BitBake User Manual

BitBake Team

   Copyright (c) 2004, 2005, 2006 Chris Larson, Phil Blundell

   This work is licensed under the Creative Commons Attribution
   License. To view a copy of this license, visit
   http://creativecommons.org/licenses/by/2.5/ or send a letter to
   Creative Commons, 559 Nathan Abbott Way, Stanford, California
   94305, USA.
     __________________________________________________________

   Table of Contents

   1. Introduction

        Overview
        Background and Goals

   2. Metadata

        Description

              Basic variable setting
              Variable expansion
              Immediate variable expansion (:=)
              Appending (+=) and prepending (=+)
              Appending (.=) and prepending (=.) without spaces
              Conditional metadata set
              Conditional appending
              Inclusion
              Requiring Inclusion
              Python variable expansion
              Defining executable metadata
              Defining python functions into the global python
                      namespace

              Variable Flags
              Inheritance
              Tasks
              Events

        Dependency Handling

              Dependencies internal to the .bb file
              DEPENDS
              RDEPENDS
              Recursive DEPENDS
              Recursive RDEPENDS
              Inter Task

        Parsing

              Configuration Files
              Classes
              .bb Files

   3. File Download support

        Overview
        Local File Fetcher
        CVS File Fetcher
        HTTP/FTP Fetcher
        SVK Fetcher
        SVN Fetcher
        GIT Fetcher

   4. Commands

        bbread
        bitbake

              Introduction
              Usage and Syntax
              Special variables
              Metadata

   List of Examples

   4.1. Executing a task against a single .bb
   4.2. Executing tasks against a set of .bb files
   4.3. Generating dependency graphs
   4.4. Setting BBFILES
   4.5. Depending on another .bb
   4.6. Using PROVIDES
   4.7. Specifying version preference
   4.8. Using "bbfile collections"

Chapter 1. Introduction

   Table of Contents

   Overview
   Background and Goals

Overview

   BitBake is, at its simplest, a tool for executing tasks and
   managing metadata. As such, its similarities to GNU make and
   other build tools are readily apparent. It was inspired by
   Portage, the package management system used by the Gentoo Linux
   distribution. BitBake is the basis of the OpenEmbedded project,
   which is being used to build and maintain a number of embedded
   Linux distributions, including OpenZaurus and Familiar.

Background and Goals

   Prior to BitBake, no other build tool adequately met the needs
   of an aspiring embedded Linux distribution. All of the
   buildsystems used by traditional desktop Linux distributions
   lacked important functionality, and none of the ad-hoc
   buildroot systems, prevalent in the embedded space, were
   scalable or maintainable.

   Some important goals for BitBake were:
     * Handle crosscompilation.
     * Handle interpackage dependencies (build time on target
       architecture, build time on native architecture, and
       runtime).
     * Support running any number of tasks within a given package,
       including, but not limited to, fetching upstream sources,
       unpacking them, patching them, configuring them, et cetera.
     * Must be linux distribution agnostic (both build and
       target).
     * Must be architecture agnostic
     * Must support multiple build and target operating systems
       (including cygwin, the BSDs, etc).
     * Must be able to be self contained, rather than tightly
       integrated into the build machine's root filesystem.
     * There must be a way to handle conditional metadata (on
       target architecture, operating system, distribution,
       machine).
     * It must be easy for the person using the tools to supply
       their own local metadata and packages to operate against.
     * Must make it easy to collaborate between multiple projects
       using BitBake for their builds.
     * Should provide an inheritance mechanism to share common
       metadata between many packages.
     * Et cetera...

   BitBake satisfies all these and many more. Flexibility and
   power have always been the priorities. It is highly extensible,
   supporting embedded Python code and execution of any arbitrary
   tasks.

Chapter 2. Metadata

   Table of Contents

   Description

        Basic variable setting
        Variable expansion
        Immediate variable expansion (:=)
        Appending (+=) and prepending (=+)
        Appending (.=) and prepending (=.) without spaces
        Conditional metadata set
        Conditional appending
        Inclusion
        Requiring Inclusion
        Python variable expansion
        Defining executable metadata
        Defining python functions into the global python namespace
        Variable Flags
        Inheritance
        Tasks
        Events

   Dependency Handling

        Dependencies internal to the .bb file
        DEPENDS
        RDEPENDS
        Recursive DEPENDS
        Recursive RDEPENDS
        Inter Task

   Parsing

        Configuration Files
        Classes
        .bb Files

Description

   BitBake metadata can be classified into 3 major areas:
     * Configuration Files
     * .bb Files
     * Classes

   What follows are a large number of examples of BitBake
   metadata. Any syntax which isn't supported in any of the
   aforementioned areas will be documented as such.

