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">
9 <productname>systemd</productname>
12 <contrib>Developer</contrib>
13 <firstname>Kay</firstname>
14 <surname>Sievers</surname>
15 <email>kay@vrfy.org</email>
21 <refentrytitle>udevd</refentrytitle>
22 <manvolnum>8</manvolnum>
23 <refmiscinfo class="version"></refmiscinfo>
27 <refname>udevd</refname><refpurpose>event managing daemon</refpurpose>
32 <command>udevd</command>
33 <arg><option>--daemon</option></arg>
34 <arg><option>--debug</option></arg>
35 <arg><option>--children-max=</option></arg>
36 <arg><option>--exec-delay=</option></arg>
37 <arg><option>--resolve-names=early|late|never</option></arg>
38 <arg><option>--version</option></arg>
39 <arg><option>--help</option></arg>
43 <refsect1><title>Description</title>
44 <para>udevd listens to kernel uevents. For every event, udevd executes matching
45 instructions specified in udev rules. See <citerefentry>
46 <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
47 </citerefentry>.</para>
48 <para>On startup the content of the directory <filename>/usr/lib/udev/devices</filename>
49 is copied to <filename>/dev</filename>. If kernel modules specify static device
50 nodes, these nodes are created even without a corresponding kernel device, to
51 allow on-demand loading of kernel modules. Matching permissions specified in udev
52 rules are applied to these static device nodes.</para>
53 <para>The behavior of the running daemon can be changed with
54 <command>udevadm control</command>.</para>
57 <refsect1><title>Options</title>
60 <term><option>--daemon</option></term>
62 <para>Detach and run in the background.</para>
66 <term><option>--debug</option></term>
68 <para>Print debug messages to stderr.</para>
72 <term><option>--children-max=</option></term>
74 <para>Limit the number of parallel executed events.</para>
78 <term><option>--exec-delay=</option></term>
80 <para>Number of seconds to delay the execution of RUN instructions.
81 This might be useful when debugging system crashes during coldplug
82 cause by loading non-working kernel modules.</para>
86 <term><option>--resolve-names=</option></term>
88 <para>Specify when udevd should resolve names of users and groups.
89 When set to <option>early</option> (the default) names will be
90 resolved when the rules are parsed. When set to
91 <option>late</option> names will be resolved for every event.
92 When set to <option>never</option> names will never be resolved
93 and all devices will be owned by root.</para>
97 <term><option>--version</option></term>
99 <para>Print version number.</para>
103 <term><option>--help</option></term>
105 <para>Print help text.</para>
111 <refsect1><title>Environment</title>
114 <term><varname>UDEV_LOG=</varname></term>
116 <para>Set the logging priority.</para>
122 <refsect1><title>Kernel command line</title>
125 <term><varname>udev.log-priority=</varname></term>
127 <para>Set the logging priority.</para>
131 <term><varname>udev.children-max=</varname></term>
133 <para>Limit the number of parallel executed events.</para>
137 <term><varname>udev.exec-delay=</varname></term>
139 <para>Number of seconds to delay the execution of RUN instructions.
140 This might be useful when debugging system crashes during coldplug
141 cause by loading non-working kernel modules.</para>
148 <title>See Also</title>
150 <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
151 </citerefentry>, <citerefentry>
152 <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
153 </citerefentry></para>