systemd-stable/man/systemd-udevd.service.xml

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<refentry id="systemd-udevd.service">
  <refentryinfo>
    <title>systemd-udevd.service</title>
    <productname>systemd</productname>
    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Kay</firstname>
        <surname>Sievers</surname>
        <email>kay@vrfy.org</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-udevd.service</refentrytitle>
    <manvolnum>8</manvolnum>
    <refmiscinfo class="version"></refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>systemd-udevd.service</refname>
    <refname>systemd-udevd-control.socket</refname>
    <refname>systemd-udevd-kernel.socket</refname>
    <refname>systemd-udevd</refname>
    <refpurpose>Device event managing daemon</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>systemd-udevd.service</filename></para>
    <para><filename>systemd-udevd-control.socket</filename></para>
    <para><filename>systemd-udevd-kernel.socket</filename></para>

    <cmdsynopsis>
      <command>/usr/lib/systemd/systemd-udevd</command>
      <arg><option>--daemon</option></arg>
      <arg><option>--debug</option></arg>
      <arg><option>--children-max=</option></arg>
      <arg><option>--exec-delay=</option></arg>
      <arg><option>--resolve-names=early|late|never</option></arg>
      <arg><option>--version</option></arg>
      <arg><option>--help</option></arg>
    </cmdsynopsis>

  </refsynopsisdiv>

  <refsect1><title>Description</title>
    <para><command>systemd-udevd</command> listens to kernel uevents.
      For every event, systemd-udevd executes matching instructions
      specified in udev rules. See <citerefentry>
      <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
      </citerefentry>.</para>
    <para>The behavior of the running daemon can be changed with
    <command>udevadm control</command>.</para>
  </refsect1>

  <refsect1><title>Options</title>
    <variablelist>
      <varlistentry>
        <term><option>--daemon</option></term>
        <listitem>
          <para>Detach and run in the background.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--debug</option></term>
        <listitem>
          <para>Print debug messages to stderr.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--children-max=</option></term>
        <listitem>
          <para>Limit the number of events executed in parallel.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--exec-delay=</option></term>
        <listitem>

          <para>Delay the execution of RUN instruction by the given
          number of seconds. This option might be useful when
          debugging system crashes during coldplug caused by loading
          non-working kernel modules.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--resolve-names=</option></term>
        <listitem>
          <para>Specify when systemd-udevd should resolve names of users and groups.
          When set to <option>early</option> (the default) names will be
          resolved when the rules are parsed.  When set to
          <option>late</option> names will be resolved for every event.
          When set to <option>never</option> names will never be resolved
          and all devices will be owned by root.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--version</option></term>
        <listitem>
          <para>Print version number.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--help</option></term>
        <listitem>
          <para>Print help text.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1><title>Environment</title>
    <variablelist class='environment-variables'>
      <varlistentry>
        <term><varname>$UDEV_LOG=</varname></term>
        <listitem>
          <para>Set the logging priority.</para>
        </listitem>
      </varlistentry>
    </variablelist>
 </refsect1>

  <refsect1><title>Kernel command line</title>
    <variablelist class='kernel-commandline-options'>
      <para>Parameters starting with "rd." will be read when
      <command>systemd-udevd</command> is used in an initrd.</para>
      <varlistentry>
        <term><varname>udev.log-priority=</varname></term>
        <term><varname>rd.udev.log-priority=</varname></term>
        <listitem>
          <para>Set the logging priority.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>udev.children-max=</varname></term>
        <term><varname>rd.udev.children-max=</varname></term>
        <listitem>
          <para>Limit the number of events executed in parallel.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>udev.exec-delay=</varname></term>
        <term><varname>rd.udev.exec-delay=</varname></term>
        <listitem>
          <para>Delay the execution of RUN instruction by the given
          number of seconds. This option might be useful when
          debugging system crashes during coldplug caused by loading
          non-working kernel modules.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>net.ifnames=</varname></term>
        <listitem>
          <para>Network interfaces are renamed to give them predictable names
          when possible. It is enabled by default, specifying 0 disables it.</para>
        </listitem>
      </varlistentry>
    </variablelist>
    <!-- when adding entries here, consider also adding them
         in kernel-command-line.xml -->
 </refsect1>

 <refsect1><title>Configuration file</title>
   <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
   It consists of a set of variables allowing the user to override default udev values. All
   empty lines or lines beginning with '#' are ignored. The following variables can be
   set:</para>
   <variablelist>
     <varlistentry>
       <term><varname>udev_log</varname></term>
       <listitem>
         <para>The logging priority. Valid values are the numerical syslog priorities
         or their textual representations: <option>err</option>, <option>info</option>
         and <option>debug</option>.</para>
       </listitem>
     </varlistentry>
   </variablelist>
 </refsect1>

  <refsect1>
    <title>See Also</title>
    <para><citerefentry>
        <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
      </citerefentry>, <citerefentry>
        <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
    </citerefentry></para>
  </refsect1>
</refentry>