Basic variable setting

VARIABLE = "value"

   In this example, VARIABLE is value.

Variable expansion

   BitBake supports variables referencing one another's contents
   using a syntax which is similar to shell scripting
A = "aval"
B = "pre${A}post"

   This results in A containing aval and B containing preavalpost.

Immediate variable expansion (:=)

   := results in a variable's contents being expanded immediately,
   rather than when the variable is actually used.
T = "123"
A := "${B} ${A} test ${T}"
T = "456"
B = "${T} bval"

C = "cval"
C := "${C}append"

   In that example, A would contain test 123, B would contain 456
   bval, and C would be cvalappend.

Appending (+=) and prepending (=+)

B = "bval"
B += "additionaldata"
C = "cval"
C =+ "test"

   In this example, B is now bval additionaldata and C is test
   cval.

Appending (.=) and prepending (=.) without spaces

B = "bval"
B .= "additionaldata"
C = "cval"
C =. "test"

   In this example, B is now bvaladditionaldata and C is testcval.
   In contrast to the above Appending and Prepending operators no
   additional space will be introduced.

Conditional metadata set

   OVERRIDES is a ":" seperated variable containing each item you
   want to satisfy conditions. So, if you have a variable which is
   conditional on "arm", and "arm" is in OVERRIDES, then the "arm"
   specific version of the variable is used rather than the
   non-conditional version. Example:
OVERRIDES = "architecture:os:machine"
TEST = "defaultvalue"
TEST_os = "osspecificvalue"
TEST_condnotinoverrides = "othercondvalue"

   In this example, TEST would be osspecificvalue, due to the
   condition "os" being in OVERRIDES.

Conditional appending

   BitBake also supports appending and prepending to variables
   based on whether something is in OVERRIDES. Example:
DEPENDS = "glibc ncurses"
OVERRIDES = "machine:local"
DEPENDS_append_machine = " libmad"

   In this example, DEPENDS is set to glibc ncurses libmad.

Inclusion

   Next, there is the include directive, which causes BitBake to
   parse in whatever file you specify, and insert it at that
   location, which is not unlike make. However, if the path
   specified on the include line is a relative path, BitBake will
   locate the first one it can find within BBPATH.

Requiring Inclusion

   In contrast to the include directive, require will raise an
   ParseError if the to be included file can not be found.
   Otherwise it will behave just like the include directive.

Python variable expansion

DATE = "${@time.strftime('%Y%m%d',time.gmtime())}"

   This would result in the DATE variable containing today's date.

Defining executable metadata

   NOTE: This is only supported in .bb and .bbclass files.
do_mytask () {
    echo "Hello, world!"
}

   This is essentially identical to setting a variable, except
   that this variable happens to be executable shell code.
python do_printdate () {
    import time
    print time.strftime('%Y%m%d', time.gmtime())
}

   This is the similar to the previous, but flags it as python so
   that BitBake knows it is python code.

Defining python functions into the global python namespace

   NOTE: This is only supported in .bb and .bbclass files.
def get_depends(bb, d):
    if bb.data.getVar('SOMECONDITION', d, True):
        return "dependencywithcond"
    else:
        return "dependency"

SOMECONDITION = "1"
DEPENDS = "${@get_depends(bb, d)}"

   This would result in DEPENDS containing dependencywithcond.

Variable Flags

   Variables can have associated flags which provide a way of
   tagging extra information onto a variable. Several flags are
   used internally by bitbake but they can be used externally too
   if needed. The standard operations mentioned above also work on
   flags.
VARIABLE[SOMEFLAG] = "value"

   In this example, VARIABLE has a flag, SOMEFLAG which is set to
   value.

Inheritance

   NOTE: This is only supported in .bb and .bbclass files.

