The BitBake command
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 BitBake files. It expects that
BBFILES is defined, which is a space separated 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. While the target that
failed, and those that depend on it, cannot be remade, the
other dependencies of these 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 BitBake shell. -c CMD, --cmd=CMD Specify task
to execute. Note that this only executes the specified task
for the providee and the packages it depends on, i.e.
'compile' does not implicitly call stage for the dependencies
(IOW: use only if you know what you are doing). Depending on
the base.bbclass a listtasks task is defined and will show
available 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 more than once. -n, --dry-run don't execute,
just go through the motions -p, --parse-only quit after
parsing the BB files (developers only) -s, --show-versions
show current and preferred versions of all packages -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 packages in the dot syntax
-I IGNORED_DOT_DEPS, --ignore-deps=IGNORED_DOT_DEPS Stop
processing at the given list of dependencies when generating
dependency graphs. This can help to make the graph more
appealing -l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS Show
debug logging for the specified logging domains -P, --profile
profile the command and print a report
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
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 to specify
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
Generating dependency graphs
BitBake is able to generate dependency graphs using
the dot syntax. These graphs can be converted to images
using the
dotapplication from
Graphviz. Two
files will be written into the current working directory,
depends.dotcontaining dependency
information at the package level and
task-depends.dotcontaining a breakdown
of the dependencies at the task level. To stop depending on
common depends, one can use the
-I dependto omit these from the graph.
This can lead to more readable graphs. This way,
DEPENDSfrom inherited classes such as
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
BBFILESvariable is how the BitBake tool
locates its files. This variable is a space separated list of
files that are available, and supports wildcards.
Setting BBFILES
BBFILES=
"/path/to/bbfiles/*.bb"
With regard to dependencies, it expects the .bb to define
a
DEPENDSvariable, which contains a space
separated list of
package names
, which themselves are the
PNvariable. The
PNvariable is, in general, set to a
component of the .bb filename by default.
Depending on another .bb
a.bb:
PN = "package-a" DEPENDS +=
"package-b"
b.bb:
PN = "package-b"
Using PROVIDES
This example shows the usage of the
PROVIDESvariable, 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, we have 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"
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_PREFERENCEset 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 preference for the default
selected version. In addition, the user can specify their
preferred version.
If the first .bb is named
a_1.1.bb, then the
PNvariable will be set to
a
, and the
PVvariable 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"
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"