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Welcome to the BitBake User Manual.
This manual provides information on the BitBake tool.
The information attempts to be as independent as possible regarding
systems that use BitBake, such as OpenEmbedded and the
In some cases, scenarios or examples within the context of
a build system are used in the manual to help with understanding.
For these cases, the manual clearly states the context.
Fundamentally, BitBake is a generic task execution
engine that allows shell and Python tasks to be run
efficiently and in parallel while working within
complex inter-task dependency constraints.
One of BitBake's main users, OpenEmbedded, takes this core
and builds embedded Linux software stacks using
a task-oriented approach.
Conceptually, BitBake is similar to GNU Make in
some regards but has significant differences:
BitBake executes tasks according to provided
metadata that builds up the tasks.
Metadata is stored in recipe (<filename>.bb</filename>)
and related recipe "append" (<filename>.bbappend</filename>)
files, configuration (<filename>.conf</filename>) and
underlying include (<filename>.inc</filename>) files, and
in class (<filename>.bbclass</filename>) files.
The metadata provides
BitBake with instructions on what tasks to run and
the dependencies between those tasks.
BitBake includes a fetcher library for obtaining source
code from various places such as local files, source control
systems, or websites.
The instructions for each unit to be built (e.g. a piece
of software) are known as "recipe" files and
contain all the information about the unit
(dependencies, source file locations, checksums, description
and so on).
BitBake includes a client/server abstraction and can
be used from a command line or used as a service over
XML-RPC and has several different user interfaces.
<title>History and Goals</title>
BitBake was originally a part of the OpenEmbedded project.
It was inspired by the Portage package management system
used by the Gentoo Linux distribution.
On December 7, 2004, OpenEmbedded project team member
Chris Larson split the project into two distinct pieces:
<listitem><para>BitBake, a generic task executor</para></listitem>
<listitem><para>OpenEmbedded, a metadata set utilized by
Today, BitBake is the primary basis of the
project, which is being used to build and maintain Linux
distributions such as the
<ulink url='http://www.angstrom-distribution.org/'>Angstrom Distribution</ulink>,
and which is also being used as the build tool for Linux projects
such as the
<ulink url='http://www.yoctoproject.org'>Yocto Project</ulink>.
Prior to BitBake, no other build tool adequately met the needs of
an aspiring embedded Linux distribution.
All of the build systems used by traditional desktop Linux
distributions lacked important functionality, and none of the
ad hoc Buildroot-based systems, prevalent in the
embedded space, were scalable or maintainable.
Some important original goals for BitBake were:
Handle inter-package 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, and so forth.
Be Linux distribution agnostic for both build and
Be architecture agnostic.
Support multiple build and target operating systems
(e.g. Cygwin, the BSDs, and so forth).
Be self contained, rather than tightly
integrated into the build machine's root
Handle conditional metadata on the target architecture,
operating system, distribution, and machine.
Be easy to use the tools to supply local metadata and packages
against which to operate.
Be easy to use BitBake to collaborate between multiple
projects for their builds.
Provide an inheritance mechanism to share
common metadata between many packages.
Over time it became apparent that some further requirements
Handle variants of a base recipe (e.g. native, sdk,
Split metadata into layers and allow layers
to enhance or override other layers.
Allow representation of a given set of input variables
to a task as a checksum.
Based on that checksum, allow acceleration of builds
with prebuilt components.
BitBake satisfies all the original requirements and many more
with extensions being made to the basic functionality to
reflect the additional requirements.
Flexibility and power have always been the priorities.
BitBake is highly extensible and supports embedded Python code and
execution of any arbitrary tasks.
BitBake is a program written in the Python language.
At the highest level, BitBake interprets metadata, decides
what tasks are required to run, and executes those tasks.
Similar to GNU Make, BitBake controls how software is
GNU Make achieves its control through "makefiles", while
BitBake uses "recipes".
BitBake extends the capabilities of a simple
tool like GNU Make by allowing for the definition of much more
complex tasks, such as assembling entire embedded Linux
The remainder of this section introduces several concepts
that should be understood in order to better leverage
the power of BitBake.
