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>
28 <refname>systemd-udevd.service</refname>
29 <refname>systemd-udevd-control.socket</refname>
30 <refname>systemd-udevd-kernel.socket</refname>
31 <refname>systemd-udevd</refname>
32 <refpurpose>Device event managing daemon</refpurpose>
36 <para><filename>systemd-udevd.service</filename></para>
37 <para><filename>systemd-udevd-control.socket</filename></para>
38 <para><filename>systemd-udevd-kernel.socket</filename></para>
41 <command>/usr/lib/systemd/systemd-udevd</command>
42 <arg><option>--daemon</option></arg>
43 <arg><option>--debug</option></arg>
44 <arg><option>--children-max=</option></arg>
45 <arg><option>--exec-delay=</option></arg>
46 <arg><option>--event-timeout=</option></arg>
47 <arg><option>--resolve-names=early|late|never</option></arg>
48 <arg><option>--version</option></arg>
49 <arg><option>--help</option></arg>
54 <refsect1><title>Description</title>
55 <para><command>systemd-udevd</command> listens to kernel uevents.
56 For every event, systemd-udevd executes matching instructions
57 specified in udev rules. See <citerefentry>
58 <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
59 </citerefentry>.</para>
61 <para>The behavior of the daemon can be configured using
62 <citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
63 its command line options, environment variables, and on the kernel
64 command line, or changed dynamically with <command>udevadm
69 <refsect1><title>Options</title>
72 <term><option>--daemon</option></term>
74 <para>Detach and run in the background.</para>
79 <term><option>--debug</option></term>
81 <para>Print debug messages to standard error.</para>
86 <term><option>--children-max=</option></term>
88 <para>Limit the number of events executed in parallel.</para>
93 <term><option>--exec-delay=</option></term>
95 <para>Delay the execution of <varname>RUN</varname>
96 instructions by the given number of seconds. This option
97 might be useful when debugging system crashes during
98 coldplug caused by loading non-working kernel
104 <term><option>--event-timeout=</option></term>
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 30 seconds.</para>
112 <term><option>--resolve-names=</option></term>
114 <para>Specify when systemd-udevd should resolve names of users and groups.
115 When set to <option>early</option> (the default), names will be
116 resolved when the rules are parsed. When set to
117 <option>late</option>, names will be resolved for every event.
118 When set to <option>never</option>, names will never be resolved
119 and all devices will be owned by root.</para>
124 <term><option>--help</option></term>
126 <xi:include href="standard-options.xml" xpointer="help-text" />
128 <xi:include href="standard-options.xml" xpointer="version" />
132 <refsect1><title>Environment</title>
133 <variablelist class='environment-variables'>
135 <term><varname>$UDEV_LOG=</varname></term>
137 <para>Set the log level.</para>
143 <refsect1><title>Kernel command line</title>
144 <variablelist class='kernel-commandline-options'>
145 <para>Parameters starting with "rd." will be read when
146 <command>systemd-udevd</command> is used in an initrd.</para>
148 <term><varname>udev.log-priority=</varname></term>
149 <term><varname>rd.udev.log-priority=</varname></term>
151 <para>Set the log level.</para>
155 <term><varname>udev.children-max=</varname></term>
156 <term><varname>rd.udev.children-max=</varname></term>
158 <para>Limit the number of events executed in parallel.</para>
162 <term><varname>udev.exec-delay=</varname></term>
163 <term><varname>rd.udev.exec-delay=</varname></term>
165 <para>Delay the execution of <varname>RUN</varname> instructions by the given
166 number of seconds. This option might be useful when
167 debugging system crashes during coldplug caused by loading
168 non-working kernel modules.</para>
172 <term><varname>udev.event-timeout=</varname></term>
173 <term><varname>rd.udev.event-timeout=</varname></term>
175 <para>Wait for events to finish up to the given number
176 of seconds. This option might be useful if events are
177 terminated due to kernel drivers taking too long to initialize.</para>
181 <term><varname>net.ifnames=</varname></term>
183 <para>Network interfaces are renamed to give them predictable names
184 when possible. It is enabled by default; specifying 0 disables it.</para>
188 <!-- when adding entries here, consider also adding them
189 in kernel-command-line.xml -->
193 <title>See Also</title>
195 <citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
196 <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
197 <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>