   The inherit directive is a means of specifying what classes of
   functionality your .bb requires. It is a rudamentary form of
   inheritence. For example, you can easily abstract out the tasks
   involved in building a package that uses autoconf and automake,
   and put that into a bbclass for your packages to make use of. A
   given bbclass is located by searching for
   classes/filename.oeclass in BBPATH, where filename is what you
   inherited.

Tasks

   NOTE: This is only supported in .bb and .bbclass files.

   In BitBake, each step that needs to be run for a given .bb is
   known as a task. There is a command addtask to add new tasks
   (must be a defined python executable metadata and must start
   with "do_") and describe intertask dependencies.
python do_printdate () {
    import time
    print time.strftime('%Y%m%d', time.gmtime())
}

addtask printdate before do_build

   This defines the necessary python function and adds it as a
   task which is now a dependency of do_build (the default task).
   If anyone executes the do_build task, that will result in
   do_printdate being run first.

Events

   NOTE: This is only supported in .bb and .bbclass files.

   BitBake allows to install event handlers. Events are triggered
   at certain points during operation, such as, the beginning of
   operation against a given .bb, the start of a given task, task
   failure, task success, et cetera. The intent was to make it
   easy to do things like email notifications on build failure.
addhandler myclass_eventhandler
python myclass_eventhandler() {
    from bb.event import NotHandled, getName
    from bb import data

    print "The name of the Event is %s" % getName(e)
    print "The file we run for is %s" % data.getVar('FILE', e.data, True
)

    return NotHandled
}

   This event handler gets called every time an event is
   triggered. A global variable e is defined. e.data contains an
   instance of bb.data. With the getName(e) method one can get the
   name of the triggered event.

   The above event handler prints the name of the event and the
   content of the FILE variable.

Dependency Handling

   Bitbake 1.7.x onwards works with the metadata at the task level
   since this is optimal when dealing with multiple threads of
   execution. A robust method of specifing task dependencies is
   therefore needed.

Dependencies internal to the .bb file

   Where the dependencies are internal to a given .bb file, the
   dependencies are handled by the previously detailed addtask
   directive.

DEPENDS

   DEPENDS is taken to specify build time dependencies. The
   'deptask' flag for tasks is used to signify the task of each
   DEPENDS which must have completed before that task can be
   executed.
do_configure[deptask] = "do_populate_staging"

   means the do_populate_staging task of each item in DEPENDS must
   have completed before do_configure can execute.

RDEPENDS

   RDEPENDS is taken to specify runtime dependencies. The
   'rdeptask' flag for tasks is used to signify the task of each
   RDEPENDS which must have completed before that task can be
   executed.
do_package_write[rdeptask] = "do_package"

   means the do_package task of each item in RDEPENDS must have
   completed before do_package_write can execute.

Recursive DEPENDS

   These are specified with the 'recdeptask' flag and is used
   signify the task(s) of each DEPENDS which must have completed
   before that task can be executed. It applies recursively so
   also, the DEPENDS of each item in the original DEPENDS must be
   met and so on.

Recursive RDEPENDS

   These are specified with the 'recrdeptask' flag and is used
   signify the task(s) of each RDEPENDS which must have completed
   before that task can be executed. It applies recursively so
   also, the RDEPENDS of each item in the original RDEPENDS must
   be met and so on. It also runs all DEPENDS first too.

Inter Task

   The 'depends' flag for tasks is a more generic form of which
   allows an interdependency on specific tasks rather than
   specifying the data in DEPENDS or RDEPENDS.
do_patch[depends] = "quilt-native:do_populate_staging"

   means the do_populate_staging task of the target quilt-native
   must have completed before the do_patch can execute.

Parsing

Configuration Files

   The first of the classifications of metadata in BitBake is
   configuration metadata. This metadata is global, and therefore
   affects all packages and tasks which are executed. Currently,
   BitBake has hardcoded knowledge of a single configuration file.
   It expects to find 'conf/bitbake.conf' somewhere in the user
   specified BBPATH. That configuration file generally has include
   directives to pull in any other metadata (generally files
   specific to architecture, machine, local and so on.

   Only variable definitions and include directives are allowed in
   .conf files.

Classes

   BitBake classes are our rudamentary inheritence mechanism. As
   briefly mentioned in the metadata introduction, they're parsed
   when an inherit directive is encountered, and they are located
   in classes/ relative to the dirs in BBPATH.