BitBake Recipes, which are denoted by the file extension
<filename>.bb</filename>, are the most basic metadata files.
These recipe files provide BitBake with the following:
<listitem><para>Descriptive information about the
package (author, homepage, license, and so on)</para></listitem>
<listitem><para>The version of the recipe</para></listitem>
<listitem><para>Existing dependencies (both build
and runtime dependencies)</para></listitem>
<listitem><para>Where the source code resides and
how to fetch it</para></listitem>
<listitem><para>Whether the source code requires
any patches, where to find them, and how to apply
<listitem><para>How to configure and compile the
<listitem><para>Where on the target machine to install the
package or packages created</para></listitem>
Within the context of BitBake, or any project utilizing BitBake
as its build system, files with the <filename>.bb</filename>
extension are referred to as recipes.
The term "package" is also commonly used to describe recipes.
However, since the same word is used to describe packaged
output from a project, it is best to maintain a single
descriptive term - "recipes".
Put another way, a single "recipe" file is quite capable
of generating a number of related but separately installable
In fact, that ability is fairly common.
Configuration files, which are denoted by the
<filename>.conf</filename> extension, define
various configuration variables that govern the project's build
These files fall into several areas that define
machine configuration options, distribution configuration
options, compiler tuning options, general common
configuration options, and user configuration options.
The main configuration file is the sample
<filename>bitbake.conf</filename> file, which is
located within the BitBake source tree
Class files, which are denoted by the
<filename>.bbclass</filename> extension, contain
information that is useful to share between metadata files.
The BitBake source tree currently comes with one class metadata file
You can find this file in the
The <filename>base.bbclass</filename> class files is special since it
is always included automatically for all recipes
This class contains definitions for standard basic tasks such
as fetching, unpacking, configuring (empty by default),
compiling (runs any Makefile present), installing (empty by
default) and packaging (empty by default).
These tasks are often overridden or extended by other classes
added during the project development process.
Layers allow you to isolate different types of
customizations from each other.
While you might find it tempting to keep everything in one layer
when working on a single project, the more modular you organize
your metadata, the easier it is to cope with future changes.
To illustrate how you can use layers to keep things modular,
consider customizations you might make to support a specific target machine.
These types of customizations typically reside in a special layer,
rather than a general layer, called a Board Support Package (BSP)
Furthermore, the machine customizations should be isolated from
recipes and metadata that support a new GUI environment, for
This situation gives you a couple of layers: one for the machine
configurations and one for the GUI environment.
It is important to understand, however, that the BSP layer can still
make machine-specific additions to recipes within
the GUI environment layer without polluting the GUI layer itself
with those machine-specific changes.
You can accomplish this through a recipe that is a BitBake append
Append files, which are files that have the
<filename>.bbappend</filename> file extension, extend or
override information in an existing recipe file.
BitBake expects every append file to have a corresponding recipe file.
Furthermore, the append file and corresponding recipe file
must use the same root filename.
The filenames can differ only in the file type suffix used
(e.g. <filename>formfactor_0.0.bb</filename> and
Information in append files extends or
overrides the information in the underlying,
similarly-named recipe files.
When you name an append file, you can use the
wildcard character (%) to allow for matching recipe names.
For example, suppose you have an append file named
That append file would match any <filename>busybox_1.21.x.bb</filename>
version of the recipe.
So, the append file would match the following recipe names:
If the <filename>busybox</filename> recipe was updated to
<filename>busybox_1.3.0.bb</filename>, the append name would not
However, if you named the append file
<filename>busybox_1.%.bbappend</filename>, then you would have a match.
In the most general case, you could name the append file something as
simple as <filename>busybox_%.bbappend</filename> to be entirely
You can obtain BitBake several different ways:
Using Git to clone the BitBake source code repository
is the recommended method for obtaining BitBake.
Cloning the repository makes it easy to get bug fixes
and have access to stable branches and the master
Once you have cloned BitBake, you should use
the latest stable
branch for development since the master branch is for
BitBake development and might contain less stable changes.
<para>You usually need a version of BitBake
that matches the metadata you are using.
