# Reference: Variables Glossary

This section lists common variables used in the Yocto Project and gives an overview of their function and contents.

A B C D E F H I K L M P R S T W

### A

AUTHOR

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

AUTOREV

  Specifies to use the current (newest) source revision. This variable is with the `SRCREV` variable.

### B

BB_NUMBER_THREADS

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

BBFILE_COLLECTIONS

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

BBFILE_PATTERN

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

BBFILE_PRIORITY

  Assigns the priority for recipe files in each layer.

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

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

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

BBFILES

  List of recipe files used by BitBake to build software

BBPATH

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

BBINCLUDELOGS

  Variable that controls how BitBake displays logs on build failure.

BBLAYERS

  Lists the layers to enable during the Yocto Project build. This variable is defined in the `bblayers.conf` configuration file in the Yocto Project build directory. Here is an example:

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

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

  Bare name of package with any suffixes like -cross -native removed.

### C

CFLAGS

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

COMPATIBLE_MACHINE

  A regular expression which evaluates to match the machines the recipe works with. It stops recipes being run on machines for which they are not compatible. This is particularly useful with kernels. It also helps to increase parsing speed as further parsing of the recipe is skipped if it is found the current machine is not compatible.

CONFIG_SITE

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

### D

D

  The destination directory.

DEBUG_BUILD

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

DEBUG_OPTIMIZATION

  The options to pass in `TARGET_CFLAGS` and `CFLAGS` when compiling a system for debugging. This variable defaults to "-O -fno-omit-frame-pointer -g".

DEFAULT_PREFERENCE

  Specifies the priority of recipes.

DEPENDS

  A list of build-time dependencies for a given recipe. The variable indicates recipes that must have been staged before a particular recipe can configure.

DESCRIPTION

  The package description used by package managers.

DESTDIR

  the destination directory.

DISTRO

  The short name of the distribution.

DISTRO_EXTRA_RDEPENDS

  The list of packages required by the distribution.

DISTRO_EXTRA_RRECOMMENDS

  The list of packages which extend usability of the image. Those packages will automatically be installed but can be removed by user.

DISTRO_FEATURES

  The features of the distribution.

DISTRO_NAME

  The long name of the distribution.

DISTRO_PN_ALIAS

  Alias names used for the recipe in various Linux distributions.

  See Handling a Package Name Alias section for more information.

DISTRO_VERSION

  the version of the distribution.

DL_DIR

  The directory where all fetched sources will be stored.

### E

ENABLE_BINARY_LOCALE_GENERATION

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

EXTRA_IMAGE_FEATURES

  Allows extra packages to be added to the generated images. You set this variable in the `local.conf` configuration file. Note that some image features are also added using the `IMAGE_FEATURES` variable generally configured in image recipes. You can use this variable to add more features in addition to those. Here are some examples of features you can add:

           "dbg-pkgs" - Adds -dbg packages for all installed packages
                        including symbol information for debugging and
                        profiling.

           "dev-pkgs" - Adds -dev packages for all installed packages.
                        This is useful if you want to develop against
                        the libraries in the image.

           "tools-sdk" - Adds development tools such as gcc, make,
                         pkgconfig and so forth.

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

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

           "tools-testapps" - Adds useful testing tools such as
                              ts_print, aplay, arecord and so
                              forth.

           "debug-tweaks" - Makes an image suitable for development.
                            For example, ssh root access has a blank
                            password.  There are other application
                            targets too, see
                            meta/classes/poky-image.bbclass
                            and meta/packages/tasks/task-poky.bb
                            for more details.

EXTRA_OECMAKE

  Additional `cmake` options.

EXTRA_OECONF

  Additional `configure` script options.

EXTRA_OEMAKE

  Additional GNU `make` options.

### F

FILES

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

FULL_OPTIMIZATION

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

### H

HOMEPAGE

  Website where more info about package can be found

### I

IMAGE_FEATURES

  The list of features present in images. Typically, you configure this variable in image recipes. Note that you can add extra features to the image by using the `EXTRA_IMAGE_FEATURES` variable. See the Reference: Images section for the list of features present in images built by the Yocto Project.

IMAGE_FSTYPES

  Formats of root filesystem images that you want to have created.

IMAGE_INSTALL

  The list of packages used to build images.

INC_PR

  Defines the Package revision. You manually combine values for `INC_PR` into the `PR` field of the parent recipe. When you change this variable, you change the `PR` value for every person that includes the file.

