lfs-book/chapter06/udev.xml

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<sect1 id="ch-system-udev" role="wrap">
<title>Udev-&udev-version;</title>
<?dbhtml filename="udev.html"?>

<indexterm zone="ch-system-udev"><primary sortas="a-Udev">Udev</primary></indexterm>

<sect2 role="package"><title/>
<para>The Udev package contains programs for dynamic creation of device nodes.</para>

<segmentedlist>
<segtitle>&buildtime;</segtitle>
<segtitle>&diskspace;</segtitle>
<seglistitem><seg>0.1 SBU</seg><seg>6.7 MB</seg></seglistitem>
</segmentedlist>

<segmentedlist>
<segtitle>&dependencies;</segtitle>
<seglistitem><seg>Coreutils and Make</seg></seglistitem>
</segmentedlist>

</sect2>

<sect2 role="installation">
<title>Installation of Udev</title>

<para>Compile the package:</para>

<screen><userinput>make udevdir=/dev</userinput></screen>

<variablelist>
<varlistentry>
<term><parameter>udevdir=/dev</parameter></term>
<listitem><para>This tells <command>udev</command> in which directory
devices nodes are to be created.</para></listitem>
</varlistentry>
</variablelist>

<para>To test the results, issue:
<userinput>make test</userinput>.</para>

<para>Install the package:</para>

<screen><userinput>make DESTDIR=/ udevdir=/dev install</userinput></screen>

<para>The meaning of the make option:</para>

<variablelist>
  <varlistentry>
    <term><parameter>DESTDIR=/</parameter>
    </term>
    <listitem>
      <para>This prevents the Udev build process from killing any
        <command>udevd</command> processes that may be running on the host
        system.
      </para>
    </listitem>
  </varlistentry>
</variablelist>

<para>Udev's configuration is far from ideal by default, so install
the configuration files here:</para>

<screen><userinput>cp -v ../&udev-config-file; /etc/udev/rules.d/25-lfs.rules</userinput></screen>

<!-- Edit Me -->
<para>Run the <command>udevstart</command> program to create our full
complement of device nodes.</para>

<screen><userinput>/sbin/udevstart</userinput></screen>

</sect2>

<sect2 id="contents-udev" role="content"><title>Contents of Udev</title>

<segmentedlist>
<segtitle>Installed programs</segtitle>
<segtitle>Installed directory</segtitle>
<seglistitem><seg>udev, udevd, udevsend, udevstart, udevinfo, and udevtest</seg>
<seg>/etc/udev</seg></seglistitem>
</segmentedlist>

<variablelist><bridgehead renderas="sect3">Short Descriptions</bridgehead>
<?dbfo list-presentation="list"?>
<?dbhtml list-presentation="table"?>
                                                                                
<varlistentry id="udev">
<term><command>udev</command></term>
<listitem>
<para>Creates device nodes in <filename
class="directory">/dev</filename> or renames network interfaces (not
in LFS) in response to hotplug events</para>
<indexterm zone="ch-system-udev udev"><primary sortas="b-udev">udev</primary></indexterm>
<beginpage/></listitem></varlistentry>

<varlistentry id="udevd">
<term><command>udevd</command></term>
<listitem>
<para>A daemon that reorders hotplug events before submitting them to
<command>udev</command>,
thus avoiding various race conditions</para>
<indexterm zone="ch-system-udev udevd"><primary sortas="b-udevd">udevd</primary></indexterm>
</listitem></varlistentry>

<varlistentry id="udevsend">
<term><command>udevsend</command></term>
<listitem>
<para>Delivers hotplug events to <command>udevd</command></para>
<indexterm zone="ch-system-udev udevsend"><primary sortas="b-udevsend">udevsend</primary></indexterm>
</listitem></varlistentry>

<varlistentry id="udevstart">
<term><command>udevstart</command></term>
<listitem>
<para>Creates device nodes in <filename
class="directory">/dev</filename> that correspond to drivers compiled directly
into the kernel; it performs that task by simulating hotplug events presumably
dropped by the kernel before invocation of this program (e.g., because the root
filesystem has not been mounted) and submitting such synthetic hotplug events
to <command>udev</command></para>
<indexterm zone="ch-system-udev udevstart"><primary sortas="b-udevstart">udevstart</primary></indexterm>
</listitem>
</varlistentry>

<varlistentry id="udevinfo">
<term><command>udevinfo</command></term>
<listitem>
<para>Allows users to query the <command>udev</command> database for
information on any device currently present on the system; it also
provides a way to query any device in the <systemitem
class="filesystem">sysfs</systemitem> tree to help create udev
rules</para>
<indexterm zone="ch-system-udev udevinfo"><primary sortas="b-udevinfo">udevinfo</primary></indexterm>
</listitem></varlistentry>

<varlistentry id="udevtest">
<term><command>udevtest</command></term>
<listitem>
<para>Simulates a <command>udev</command> run for the given device,
and prints out the name of the node the real <command>udev</command> would
have created or (not in LFS) the name of the renamed network interface</para>
<indexterm zone="ch-system-udev udevtest"><primary sortas="b-udevtest">udevtest</primary></indexterm>
</listitem></varlistentry>

<varlistentry id="etc-udev">
<term><filename class="directory">/etc/udev</filename></term>
<listitem>
<para>Contains <command>udev</command> configuation files,
device permissions, and rules for device naming</para>
<indexterm zone="ch-system-udev etc-udev"><primary sortas="e-/etc/udev">/etc/udev</primary></indexterm>
</listitem></varlistentry>
</variablelist>
</sect2>

</sect1>