The metadata is generally backwards compatible but
not forward compatible.</para>
<para>Here is an example that clones the BitBake repository:
$ git clone git://git.openembedded.org/bitbake
This command clones the BitBake Git repository into a
directory called <filename>bitbake</filename>.
Alternatively, you can
designate a directory after the
<filename>git clone</filename> command
if you want to call the new directory something
other than <filename>bitbake</filename>.
Here is an example that names the directory
$ git clone git://git.openembedded.org/bitbake bbdev
<listitem><para><emphasis>Installation using your Distribution
Package Management System:</emphasis>
This method is not
recommended because the BitBake version that is
provided by your distribution, in most cases,
releases behind a snapshot of the BitBake repository.
<listitem><para><emphasis>Taking a snapshot of BitBake:</emphasis>
Downloading a snapshot of BitBake from the
source code repository gives you access to a known
branch or release of BitBake.
Cloning the Git repository, as described earlier,
is the preferred method for getting BitBake.
Cloning the repository makes it easier to update as
patches are added to the stable branches.
<para>The following example downloads a snapshot of
BitBake version 1.17.0:
$ wget http://git.openembedded.org/bitbake/snapshot/bitbake-1.17.0.tar.gz
$ tar zxpvf bitbake-1.17.0.tar.gz
After extraction of the tarball using the tar utility,
you have a directory entitled
<listitem><para><emphasis>Using the BitBake that Comes With Your
A final possibility for getting a copy of BitBake is that it
already comes with your checkout of a larger Bitbake-based build
system, such as Poky or Yocto Project.
Rather than manually checking out individual layers and
gluing them together yourself, you can check
out an entire build system.
The checkout will already include a version of BitBake that
has been thoroughly tested for compatibility with the other
For information on how to check out a particular BitBake-based
build system, consult that build system's supporting documentation.
<title>The BitBake Command</title>
The <filename>bitbake</filename> command is the primary interface
to the BitBake tool.
This section presents the BitBake command syntax and provides
several execution examples.
<title>Usage and syntax</title>
Following is the usage and syntax for BitBake:
$ bitbake -h
Usage: bitbake [options] [recipename/target recipe:do_task ...]
Executes the specified task (default is 'build') for a given set of target recipes (.bb files).
It is assumed there is a conf/bblayers.conf available in cwd or in BBPATH which
will provide the layer, BBFILES and other configuration information.
--version show program's version number and exit
-h, --help show this help message and exit
-b BUILDFILE, --buildfile=BUILDFILE
Execute tasks from a specific .bb recipe directly.
WARNING: Does not handle any dependencies from other
-k, --continue Continue as much as possible after an error. While the
target that failed and anything depending on it cannot
be built, as much as possible will be built before
-a, --tryaltconfigs Continue with builds by trying to use alternative
providers where possible.
-f, --force Force the specified targets/task to run (invalidating
any existing stamp file).
-c CMD, --cmd=CMD Specify the task to execute. The exact options
available depend on the metadata. Some examples might
be 'compile' or 'populate_sysroot' or 'listtasks' may
give a list of the tasks available.
-C INVALIDATE_STAMP, --clear-stamp=INVALIDATE_STAMP
Invalidate the stamp for the specified task such as
'compile' and then run the default task for the
-r PREFILE, --read=PREFILE
Read the specified file before bitbake.conf.
-R POSTFILE, --postread=POSTFILE
Read the specified file after bitbake.conf.
-v, --verbose Output more log message data to the terminal.
-D, --debug Increase the debug level. You can specify this more
-n, --dry-run Don't execute, just go through the motions.
-S SIGNATURE_HANDLER, --dump-signatures=SIGNATURE_HANDLER
Dump out the signature construction information, with
no task execution. The SIGNATURE_HANDLER parameter is
passed to the handler. Two common values are none and
printdiff but the handler may define more/less. none
means only dump the signature, printdiff means compare
the dumped signature with the cached one.
-p, --parse-only Quit after parsing the BB recipes.
-s, --show-versions Show current and preferred versions of all recipes.
-e, --environment Show the global or per-recipe environment complete
with information about where variables were
-g, --graphviz Save dependency tree information for the specified
targets in the dot syntax.
