lfs/chapter08/udev.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>

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

  <sect1info condition="script">
    <productname>udev</productname>
    <productnumber>&systemd-version;</productnumber>
    <address>&systemd-url;</address>
  </sect1info>

  <title>Udev from Systemd-&systemd-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-fin-sbu;</seg>
        <seg>&udev-fin-du;</seg>
      </seglistitem>
    </segmentedlist>
  </sect2>

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

    <para>Udev is part of the systemd-&systemd-version; package. Use
    the systemd-&systemd-version;.tar.xz file as the source tarball.</para>

    <para>Remove two unneeded groups,
    <systemitem class="groupname">render</systemitem> and
    <systemitem class="groupname">sgx</systemitem>, from the default udev
    rules:</para>

 <screen><userinput remap="pre">sed -i -e 's/GROUP="render"/GROUP="video"/' \
       -e 's/GROUP="sgx", //' rules.d/50-udev-default.rules.in</userinput></screen>

    <para>Remove one udev rule requiring a full Systemd installation:</para>

 <screen><userinput remap="pre">sed '/systemd-sysctl/s/^/#/' -i rules.d/99-systemd.rules.in</userinput></screen>

    <para>Prepare Udev for compilation:</para>

<screen><userinput remap="configure">mkdir -p build
cd       build

meson setup \
      --prefix=/usr                 \
      --buildtype=release           \
      -Dmode=release                \
      -Ddev-kvm-mode=0660           \
      -Dlink-udev-shared=false      \
      ..</userinput></screen>

    <variablelist>
      <title>The meaning of the meson options:</title>

      <varlistentry>
        <term><parameter>--buildtype=release</parameter></term>
        <listitem>
          <para>This switch overrides the default buildtype
          (<quote>debug</quote>), which produces unoptimized
          binaries.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dmode=release</parameter></term>
        <listitem>
          <para>Disable some features considered experimental by upstream.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Ddev-kvm-mode=0660</parameter></term>
        <listitem>
          <para>The default udev rule would allow all users to access
          <filename class='devicefile'>/dev/kvm</filename>.  The editors
          consider it dangerous.  This option overrides it.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dlink-udev-shared=false</parameter></term>
        <listitem>
          <para>This option prevents udev from linking to the internal
          systemd shared library,
          <systemitem class='library'>libsystemd-shared</systemitem>.
          This library is designed to be shared by many Systemd components
          and it's too overkill for a udev-only installation.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Only build the components needed for udev:</para>

    <screen><userinput remap="make">ninja udevadm systemd-hwdb \
      $(grep -o -E "^build (src/libudev|src/udev|rules.d|hwdb.d)[^:]*" \
        build.ninja | awk '{ print $2 }')                              \
      $(realpath libudev.so --relative-to .)</userinput></screen>

    <para>Remove one udev rule file requiring a full Systemd
    installation:</para>

<screen><userinput remap="make">rm rules.d/90-vconsole.rules</userinput></screen>

    <para>Install the package:</para>

    <screen><userinput remap="install">install -vm755 -d {/usr/lib,/etc}/udev/{hwdb,rules}.d
install -vm755 -d /usr/{lib,share}/pkgconfig
install -vm755 udevadm                     /usr/bin/
install -vm755 systemd-hwdb                /usr/bin/udev-hwdb
ln      -svfn  ../bin/udevadm              /usr/sbin/udevd
cp      -av    libudev.so{,*[0-9]}         /usr/lib/
install -vm644 ../src/libudev/libudev.h    /usr/include/
install -vm644 src/libudev/*.pc            /usr/lib/pkgconfig/
install -vm644 src/udev/*.pc               /usr/share/pkgconfig/
install -vm644 ../src/udev/udev.conf       /etc/udev/
install -vm644 rules.d/* ../rules.d/{*.rules,README} /usr/lib/udev/rules.d/
install -vm644 hwdb.d/*  ../hwdb.d/{*.hwdb,README}   /usr/lib/udev/hwdb.d/
install -vm755 $(find src/udev -type f | grep -F -v ".") /usr/lib/udev</userinput></screen>

    <para>Install some custom rules and support files useful in an LFS
    environment:</para>

<screen><userinput remap="install">tar -xvf ../../&udev-lfs-version;.tar.xz
make -f &udev-lfs-version;/Makefile.lfs install</userinput></screen>

    <para>Install the man pages:</para>

    <!-- Please make sure systemd man pages tarball has a common leading
         component in the path.  -->
<screen><userinput remap="install">tar -xf ../../systemd-man-pages-&systemd-man-version;.tar.xz                            \
    --no-same-owner --strip-components=1                              \
    -C /usr/share/man --wildcards '*/udev*' '*/libudev*'              \
                                  '*/systemd-'{hwdb,udevd.service}.8
sed 's/systemd\(\\\?-\)/udev\1/' /usr/share/man/man8/systemd-hwdb.8   \
                               > /usr/share/man/man8/udev-hwdb.8
sed 's|lib.*udevd|sbin/udevd|'                                        \
    /usr/share/man/man8/systemd-udevd.service.8                       \
  > /usr/share/man/man8/udevd.8
rm  /usr/share/man/man8/systemd-*.8</userinput></screen>

  </sect2>

  <sect2 id="conf-udev" role="configuration">
    <title>Configuring Udev</title>

    <indexterm zone="conf-udev">
      <primary sortas="a-Udev">Udev</primary>
      <secondary>configuring</secondary>
    </indexterm>

    <indexterm zone="conf-udev">
      <primary sortas="e-/etc/udev/hwdb.bin">/etc/udev/hwdb.bin</primary>
    </indexterm>

    <para>Information about hardware devices is maintained in the
    <filename class="directory">/etc/udev/hwdb.d</filename> and
    <filename class="directory">/usr/lib/udev/hwdb.d</filename> directories.
    <application>Udev</application> needs that information to be compiled
    into a binary database <filename>/etc/udev/hwdb.bin</filename>. Create the
    initial database:</para>

<screen><userinput>udev-hwdb update</userinput></screen>

    <para>This command needs to be run each time the hardware information is
    updated.</para>

  </sect2>

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

    <segmentedlist>
      <segtitle>Installed programs</segtitle>
      <segtitle>Installed libraries</segtitle>
      <segtitle>Installed directories</segtitle>

      <seglistitem>
        <seg>udevadm, udevd (symlink to udevadm), and udev-hwdb</seg>

        <seg>libudev.so</seg>

        <seg>/etc/udev and /usr/lib/udev</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>
      <varlistentry id="udevadm" revision="sysv">
        <term><command>udevadm</command></term>
        <listitem>
          <para>Generic udev administration tool: controls the udevd daemon,
          provides info from the Udev database, monitors uevents, waits for
          uevents to finish, tests Udev configuration, and triggers uevents
          for a given device</para>
          <indexterm zone="ch-system-udev udevadm">
            <primary sortas="b-udevadm">udevadm</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="udev-hwdb">
        <term><command>udev-hwdb</command></term>
        <listitem>
          <para>Updates or queries the hardware database.</para>
          <indexterm zone="ch-system-udev udev-hwdb">
            <primary sortas="b-udev-hwdb">udev-hwdb</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libudev">
        <term><filename class="libraryfile">libudev</filename></term>
        <listitem>
          <para>A library interface to udev device information</para>
          <indexterm zone="ch-system-udev libudev">
            <primary sortas="c-libudev">libudev</primary>
          </indexterm>
        </listitem>
      </varlistentry>

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