  The following example shows how to use the `INC_PR` variable given a common `.inc` file that defines the variable. Once defined, you can use the variable to set the `PR` value:

       recipes-graphics/xorg-font/font-util_1.1.1.bb:PR - "$(INC_PR).1"
       recipes-graphics/xorg-font/xorg-font-common.inc:INC_PR - "r1"
       recipes-graphics/xorg-font/encondings_1.0.3.bb:PR - "$(INC_PR).1"
       recipes-graphics/xorg-font/fiont-alias_1.0.2.bb:PR - "$(INC_PR).0"

INHIBIT_PACKAGE_STRIP

  Causes the build to not strip binaries in resulting packages.

INHERIT

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

INITSCRIPT_PACKAGES

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

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

INITSCRIPT_NAME

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

  This variable is used in recipes when using `update-rc.d.bbclass`. The variable is Mandatory.

INITSCRIPT_PARAMS

  Specifies the options to pass to `update-rc.d`. An example is `start 99 5 2 . stop 20 0 1 6 .`, which gives the script a runlevel of 99, starts the script in initlevels 2 and 5, and stops the script in levels 0, 1 and 6.

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

### K

KERNEL_IMAGETYPE

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

### L

LAYERDEPENDS

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

LAYERDIR

  When used inside the `layer.conf` configuration file, this variable provides the path of the current layer. This variable requires immediate expansion (see the BitBake manual) as lazy expansion can result in the expansion happening in the wrong directory and therefore giving the wrong value.

LAYERVERSION

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

LICENSE

  The list of package source licenses.

LIC_FILES_CHKSUM

  Checksums of the license text in the recipe source code.

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

  This variable must be defined for all recipes (unless `LICENSE` is set to "CLOSED")

  For more information, see the Track License Change section

### M

MACHINE

  Specifies the target device.

MACHINE_ESSENTIAL_RDEPENDS

  Specifies the list of packages required to boot the device.

MACHINE_ESSENTIAL_RRECOMMENDS

  Specifies the list of packages required to boot the device (usually additional kernel modules).

MACHINE_EXTRA_RDEPENDS

  Specifies the list of packages required to use the devices

MACHINE_EXTRA_RRECOMMENDS

  Specifies the list of packages useful to use the device (e.g. additional kernel modules)

MACHINE_FEATURES

  Specifies the list of device features. See the Machine section for more information.

MAINTAINER

  The email address of the distribution maintainer.

### P

PACKAGE_ARCH

  The architecture of the resulting package.

PACKAGE_CLASSES

  This variable, which is set in the `local.conf` configuration file found in the Yocto Project file's `conf` directory, specifies the package manager to use when packaging data. You can provide one or more arguments for the variable with the first argument being the package manager used to create images:

           PACKAGE_CLASSES ?= "package_rpm package_deb package_ipk"

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

  The long form description of the binary package for packaging systems such as `ipkg`, `rpm` or `debian`. By default, this variable inherits `DESCRIPTION`.

PACKAGE_EXTRA_ARCHS

  Specifies the list of architectures compatible with the device CPU. This variable is useful when you build for several different devices that use miscellaneous processors such as XScale and ARM926-EJS).

PACKAGE_SUMMARY

  The short (72 character limit suggested) summary of the binary package for packaging systems such as `ipkg`, `rpm` or `debian`. By default, this variable inherits `DESCRIPTION`.

PACKAGES

  The list of packages to be created from the recipe. The default value is "${PN}-dbg ${PN} ${PN}-doc ${PN}-dev".

PARALLEL_MAKE

  Specifies extra options that are passed to the `make` command during the compile tasks. This variable is usually in the form `-j 4`, where the number represents the maximum number of parallel threads make can run. If you development host supports multiple cores a good rule of thumb is to set this variable to one and a half times the number of cores on the host.

PN

  The name of the package.

PR

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

PV

  The version of the package. The version is normally extracted from the recipe name. For example, if the recipe is named `expat_2.0.1.bb`, then `PV` will be `2.0.1`. `PV` is generally not overridden within a recipe unless it is building an unstable version from a source code repository (e.g. Git or Subversion).

PE

  the epoch of the package. The default value is "0". The field is used to make upgrades possible when the versioning scheme changes in some backwards incompatible way.

PREFERRED_PROVIDER

  If multiple recipes provide an item, this variable determines which recipe should be given preference. The variable should be set to the `$PN` of the recipe to which you want to give precedence.

PREFERRED_VERSION

  If there are multiple versions of recipes available, this variable determines which recipe should be given preference. The variable should be set to the `$PV` of the recipe to whichy you want to give precedence.

