man/systemd-udevd.service.xml

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   8
   9 <refentry id="systemd-udevd.service"
  10           xmlns:xi="http://www.w3.org/2001/XInclude">
  11
  12   <refentryinfo>
  13     <title>systemd-udevd.service</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>systemd-udevd.service</refentrytitle>
  19     <manvolnum>8</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>systemd-udevd.service</refname>
  24     <refname>systemd-udevd-control.socket</refname>
  25     <refname>systemd-udevd-kernel.socket</refname>
  26     <refname>systemd-udevd</refname>
  27     <refpurpose>Device event managing daemon</refpurpose>
  28   </refnamediv>
  29
  30   <refsynopsisdiv>
  31     <para><filename>systemd-udevd.service</filename></para>
  32     <para><filename>systemd-udevd-control.socket</filename></para>
  33     <para><filename>systemd-udevd-kernel.socket</filename></para>
  34
  35     <cmdsynopsis>
  36       <command>/usr/lib/systemd/systemd-udevd</command>
  37       <arg><option>--daemon</option></arg>
  38       <arg><option>--debug</option></arg>
  39       <arg><option>--children-max=</option></arg>
  40       <arg><option>--exec-delay=</option></arg>
  41       <arg><option>--event-timeout=</option></arg>
  42       <arg><option>--resolve-names=early|late|never</option></arg>
  43       <arg><option>--version</option></arg>
  44       <arg><option>--help</option></arg>
  45     </cmdsynopsis>
  46
  47   </refsynopsisdiv>
  48
  49   <refsect1><title>Description</title>
  50     <para><command>systemd-udevd</command> listens to kernel uevents.
  51     For every event, systemd-udevd executes matching instructions
  52     specified in udev rules. See <citerefentry>
  53     <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
  54     </citerefentry>.</para>
  55
  56     <para>The behavior of the daemon can be configured using
  57     <citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  58     its command line options, environment variables, and on the kernel
  59     command line, or changed dynamically with <command>udevadm
  60     control</command>.
  61     </para>
  62   </refsect1>
  63
  64   <refsect1><title>Options</title>
  65     <variablelist>
  66       <varlistentry>
  67         <term><option>-d</option></term>
  68         <term><option>--daemon</option></term>
  69         <listitem>
  70           <para>Detach and run in the background.</para>
  71         </listitem>
  72       </varlistentry>
  73
  74       <varlistentry>
  75         <term><option>-D</option></term>
  76         <term><option>--debug</option></term>
  77         <listitem>
  78           <para>Print debug messages to standard error.</para>
  79         </listitem>
  80       </varlistentry>
  81
  82       <varlistentry>
  83         <term><option>-c=</option></term>
  84         <term><option>--children-max=</option></term>
  85         <listitem>
  86           <para>Limit the number of events executed in parallel.</para>
  87         </listitem>
  88       </varlistentry>
  89
  90       <varlistentry>
  91         <term><option>-e=</option></term>
  92         <term><option>--exec-delay=</option></term>
  93         <listitem>
  94           <para>Delay the execution of <varname>RUN</varname>
  95           instructions by the given number of seconds. This option
  96           might be useful when debugging system crashes during
  97           coldplug caused by loading non-working kernel
  98           modules.</para>
  99         </listitem>
 100       </varlistentry>
 101
 102       <varlistentry>
 103         <term><option>-t=</option></term>
 104         <term><option>--event-timeout=</option></term>
 105         <listitem>
 106           <para>Set the number of seconds to wait for events to finish. After
 107           this time, the event will be terminated. The default is 180 seconds.</para>
 108         </listitem>
 109       </varlistentry>
 110
 111       <varlistentry>
 112         <term><option>-N=</option></term>
 113         <term><option>--resolve-names=</option></term>
 114         <listitem>
 115           <para>Specify when systemd-udevd should resolve names of users and groups.
 116           When set to <option>early</option> (the default), names will be
 117           resolved when the rules are parsed.  When set to
 118           <option>late</option>, names will be resolved for every event.
 119           When set to <option>never</option>, names will never be resolved
 120           and all devices will be owned by root.</para>
 121         </listitem>
 122       </varlistentry>
 123
 124       <xi:include href="standard-options.xml" xpointer="help" />
 125       <xi:include href="standard-options.xml" xpointer="version" />
 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 log level.</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 <varname>RUN</varname> instructions 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>udev.event_timeout=</varname></term>
 159         <term><varname>rd.udev.event_timeout=</varname></term>
 160         <listitem>
 161           <para>Wait for events to finish up to the given number
 162           of seconds. This option might be useful if events are
 163           terminated due to kernel drivers taking too long to initialize.</para>
 164         </listitem>
 165       </varlistentry>
 166       <varlistentry>
 167         <term><varname>net.ifnames=</varname></term>
 168         <listitem>
 169           <para>Network interfaces are renamed to give them predictable names
 170           when possible. It is enabled by default; specifying 0 disables it.</para>
 171         </listitem>
 172       </varlistentry>
 173       <varlistentry>
 174         <term><varname>net.naming-scheme=</varname></term>
 175         <listitem>
 176           <para>Network interfaces are renamed to give them predictable names when possible (unless
 177           <varname>net.ifnames=0</varname> is specified, see above). The names are derived from various
 178           device metadata fields. Newer versions of <filename>systemd-udevd.service</filename> take more of
 179           these fields into account, improving (and thus possibly changing) the names used for the same
 180           devices. With this kernel command line option it is possible to pick a specific version of this
 181           algorithm. It expects a naming scheme identifier as argument. Currently the following identifiers
 182           are known: <literal>v238</literal>, <literal>v239</literal>, <literal>v240</literal> which each
 183           implement the naming scheme that was the default in the indicated systemd version. In addition,
 184           <literal>latest</literal> may be used to designate the latest scheme known (to this particular
 185           version of <filename>systemd-udevd.service</filename>).</para>
 186
 187           <para>Note that selecting a specific scheme is not sufficient to fully stabilize interface naming:
 188           the naming is generally derived from driver attributes exposed by the kernel. As the kernel is
 189           updated, previously missing attributes <filename>systemd-udevd.service</filename> is checking might
 190           appear, which affects older name derivation algorithms, too.</para>
 191         </listitem>
 192       </varlistentry>
 193     </variablelist>
 194     <!-- when adding entries here, consider also adding them
 195          in kernel-command-line.xml -->
 196  </refsect1>
 197
 198   <refsect1>
 199     <title>See Also</title>
 200     <para>
 201       <citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 202       <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 203       <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 204     </para>
 205   </refsect1>
 206 </refentry>