. BitBake sets this variable during the
-   parsing process to identify the file being parsed. BitBake also sets
-   this variable when a recipe is being executed to identify the recipe
-   file.
-
-FILESPATH
-   Specifies directories BitBake uses when searching for patches and
-   files. The "local" fetcher module uses these directories when
-   handling ``file://`` URLs. The variable behaves like a shell ``PATH``
-   environment variable. The value is a colon-separated list of
-   directories that are searched left-to-right in order.
-
-GITDIR
-   The directory in which a local copy of a Git repository is stored
-   when it is cloned.
-
-HGDIR
-   The directory in which files checked out of a Mercurial system are
-   stored.
-
-HOMEPAGE
-   Website where more information about the software the recipe is
-   building can be found.
-
-INHERIT
-   Causes the named class or classes to be inherited globally. Anonymous
-   functions in the class or classes are not executed for the base
-   configuration and in each individual recipe. The OpenEmbedded build
-   system ignores changes to ``INHERIT`` in individual recipes.
-
-   For more information on ``INHERIT``, see the "```INHERIT``
-   Configuration Directive <#inherit-configuration-directive>`__"
-   section.
-
-LAYERDEPENDS
-   Lists the layers, separated by spaces, upon which this recipe
-   depends. Optionally, you can specify a specific layer version for a
-   dependency by adding it to the end of the layer name with a colon,
-   (e.g. "anotherlayer:3" to be compared against
-   ```LAYERVERSION`` <#var-bb-LAYERVERSION>`__\ ``_anotherlayer`` in
-   this case). BitBake produces an error if any dependency is missing or
-   the version numbers do not match exactly (if specified).
-
-   You use this variable in the ``conf/layer.conf`` file. You must also
-   use the specific layer name as a suffix to the variable (e.g.
-   ``LAYERDEPENDS_mylayer``).
-
-LAYERDIR
-   When used inside the ``layer.conf`` configuration file, this variable
-   provides the path of the current layer. This variable is not
-   available outside of ``layer.conf`` and references are expanded
-   immediately when parsing of the file completes.
-
-LAYERDIR_RE
-   When used inside the ``layer.conf`` configuration file, this variable
-   provides the path of the current layer, escaped for use in a regular
-   expression (```BBFILE_PATTERN`` <#var-bb-BBFILE_PATTERN>`__). 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 variable within
-   ```LAYERDEPENDS`` <#var-bb-LAYERDEPENDS>`__ for another layer in
-   order to depend on a specific version of the layer.
-
-   You use this variable in the ``conf/layer.conf`` file. You must also
-   use the specific layer name as a suffix to the variable (e.g.
-   ``LAYERDEPENDS_mylayer``).
-
-LICENSE
-   The list of source licenses for the recipe.
-
-MIRRORS
-   Specifies additional paths from which BitBake 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`` <#var-bb-PREMIRRORS>`__, the
-   upstream source, and then locations specified by ``MIRRORS`` in that
-   order.
-
-MULTI_PROVIDER_WHITELIST
-   Allows you to suppress BitBake warnings caused when building two
-   separate recipes that provide the same output.
-
-   BitBake normally issues a warning when building two different recipes
-   where each provides the same output. This scenario is usually
-   something the user does not want. However, cases do exist where it
-   makes sense, particularly in the ``virtual/*`` namespace. You can use
-   this variable to suppress BitBake's warnings.
-
-   To use the variable, list provider names (e.g. recipe names,
-   ``virtual/kernel``, and so forth).
-
-OVERRIDES
-   BitBake uses ``OVERRIDES`` to control what variables are overridden
-   after BitBake parses recipes and configuration files.
-
-   Following is a simple example that uses an overrides list based on
-   machine architectures: OVERRIDES = "arm:x86:mips:powerpc" You can
-   find information on how to use ``OVERRIDES`` in the "`Conditional
-   Syntax (Overrides) <#conditional-syntax-overrides>`__" section.
-
-P4DIR
-   The directory in which a local copy of a Perforce depot is stored
-   when it is fetched.
-
-PACKAGES
-   The list of packages the recipe creates.
-
-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`` <#var-bb-RDEPENDS>`__) of another
-   package is satisfied during the build through the
-   ``PACKAGES_DYNAMIC`` variable, but a package with the module name is
-   never actually produced, then the other package will be broken.
-
-PE
-   The epoch of the recipe. By default, this variable is unset. The
-   variable is used to make upgrades possible when the versioning scheme
-   changes in some backwards incompatible way.
-
-PERSISTENT_DIR
-   Specifies the directory BitBake uses to store data that should be
-   preserved between builds. In particular, the data stored is the data
-   that uses BitBake's persistent data API and the data used by the PR
-   Server and PR Service.
-
-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/``).
-
-PN
-   The recipe name.
-
-PR
-   The revision of the recipe.
-
-PREFERRED_PROVIDER
-   Determines which recipe should be given preference when multiple
-   recipes provide the same item. You should always suffix the variable
-   with the name of the provided item, and you should set it to the
-   ```PN`` <#var-bb-PN>`__ of the recipe to which you want to give
-   precedence. Some examples: PREFERRED_PROVIDER_virtual/kernel ?=
-   "linux-yocto" PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"
-   PREFERRED_PROVIDER_virtual/libgl ?= "mesa"
-
-PREFERRED_PROVIDERS
-   Determines which recipe should be given preference for cases where
-   multiple recipes provide the same item. Functionally,
-   ``PREFERRED_PROVIDERS`` is identical to
-   ```PREFERRED_PROVIDER`` <#var-bb-PREFERRED_PROVIDER>`__. However, the
-   ``PREFERRED_PROVIDERS`` variable lets you define preferences for
-   multiple situations using the following form: PREFERRED_PROVIDERS =
-   "xxx:yyy aaa:bbb ..." This form is a convenient replacement for the
-   following: PREFERRED_PROVIDER_xxx = "yyy" PREFERRED_PROVIDER_aaa =
-   "bbb"
-
-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`` <#var-bb-PN>`__ you want to
-   select, and you should set ```PV`` <#var-bb-PV>`__ accordingly for
-   precedence.
