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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
<appendix id='kernel-dev-faq'>
<title>Kernel Development FAQ</title>
<section id='kernel-dev-faq-section'>
<title>Common Questions and Solutions</title>
<para>
The following lists some solutions for common questions.
<qandaset>
<qandaentry>
<question>
<para>
How do I use my own Linux kernel <filename>.config</filename>
file?
</para>
</question>
<answer>
<para>
Refer to the "<link linkend='changing-the-configuration'>Changing the Configuration</link>"
section for information.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
How do I create configuration fragments?
</para>
</question>
<answer>
<para>
Refer to the
"<link linkend='creating-config-fragments'>Creating Configuration Fragments</link>"
section for information.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
How do I use my own Linux kernel sources?
</para>
</question>
<answer>
<para>
Refer to the "<link linkend='working-with-your-own-sources'>Working With Your Own Sources</link>"
section for information.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
How do I install/not-install the kernel image on the rootfs?
</para>
</question>
<answer>
<para>
The kernel image (e.g. <filename>vmlinuz</filename>) is provided
by the <filename>kernel-image</filename> package.
Image recipes depend on <filename>kernel-base</filename>.
To specify whether or not the kernel
image is installed in the generated root filesystem, override
<filename>RDEPENDS_kernel-base</filename> to include or not
include "kernel-image".</para>
<para>See the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
section in the Yocto Project Development Tasks Manual
for information on how to use an append file to
override metadata.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
How do I install a specific kernel module?
</para>
</question>
<answer>
<para>
Linux kernel modules are packaged individually.
To ensure a specific kernel module is included in an image,
include it in the appropriate machine
<ulink url='&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS'><filename>RRECOMMENDS</filename></ulink>
variable.</para>
<para>These other variables are useful for installing specific
modules:
<literallayout class='monospaced'>
<ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</filename></ulink>
<ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink>
<ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RDEPENDS'><filename>MACHINE_EXTRA_RDEPENDS</filename></ulink>
<ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RRECOMMENDS'><filename>MACHINE_EXTRA_RRECOMMENDS</filename></ulink>
</literallayout>
For example, set the following in the <filename>qemux86.conf</filename>
file to include the <filename>ab123</filename> kernel modules
with images built for the <filename>qemux86</filename> machine:
<literallayout class='monospaced'>
MACHINE_EXTRA_RRECOMMENDS += "kernel-module-ab123"
</literallayout>
For more information, see the
"<link linkend='incorporating-out-of-tree-modules'>Incorporating Out-of-Tree Modules</link>"
section.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
How do I change the Linux kernel command line?
</para>
</question>
<answer>
<para>
The Linux kernel command line is typically specified in
the machine config using the <filename>APPEND</filename> variable.
For example, you can add some helpful debug information doing
the following:
<literallayout class='monospaced'>
APPEND += "printk.time=y initcall_debug debug"
</literallayout>
</para>
</answer>
</qandaentry>
</qandaset>
</para>
</section>
</appendix>
<!--
vim: expandtab tw=80 ts=4
-->
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