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docs/manual: add section about dependency graphs

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Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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Thomas Petazzoni 2014-02-23 16:04:31 +01:00 committed by Peter Korsgaard
parent 2f886ee34a
commit e78cc3af51
1 changed files with 52 additions and 0 deletions
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docs/manual/common-usage.txt
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@ -149,3 +149,55 @@ of an ext2 filesystem may be corrupted; or, if you have sparse files in
your filesystem, those parts may not be all-zeroes when read back). You
should only use sparse files when handling files on the build machine, not
when transferring them to an actual device that will be used on the target.
Graphing the dependencies between packages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[[graph-depends]]
One of Buildroot's jobs is to know the dependencies between packages,
and make sure they are built in the right order. These dependencies
can sometimes be quite complicated, and for a given system, it is
often not easy to understand why such or such package was brought into
the build by Buildroot.
In order to help understanding the dependencies, and therefore better
understand what is the role of the different components in your
embedded Linux system, Buildroot is capable of generating dependency
graphs.
To generate a dependency graph of the full system you have compiled,
simply run:
------------------------
make graph-depends
------------------------
You will find the generated graph in
+output/graphs/graph-depends.pdf+.
If your system is quite large, the dependency graph may be too complex
and difficult to read. It is therefore possible to generate the
dependency graph just for a given package:
------------------------
make <pkg>-graph-depends
------------------------
You will find the generated graph in
+output/graph/<pkg>-graph-depends.pdf+.
Note that the dependency graphs are generated using the +dot+ tool
from the _Graphviz_ project, which you must have installed on your
system to use this feature. In most distributions, it is available as
the +graphviz+ package.
By default, the dependency graphs are generated in the PDF
format. However, by passing the +GRAPH_OUT+ environment variable, you
can switch to other output formats, such as PNG, PostScript or
SVG. All formats supported by the +-T+ option of the +dot+ tool are
supported.
--------------------------------
GRAPH_OUT=svg make graph-depends
--------------------------------