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<refentry id="udevd">
  <refentryinfo>
    <title>udevd</title>
    <productname>udev</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>udevd</refentrytitle>
    <manvolnum>8</manvolnum>
    <refmiscinfo class="version"></refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>udevd</refname><refpurpose>event managing daemon</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>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>udevd listens to kernel uevents. For every event, udevd executes matching
    instructions specified in udev rules. See <citerefentry>
        <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
      </citerefentry>.</para>
    <para>On startup the content of the directory <filename>/usr/lib/udev/devices</filename>
    is copied to <filename>/dev</filename>. If kernel modules specify static device
    nodes, these nodes are created even without a corresponding kernel device, to
    allow on-demand loading of kernel modules. Matching permissions specified in udev
    rules are applied to these static device nodes.</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 parallel executed events.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--exec-delay=</option></term>
        <listitem>
          <para>Number of seconds to delay the execution of RUN instructions.
          This might be useful when debugging system crashes during coldplug
          cause by loading non-working kernel modules.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><option>--resolve-names=</option></term>
        <listitem>
          <para>Specify when 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>
      <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>
      <varlistentry>
        <term><varname>udev.log-priority=</varname></term>
        <listitem>
          <para>Set the logging priority.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>udev.children-max=</varname></term>
        <listitem>
          <para>Limit the number of parallel executed events.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>udev.exec-delay=</varname></term>
        <listitem>
          <para>Number of seconds to delay the execution of RUN instructions.
          This might be useful when debugging system crashes during coldplug
          cause by loading non-working kernel modules.</para>
        </listitem>
      </varlistentry>
    </variablelist>
 </refsect1>

  <refsect1><title>Author</title>
    <para>Written by Kay Sievers <email>kay.sievers@vrfy.org</email>.</para>
  </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>