-
-   The ``PREFERRED_VERSION`` variable supports limited wildcard use
-   through the "``%``" character. You can use the character to match any
-   number of characters, which can be useful when specifying versions
-   that contain long revision numbers that potentially change. Here are
-   two examples: PREFERRED_VERSION_python = "2.7.3"
-   PREFERRED_VERSION_linux-yocto = "4.12%"
-
-   .. note::
-
-      The use of the "
-      %
-      " character is limited in that it only works at the end of the
-      string. You cannot use the wildcard character in any other
-      location of the string.
-
-PREMIRRORS
-   Specifies additional paths from which BitBake 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`` <#var-bb-MIRRORS>`__ in that
-   order.
-
-   Typically, you would add a specific server for the build system to
-   attempt before any others by adding something like the following to
-   your configuration: 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.
-
-PROVIDES
-   A list of aliases by which a particular recipe can be known. By
-   default, a recipe's own ``PN`` is implicitly already in its
-   ``PROVIDES`` list. If a recipe uses ``PROVIDES``, the additional
-   aliases are synonyms for the recipe and can be useful satisfying
-   dependencies of other recipes during the build as specified by
-   ``DEPENDS``.
-
-   Consider the following example ``PROVIDES`` statement from a recipe
-   file ``libav_0.8.11.bb``: PROVIDES += "libpostproc" The ``PROVIDES``
-   statement results in the "libav" recipe also being known as
-   "libpostproc".
-
-   In addition to providing recipes under alternate names, the
-   ``PROVIDES`` mechanism is also used to implement virtual targets. A
-   virtual target is a name that corresponds to some particular
-   functionality (e.g. a Linux kernel). Recipes that provide the
-   functionality in question list the virtual target in ``PROVIDES``.
-   Recipes that depend on the functionality in question can include the
-   virtual target in ```DEPENDS`` <#var-bb-DEPENDS>`__ to leave the
-   choice of provider open.
-
-   Conventionally, virtual targets have names on the form
-   "virtual/function" (e.g. "virtual/kernel"). The slash is simply part
-   of the name and has no syntactical significance.
-
-PRSERV_HOST
-   The network based ```PR`` <#var-bb-PR>`__ service host and port.
-
-   Following is an example of how the ``PRSERV_HOST`` variable is set:
-   PRSERV_HOST = "localhost:0" You must set the variable if you want to
-   automatically start a local PR service. You can set ``PRSERV_HOST``
-   to other values to use a remote PR service.
-
-PV
-   The version of the recipe.
-
-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.
-
-   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.
-
-   BitBake 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`` <#var-bb-DEPENDS>`__ variable.
-
-REPODIR
-   The directory in which a local copy of a ``google-repo`` directory is
-   stored when it is synced.
-
-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``).
-
-   As with all package-controlling variables, you must always use the
-   variable in conjunction with a package name override. Here is an
-   example: RPROVIDES_${PN} = "widget-abi-2"
-
-RRECOMMENDS
-   A list of packages that extends the usability of a package being
-   built. The package being built does not depend on this list of
-   packages in order to successfully build, but needs them for the
-   extended usability. To specify runtime dependencies for packages, see
-   the ``RDEPENDS`` variable.
-
-   BitBake supports specifying versioned recommends. Although the syntax
-   varies depending on the packaging format, BitBake hides these
-   differences from you. Here is the general syntax to specify versions
-   with the ``RRECOMMENDS`` variable: RRECOMMENDS_${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)"
-
-SECTION
-   The section in which packages should be categorized.
-
-SRC_URI
-   The list of source files - local or remote. This variable tells
-   BitBake which bits to pull for the build and how to pull them. For
-   example, if the recipe or append file needs to fetch a single tarball
-   from the Internet, the recipe or append file uses a ``SRC_URI`` entry
-   that specifies that tarball. On the other hand, if the recipe or
-   append file needs to fetch a tarball and include a custom file, the
-   recipe or append file needs an ``SRC_URI`` variable that specifies
-   all those sources.
-
-   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`` <#var-bb-FILESPATH>`__ variable.
-
-   -  *``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.
-
-   -  *``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.
-
-   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. 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.
-
-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).
-
-SRCREV
-   The revision of the source code used to build the package. This
-   variable applies only when using Subversion, Git, Mercurial and
-   Bazaar. If you want to build a fixed revision and you want to avoid
-   performing a query on the remote repository every time BitBake parses
-   your recipe, you should specify a ``SRCREV`` that is a full revision
-   identifier and not just a tag.
-
-SRCREV_FORMAT
-   Helps construct valid ```SRCREV`` <#var-bb-SRCREV>`__ values when
-   multiple source controlled URLs are used in
-   ```SRC_URI`` <#var-bb-SRC_URI>`__.
-
-   The system needs help constructing these values under these
-   circumstances. Each component in the ``SRC_URI`` is assigned a name
-   and these are referenced in the ``SRCREV_FORMAT`` variable. Consider
-   an example with URLs named "machine" and "meta". In this case,
-   ``SRCREV_FORMAT`` could look like "machine_meta" and those names
-   would have the SCM versions substituted into each position. Only one
-   ``AUTOINC`` placeholder is added and if needed. And, this placeholder
-   is placed at the start of the returned string.
-
-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.
+         You must set this variable in the external environment in order
+         for it to work.
 
-STAMPCLEAN
-   Specifies the base path used to create recipe stamp files. Unlike the
-   ```STAMP`` <#var-bb-STAMP>`__ variable, ``STAMPCLEAN`` can contain
-   wildcards to match the range of files a clean operation should
-   remove. BitBake uses a clean operation to remove any other stamps it
-   should be removing when creating a new stamp.
+   BB_ENV_EXTRAWHITE
+      Specifies an additional set of variables to allow through (whitelist)
+      from the external environment into BitBake's datastore. This list of
+      variables are on top of the internal list set in
+      ```BB_ENV_WHITELIST`` <#var-bb-BB_ENV_WHITELIST>`__.
 
-SUMMARY
-   A short summary for the recipe, which is 72 characters or less.
+      .. note::
+
+         You must set this variable in the external environment in order
+         for it to work.
