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dev-manual: Applied review comments to building tiny section. 

Fixes YOCTO #2568

These changes are based on Darren Hart's second review of this
new section.

(From yocto-docs rev: b61ef2b6cf96b45666e0f75753b76e0f875663b5)

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 2013-04-01 09:18:34 -07:00 committed by Richard Purdie
parent e4f0cc178e
commit 184a6f0c88
1 changed files with 70 additions and 17 deletions
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documentation/dev-manual/dev-manual-common-tasks.xml
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@ -2209,8 +2209,8 @@
<para> <para>
This section presents information that shows you how you can This section presents information that shows you how you can
trim your distribution to even smaller sizes than the trim your distribution to even smaller sizes than the
8 Mbytes <filename>poky-tiny</filename> distribution that <filename>poky-tiny</filename> distribution, which is around
can be built out-of-the-box using the Yocto Project. 5 Mbytes, that can be built out-of-the-box using the Yocto Project.
</para> </para>
<section id='tiny-system-overview'> <section id='tiny-system-overview'>
@ -2269,19 +2269,21 @@
<title>Understand What Gives Your Image Size</title> <title>Understand What Gives Your Image Size</title>
<para> <para>
You will need to have an image from which you can It is easiest to have something to start with when creating
work. your own distribution.
The Yocto Project ships with the ability to create a You can use the Yocto Project out-of-the-box to create the
<filename>poky-tiny</filename> distribution. <filename>poky-tiny</filename> distribution.
This distribution consists of a small, sub-8 Mbyte kernel Ulitmately, you will want to make changes in your own
that works with two shipped Board Support Packages (BSPs): distribution that are likely modeled after
Fish River Island 2 and QEMU. <filename>poky-tiny</filename>.
You can use this distribution as a starting point and trim <note>
the size down from there. To use <filename>poky-tiny</filename> in your build,
If you need to build out the <filename>poky-tiny</filename> set the <filename>DISTRO</filename> variable in your
distribution, see the <filename>local.conf</filename> file to "poky-tiny"
"<link linkend='creating-your-own-distribution'>Creating Your Own Distribution</link>" as described in the
section for information. "<link linkend='creating-your-own-distribution'>Creating Your Own Distribution</link>"
section.
</note>
</para> </para>
<para> <para>
@ -2292,8 +2294,9 @@
in the code), and BSS (uninitialized data) sections. in the code), and BSS (uninitialized data) sections.
Dynamic memory contains memory that is allocated at runtime, Dynamic memory contains memory that is allocated at runtime,
stacks, hash tables, and so forth. stacks, hash tables, and so forth.
Temporary memory is decompressed from the expanded kernel Temporary memory is recovered after the boot process.
after boot and also includes the <filename>__init__</filename> This memory consists of memory used for decompressing
the kernel and for the <filename>__init__</filename>
functions. functions.
</para> </para>
@ -2304,7 +2307,8 @@
the <filename>scripts</filename> directory: the <filename>scripts</filename> directory:
<itemizedlist> <itemizedlist>
<listitem><para><filename>ksize.py</filename>: Reports <listitem><para><filename>ksize.py</filename>: Reports
component sizes for the kernel files.</para></listitem> component sizes for the kernel build objects.
</para></listitem>
<listitem><para><filename>dirsize.py</filename>: Reports <listitem><para><filename>dirsize.py</filename>: Reports
component sizes for the root filesystem.</para></listitem> component sizes for the root filesystem.</para></listitem>
</itemizedlist> </itemizedlist>
@ -2503,6 +2507,55 @@
</para> </para>
</section> </section>
<section id='look-for-other-ways-to-minimize-size'>
<title>Look for Other Ways to Minimize Size</title>
<para>
Depending on your particular circumstances, other areas that you
can trim likely exist.
The key to finding these areas is through tools and methods
described here combined with experimentation and iteration.
Here are a couple of areas to experiment with:
<itemizedlist>
<listitem><para><filename>eglibc</filename>:
In general, follow this process:
<orderedlist>
<listitem><para>Remove <filename>eglibc</filename>
features from
<ulink url='&YOCTO_DOCS_REF_URL;#var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></ulink>
that you think you don't need.</para></listitem>
<listitem><para>Build your distribution.
</para></listitem>
<listitem><para>If the build fails due to missing
symbols in a package, determine if you can
reconfigure the package to not need those
features.
For example, change the configuration to not
support wide character support as is done for
<filename>ncurses</filename>.
Or, if support for those characters is needed,
determine what <filename>eglibc</filename>
features provide the support and restore the
configuration.
</para></listitem>
<listitem><para>Rebuild and repeat the process.
</para></listitem>
</orderedlist></para></listitem>
<listitem><para><filename>busybox</filename>:
For BusyBox, use a process similar as described for
<filename>eglibc</filename>.
A difference is you will need to boot the resulting
system to see if you are able to do everything you
expect from the running system.
You need to be sure to integrate configuration fragments
into Busybox because BusyBox handles its own core
features and then allows you to add configuration
fragments on top.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='iterate-on-the-process'> <section id='iterate-on-the-process'>
<title>Iterate on the Process</title> <title>Iterate on the Process</title>