-I EXTRA_ASSUME_PROVIDED, --ignore-deps=EXTRA_ASSUME_PROVIDED
Assume these dependencies don't exist and are already
provided (equivalent to ASSUME_PROVIDED). Useful to
make dependency graphs more appealing
-l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS
Show debug logging for the specified logging domains
-P, --profile Profile the command and save reports.
-u UI, --ui=UI The user interface to use (taskexp, knotty or
ncurses - default knotty).
-t SERVERTYPE, --servertype=SERVERTYPE
Choose which server type to use (process or xmlrpc -
--token=XMLRPCTOKEN Specify the connection token to be used when
connecting to a remote server.
--revisions-changed Set the exit code depending on whether upstream
floating revisions have changed or not.
--server-only Run bitbake without a UI, only starting a server
-B BIND, --bind=BIND The name/address for the bitbake server to bind to.
--no-setscene Do not run any setscene tasks. sstate will be ignored
and everything needed, built.
--setscene-only Only run setscene tasks, don't run any real tasks.
Connect to the specified server.
-m, --kill-server Terminate the remote server.
--observe-only Connect to a server as an observing-only client.
--status-only Check the status of the remote bitbake server.
-w WRITEEVENTLOG, --write-log=WRITEEVENTLOG
Writes the event log of the build to a bitbake event
json file. Use '' (empty string) to assign the name
This section presents some examples showing how to use BitBake.
<title>Executing a Task Against a Single Recipe</title>
Executing tasks for a single recipe file is relatively simple.
You specify the file in question, and BitBake parses
it and executes the specified task.
If you do not specify a task, BitBake executes the default
task, which is "build”.
BitBake obeys inter-task dependencies when doing
The following command runs the build task, which is
the default task, on the <filename>foo_1.0.bb</filename>
$ bitbake -b foo_1.0.bb
The following command runs the clean task on the
<filename>foo.bb</filename> recipe file:
$ bitbake -b foo.bb -c clean
The "-b" option explicitly does not handle recipe
Other than for debugging purposes, it is instead
recommended that you use the syntax presented in the
<title>Executing Tasks Against a Set of Recipe Files</title>
There are a number of additional complexities introduced
when one wants to manage multiple <filename>.bb</filename>
Clearly there needs to be a way to tell BitBake what
files are available and, of those, which you
want to execute.
There also needs to be a way for each recipe
to express its dependencies, both for build-time and
There must be a way for you to express recipe preferences
when multiple recipes provide the same functionality, or when
there are multiple versions of a recipe.
The <filename>bitbake</filename> command, when not using
"--buildfile" or "-b" only accepts a "PROVIDES".
You cannot provide anything else.
By default, a recipe file generally "PROVIDES" its
"packagename" as shown in the following example:
$ bitbake foo
This next example "PROVIDES" the package name and also uses
the "-c" option to tell BitBake to just execute the
$ bitbake -c clean foo
<title>Executing a List of Task and Recipe Combinations</title>
The BitBake command line supports specifying different
tasks for individual targets when you specify multiple
For example, suppose you had two targets (or recipes)
<filename>mysecondrecipe</filename> and you needed
BitBake to run <filename>taskA</filename> for the first
recipe and <filename>taskB</filename> for the second
$ bitbake myfirstrecipe:do_taskA mysecondrecipe:do_taskB
<title>Generating Dependency Graphs</title>
BitBake is able to generate dependency graphs using
the <filename>dot</filename> syntax.
You can convert these graphs into images using the
<filename>dot</filename> tool from
When you generate a dependency graph, BitBake writes four files
to the current working directory:
Shows BitBake's knowledge of dependencies between
Shows dependencies between build-time targets
Shows dependencies between tasks.
Shows a simple list of targets that are to be built.
To stop depending on common depends, use the "-I" depend
option and BitBake omits them from the graph.
Leaving this information out can produce more readable graphs.
This way, you can remove from the graph
<filename>DEPENDS</filename> from inherited classes
such as <filename>base.bbclass</filename>.
Here are two examples that create dependency graphs.
The second example omits depends common in OpenEmbedded from
$ bitbake -g foo
$ bitbake -g -I virtual/kernel -I eglibc foo