+
+   BB_FETCH_PREMIRRORONLY
+      When set to "1", causes BitBake's fetcher module to only search
+      ```PREMIRRORS`` <#var-bb-PREMIRRORS>`__ for files. BitBake will not
+      search the main ```SRC_URI`` <#var-bb-SRC_URI>`__ or
+      ```MIRRORS`` <#var-bb-MIRRORS>`__.
+
+   BB_FILENAME
+      Contains the filename of the recipe that owns the currently running
+      task. For example, if the ``do_fetch`` task that resides in the
+      ``my-recipe.bb`` is executing, the ``BB_FILENAME`` variable contains
+      "/foo/path/my-recipe.bb".
+
+   BBFILES_DYNAMIC
+      Activates content depending on presence of identified layers.  You
+      identify the layers by the collections that the layers define.
+
+      Use the ``BBFILES_DYNAMIC`` variable to avoid ``.bbappend`` files whose
+      corresponding ``.bb`` file is in a layer that attempts to modify other
+      layers through ``.bbappend`` but does not want to introduce a hard
+      dependency on those other layers.
+
+      Additionally you can prefix the rule with "!" to add ``.bbappend`` and
+      ``.bb`` files in case a layer is not present.  Use this avoid hard
+      dependency on those other layers.
+
+      Use the following form for ``BBFILES_DYNAMIC``: ::
+
+         collection_name:filename_pattern
+
+      The following example identifies two collection names and two filename
+      patterns: ::
+
+         BBFILES_DYNAMIC += "\
+             clang-layer:${LAYERDIR}/bbappends/meta-clang/*/*/*.bbappend \
+             core:${LAYERDIR}/bbappends/openembedded-core/meta/*/*/*.bbappend \
+         "
+
+      When the collection name is prefixed with "!" it will add the file pattern in case
+      the layer is absent: ::
+
+         BBFILES_DYNAMIC += "\
+             !clang-layer:${LAYERDIR}/backfill/meta-clang/*/*/*.bb \
+         "
+
+      This next example shows an error message that occurs because invalid
+      entries are found, which cause parsing to abort: ::
+
+         ERROR: BBFILES_DYNAMIC entries must be of the form {!}<collection name>:<filename pattern>, not:
+         /work/my-layer/bbappends/meta-security-isafw/*/*/*.bbappend
+         /work/my-layer/bbappends/openembedded-core/meta/*/*/*.bbappend
+
+   BB_GENERATE_MIRROR_TARBALLS
+      Causes tarballs of the Git repositories, including the Git metadata,
+      to be placed in the ```DL_DIR`` <#var-bb-DL_DIR>`__ directory. Anyone
+      wishing to create a source mirror would want to enable this variable.
+
+      For performance reasons, creating and placing tarballs of the Git
+      repositories is not the default action by BitBake.
+      BB_GENERATE_MIRROR_TARBALLS = "1"
+
+   BB_HASHCONFIG_WHITELIST
+      Lists variables that are excluded from base configuration checksum,
+      which is used to determine if the cache can be reused.
+
+      One of the ways BitBake determines whether to re-parse the main
+      metadata is through checksums of the variables in the datastore of
+      the base configuration data. There are variables that you typically
+      want to exclude when checking whether or not to re-parse and thus
+      rebuild the cache. As an example, you would usually exclude ``TIME``
+      and ``DATE`` because these variables are always changing. If you did
+      not exclude them, BitBake would never reuse the cache.
+
+   BB_HASHBASE_WHITELIST
+      Lists variables that are excluded from checksum and dependency data.
+      Variables that are excluded can therefore change without affecting
+      the checksum mechanism. A common example would be the variable for
+      the path of the build. BitBake's output should not (and usually does
+      not) depend on the directory in which it was built.
+
+   BB_HASHCHECK_FUNCTION
+      Specifies the name of the function to call during the "setscene" part
+      of the task's execution in order to validate the list of task hashes.
+      The function returns the list of setscene tasks that should be
+      executed.
+
+      At this point in the execution of the code, the objective is to
+      quickly verify if a given setscene function is likely to work or not.
+      It's easier to check the list of setscene functions in one pass than
+      to call many individual tasks. The returned list need not be
+      completely accurate. A given setscene task can still later fail.
+      However, the more accurate the data returned, the more efficient the
+      build will be.
+
+   BB_INVALIDCONF
+      Used in combination with the ``ConfigParsed`` event to trigger
+      re-parsing the base metadata (i.e. all the recipes). The
+      ``ConfigParsed`` event can set the variable to trigger the re-parse.
+      You must be careful to avoid recursive loops with this functionality.
+
+   BB_LOGCONFIG
+      Specifies the name of a config file that contains the user logging
+      configuration. See `Logging <#logging>`__ for additional information
+
+   BB_LOGFMT
+      Specifies the name of the log files saved into
+      ``${``\ ```T`` <#var-bb-T>`__\ ``}``. By default, the ``BB_LOGFMT``
+      variable is undefined and the log file names get created using the
+      following form: log.{task}.{pid} If you want to force log files to
+      take a specific name, you can set this variable in a configuration
+      file.
+
+   BB_NICE_LEVEL
+      Allows BitBake to run at a specific priority (i.e. nice level).
+      System permissions usually mean that BitBake can reduce its priority
+      but not raise it again. See
+      ```BB_TASK_NICE_LEVEL`` <#var-bb-BB_TASK_NICE_LEVEL>`__ for
+      additional information.
+
+   BB_NO_NETWORK
+      Disables network access in the BitBake fetcher modules. With this
+      access disabled, any command that attempts to access the network
+      becomes an error.
+
+      Disabling network access is useful for testing source mirrors,
+      running builds when not connected to the Internet, and when operating
+      in certain kinds of firewall environments.
+
+   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.
+
+   BB_NUMBER_PARSE_THREADS
+      Sets the number of threads BitBake uses when parsing. By default, the
+      number of threads is equal to the number of cores on the system.
+
+   BB_ORIGENV
+      Contains a copy of the original external environment in which BitBake
+      was run. The copy is taken before any whitelisted variable values are
+      filtered into BitBake's datastore.
+
+      .. note::
+
+         The contents of this variable is a datastore object that can be
+         queried using the normal datastore operations.
