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Add a section about using modules.

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PR:		87445
Reviewed by:	brueffer, remko
This commit is contained in:
Tom Rhodes 2008-08-03 14:39:40 +00:00
parent c3a59abed8
commit 12df008bb1
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=32612
1 changed files with 47 additions and 0 deletions

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en_US.ISO8859-1/books/handbook/kernelconfig/chapter.sgml
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@ -210,6 +210,53 @@ ath_hal(4) - Atheros Hardware Access Layer (HAL)</programlisting>
a custom kernel should appear less daunting.</para>
</sect1>
<sect1 id="kernelconfig-modules">
<title>Kernel Drivers, Subsystems, and Modules</title>
<indexterm>
<primary>kernel</primary>
<secondary>drivers / modules / subsystems</secondary>
</indexterm>
<para>Before building a custom kernel, consider the reasons for
doing so. If there is a need for specific hardware support,
it may already exist as a module.</para>
<para>Kernel modules exist in the
<filename role="directory">/boot/kernel</filename> directory
and may be dynamically loaded into the running kernel using
&man.kldload.8;. Most, if not all kernel drivers have a
specific module and manual page. For example, the last section
noted the <devicename>ath</devicename> wireless Ethernet driver.
This device has the following information in its manual
page:</para>
<programlisting>Alternatively, to load the driver as a module at boot time, place the
following line in &man.loader.conf.5:
if_ath_load="YES"</programlisting>
<para>As instructed, adding the <literal>if_ath_load="YES"</literal>
line to the <filename>/boot/loader.conf</filename> file will
enable loading this module dynamically at boot time.</para>
<para>In some cases; however, there is no associated module. This
is mostly true for certain subsystems and very important drivers,
for instance, the fast file system (<acronym>FFS</acronym>) is a
required option in the kernel. As is network support (INET).
Unfortunately the only way to tell if a driver is required is to
check for the module itself.</para>
<warning>
<para>It is considerably easy to remove built in support for a
device or option and have a broken kernel. For example, if
the &man.ata.4; driver is pulled from the kernel configuration
file, a system using <acronym>ATA</acronym> disk drivers may
not boot without the line added to
<filename>loader.conf</filename>. When in doubt, check for
the module and then just leave support in the kernel.</para>
</warning>
</sect1>
<sect1 id="kernelconfig-building">
<title>Building and Installing a Custom Kernel</title>
<indexterm>