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240 lines
10 KiB
XML
240 lines
10 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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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>-s</option></term>
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<term><option>--timeout-signal=</option></term>
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<listitem>
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<para>Set the signal which <filename>systemd-udevd</filename> will send to
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forked off processes after reaching event timeout. The setting can be overridden
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at boot time with the kernel command line option
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<varname>udev.timeout_signal=</varname>. Setting to <constant>SIGABRT</constant>
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may be helpful in order to debug worker timeouts. Defaults to
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<constant>SIGKILL</constant>. Note that setting the option on the command line
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overrides the setting from the configuration file.
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</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 prefixed with "rd." will be read when <command>systemd-udevd</command> is used in an
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initrd, those without will be processed both in the initrd and on the host.</para>
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<varlistentry>
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<term><varname>udev.log_level=</varname></term>
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<term><varname>rd.udev.log_level=</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>udev.timeout_signal=</varname></term>
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<term><varname>rd.udev.timeout_signal=</varname></term>
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<listitem>
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<para>Specifies a signal that <filename>systemd-udevd</filename> will send to
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workers on timeout. Note that kernel command line option overrides both the
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setting in the configuration file and the one on the program command line.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>udev.blockdev_read_only</varname></term>
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<term><varname>rd.udev.blockdev_read_only</varname></term>
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<listitem>
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<para>If specified, mark all physical block devices read-only as they appear. Synthetic block
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devices (such as loopback block devices or device mapper devices) are left as they are. This is
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useful to guarantee that the contents of physical block devices remains unmodified during runtime,
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for example to implement fully stateless systems, for testing or for recovery situations where
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corrupted file systems shall not be corrupted further through accidental modification.</para>
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<para>A block device may be marked writable again by issuing the <command>blockdev
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--setrw</command> command, see <citerefentry
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project='man-pages'><refentrytitle>blockdev</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for details.</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). With this kernel command line option it
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is possible to pick a specific version of this algorithm and override the default chosen at
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compilation time. Expects one of the naming scheme identifiers listed in
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<citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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or <literal>latest</literal> to select the latest scheme known (to this particular version of
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<filename>systemd-udevd.service</filename>).</para>
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<para>Note that selecting a specific scheme is not sufficient to fully stabilize interface naming:
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the naming is generally derived from driver attributes exposed by the kernel. As the kernel is
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updated, previously missing attributes <filename>systemd-udevd.service</filename> is checking might
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appear, which 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 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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