+
+   BB_PRESERVE_ENV
+      Disables whitelisting and instead allows all variables through from
+      the external environment into BitBake's datastore.
+
+      .. note::
+
+         You must set this variable in the external environment in order
+         for it to work.
+
+   BB_RUNFMT
+      Specifies the name of the executable script files (i.e. run files)
+      saved into ``${``\ ```T`` <#var-bb-T>`__\ ``}``. By default, the
+      ``BB_RUNFMT`` variable is undefined and the run file names get
+      created using the following form: run.{task}.{pid} If you want to
+      force run files to take a specific name, you can set this variable in
+      a configuration file.
+
+   BB_RUNTASK
+      Contains the name of the currently executing task. The value includes
+      the "do_" prefix. For example, if the currently executing task is
+      ``do_config``, the value is "do_config".
+
+   BB_SCHEDULER
+      Selects the name of the scheduler to use for the scheduling of
+      BitBake tasks. Three options exist:
+
+      -  *basic* - The basic framework from which everything derives. Using
+         this option causes tasks to be ordered numerically as they are
+         parsed.
+
+      -  *speed* - Executes tasks first that have more tasks depending on
+         them. The "speed" option is the default.
+
+      -  *completion* - Causes the scheduler to try to complete a given
+         recipe once its build has started.
+
+   BB_SCHEDULERS
+      Defines custom schedulers to import. Custom schedulers need to be
+      derived from the ``RunQueueScheduler`` class.
+
+      For information how to select a scheduler, see the
+      ```BB_SCHEDULER`` <#var-bb-BB_SCHEDULER>`__ variable.
+
+   BB_SETSCENE_DEPVALID
+      Specifies a function BitBake calls that determines whether BitBake
+      requires a setscene dependency to be met.
+
+      When running a setscene task, BitBake needs to know which
+      dependencies of that setscene task also need to be run. Whether
+      dependencies also need to be run is highly dependent on the metadata.
+      The function specified by this variable returns a "True" or "False"
+      depending on whether the dependency needs to be met.
+
+   BB_SETSCENE_VERIFY_FUNCTION2
+      Specifies a function to call that verifies the list of planned task
+      execution before the main task execution happens. The function is
+      called once BitBake has a list of setscene tasks that have run and
+      either succeeded or failed.
+
+      The function allows for a task list check to see if they make sense.
+      Even if BitBake was planning to skip a task, the returned value of
+      the function can force BitBake to run the task, which is necessary
+      under certain metadata defined circumstances.
+
+   BB_SIGNATURE_EXCLUDE_FLAGS
+      Lists variable flags (varflags) that can be safely excluded from
+      checksum and dependency data for keys in the datastore. When
+      generating checksum or dependency data for keys in the datastore, the
+      flags set against that key are normally included in the checksum.
+
+      For more information on varflags, see the "`Variable
+      Flags <#variable-flags>`__" section.
+
+   BB_SIGNATURE_HANDLER
+      Defines the name of the signature handler BitBake uses. The signature
+      handler defines the way stamp files are created and handled, if and
+      how the signature is incorporated into the stamps, and how the
+      signature itself is generated.
+
+      A new signature handler can be added by injecting a class derived
+      from the ``SignatureGenerator`` class into the global namespace.
+
+   BB_SRCREV_POLICY
+      Defines the behavior of the fetcher when it interacts with source
+      control systems and dynamic source revisions. The
+      ``BB_SRCREV_POLICY`` variable is useful when working without a
+      network.
+
+      The variable can be set using one of two policies:
+
+      -  *cache* - Retains the value the system obtained previously rather
+         than querying the source control system each time.
+
+      -  *clear* - Queries the source controls system every time. With this
+         policy, there is no cache. The "clear" policy is the default.
+
+   BB_STAMP_POLICY
+      Defines the mode used for how timestamps of stamp files are compared.
+      You can set the variable to one of the following modes:
+
+      -  *perfile* - Timestamp comparisons are only made between timestamps
+         of a specific recipe. This is the default mode.
+
+      -  *full* - Timestamp comparisons are made for all dependencies.
+
+      -  *whitelist* - Identical to "full" mode except timestamp
+         comparisons are made for recipes listed in the
+         ```BB_STAMP_WHITELIST`` <#var-bb-BB_STAMP_WHITELIST>`__ variable.
+
+      .. note::
+
+         Stamp policies are largely obsolete with the introduction of
+         setscene tasks.
+
+   BB_STAMP_WHITELIST
+      Lists files whose stamp file timestamps are compared when the stamp
+      policy mode is set to "whitelist". For information on stamp policies,
+      see the ```BB_STAMP_POLICY`` <#var-bb-BB_STAMP_POLICY>`__ variable.
+
+   BB_STRICT_CHECKSUM
+      Sets a more strict checksum mechanism for non-local URLs. Setting
+      this variable to a value causes BitBake to report an error if it
+      encounters a non-local URL that does not have at least one checksum
+      specified.
+
+   BB_TASK_IONICE_LEVEL
+      Allows adjustment of a task's Input/Output priority. During
+      Autobuilder testing, random failures can occur for tasks due to I/O
+      starvation. These failures occur during various QEMU runtime
+      timeouts. You can use the ``BB_TASK_IONICE_LEVEL`` variable to adjust
+      the I/O priority of these tasks.
+
+      .. note::
+
+         This variable works similarly to the
+         BB_TASK_NICE_LEVEL
+         variable except with a task's I/O priorities.
+
+      Set the variable as follows: BB_TASK_IONICE_LEVEL = "class.prio" For
+      class, the default value is "2", which is a best effort. You can use
+      "1" for realtime and "3" for idle. If you want to use realtime, you
+      must have superuser privileges.
+
+      For prio, you can use any value from "0", which is the highest
+      priority, to "7", which is the lowest. The default value is "4". You
+      do not need any special privileges to use this range of priority
+      values.
+
+      .. note::
+
+         In order for your I/O priority settings to take effect, you need
+         the Completely Fair Queuing (CFQ) Scheduler selected for the
+         backing block device. To select the scheduler, use the following
+         command form where
+         device
+         is the device (e.g. sda, sdb, and so forth):
+         ::
+
+                  $ sudo sh -c “echo cfq > /sys/block/device/queu/scheduler
+
+
+   BB_TASK_NICE_LEVEL
+      Allows specific tasks to change their priority (i.e. nice level).