.bb Files

   A BitBake (.bb) file is a logical unit of tasks to be executed.
   Normally this is a package to be built. Inter-.bb dependencies
   are obeyed. The files themselves are located via the BBFILES
   variable, which is set to a space seperated list of .bb files,
   and does handle wildcards.

Chapter 3. File Download support

   Table of Contents

   Overview
   Local File Fetcher
   CVS File Fetcher
   HTTP/FTP Fetcher
   SVK Fetcher
   SVN Fetcher
   GIT Fetcher

Overview

   BitBake provides support to download files this procedure is
   called fetching. The SRC_URI is normally used to indicate
   BitBake which files to fetch. The next sections will describe
   th available fetchers and the options they have. Each Fetcher
   honors a set of Variables and a per URI parameters separated by
   a ";" consisting of a key and a value. The semantic of the
   Variables and Parameters are defined by the Fetcher. BitBakes
   tries to have a consistent semantic between the different
   Fetchers.

Local File Fetcher

   The URN for the Local File Fetcher is file. The filename can be
   either absolute or relative. If the filename is relative
   FILESPATH and FILESDIR will be used to find the appropriate
   relative file depending on the OVERRIDES. Single files and
   complete directories can be specified.
SRC_URI= "file://relativefile.patch"
SRC_URI= "file://relativefile.patch;this=ignored"
SRC_URI= "file:///Users/ich/very_important_software"

CVS File Fetcher

   The URN for the CVS Fetcher is cvs. This Fetcher honors the
   variables DL_DIR, SRCDATE, FETCHCOMMAND_cvs, UPDATECOMMAND_cvs.
   DL_DIRS specifies where a temporary checkout is saved, SRCDATE
   specifies which date to use when doing the fetching (the
   special value of "now" will cause the checkout to be updated on
   every build), FETCHCOMMAND and UPDATECOMMAND specify which
   executables should be used when doing the CVS checkout or
   update.

   The supported Parameters are module, tag, date, method,
   localdir, rsh. The module specifies which module to check out,
   the tag describes which CVS TAG should be used for the checkout
   by default the TAG is empty. A date can be specified to
   override the SRCDATE of the configuration to checkout a
   specific date. The special value of "now" will cause the
   checkout to be updated on every build.method is by default
   pserver, if ext is used the rsh parameter will be evaluated and
   CVS_RSH will be set. Finally localdir is used to checkout into
   a special directory relative to CVSDIR>.
SRC_URI = "cvs://CVSROOT;module=mymodule;tag=some-version;method=ext"
SRC_URI = "cvs://CVSROOT;module=mymodule;date=20060126;localdir=usethat"

HTTP/FTP Fetcher

   The URNs for the HTTP/FTP are http, https and ftp. This Fetcher
   honors the variables DL_DIR, FETCHCOMMAND_wget, PREMIRRORS,
   MIRRORS. The DL_DIR defines where to store the fetched file,
   FETCHCOMMAND contains the command used for fetching. "${URI}"
   and "${FILES}" will be replaced by the uri and basename of the
   to be fetched file. PREMIRRORS will be tried first when
   fetching a file if that fails the actual file will be tried and
   finally all MIRRORS will be tried.

   The only supported Parameter is md5sum. After a fetch the
   md5sum of the file will be calculated and the two sums will be
   compared.
SRC_URI = "http://oe.handhelds.org/not_there.aac;md5sum=12343"
SRC_URI = "ftp://oe.handhelds.org/not_there_as_well.aac;md5sum=1234"
SRC_URI = "ftp://you@oe.handheld.sorg/home/you/secret.plan;md5sum=1234"

SVK Fetcher

   Currently NOT supported

SVN Fetcher

   The URN for the SVN Fetcher is svn.

   This Fetcher honors the variables FETCHCOMMAND_svn, DL_DIR,
   SRCDATE. FETCHCOMMAND contains the subversion command, DL_DIR
   is the directory where tarballs will be saved, SRCDATE
   specifies which date to use when doing the fetching (the
   special value of "now" will cause the checkout to be updated on
   every build).

