
BitBake User Manual

BitBake Team

   Copyright © 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/2.0/ 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

              Inheritance
              Tasks
              Events

        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
              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. Setting BBFILES
   4.4. Depending on another .bb
   4.5. Using PROVIDES
   4.6. Specifying version preference
   4.7. 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
        Inheritance
        Tasks
        Events

   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.

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 also implements a means of registering 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, Tru
e)

    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.

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, 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. 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 suppoered

SVN Fetcher

   The URN for the SVN Fetcher is svn.

   The Variables FETCHCOMMAND_svn, DL_DIR are used by the SVN Fetcher.
   FETCHCOMMAND  contains  the  subversion command, DL_DIR is the
   directory where tarballs will be saved.

   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;da
te=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
        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 Bit
Bake files.
It expects that BBFILES is defined, which is a space seperated list of
files 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
than a
                        package from BBFILES.
  -k, --continue        continue as much as possible after an error. Wh
ile the
                        target that failed, and those that depend on it
,
                        cannot be remade, the other dependencies of the
se
                        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.
  -c CMD, --cmd=CMD     Specify task to execute. Note that this only ex
ecutes
                        the specified task for the providee and the pac
kages
                        it depends on, i.e. 'compile' does not implicit
ly call
                        stage for the dependencies (IOW: use only if yo
u know
                        what you are doing)
  -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
  -n, --dry-run         don't execute, just go through the motions
  -p, --parse-only      quit after parsing the BB files (developers onl
y)
  -d, --disable-psyco   disable using the psyco just-in-time compiler (
not
                        recommended)
  -s, --show-versions   show current and preferred versions of all pack
ages
  -e, --environment     show the global or per-package environment (thi
s is
                        what used to be bbread)

   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

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 4.3. 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 4.4. Depending on another .bb

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

   b.bb:
PN = "package-b"

   Example 4.5. 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 4.6. 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 4.7. 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/*/*.
bb"
BBFILE_COLLECTIONS = "upstream local"
BBFILE_PATTERN_upstream = "^/stuff/openembedded/"
BBFILE_PATTERN_local = "^/stuff/openembedded.modified/"
BBFILE_PRIORITY_upstream = "5"
BBFILE_PRIORITY_local = "10"