+
+      You can use this variable in combination with task overrides to raise
+      or lower priorities of specific tasks. For example, on the `Yocto
+      Project <http://www.yoctoproject.org>`__ autobuilder, QEMU emulation
+      in images is given a higher priority as compared to build tasks to
+      ensure that images do not suffer timeouts on loaded systems.
+
+   BB_TASKHASH
+      Within an executing task, this variable holds the hash of the task as
+      returned by the currently enabled signature generator.
+
+   BB_VERBOSE_LOGS
+      Controls how verbose BitBake is during builds. If set, shell scripts
+      echo commands and shell script output appears on standard out
+      (stdout).
+
+   BB_WORKERCONTEXT
+      Specifies if the current context is executing a task. BitBake sets
+      this variable to "1" when a task is being executed. The value is not
+      set when the task is in server context during parsing or event
+      handling.
+
+   BBCLASSEXTEND
+      Allows you to extend a recipe so that it builds variants of the
+      software. Some examples of these variants for recipes from the
+      OpenEmbedded-Core metadata are "natives" such as ``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 variable to your recipe.
+      Here are two examples. The "native" variants are from the
+      OpenEmbedded-Core metadata: BBCLASSEXTEND =+ "native nativesdk"
+      BBCLASSEXTEND =+ "multilib:multilib_name"
+
+      .. note::
+
+         Internally, the ``BBCLASSEXTEND`` mechanism generates recipe
+         variants by rewriting variable values and applying overrides such
+         as ``_class-native``. For example, to generate a native version of
+         a recipe, a ```DEPENDS`` <#var-bb-DEPENDS>`__ on "foo" is
+         rewritten to a ``DEPENDS`` on "foo-native".
+
+         Even when using ``BBCLASSEXTEND``, the recipe is only parsed once.
+         Parsing once adds some limitations. For example, it is not
+         possible to include a different file depending on the variant,
+         since ``include`` statements are processed when the recipe is
+         parsed.
+
+   BBDEBUG
+      Sets the BitBake debug output level to a specific value as
+      incremented by the ``-D`` command line option.
+
+      .. note::
+
+         You must set this variable in the external environment in order
+         for it to work.
+
+   BBFILE_COLLECTIONS
+      Lists the names of configured layers. These names are used to find
+      the other ``BBFILE_*`` variables. Typically, each layer appends its
+      name to this variable in its ``conf/layer.conf`` file.
+
+   BBFILE_PATTERN
+      Variable that expands to match files from
+      ```BBFILES`` <#var-bb-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`` <#var-bb-PV>`__ variable).
+      For example, a layer that has a recipe with a higher ``PV`` value but
+      for which the ``BBFILE_PRIORITY`` is set to have a lower precedence
+      still has a lower precedence.
+
+      A larger value for the ``BBFILE_PRIORITY`` variable results in a
+      higher precedence. For example, the value 6 has a higher precedence
+      than the value 5. If not specified, the ``BBFILE_PRIORITY`` variable
+      is set based on layer dependencies (see the ``LAYERDEPENDS`` variable
+      for more information. The default priority, if unspecified for a
+      layer with no dependencies, is the lowest defined priority + 1 (or 1
+      if no priorities are defined).
+
+      .. tip::
+
+         You can use the command
+         bitbake-layers show-layers
+         to list all configured layers along with their priorities.
+
+   BBFILES
+      A space-separated list of recipe files BitBake uses to build
+      software.
+
+      When specifying recipe files, you can pattern match using Python's
+      ```glob`` <https://docs.python.org/3/library/glob.html>`__ syntax.
+      For details on the syntax, see the documentation by following the
+      previous link.
+
+   BBINCLUDED
+      Contains a space-separated list of all of all files that BitBake's
+      parser included during parsing of the current file.
+
+   BBINCLUDELOGS
+      If set to a value, enables printing the task log when reporting a
+      failed task.
+
+   BBINCLUDELOGS_LINES
+      If ```BBINCLUDELOGS`` <#var-bb-BBINCLUDELOGS>`__ is set, specifies
+      the maximum number of lines from the task log file to print when
+      reporting a failed task. If you do not set ``BBINCLUDELOGS_LINES``,
+      the entire log is printed.
+
+   BBLAYERS
+      Lists the layers to enable during the build. This variable is defined
+      in the ``bblayers.conf`` configuration file in the build directory.
+      Here is an example: BBLAYERS = " \\ /home/scottrif/poky/meta \\
+      /home/scottrif/poky/meta-yocto \\ /home/scottrif/poky/meta-yocto-bsp
+      \\ /home/scottrif/poky/meta-mykernel \\ " This example enables four
+      layers, one of which is a custom, user-defined layer named
+      ``meta-mykernel``.
+
+   BBLAYERS_FETCH_DIR
+      Sets the base location where layers are stored. This setting is used
+      in conjunction with ``bitbake-layers layerindex-fetch`` and tells
+      ``bitbake-layers`` where to place the fetched layers.
+
+   BBMASK
+      Prevents BitBake from processing recipes and recipe append files.
+
+      You can use the ``BBMASK`` variable to "hide" these ``.bb`` and
+      ``.bbappend`` files. BitBake ignores any recipe or recipe append
+      files that match any of the expressions. It is as if BitBake does not
+      see them at all. Consequently, matching files are not parsed or
+      otherwise used by BitBake.
+
+      The values you provide are passed to Python's regular expression
+      compiler. Consequently, the syntax follows Python's Regular
+      Expression (re) syntax. The expressions are compared against the full
+      paths to the files. For complete syntax information, see Python's
+      documentation at ` <http://docs.python.org/3/library/re.html#re>`__.