POKY_EXTRA_INSTALL

  Specifies the list of packages to be added to the image. This variable should only be set in the `local.conf` configuration file found in the Yocto Project's build directory.

POKYLIBC

  The `libc` implementation selector. You can select `glibc`, `eglibc`, or `uclibc`.

POKYMODE

  The toolchain selector. This variable has been replaced by `TCMODE`. The `POKYMODE` would select the external toolchain built from the Yocto Project or a few supported combinations of upstream GCC or CodeSourcery Labs toolchain.

### R

RCONFLICTS

  The list of packages that conflict with this package. Note that the package will not be installed if the conflicting packages are not first removed.

RDEPENDS

  A list of run-time dependencies for a package. These packages need to be installed alongside the package to which they apply. This enables the package to run correctly. For example, consider a Perl script, which depends on the Perl package. Since this variable applies to output packages, there would usually be an override attached to this variable such as `RDEPENDS_${PN}-dev`. Names in this field must appear as they appear in the `PACKAGES` namespace before any renaming of the output package by classes like `debian.bbclass`.

ROOT_FLASH_SIZE

  The size of root filesystem as measured in megabytes.

RRECOMMENDS

  The list of packages that extend usability of the package. The packages are automatically installed but can be removed by user.

RREPLACES

  The list of packages that are replaced with this package.

### S

S

  The path to unpacked sources. By default, this path is "${WORKDIR}/${PN}-${PV}".

SECTION

  The section where package should be put. Package managers use this variable.

SELECTED_OPTIMIZATION

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

SERIAL_CONSOLE

  The speed and device for the serial port used to attach the serial console. This variable is given to the kernel as the "console" parameter and after booting occurs `getty` is started on that port so remote login is possible.

SSTATE_DIR

  The directory for the shared state.

SHELLCMDS

  A list of commands to run within the shell. The list is used by `TERMCMDRUN`.

SITEINFO_ENDIANNESS

  Specifies the endian byte order of the target system. The variable is either "le" for little-endian or "be" for big-endian.

SITEINFO_BITS

  Specifies the number of bits for the target system CPU. The variable is either "32" or "64".

SRC_URI

  The list of source files - local or remote.

SRC_URI_OVERRIDES_PACKAGE_ARCH

  By default, the Yocto Project automatically detects whether `SRC_URI` contains files that are machine-specific. If so, the Yocto Project automatically changes `PACKAGE_ARCH`. Setting this variable to "0" disables this behaviour.

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 to Subversion, Git, Mercurial and Bazaar only. Note that if you wish to build a fixed revision and you wish to avoid performing a query on the remote repository every time BitBake parses your recipe, you should specify a `SRCREV` that is a full revision identifier and not just a tag.

STAGING_KERNEL_DIR

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

STAMPS

  The directory (usually `TMPDIR/stamps`) with timestamps of executed tasks.

SUMMARY

  The short (72 characters or less) summary of the binary package for packaging systems such as `ipkg`, `rpm` or `debian`. By default, this variable inherits `DESCRIPTION`.

### T

TARGET_ARCH

  The architecture of the device being built. While a number of values are possible, the Yocto Project primarily supports `arm` and `i586`.

TARGET_CFLAGS

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

TARGET_FPU

  Specifies the method for handling FPU code. For FPU-less targets, which include most ARM CPUs, the variable must be set to "soft". If not, the kernel emulation gets used, which results in a performance penalty.

TARGET_OS

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

TCMODE

  The toolchain selector. This variable replaces `POKYMODE`. The variable determines which of the files in `meta/conf/distro/include/tcmode-*` is used. By default, `TCMODE` is set to "default", which chooses `tcmode-default.inc`.

  The variable is similar to `TCLIBC`, which controls the `libc` used: `eglibc` or `uclibc`.

TERMCMD

  This command is used by BitBake to launch a terminal window with a shell. The shell is unspecified so the user's default shell is used. By default, the variable is set to "xterm" but it can be any X11 terminal application or a terminal multiplexer such as screen.

  While `KONSOLE_TERMCMD` and `KONSOLE_TERMCMDRUN` are provided and will work with KDE's Konsole terminal application Konsole from KDE 3, Konsole in KDE 4.0 and later versions will no longer work here due to the fact that it now launches in the background by default, and it is not practically possible to wait until it has terminated. It is hoped that this can be fixed in a future version.

TERMCMDRUN

  This variable is similar to `TERMCMD`. However, instead of running the user's shell, the command specified by the `SHELLCMDS` variable is run.

### W

WORKDIR

  The path to directory in `tmp/work/` where the package is built.