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1 <?xml version='1.0'?>
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">
5
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     <!-- when adding entries here, consider also adding them
166          in kernel-command-line.xml -->
167  </refsect1>
168
169  <refsect1><title>Configuration file</title>
170    <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
171    It consists of a set of variables allowing the user to override default udev values. All
172    empty lines or lines beginning with '#' are ignored. The following variables can be
173    set:</para>
174    <variablelist>
175      <varlistentry>
176        <term><varname>udev_log</varname></term>
177        <listitem>
178          <para>The logging priority. Valid values are the numerical syslog priorities
179          or their textual representations: <option>err</option>, <option>info</option>
180          and <option>debug</option>.</para>
181        </listitem>
182      </varlistentry>
183    </variablelist>
184  </refsect1>
185
186   <refsect1>
187     <title>See Also</title>
188     <para><citerefentry>
189         <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
190       </citerefentry>, <citerefentry>
191         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
192     </citerefentry></para>
193   </refsect1>
194 </refentry>