+
+      The following example uses a complete regular expression to tell
+      BitBake to ignore all recipe and recipe append files in the
+      ``meta-ti/recipes-misc/`` directory: BBMASK = "meta-ti/recipes-misc/"
+      If you want to mask out multiple directories or recipes, you can
+      specify multiple regular expression fragments. This next example
+      masks out multiple directories and individual recipes: BBMASK +=
+      "/meta-ti/recipes-misc/ meta-ti/recipes-ti/packagegroup/" BBMASK +=
+      "/meta-oe/recipes-support/" BBMASK += "/meta-foo/.*/openldap" BBMASK
+      += "opencv.*\.bbappend" BBMASK += "lzma"
+
+      .. note::
+
+         When specifying a directory name, use the trailing slash character
+         to ensure you match just that directory name.
+
+   BBMULTICONFIG
+      Enables BitBake to perform multiple configuration builds and lists
+      each separate configuration (multiconfig). You can use this variable
+      to cause BitBake to build multiple targets where each target has a
+      separate configuration. Define ``BBMULTICONFIG`` in your
+      ``conf/local.conf`` configuration file.
+
+      As an example, the following line specifies three multiconfigs, each
+      having a separate configuration file: BBMULTIFONFIG = "configA
+      configB configC" Each configuration file you use must reside in the
+      build directory within a directory named ``conf/multiconfig`` (e.g.
+      build_directory\ ``/conf/multiconfig/configA.conf``).
+
+      For information on how to use ``BBMULTICONFIG`` in an environment
+      that supports building targets with multiple configurations, see the
+      "`Executing a Multiple Configuration
+      Build <#executing-a-multiple-configuration-build>`__" section.
+
+   BBPATH
+      Used by BitBake to locate class (``.bbclass``) and configuration
+      (``.conf``) 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. The variable
+      is only used when you employ memory-resident BitBake.
+
+   BBTARGETS
+      Allows you to use a configuration file to add to the list of
+      command-line target recipes you want to build.
+
+   BBVERSIONS
+      Allows a single recipe to build multiple versions of a project from a
+      single recipe file. You also able to specify conditional metadata
+      using the ```OVERRIDES`` <#var-bb-OVERRIDES>`__ mechanism for a
+      single version or for an optionally named range of versions.
+
+      For more information on ``BBVERSIONS``, see the "`Variants - Class
+      Extension Mechanism <#variants-class-extension-mechanism>`__"
+      section.
+
+   BITBAKE_UI
+      Used to specify the UI module to use when running BitBake. Using this
+      variable is equivalent to using the ``-u`` command-line option.
+
+      .. note::
+
+         You must set this variable in the external environment in order
+         for it to work.
+
+   BUILDNAME
+      A name assigned to the build. The name defaults to a datetime stamp
+      of when the build was started but can be defined by the metadata.
+
+   BZRDIR
+      The directory in which files checked out of a Bazaar system are
+      stored.
+
+   CACHE
+      Specifies the directory BitBake uses to store a cache of the metadata
+      so it does not need to be parsed every time BitBake is started.
+
+   CVSDIR
+      The directory in which files checked out under the CVS system are
+      stored.
+
+   DEFAULT_PREFERENCE
+      Specifies a weak bias for recipe selection priority.
+
+      The most common usage of this is variable is to set it to "-1" within
+      a recipe for a development version of a piece of software. Using the
+      variable in this way causes the stable version of the recipe to build
+      by default in the absence of ``PREFERRED_VERSION`` being used to
+      build the development version.
+
+      .. note::
+
+         The bias provided by
+         DEFAULT_PREFERENCE
+         is weak and is overridden by
+         BBFILE_PRIORITY
+         if that variable is different between two layers that contain
+         different versions of the same recipe.
+
+   DEPENDS
+      Lists a recipe's build-time dependencies (i.e. other recipe files).
+
+      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`` <#var-bb-RDEPENDS>`__ variable.
+
+   DESCRIPTION
+      A long description for the recipe.
+
+   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`` <#var-bb-BB_GENERATE_MIRROR_TARBALLS>`__
+      variable.
+
+   EXCLUDE_FROM_WORLD
+      Directs BitBake to exclude a recipe from world builds (i.e.
+      ``bitbake world``). During world builds, BitBake locates, parses and
+      builds all recipes found in every layer exposed in the
+      ``bblayers.conf`` configuration file.
+
+      To exclude a recipe from a world build using this variable, set the
+      variable to "1" in the recipe.
+
+      .. note::
+
+         Recipes added to
+         EXCLUDE_FROM_WORLD
+         may still be built during a world build in order to satisfy
+         dependencies of other recipes. Adding a recipe to
+         EXCLUDE_FROM_WORLD
+         only ensures that the recipe is not explicitly added to the list
+         of build targets in a world build.
+
+   FAKEROOT
+      Contains the command to use when running a shell script in a fakeroot
+      environment. The ``FAKEROOT`` variable is obsolete and has been
+      replaced by the other ``FAKEROOT*`` variables. See these entries in
+      the glossary for more information.
+
+   FAKEROOTBASEENV
+      Lists environment variables to set when executing the command defined
+      by ```FAKEROOTCMD`` <#var-bb-FAKEROOTCMD>`__ that starts the
+      bitbake-worker process in the fakeroot environment.
+
+   FAKEROOTCMD
+      Contains the command that starts the bitbake-worker process in the
+      fakeroot environment.
+
+   FAKEROOTDIRS
+      Lists directories to create before running a task in the fakeroot
+      environment.
+
+   FAKEROOTENV
+      Lists environment variables to set when running a task in the
+      fakeroot environment. For additional information on environment
+      variables and the fakeroot environment, see the
+      ```FAKEROOTBASEENV`` <#var-bb-FAKEROOTBASEENV>`__ variable.
+
+   FAKEROOTNOENV
+      Lists environment variables to set when running a task that is not in
+      the fakeroot environment. For additional information on environment
+      variables and the fakeroot environment, see the
+      ```FAKEROOTENV`` <#var-bb-FAKEROOTENV>`__ variable.
+
+   FETCHCMD
+      Defines the command the BitBake fetcher module executes when running
+      fetch operations. You need to use an override suffix when you use the
+      variable (e.g. ``FETCHCMD_git`` or ``FETCHCMD_svn``).
+
+   FILE
+      Points at the current file. BitBake sets this variable during the
+      parsing process to identify the file being parsed. BitBake also sets
+      this variable when a recipe is being executed to identify the recipe
+      file.
