man/systemd-udevd.service.xml

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   6 <refentry id="systemd-udevd.service">
   7   <refentryinfo>
   8     <title>systemd-udevd.service</title>
   9     <productname>systemd</productname>
  10     <authorgroup>
  11       <author>
  12         <contrib>Developer</contrib>
  13         <firstname>Kay</firstname>
  14         <surname>Sievers</surname>
  15         <email>kay@vrfy.org</email>
  16       </author>
  17     </authorgroup>
  18   </refentryinfo>
  19
  20   <refmeta>
  21     <refentrytitle>systemd-udevd.service</refentrytitle>
  22     <manvolnum>8</manvolnum>
  23     <refmiscinfo class="version"></refmiscinfo>
  24   </refmeta>
  25
  26   <refnamediv>
  27     <refname>systemd-udevd.service</refname>
  28     <refname>systemd-udevd-control.socket</refname>
  29     <refname>systemd-udevd-kernel.socket</refname>
  30     <refname>systemd-udevd</refname>
  31     <refpurpose>Device event managing daemon</refpurpose>
  32   </refnamediv>
  33
  34   <refsynopsisdiv>
  35     <para><filename>systemd-udevd.service</filename></para>
  36     <para><filename>systemd-udevd-control.socket</filename></para>
  37     <para><filename>systemd-udevd-kernel.socket</filename></para>
  38
  39     <cmdsynopsis>
  40       <command>/usr/lib/systemd/systemd-udevd</command>
  41       <arg><option>--daemon</option></arg>
  42       <arg><option>--debug</option></arg>
  43       <arg><option>--children-max=</option></arg>
  44       <arg><option>--exec-delay=</option></arg>
  45       <arg><option>--resolve-names=early|late|never</option></arg>
  46       <arg><option>--version</option></arg>
  47       <arg><option>--help</option></arg>
  48     </cmdsynopsis>
  49
  50   </refsynopsisdiv>
  51
  52   <refsect1><title>Description</title>
  53     <para><command>systemd-udevd</command> listens to kernel uevents.
  54       For every event, systemd-udevd executes matching instructions
  55       specified in udev rules. See <citerefentry>
  56       <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
  57       </citerefentry>.</para>
  58     <para>The behavior of the running daemon can be changed with
  59     <command>udevadm control</command>.</para>
  60   </refsect1>
  61
  62   <refsect1><title>Options</title>
  63     <variablelist>
  64       <varlistentry>
  65         <term><option>--daemon</option></term>
  66         <listitem>
  67           <para>Detach and run in the background.</para>
  68         </listitem>
  69       </varlistentry>
  70       <varlistentry>
  71         <term><option>--debug</option></term>
  72         <listitem>
  73           <para>Print debug messages to stderr.</para>
  74         </listitem>
  75       </varlistentry>
  76       <varlistentry>
  77         <term><option>--children-max=</option></term>
  78         <listitem>
  79           <para>Limit the number of events executed in parallel.</para>
  80         </listitem>
  81       </varlistentry>
  82       <varlistentry>
  83         <term><option>--exec-delay=</option></term>
  84         <listitem>
  85
  86           <para>Delay the execution of RUN instruction by the given
  87           number of seconds. This option might be useful when
  88           debugging system crashes during coldplug caused by loading
  89           non-working kernel modules.</para>
  90         </listitem>
  91       </varlistentry>
  92       <varlistentry>
  93         <term><option>--resolve-names=</option></term>
  94         <listitem>
  95           <para>Specify when systemd-udevd should resolve names of users and groups.
  96           When set to <option>early</option> (the default) names will be
  97           resolved when the rules are parsed.  When set to
  98           <option>late</option> names will be resolved for every event.
  99           When set to <option>never</option> names will never be resolved
 100           and all devices will be owned by root.</para>
 101         </listitem>
 102       </varlistentry>
 103       <varlistentry>
 104         <term><option>--version</option></term>
 105         <listitem>
 106           <para>Print version number.</para>
 107         </listitem>
 108       </varlistentry>
 109       <varlistentry>
 110         <term><option>--help</option></term>
 111         <listitem>
 112           <para>Print help text.</para>
 113         </listitem>
 114       </varlistentry>
 115     </variablelist>
 116   </refsect1>
 117
 118   <refsect1><title>Environment</title>
 119     <variablelist class='environment-variables'>
 120       <varlistentry>
 121         <term><varname>$UDEV_LOG=</varname></term>
 122         <listitem>
 123           <para>Set the logging priority.</para>
 124         </listitem>
 125       </varlistentry>
 126     </variablelist>
 127  </refsect1>
 128
 129   <refsect1><title>Kernel command line</title>
 130     <variablelist class='kernel-commandline-options'>
 131       <para>Parameters starting with "rd." will be read when
 132       <command>systemd-udevd</command> is used in an initrd.</para>
 133       <varlistentry>
 134         <term><varname>udev.log-priority=</varname></term>
 135         <term><varname>rd.udev.log-priority=</varname></term>
 136         <listitem>
 137           <para>Set the logging priority.</para>
 138         </listitem>
 139       </varlistentry>
 140       <varlistentry>
 141         <term><varname>udev.children-max=</varname></term>
 142         <term><varname>rd.udev.children-max=</varname></term>
 143         <listitem>
 144           <para>Limit the number of events executed in parallel.</para>
 145         </listitem>
 146       </varlistentry>
 147       <varlistentry>
 148         <term><varname>udev.exec-delay=</varname></term>
 149         <term><varname>rd.udev.exec-delay=</varname></term>
 150         <listitem>
 151           <para>Delay the execution of RUN instruction by the given
 152           number of seconds. This option might be useful when
 153           debugging system crashes during coldplug caused by loading
 154           non-working kernel modules.</para>
 155         </listitem>
 156       </varlistentry>
 157       <varlistentry>
 158         <term><varname>net.ifnames=</varname></term>
 159         <listitem>
 160           <para>Network interfaces are renamed to give them predictable names
 161           when possible. It is enabled by default, specifying 0 disables it.</para>
 162         </listitem>
 163       </varlistentry>
 164     </variablelist>
 165  </refsect1>
 166
 167  <refsect1><title>Configuration file</title>
 168    <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
 169    It consists of a set of variables allowing the user to override default udev values. All
 170    empty lines or lines beginning with '#' are ignored. The following variables can be
 171    set:</para>
 172    <variablelist>
 173      <varlistentry>
 174        <term><varname>udev_log</varname></term>
 175        <listitem>
 176          <para>The logging priority. Valid values are the numerical syslog priorities
 177          or their textual representations: <option>err</option>, <option>info</option>
 178          and <option>debug</option>.</para>
 179        </listitem>
 180      </varlistentry>
 181    </variablelist>
 182  </refsect1>
 183
 184   <refsect1>
 185     <title>See Also</title>
 186     <para><citerefentry>
 187         <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
 188       </citerefentry>, <citerefentry>
 189         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 190     </citerefentry></para>
 191   </refsect1>
 192 </refentry>