   The supported Parameters are proto, rev. proto is the
   subversion prototype, rev is the subversions revision.
SRC_URI = "svn://svn.oe.handhelds.org/svn;module=vip;proto=http;rev=667"
SRC_URI = "svn://svn.oe.handhelds.org/svn/;module=opie;proto=svn+ssh;dat
e=20060126"

GIT Fetcher

   The URN for the GIT Fetcher is git.

   The Variables DL_DIR, GITDIR are used. DL_DIR will be used to
   store the checkedout version. GITDIR will be used as the base
   directory where the git tree is cloned to.

   The Parameters are tag, protocol. tag is a git tag, the default
   is "master". protocol is the git protocol to use and defaults
   to "rsync".
SRC_URI = "git://git.oe.handhelds.org/git/vip.git;tag=version-1"
SRC_URI = "git://git.oe.handhelds.org/git/vip.git;protocol=http"

Chapter 4. Commands

   Table of Contents

   bbread
   bitbake

        Introduction
        Usage and Syntax
        Special variables
        Metadata

bbread

   bbread is a command for displaying BitBake metadata. When run
   with no arguments, it has the core parse 'conf/bitbake.conf',
   as located in BBPATH, and displays that. If you supply a file
   on the commandline, such as a .bb, then it parses that
   afterwards, using the aforementioned configuration metadata.

   NOTE: the stand a lone bbread command was removed. Instead of
   bbread use bitbake -e.

bitbake

Introduction

   bitbake is the primary command in the system. It facilitates
   executing tasks in a single .bb file, or executing a given task
   on a set of multiple .bb files, accounting for
   interdependencies amongst them.

Usage and Syntax

$ bitbake --help
usage: bitbake [options] [package ...]

Executes the specified task (default is 'build') for a given set of BitB
ake files.
It expects that BBFILES is defined, which is a space seperated list of f
iles to
be executed.  BBFILES does support wildcards.
Default BBFILES are the .bb files in the current directory.

options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -b BUILDFILE, --buildfile=BUILDFILE
                        execute the task against this .bb file, rather t
han a
                        package from BBFILES.
  -k, --continue        continue as much as possible after an error. Whi
le the
                        target that failed, and those that depend on it,
                        cannot be remade, the other dependencies of thes
e
                        targets can be processed all the same.
  -f, --force           force run of specified cmd, regardless of stamp
status
  -i, --interactive     drop into the interactive mode also called the B
itBake
                        shell.
  -c CMD, --cmd=CMD     Specify task to execute. Note that this only exe
cutes
                        the specified task for the providee and the pack
ages
                        it depends on, i.e. 'compile' does not implicitl
y call
                        stage for the dependencies (IOW: use only if you
 know
                        what you are doing). Depending on the base.bbcla
ss a
                        listtasks tasks is defined and will show availab
le
                        tasks
  -r FILE, --read=FILE  read the specified file before bitbake.conf
  -v, --verbose         output more chit-chat to the terminal
  -D, --debug           Increase the debug level. You can specify this m
ore
                        than once.
  -n, --dry-run         don't execute, just go through the motions
  -p, --parse-only      quit after parsing the BB files (developers only
)
  -d, --disable-psyco   disable using the psyco just-in-time compiler (n
ot
                        recommended)
  -s, --show-versions   show current and preferred versions of all packa
ges
  -e, --environment     show the global or per-package environment (this
 is
                        what used to be bbread)
  -g, --graphviz        emit the dependency trees of the specified packa
ges in
                        the dot syntax
  -I IGNORED_DOT_DEPS, --ignore-deps=IGNORED_DOT_DEPS
                        Stop processing at the given list of dependencie
s when
                        generating dependency graphs. This can help to m
ake
                        the graph more appealing
  -l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS
                        Show debug logging for the specified logging dom
ains
  -P, --profile         profile the command and print a report


   Example 4.1. Executing a task against a single .bb

   Executing tasks for a single file is relatively simple. You
   specify the file in question, and bitbake parses it and
   executes the specified task (or "build" by default). It obeys
   intertask dependencies when doing so.

   "clean" task:
$ bitbake -b blah_1.0.bb -c clean

   "build" task:
$ bitbake -b blah_1.0.bb

   Example 4.2. Executing tasks against a set of .bb files

   There are a number of additional complexities introduced when
   one wants to manage multiple .bb files. Clearly there needs to
   be a way to tell bitbake what files are available, and of
   those, which we want to execute at this time. There also needs
   to be a way for each .bb to express its dependencies, both for
   build time and runtime. There must be a way for the user to
   express their preferences when multiple .bb's provide the same
   functionality, or when there are multiple versions of a .bb.