+
+   FILESPATH
+      Specifies directories BitBake uses when searching for patches and
+      files. The "local" fetcher module uses these directories when
+      handling ``file://`` URLs. The variable behaves like a shell ``PATH``
+      environment variable. The value is a colon-separated list of
+      directories that are searched left-to-right in order.
+
+   GITDIR
+      The directory in which a local copy of a Git repository is stored
+      when it is cloned.
+
+   HGDIR
+      The directory in which files checked out of a Mercurial system are
+      stored.
+
+   HOMEPAGE
+      Website where more information about the software the recipe is
+      building can be found.
+
+   INHERIT
+      Causes the named class or classes to be inherited globally. Anonymous
+      functions in the class or classes are not executed for the base
+      configuration and in each individual recipe. The OpenEmbedded build
+      system ignores changes to ``INHERIT`` in individual recipes.
+
+      For more information on ``INHERIT``, see the "```INHERIT``
+      Configuration Directive <#inherit-configuration-directive>`__"
+      section.
+
+   LAYERDEPENDS
+      Lists the layers, separated by spaces, upon which this recipe
+      depends. Optionally, you can specify a specific layer version for a
+      dependency by adding it to the end of the layer name with a colon,
+      (e.g. "anotherlayer:3" to be compared against
+      ```LAYERVERSION`` <#var-bb-LAYERVERSION>`__\ ``_anotherlayer`` in
+      this case). BitBake produces an error if any dependency is missing or
+      the version numbers do not match exactly (if specified).
+
+      You use this variable in the ``conf/layer.conf`` file. You must also
+      use the specific layer name as a suffix to the variable (e.g.
+      ``LAYERDEPENDS_mylayer``).
+
+   LAYERDIR
+      When used inside the ``layer.conf`` configuration file, this variable
+      provides the path of the current layer. This variable is not
+      available outside of ``layer.conf`` and references are expanded
+      immediately when parsing of the file completes.
+
+   LAYERDIR_RE
+      When used inside the ``layer.conf`` configuration file, this variable
+      provides the path of the current layer, escaped for use in a regular
+      expression (```BBFILE_PATTERN`` <#var-bb-BBFILE_PATTERN>`__). 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 variable within
+      ```LAYERDEPENDS`` <#var-bb-LAYERDEPENDS>`__ for another layer in
+      order to depend on a specific version of the layer.
+
+      You use this variable in the ``conf/layer.conf`` file. You must also
+      use the specific layer name as a suffix to the variable (e.g.
+      ``LAYERDEPENDS_mylayer``).
+
+   LICENSE
+      The list of source licenses for the recipe.
+
+   MIRRORS
+      Specifies additional paths from which BitBake 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`` <#var-bb-PREMIRRORS>`__, the
+      upstream source, and then locations specified by ``MIRRORS`` in that
+      order.
+
+   MULTI_PROVIDER_WHITELIST
+      Allows you to suppress BitBake warnings caused when building two
+      separate recipes that provide the same output.
+
+      BitBake normally issues a warning when building two different recipes
+      where each provides the same output. This scenario is usually
+      something the user does not want. However, cases do exist where it
+      makes sense, particularly in the ``virtual/*`` namespace. You can use
+      this variable to suppress BitBake's warnings.
+
+      To use the variable, list provider names (e.g. recipe names,
+      ``virtual/kernel``, and so forth).
+
+   OVERRIDES
+      BitBake uses ``OVERRIDES`` to control what variables are overridden
+      after BitBake parses recipes and configuration files.
+
+      Following is a simple example that uses an overrides list based on
+      machine architectures: OVERRIDES = "arm:x86:mips:powerpc" You can
+      find information on how to use ``OVERRIDES`` in the "`Conditional
+      Syntax (Overrides) <#conditional-syntax-overrides>`__" section.
+
+   P4DIR
+      The directory in which a local copy of a Perforce depot is stored
+      when it is fetched.
+
+   PACKAGES
+      The list of packages the recipe creates.
+
+   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`` <#var-bb-RDEPENDS>`__) of another
+      package is satisfied during the build through the
+      ``PACKAGES_DYNAMIC`` variable, but a package with the module name is
+      never actually produced, then the other package will be broken.
+
+   PE
+      The epoch of the recipe. By default, this variable is unset. The
+      variable is used to make upgrades possible when the versioning scheme
+      changes in some backwards incompatible way.
+
+   PERSISTENT_DIR
+      Specifies the directory BitBake uses to store data that should be
+      preserved between builds. In particular, the data stored is the data
+      that uses BitBake's persistent data API and the data used by the PR
+      Server and PR Service.
+
+   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/``).
+
+   PN
+      The recipe name.
+
+   PR
+      The revision of the recipe.
+
+   PREFERRED_PROVIDER
+      Determines which recipe should be given preference when multiple
+      recipes provide the same item. You should always suffix the variable
+      with the name of the provided item, and you should set it to the
+      ```PN`` <#var-bb-PN>`__ of the recipe to which you want to give
+      precedence. Some examples: PREFERRED_PROVIDER_virtual/kernel ?=
+      "linux-yocto" PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"
+      PREFERRED_PROVIDER_virtual/libgl ?= "mesa"
+
+   PREFERRED_PROVIDERS
+      Determines which recipe should be given preference for cases where
+      multiple recipes provide the same item. Functionally,
+      ``PREFERRED_PROVIDERS`` is identical to
+      ```PREFERRED_PROVIDER`` <#var-bb-PREFERRED_PROVIDER>`__. However, the
+      ``PREFERRED_PROVIDERS`` variable lets you define preferences for
+      multiple situations using the following form: PREFERRED_PROVIDERS =
+      "xxx:yyy aaa:bbb ..." This form is a convenient replacement for the
+      following: PREFERRED_PROVIDER_xxx = "yyy" PREFERRED_PROVIDER_aaa =
+      "bbb"
+
+   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`` <#var-bb-PN>`__ you want to
+      select, and you should set ```PV`` <#var-bb-PV>`__ accordingly for
+      precedence.
