2 <?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
4 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 <refentry id="systemd-udevd.service"
7 xmlns:xi="http://www.w3.org/2001/XInclude">
10 <title>systemd-udevd.service</title>
11 <productname>systemd</productname>
14 <contrib>Developer</contrib>
15 <firstname>Kay</firstname>
16 <surname>Sievers</surname>
17 <email>kay@vrfy.org</email>
23 <refentrytitle>systemd-udevd.service</refentrytitle>
24 <manvolnum>8</manvolnum>
25 <refmiscinfo class="version"></refmiscinfo>
29 <refname>systemd-udevd.service</refname>
30 <refname>systemd-udevd-control.socket</refname>
31 <refname>systemd-udevd-kernel.socket</refname>
32 <refname>systemd-udevd</refname>
33 <refpurpose>Device event managing daemon</refpurpose>
37 <para><filename>systemd-udevd.service</filename></para>
38 <para><filename>systemd-udevd-control.socket</filename></para>
39 <para><filename>systemd-udevd-kernel.socket</filename></para>
42 <command>/usr/lib/systemd/systemd-udevd</command>
43 <arg><option>--daemon</option></arg>
44 <arg><option>--debug</option></arg>
45 <arg><option>--children-max=</option></arg>
46 <arg><option>--exec-delay=</option></arg>
47 <arg><option>--event-timeout=</option></arg>
48 <arg><option>--resolve-names=early|late|never</option></arg>
49 <arg><option>--version</option></arg>
50 <arg><option>--help</option></arg>
55 <refsect1><title>Description</title>
56 <para><command>systemd-udevd</command> listens to kernel uevents.
57 For every event, systemd-udevd executes matching instructions
58 specified in udev rules. See <citerefentry>
59 <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
60 </citerefentry>.</para>
61 <para>The behavior of the running daemon can be changed with
62 <command>udevadm control</command>.</para>
65 <refsect1><title>Options</title>
68 <term><option>--daemon</option></term>
70 <para>Detach and run in the background.</para>
75 <term><option>--debug</option></term>
77 <para>Print debug messages to standard error.</para>
82 <term><option>--children-max=</option></term>
84 <para>Limit the number of events executed in parallel.</para>
89 <term><option>--exec-delay=</option></term>
91 <para>Delay the execution of <varname>RUN</varname>
92 instructions by the given number of seconds. This option
93 might be useful when debugging system crashes during
94 coldplug caused by loading non-working kernel
100 <term><option>--event-timeout=</option></term>
102 <para>Set the number of seconds to wait for events to finish. After
103 this time the event will be terminated. The default is 30 seconds.</para>
108 <term><option>--resolve-names=</option></term>
110 <para>Specify when systemd-udevd should resolve names of users and groups.
111 When set to <option>early</option> (the default), names will be
112 resolved when the rules are parsed. When set to
113 <option>late</option>, names will be resolved for every event.
114 When set to <option>never</option>, names will never be resolved
115 and all devices will be owned by root.</para>
120 <term><option>--help</option></term>
122 <xi:include href="standard-options.xml" xpointer="help-text" />
124 <xi:include href="standard-options.xml" xpointer="version" />
128 <refsect1><title>Environment</title>
129 <variablelist class='environment-variables'>
131 <term><varname>$UDEV_LOG=</varname></term>
133 <para>Set the logging priority.</para>
139 <refsect1><title>Kernel command line</title>
140 <variablelist class='kernel-commandline-options'>
141 <para>Parameters starting with "rd." will be read when
142 <command>systemd-udevd</command> is used in an initrd.</para>
144 <term><varname>udev.log-priority=</varname></term>
145 <term><varname>rd.udev.log-priority=</varname></term>
147 <para>Set the logging priority.</para>
151 <term><varname>udev.children-max=</varname></term>
152 <term><varname>rd.udev.children-max=</varname></term>
154 <para>Limit the number of events executed in parallel.</para>
158 <term><varname>udev.exec-delay=</varname></term>
159 <term><varname>rd.udev.exec-delay=</varname></term>
161 <para>Delay the execution of <varname>RUN</varname> instructions by the given
162 number of seconds. This option might be useful when
163 debugging system crashes during coldplug caused by loading
164 non-working kernel modules.</para>
168 <term><varname>udev.event-timeout=</varname></term>
169 <term><varname>rd.udev.event-timeout=</varname></term>
171 <para>Wait for events to finish up to the given number
172 of seconds. This option might be useful if events are
173 terminated due to kernel drivers taking too long to initialize.</para>
177 <term><varname>net.ifnames=</varname></term>
179 <para>Network interfaces are renamed to give them predictable names
180 when possible. It is enabled by default; specifying 0 disables it.</para>
184 <!-- when adding entries here, consider also adding them
185 in kernel-command-line.xml -->
188 <refsect1><title>Configuration file</title>
189 <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
190 It consists of a set of variables allowing the user to override default udev values. All
191 empty lines or lines beginning with '#' are ignored. The following variables can be
195 <term><varname>udev_log</varname></term>
197 <para>The logging priority. Valid values are the numerical syslog priorities
198 or their textual representations: <option>err</option>, <option>info</option>
199 and <option>debug</option>.</para>
206 <title>See Also</title>
208 <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
209 </citerefentry>, <citerefentry>
210 <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
211 </citerefentry></para>