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1 <?xml version='1.0'?>
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4
5 <!--
6 SPDX-License-Identifier: LGPL-2.1+
7 -->
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 </variablelist>
174 <!-- when adding entries here, consider also adding them
175 in kernel-command-line.xml -->
176 </refsect1>
177
178 <refsect1>
179 <title>See Also</title>
180 <para>
181 <citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
182 <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
183 <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
184 </para>
185 </refsect1>
186 </refentry>