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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">
8 <title>systemd-udevd.service</title>
9 <productname>systemd</productname>
12 <contrib>Developer</contrib>
13 <firstname>Kay</firstname>
14 <surname>Sievers</surname>
15 <email>kay@vrfy.org</email>
21 <refentrytitle>systemd-udevd.service</refentrytitle>
22 <manvolnum>8</manvolnum>
23 <refmiscinfo class="version"></refmiscinfo>
27 <refname>systemd-udev.service</refname>
28 <refname>systemd-udev-control.socket</refname>
29 <refname>systemd-udev-kernel.socket</refname>
30 <refname>systemd-udevd</refname>
31 <refpurpose>Device event managing daemon</refpurpose>
35 <para><filename>systemd-udev.service</filename></para>
36 <para><filename>systemd-udev-control.socket</filename></para>
37 <para><filename>systemd-udev-kernel.socket</filename></para>
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>
52 <refsect1><title>Description</title>
53 <para>systemd-udevd listens to kernel uevents. For every event, systemd-udevd executes matching
54 instructions specified in udev rules. See <citerefentry>
55 <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
56 </citerefentry>.</para>
57 <para>The behavior of the running daemon can be changed with
58 <command>udevadm control</command>.</para>
61 <refsect1><title>Options</title>
64 <term><option>--daemon</option></term>
66 <para>Detach and run in the background.</para>
70 <term><option>--debug</option></term>
72 <para>Print debug messages to stderr.</para>
76 <term><option>--children-max=</option></term>
78 <para>Limit the number of parallel executed events.</para>
82 <term><option>--exec-delay=</option></term>
84 <para>Number of seconds to delay the execution of RUN instructions.
85 This might be useful when debugging system crashes during coldplug
86 cause by loading non-working kernel modules.</para>
90 <term><option>--resolve-names=</option></term>
92 <para>Specify when systemd-udevd should resolve names of users and groups.
93 When set to <option>early</option> (the default) names will be
94 resolved when the rules are parsed. When set to
95 <option>late</option> names will be resolved for every event.
96 When set to <option>never</option> names will never be resolved
97 and all devices will be owned by root.</para>
101 <term><option>--version</option></term>
103 <para>Print version number.</para>
107 <term><option>--help</option></term>
109 <para>Print help text.</para>
115 <refsect1><title>Environment</title>
118 <term><varname>UDEV_LOG=</varname></term>
120 <para>Set the logging priority.</para>
126 <refsect1><title>Kernel command line</title>
128 <para>The parameters starting with "rd.", will be read when udev is used in an initrd.</para>
130 <term><varname>udev.log-priority=</varname></term>
131 <term><varname>rd.udev.log-priority=</varname></term>
133 <para>Set the logging priority.</para>
137 <term><varname>udev.children-max=</varname></term>
138 <term><varname>rd.udev.children-max=</varname></term>
140 <para>Limit the number of parallel executed events.</para>
144 <term><varname>udev.exec-delay=</varname></term>
145 <term><varname>rd.udev.exec-delay=</varname></term>
147 <para>Number of seconds to delay the execution of RUN instructions.
148 This might be useful when debugging system crashes during coldplug
149 cause by loading non-working kernel modules.</para>
156 <title>See Also</title>
158 <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
159 </citerefentry>, <citerefentry>
160 <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
161 </citerefentry></para>