+
+      The ``PREFERRED_VERSION`` variable supports limited wildcard use
+      through the "``%``" character. You can use the character to match any
+      number of characters, which can be useful when specifying versions
+      that contain long revision numbers that potentially change. Here are
+      two examples: PREFERRED_VERSION_python = "2.7.3"
+      PREFERRED_VERSION_linux-yocto = "4.12%"
+
+      .. note::
+
+         The use of the "
+         %
+         " character is limited in that it only works at the end of the
+         string. You cannot use the wildcard character in any other
+         location of the string.
+
+   PREMIRRORS
+      Specifies additional paths from which BitBake 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`` <#var-bb-MIRRORS>`__ in that
+      order.
+
+      Typically, you would add a specific server for the build system to
+      attempt before any others by adding something like the following to
+      your configuration: 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.
+
+   PROVIDES
+      A list of aliases by which a particular recipe can be known. By
+      default, a recipe's own ``PN`` is implicitly already in its
+      ``PROVIDES`` list. If a recipe uses ``PROVIDES``, the additional
+      aliases are synonyms for the recipe and can be useful satisfying
+      dependencies of other recipes during the build as specified by
+      ``DEPENDS``.
+
+      Consider the following example ``PROVIDES`` statement from a recipe
+      file ``libav_0.8.11.bb``: PROVIDES += "libpostproc" The ``PROVIDES``
+      statement results in the "libav" recipe also being known as
+      "libpostproc".
+
+      In addition to providing recipes under alternate names, the
+      ``PROVIDES`` mechanism is also used to implement virtual targets. A
+      virtual target is a name that corresponds to some particular
+      functionality (e.g. a Linux kernel). Recipes that provide the
+      functionality in question list the virtual target in ``PROVIDES``.
+      Recipes that depend on the functionality in question can include the
+      virtual target in ```DEPENDS`` <#var-bb-DEPENDS>`__ to leave the
+      choice of provider open.
+
+      Conventionally, virtual targets have names on the form
+      "virtual/function" (e.g. "virtual/kernel"). The slash is simply part
+      of the name and has no syntactical significance.
+
+   PRSERV_HOST
+      The network based ```PR`` <#var-bb-PR>`__ service host and port.
+
+      Following is an example of how the ``PRSERV_HOST`` variable is set:
+      PRSERV_HOST = "localhost:0" You must set the variable if you want to
+      automatically start a local PR service. You can set ``PRSERV_HOST``
+      to other values to use a remote PR service.
+
+   PV
+      The version of the recipe.
+
+   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.
+
+      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.
+
+      BitBake 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`` <#var-bb-DEPENDS>`__ variable.
+
+   REPODIR
+      The directory in which a local copy of a ``google-repo`` directory is
+      stored when it is synced.
+
+   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``).
+
+      As with all package-controlling variables, you must always use the
+      variable in conjunction with a package name override. Here is an
+      example: RPROVIDES_${PN} = "widget-abi-2"
+
+   RRECOMMENDS
+      A list of packages that extends the usability of a package being
+      built. The package being built does not depend on this list of
+      packages in order to successfully build, but needs them for the
+      extended usability. To specify runtime dependencies for packages, see
+      the ``RDEPENDS`` variable.
+
+      BitBake supports specifying versioned recommends. Although the syntax
+      varies depending on the packaging format, BitBake hides these
+      differences from you. Here is the general syntax to specify versions
+      with the ``RRECOMMENDS`` variable: RRECOMMENDS_${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)"
+
+   SECTION
+      The section in which packages should be categorized.
+
+   SRC_URI
+      The list of source files - local or remote. This variable tells
+      BitBake which bits to pull for the build and how to pull them. For
+      example, if the recipe or append file needs to fetch a single tarball
+      from the Internet, the recipe or append file uses a ``SRC_URI`` entry
+      that specifies that tarball. On the other hand, if the recipe or
+      append file needs to fetch a tarball and include a custom file, the
+      recipe or append file needs an ``SRC_URI`` variable that specifies
+      all those sources.
+
+      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`` <#var-bb-FILESPATH>`__ variable.
+
+      -  *``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.
+
+      -  *``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.
+
+      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. 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.
+
+   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).
+
+   SRCREV
+      The revision of the source code used to build the package. This
+      variable applies only when using Subversion, Git, Mercurial and
+      Bazaar. If you want to build a fixed revision and you want to avoid
+      performing a query on the remote repository every time BitBake parses
+      your recipe, you should specify a ``SRCREV`` that is a full revision
+      identifier and not just a tag.
+
+   SRCREV_FORMAT
+      Helps construct valid ```SRCREV`` <#var-bb-SRCREV>`__ values when
+      multiple source controlled URLs are used in
+      ```SRC_URI`` <#var-bb-SRC_URI>`__.
+
+      The system needs help constructing these values under these
+      circumstances. Each component in the ``SRC_URI`` is assigned a name
+      and these are referenced in the ``SRCREV_FORMAT`` variable. Consider
+      an example with URLs named "machine" and "meta". In this case,
+      ``SRCREV_FORMAT`` could look like "machine_meta" and those names
+      would have the SCM versions substituted into each position. Only one
+      ``AUTOINC`` placeholder is added and if needed. And, this placeholder
+      is placed at the start of the returned string.
+
+   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.
+
+   STAMPCLEAN
+      Specifies the base path used to create recipe stamp files. Unlike the
+      ```STAMP`` <#var-bb-STAMP>`__ variable, ``STAMPCLEAN`` can contain
+      wildcards to match the range of files a clean operation should
+      remove. BitBake uses a clean operation to remove any other stamps it
+      should be removing when creating a new stamp.
+
+   SUMMARY
+      A short summary for the recipe, which is 72 characters or less.
 
-SVNDIR
-   The directory in which files checked out of a Subversion system are
-   stored.
+   SVNDIR
+      The directory in which files checked out of a Subversion system are
+      stored.
 
-T
-   Points to a directory were BitBake places temporary files, which
-   consist mostly of task logs and scripts, when building a particular
-   recipe.
+   T
+      Points to a directory were BitBake places temporary files, which
+      consist mostly of task logs and scripts, when building a particular
+      recipe.
 
-TOPDIR
-   Points to the build directory. BitBake automatically sets this
-   variable.
+   TOPDIR
+      Points to the build directory. BitBake automatically sets this
+      variable.