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bitbake: user-manual-execution.xml: Draft of "Execution" chapter

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This is a rough draft of the chapter.  Major sections are in
place.  We need to scrub content now.

Seems like the discussion of BBFILES fit better in this
execution flow chapter.  So, I moved it above the parsing
section.

(Bitbake rev: 6c4c6fb689b88dbefe63f0062b78d8403fb80d41)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2014-02-14 13:55:42 -06:00
committed by Richard Purdie
parent 013c9d9181
commit 0c5bf41968
2 changed files with 669 additions and 732 deletions
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bitbake/doc/user-manual/user-manual-bitbakecommand.xml
+68 -94
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@@ -4,17 +4,22 @@
<chapter id="user-manual-command"> <chapter id="user-manual-command">
<title>The BitBake Command</title> <title>The BitBake Command</title>
<section id='bitbake-command-introduction'> <para>
<title>Introduction</title> BitBake is the underlying piece of the build system.
Two excellent examples are the Yocto Project and the OpenEmbedded
build systems.
Each provide an environment in which to develop embedded Linux
images, and each use BitBake as their underlying build engine.
</para>
<para> <para>
Bitbake is the primary command in the system. BitBake facilitates executing tasks in a single <filename>.bb</filename>
It facilitates executing tasks in a single <filename>.bb</filename> file, or executing a given task on a set of multiple
file, or executing a given task on a set of multiple <filename>.bb</filename> files, accounting for interdependencies
<filename>.bb</filename> files, accounting for interdependencies amongst them.
amongst them. This chapter presents the BitBake syntax, provides some execution
</para> examples, and shows you how to control BitBake with key metadata.
</section> </para>
<section id='usage-and-syntax'> <section id='usage-and-syntax'>
<title>Usage and syntax</title> <title>Usage and syntax</title>
@@ -110,7 +115,9 @@ Options:
<para> <para>
Executing tasks for a single recipe file is relatively simple. Executing tasks for a single recipe file is relatively simple.
You specify the file in question, and BitBake parses You specify the file in question, and BitBake parses
it and executes the specified task (or “build” by default). 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 BitBake obeys inter-task dependencies when doing
so. so.
</para> </para>
@@ -138,38 +145,36 @@ Options:
when one wants to manage multiple <filename>.bb</filename> when one wants to manage multiple <filename>.bb</filename>
files. files.
Clearly there needs to be a way to tell BitBake what Clearly there needs to be a way to tell BitBake what
files are available, and of those, which we files are available, and of those, which you
want to execute at this time. want to execute.
There also needs to be a way for each <filename>.bb</filename> There also needs to be a way for each recipe
to express its dependencies, both for build-time and to express its dependencies, both for build-time and
runtime. runtime.
There must be a way for the user to express their preferences There must be a way for you to express recipe preferences
when multiple recipes provide the same functionality, or when when multiple recipes provide the same functionality, or when
there are multiple versions of a <filename>.bb</filename> file. there are multiple versions of a recipe.
</para>
<para>
The next section, Metadata, outlines how to specify such things.
</para> </para>
<para> <para>
The <filename>bitbake</filename> command, when not using The <filename>bitbake</filename> command, when not using
"--buildfile", accepts a PROVIDER, not a filename or "--buildfile" or "-b" only accepts a "PROVIDER".
anything else. You cannot provide anything else.
By default, a <filename>.bb</filename> generally PROVIDES its By default, a recipe file generally "PROVIDES" its
packagename, packagename-version, and packagename-version-revision. "packagename", "packagename-version", and
"packagename-version-revision" as shown in the following
example:
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ bitbake foo $ bitbake foo
$ bitbake foo-1.0 $ bitbake foo-1.0
$ bitbake foo-1.0-r0 $ bitbake foo-1.0-r0
</literallayout>
This next example "PROVIDES" the package name and also uses
the "-c" option to tell BitBake to just excute the
<filename>do_clean</filename> task:
<literallayout class='monospaced'>
$ bitbake -c clean foo $ bitbake -c clean foo
$ bitbake virtual/whatever
$ bitbake -c clean virtual/whatever
</literallayout> </literallayout>
</para> </para>
</section> </section>
@@ -180,19 +185,31 @@ Options:
<para> <para>
BitBake is able to generate dependency graphs using BitBake is able to generate dependency graphs using
the dot syntax. the dot syntax.
These graphs can be converted to images using the dot You can convert these graphs into images using the dot
application from application from
<ulink url='http://www.graphviz.org'>Graphviz</ulink>. <ulink url='http://www.graphviz.org'>Graphviz</ulink>.
Two files will be written into the current working directory: </para>
<filename>depends.dot</filename> containing dependency information
at the package level and <filename>task-depends.dot</filename> <para>
containing a breakdown of the dependencies at the task level. When you generate a dependency graph, BitBake writes two files
To stop depending on common depends, one can use the "-I" depend to the current working directory:
option to omit these from the graph. <filename>depends.dot</filename>, which contains dependency information
This can lead to more readable graphs. at the package level, and <filename>task-depends.dot</filename>,
This way, <filename>DEPENDS</filename> from inherited classes which contains a breakdown of the dependencies at the task level.
such as <filename>base.bbclass</filename> can be removed from the </para>
graph.
<para>
To stop depending on common depends, use 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>.
</para>
<para>
Here are two exmples that create dependency graphs.
The second example omits common depends from the graph:
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ bitbake -g foo $ bitbake -g foo
@@ -202,66 +219,23 @@ Options:
</section> </section>
</section> </section>
<section id='special-variables'> <section id='controlling-bitbake'>
<title>Special Variables</title> <title>Controlling BitBake</title>
<para> <para>
Certain variables affect BitBake operation: Including variables in your recipe and class files help control
how BitBake operates.
</para> </para>
<section id='bb-number-threads'> <section id='execution-threads'>
<title><filename>BB_NUMBER_THREADS</filename></title> <title>Execution Threads</title>
<para> <para>
The number of threads BitBake should run at once (default: 1). You can control how many thread BitBake supports by using the
</para> <link linkend='var-BB_NUMBER_THREADS'><filename>BB_NUMBER_THREADS</filename></link>
</section> variable.
</section> You would set this in your <filename>local.conf</filename>
configuration file.
<section id='bitbake-command-metadata'>
<title>Metadata</title>
<para>
As you may have seen in the usage information, or in the
information about <filename>.bb</filename> files, the
<filename>BBFILES</filename> variable is how the BitBake
tool locates its files.
This variable is a space-separated list of files
that are available, and supports wildcards.
</para>
<section id='setting-bbfiles'>
<title>Setting <filename>BBFILES</filename></title>
<para>
<literallayout class='monospaced'>
BBFILES = "/path/to/bbfiles/*.bb"
</literallayout>
With regard to dependencies, it expects the
<filename>.bb</filename> to define a
<filename>DEPENDS</filename> variable, which contains a
space separated list of “package names”, which themselves
are the <filename>PN</filename> variable. The
<filename>PN</filename> variable is, in general,
set to a component of the <filename>.bb</filename>
filename by default.
</para>
</section>
<section id='depending-on-another-recipe-file'>
<title>Depending on Another Recipe File</title>
<para>
<literallayout class='monospaced'>
a.bb:
PN = "package-a"
DEPENDS += "package-b"
b.bb:
PN = "package-b"
</literallayout>
</para> </para>
</section> </section>
bitbake/doc/user-manual/user-manual-execution.xml
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