lfs-book/chapter06/udev.xml

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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
  "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>

<sect1 id="ch-system-udev" role="wrap">
  <?dbhtml filename="udev.html"?>

  <title>Udev-&udev-version;</title>

  <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>&udev-ch6-sbu;</seg>
        <seg>&udev-ch6-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

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

    <para>The udev-config tarball contains LFS-specific files used to configure
    Udev. Unpack it into the Udev source directory:</para>

<screen><userinput>tar xf ../&udev-config;.tar.bz2</userinput></screen>

    <para>Create some devices and directories that Udev cannot handle due to
    them being required very early in the boot process:</para>

<screen><userinput>install -dv /lib/{firmware,udev/devices/{pts,shm}}
mknod -m0666 /lib/udev/devices/null c 1 3
ln -sv /proc/self/fd /lib/udev/devices/fd
ln -sv /proc/self/fd/0 /lib/udev/devices/stdin
ln -sv /proc/self/fd/1 /lib/udev/devices/stdout
ln -sv /proc/self/fd/2 /lib/udev/devices/stderr
ln -sv /proc/kcore /lib/udev/devices/core</userinput></screen>

    <para>Compile the package:</para>

<screen><userinput>make EXTRAS="extras/ata_id extras/cdrom_id extras/edd_id \
            extras/firmware extras/floppy extras/path_id \
            extras/scsi_id extras/usb_id extras/volume_id"</userinput></screen>

    <variablelist>
      <title>The meaning of the make option:</title>

      <varlistentry>
        <term><parameter>EXTRAS=...</parameter></term>
        <listitem>
          <para>This builds several helper binaries that can aid in writing custom
          Udev rules.</para>
        </listitem>
      </varlistentry>

    </variablelist>

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

    <para>Note that the Udev testsuite will produce numerous messages in
    the host system's logs. These are harmless and can be ignored.</para>

    <para>Install the package:</para>

<screen><userinput>make DESTDIR=/ \
    EXTRAS="extras/ata_id extras/cdrom_id extras/edd_id \
            extras/firmware extras/floppy extras/path_id \
            extras/scsi_id extras/usb_id extras/volume_id" install</userinput></screen>

    <variablelist>
      <title>The meaning of the make parameter:</title>

      <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 has to be configured in order to work properly, as it does
    not install any configuration files by default. Install the
    LFS-specific configuration files:</para>

<screen><userinput>cp -v &udev-config;/[0-9]* /etc/udev/rules.d/</userinput></screen>

    <para>Install the documentation that explains how to create Udev rules:</para>

<screen><userinput>install -m644 -D -v docs/writing_udev_rules/index.html \
    /usr/share/doc/udev-&udev-version;/index.html</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>ata_id, cdrom_id, create_floppy_devices, edd_id, firmware_helper,
        path_id, scsi_id, udevcontrol, udevd, udevinfo, udevmonitor, udevsettle,
        udevtest, udevtrigger, usb_id, vol_id, and write_cd_aliases</seg>
        <seg>/etc/udev</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="ata_id">
        <term><command>ata_id</command></term>
        <listitem>
          <para>Provides Udev with a unique string and
          additional information (uuid, label) for an ATA drive</para>
          <indexterm zone="ch-system-udev ata_id">
            <primary sortas="b-ata_id">ata_id</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="cdrom_id">
        <term><command>cdrom_id</command></term>
        <listitem>
          <para>Provides Udev with the capabilities of a
          CD-ROM or DVD-ROM drive</para>
          <indexterm zone="ch-system-udev cdrom_id">
            <primary sortas="b-cdrom_id">cdrom_id</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="create_floppy_devices">
        <term><command>create_floppy_devices</command></term>
        <listitem>
          <para>Creates all possible floppy devices based on the CMOS type</para>
          <indexterm zone="ch-system-udev create_floppy_devices">
            <primary sortas="b-create_floppy_devices">create_floppy_devices</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="edd_id">
        <term><command>edd_id</command></term>
        <listitem>
          <para>Provides Udev with the EDD ID for a BIOS disk drive</para>
          <indexterm zone="ch-system-udev edd_id">
            <primary sortas="b-edd_id">edd_id</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="firmware_helper">
        <term><command>firmware_helper</command></term>
        <listitem>
          <para>Uploads firmware to devices</para>
          <indexterm zone="ch-system-udev firmware_helper">
            <primary sortas="b-firmware_helper">firmware_helper</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="path_id">
        <term><command>path_id</command></term>
        <listitem>
          <para>Provide the shortest possible unique hardware path to a
          device</para>
          <indexterm zone="ch-system-udev path_id">
            <primary sortas="b-path_id">path_id</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="scsi_id">
        <term><command>scsi_id</command></term>
        <listitem>
          <para>Provides Udev with a unique SCSI identifier
          based on the data returned from sending a SCSI INQUIRY command to
          the specified device</para>
          <indexterm zone="ch-system-udev scsi_id">
            <primary sortas="b-scsi_id">scsi_id</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="udevcontrol">
        <term><command>udevcontrol</command></term>
        <listitem>
          <para>Configures a number of options for the running
          <command>udevd</command> daemon, such as the log level.</para>
          <indexterm zone="ch-system-udev udevcontrol">
            <primary sortas="b-udevcontrol">udevcontrol</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="udevd">
        <term><command>udevd</command></term>
        <listitem>
          <para>A daemon that listens for uevents on the netlink socket,
          creates devices and runs the configured external programs in
          response to these uevents</para>
          <indexterm zone="ch-system-udev udevd">
            <primary sortas="b-udevd">udevd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="udevinfo">
        <term><command>udevinfo</command></term>
        <listitem>
          <para>Allows users to query the Udev 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="udevmonitor">
        <term><command>udevmonitor</command></term>
        <listitem>
          <para>Prints the event received from the kernel and the environment
          which Udev sends out after rule processing</para>
          <indexterm zone="ch-system-udev udevmonitor">
            <primary sortas="b-udevmonitor">udevmonitor</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="udevsettle">
        <term><command>udevsettle</command></term>
        <listitem>
          <para>Watches the Udev event queue and exits if all current uevents
          have been handled</para>
          <indexterm zone="ch-system-udev udevsettle">
            <primary sortas="b-udevsettle">udevsettle</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="udevtest">
        <term><command>udevtest</command></term>
        <listitem>
          <para>Simulates a uevent for the given device, and prints out the
          name of the node the real <command>udevd</command> would have created,
          or 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="udevtrigger">
        <term><command>udevtrigger</command></term>
        <listitem>
          <para>Triggers kernel device uevents to be replayed</para>
          <indexterm zone="ch-system-udev udevtrigger">
            <primary sortas="b-udevtrigger">udevtrigger</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="usb_id">
        <term><command>usb_id</command></term>
        <listitem>
          <para>Provides Udev with information about USB
          devices</para>
          <indexterm zone="ch-system-udev usb_id">
            <primary sortas="b-usb_id">usb_id</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="vol_id">
        <term><command>vol_id</command></term>
        <listitem>
          <para>Provides Udev with the label and uuid of a
          filesystem</para>
          <indexterm zone="ch-system-udev vol_id">
            <primary sortas="b-vol_id">vol_id</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="etc-udev">
        <term><filename class="directory">/etc/udev</filename></term>
        <listitem>
          <para>Contains Udev 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>