1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
|
<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="systemd-udevd.service"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-udevd.service</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-udevd.service</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-udevd.service</refname>
<refname>systemd-udevd-control.socket</refname>
<refname>systemd-udevd-kernel.socket</refname>
<refname>systemd-udevd</refname>
<refpurpose>Device event managing daemon</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>systemd-udevd.service</filename></para>
<para><filename>systemd-udevd-control.socket</filename></para>
<para><filename>systemd-udevd-kernel.socket</filename></para>
<cmdsynopsis>
<command>/usr/lib/systemd/systemd-udevd</command>
<arg><option>--daemon</option></arg>
<arg><option>--debug</option></arg>
<arg><option>--children-max=</option></arg>
<arg><option>--exec-delay=</option></arg>
<arg><option>--event-timeout=</option></arg>
<arg><option>--resolve-names=early|late|never</option></arg>
<arg><option>--version</option></arg>
<arg><option>--help</option></arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1><title>Description</title>
<para><command>systemd-udevd</command> listens to kernel uevents.
For every event, systemd-udevd executes matching instructions
specified in udev rules. See <citerefentry>
<refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
</citerefentry>.</para>
<para>The behavior of the daemon can be configured using
<citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
its command line options, environment variables, and on the kernel
command line, or changed dynamically with <command>udevadm
control</command>.
</para>
</refsect1>
<refsect1><title>Options</title>
<variablelist>
<varlistentry>
<term><option>-d</option></term>
<term><option>--daemon</option></term>
<listitem>
<para>Detach and run in the background.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-D</option></term>
<term><option>--debug</option></term>
<listitem>
<para>Print debug messages to standard error.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-c</option></term>
<term><option>--children-max=</option></term>
<listitem>
<para>Limit the number of events executed in parallel.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-e</option></term>
<term><option>--exec-delay=</option></term>
<listitem>
<para>Delay the execution of each <varname>RUN{<replaceable>program</replaceable>}</varname>
parameter by the given number of seconds. This option
might be useful when debugging system crashes during
coldplug caused by loading non-working kernel
modules.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-t</option></term>
<term><option>--event-timeout=</option></term>
<listitem>
<para>Set the number of seconds to wait for events to finish. After
this time, the event will be terminated. The default is 180 seconds.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s</option></term>
<term><option>--timeout-signal=</option></term>
<listitem>
<para>Set the signal which <filename>systemd-udevd</filename> will send to
forked off processes after reaching event timeout. The setting can be overridden
at boot time with the kernel command line option
<varname>udev.timeout_signal=</varname>. Setting to <constant>SIGABRT</constant>
may be helpful in order to debug worker timeouts. Defaults to
<constant>SIGKILL</constant>. Note that setting the option on the command line
overrides the setting from the configuration file.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-N</option></term>
<term><option>--resolve-names=</option></term>
<listitem>
<para>Specify when systemd-udevd should resolve names of users and groups.
When set to <option>early</option> (the default), names will be
resolved when the rules are parsed. When set to
<option>late</option>, names will be resolved for every event.
When set to <option>never</option>, names will never be resolved
and all devices will be owned by root.</para>
</listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
</refsect1>
<refsect1><title>Kernel command line</title>
<variablelist class='kernel-commandline-options'>
<para>Parameters prefixed with "rd." will be read when <command>systemd-udevd</command> is used in an
initrd, those without will be processed both in the initrd and on the host.</para>
<varlistentry>
<term><varname>udev.log_level=</varname></term>
<term><varname>rd.udev.log_level=</varname></term>
<listitem>
<para>Set the log level.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>udev.children_max=</varname></term>
<term><varname>rd.udev.children_max=</varname></term>
<listitem>
<para>Limit the number of events executed in parallel.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>udev.exec_delay=</varname></term>
<term><varname>rd.udev.exec_delay=</varname></term>
<listitem>
<para>Delay the execution of each <varname>RUN{<replaceable>program</replaceable>}</varname> parameter by the given
number of seconds. This option might be useful when
debugging system crashes during coldplug caused by loading
non-working kernel modules.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>udev.event_timeout=</varname></term>
<term><varname>rd.udev.event_timeout=</varname></term>
<listitem>
<para>Wait for events to finish up to the given number
of seconds. This option might be useful if events are
terminated due to kernel drivers taking too long to initialize.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>udev.timeout_signal=</varname></term>
<term><varname>rd.udev.timeout_signal=</varname></term>
<listitem>
<para>Specifies a signal that <filename>systemd-udevd</filename> will send to
workers on timeout. Note that kernel command line option overrides both the
setting in the configuration file and the one on the program command line.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>udev.blockdev_read_only</varname></term>
<term><varname>rd.udev.blockdev_read_only</varname></term>
<listitem>
<para>If specified, mark all physical block devices read-only as they appear. Synthetic block
devices (such as loopback block devices or device mapper devices) are left as they are. This is
useful to guarantee that the contents of physical block devices remains unmodified during runtime,
for example to implement fully stateless systems, for testing or for recovery situations where
corrupted file systems shall not be corrupted further through accidental modification.</para>
<para>A block device may be marked writable again by issuing the <command>blockdev
--setrw</command> command, see <citerefentry
project='man-pages'><refentrytitle>blockdev</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for details.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>net.ifnames=</varname></term>
<listitem>
<para>Network interfaces are renamed to give them predictable names
when possible. It is enabled by default; specifying 0 disables it.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>net.naming-scheme=</varname></term>
<listitem>
<para>Network interfaces are renamed to give them predictable names when possible (unless
<varname>net.ifnames=0</varname> is specified, see above). With this kernel command line option it
is possible to pick a specific version of this algorithm and override the default chosen at
compilation time. Expects one of the naming scheme identifiers listed in
<citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
or <literal>latest</literal> to select the latest scheme known (to this particular version of
<filename>systemd-udevd.service</filename>).</para>
<para>Note that selecting a specific scheme is not sufficient to fully stabilize interface naming:
the naming is generally derived from driver attributes exposed by the kernel. As the kernel is
updated, previously missing attributes <filename>systemd-udevd.service</filename> is checking might
appear, which affects older name derivation algorithms, too.</para>
</listitem>
</varlistentry>
</variablelist>
<!-- when adding entries here, consider also adding them in kernel-command-line.xml -->
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
|