   The next section, Metadata, outlines how one goes about
   specifying such things.

   Note that the bitbake command, when not using --buildfile,
   accepts a PROVIDER, not a filename or anything else. By
   default, a .bb generally PROVIDES its packagename,
   packagename-version, and packagename-version-revision.
$ bitbake blah
$ bitbake blah-1.0
$ bitbake blah-1.0-r0
$ bitbake -c clean blah
$ bitbake virtual/whatever
$ bitbake -c clean virtual/whatever

   Example 4.3. Generating dependency graphs

   BitBake is able to generate dependency graphs using the dot
   syntax. These graphs can be converted to images using the dot
   application from graphviz. Two files will be written into the
   current working directory, depends.dot containing dependency
   information at the package level and task-depends.dot
   containing a breakdown of the dependencies at the task level.
   To stop depending on common depends one can use the -I depend
   to omit these from the graph. This can lead to more readable
   graphs. E.g. this way DEPENDS from inherited classes, e.g.
   base.bbclass, can be removed from the graph.
$ bitbake -g blah
$ bitbake -g -I virtual/whatever -I bloom blah

Special variables

   Certain variables affect bitbake operation:

BB_NUMBER_THREADS

   The number of threads bitbake should run at once (default: 1).

Metadata

   As you may have seen in the usage information, or in the
   information about .bb files, the BBFILES variable is how the
   bitbake tool locates its files. This variable is a space
   seperated list of files that are available, and supports
   wildcards.

   Example 4.4. Setting BBFILES
BBFILES = "/path/to/bbfiles/*.bb"

   With regard to dependencies, it expects the .bb to define a
   DEPENDS variable, which contains a space seperated list of
   "package names", which themselves are the PN variable. The PN
   variable is, in general, by default, set to a component of the
   .bb filename.

   Example 4.5. Depending on another .bb

   a.bb:
PN = "package-a"
DEPENDS += "package-b"

   b.bb:
PN = "package-b"

   Example 4.6. Using PROVIDES

   This example shows the usage of the PROVIDES variable, which
   allows a given .bb to specify what functionality it provides.

   package1.bb:
PROVIDES += "virtual/package"

   package2.bb:
DEPENDS += "virtual/package"

   package3.bb:
PROVIDES += "virtual/package"

   As you can see, here there are two different .bb's that provide
   the same functionality (virtual/package). Clearly, there needs
   to be a way for the person running bitbake to control which of
   those providers gets used. There is, indeed, such a way.

   The following would go into a .conf file, to select package1:
PREFERRED_PROVIDER_virtual/package = "package1"

   Example 4.7. Specifying version preference

   When there are multiple "versions" of a given package, bitbake
   defaults to selecting the most recent version, unless otherwise
   specified. If the .bb in question has a DEFAULT_PREFERENCE set
   lower than the other .bb's (default is 0), then it will not be
   selected. This allows the person or persons maintaining the
   repository of .bb files to specify their preferences for the
   default selected version. In addition, the user can specify
   their preferences with regard to version.

   If the first .bb is named a_1.1.bb, then the PN variable will
   be set to "a", and the PV variable will be set to 1.1.

   If we then have an a_1.2.bb, bitbake will choose 1.2 by
   default. However, if we define the following variable in a
   .conf that bitbake parses, we can change that.
PREFERRED_VERSION_a = "1.1"

   Example 4.8. Using "bbfile collections"

   bbfile collections exist to allow the user to have multiple
   repositories of bbfiles that contain the same exact package.
   For example, one could easily use them to make one's own local
   copy of an upstream repository, but with custom modifications
   that one does not want upstream. Usage:
BBFILES = "/stuff/openembedded/*/*.bb /stuff/openembedded.modified/*/*.b
b"
BBFILE_COLLECTIONS = "upstream local"
BBFILE_PATTERN_upstream = "^/stuff/openembedded/"
BBFILE_PATTERN_local = "^/stuff/openembedded.modified/"
BBFILE_PRIORITY_upstream = "5"
BBFILE_PRIORITY_local = "10"
