mirror of
https://github.com/systemd/systemd
synced 2024-07-21 18:24:38 +00:00
f7e81fd96f
With this we can stabilize how naming works for network interfaces. A user can request through a kernel cmdline option or an env var which scheme to follow. The idea is that installers use this to set into stone (a very soft stone though) the scheme used during installation so that interface naming doesn't change afterwards anymore. Why use env vars and kernel cmdline options, and not a config file of its own? Well, first of all there's no obvious existing one to use. But more importantly: I have the feeling that this logic is kind of an incomplete hack, and I simply don't want to do advertise this as a perfectly working solution. So far we used env vars for the non-so-official options and proper config files for the official stuff. Given how incomplete this logic is (i.e. the big variable for naming remains the kernel, which might expose sysfs attributes in newer versions that we check for and didn't exist in older versions — and other problems like this), I am simply not confident in giving this first-class exposure in a primary configuration file. Fixes: #10448
203 lines
8.1 KiB
XML
203 lines
8.1 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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-->
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<refentry id="systemd-udevd.service"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-udevd.service</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-udevd.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-udevd.service</refname>
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<refname>systemd-udevd-control.socket</refname>
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<refname>systemd-udevd-kernel.socket</refname>
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<refname>systemd-udevd</refname>
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<refpurpose>Device event managing daemon</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-udevd.service</filename></para>
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<para><filename>systemd-udevd-control.socket</filename></para>
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<para><filename>systemd-udevd-kernel.socket</filename></para>
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<cmdsynopsis>
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<command>/usr/lib/systemd/systemd-udevd</command>
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<arg><option>--daemon</option></arg>
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<arg><option>--debug</option></arg>
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<arg><option>--children-max=</option></arg>
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<arg><option>--exec-delay=</option></arg>
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<arg><option>--event-timeout=</option></arg>
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<arg><option>--resolve-names=early|late|never</option></arg>
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<arg><option>--version</option></arg>
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<arg><option>--help</option></arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1><title>Description</title>
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<para><command>systemd-udevd</command> listens to kernel uevents.
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For every event, systemd-udevd executes matching instructions
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specified in udev rules. See <citerefentry>
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<refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
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</citerefentry>.</para>
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<para>The behavior of the daemon can be configured using
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<citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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its command line options, environment variables, and on the kernel
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command line, or changed dynamically with <command>udevadm
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control</command>.
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</para>
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</refsect1>
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<refsect1><title>Options</title>
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<variablelist>
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<varlistentry>
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<term><option>-d</option></term>
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<term><option>--daemon</option></term>
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<listitem>
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<para>Detach and run in the background.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-D</option></term>
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<term><option>--debug</option></term>
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<listitem>
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<para>Print debug messages to standard error.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-c=</option></term>
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<term><option>--children-max=</option></term>
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<listitem>
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<para>Limit the number of events executed in parallel.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-e=</option></term>
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<term><option>--exec-delay=</option></term>
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<listitem>
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<para>Delay the execution of <varname>RUN</varname>
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instructions by the given number of seconds. This option
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might be useful when debugging system crashes during
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coldplug caused by loading non-working kernel
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modules.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-t=</option></term>
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<term><option>--event-timeout=</option></term>
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<listitem>
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<para>Set the number of seconds to wait for events to finish. After
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this time, the event will be terminated. The default is 180 seconds.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-N=</option></term>
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<term><option>--resolve-names=</option></term>
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<listitem>
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<para>Specify when systemd-udevd should resolve names of users and groups.
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When set to <option>early</option> (the default), names will be
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resolved when the rules are parsed. When set to
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<option>late</option>, names will be resolved for every event.
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When set to <option>never</option>, names will never be resolved
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and all devices will be owned by root.</para>
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</listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="help" />
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<xi:include href="standard-options.xml" xpointer="version" />
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</variablelist>
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</refsect1>
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<refsect1><title>Kernel command line</title>
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<variablelist class='kernel-commandline-options'>
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<para>Parameters starting with "rd." will be read when
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<command>systemd-udevd</command> is used in an initrd.</para>
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<varlistentry>
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<term><varname>udev.log_priority=</varname></term>
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<term><varname>rd.udev.log_priority=</varname></term>
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<listitem>
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<para>Set the log level.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>udev.children_max=</varname></term>
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<term><varname>rd.udev.children_max=</varname></term>
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<listitem>
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<para>Limit the number of events executed in parallel.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>udev.exec_delay=</varname></term>
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<term><varname>rd.udev.exec_delay=</varname></term>
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<listitem>
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<para>Delay the execution of <varname>RUN</varname> instructions by the given
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number of seconds. This option might be useful when
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debugging system crashes during coldplug caused by loading
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non-working kernel modules.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>udev.event_timeout=</varname></term>
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<term><varname>rd.udev.event_timeout=</varname></term>
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<listitem>
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<para>Wait for events to finish up to the given number
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of seconds. This option might be useful if events are
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terminated due to kernel drivers taking too long to initialize.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>net.ifnames=</varname></term>
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<listitem>
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<para>Network interfaces are renamed to give them predictable names
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when possible. It is enabled by default; specifying 0 disables it.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>net.naming-scheme=</varname></term>
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<listitem>
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<para>Network interfaces are renamed to give them predictable names when possible (unless
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<varname>net.ifnames=0</varname> is specified, see above). The names are derived from various device metadata
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fields. Newer versions of <filename>systemd-udevd.service</filename> take more of these fields into account,
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improving (and thus possibly changing) the names used for the same devices. With this kernel command line
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option it is possible to pick a specific version of this algorithm. It expects a naming scheme identifier as
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argument. Currently the following identifiers are known: <literal>v238</literal>, <literal>v239</literal>,
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<literal>v240</literal> which each implement the naming scheme that was the default in the indicated systemd
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version. Note that selecting a specific scheme is not sufficient to fully stabilize interface naming: the
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naming is generally derived from driver attributes exposed by the kernel. As the kernel is updated,
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previously missing attributes <filename>systemd-udevd.service</filename> is checking might appear, which
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affects older name derivation algorithms, too.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<!-- when adding entries here, consider also adding them
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in kernel-command-line.xml -->
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>udev.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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