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Use proper grammar, word usage, adjective hyphenation, commas, capitalization, spelling, etc. To improve readability, some run-on sentences or sentence fragments were revised. [zj: remove the space from 'file name', 'host name', and 'time zone'.]
205 lines
9.4 KiB
XML
205 lines
9.4 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2011 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd.preset">
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<refentryinfo>
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<title>systemd.preset</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd.preset</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.preset</refname>
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<refpurpose>Service enablement presets</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/etc/systemd/system-preset/*.preset</filename></para>
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<para><filename>/run/systemd/system-preset/*.preset</filename></para>
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<para><filename>/usr/lib/systemd/system-preset/*.preset</filename></para>
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<para><filename>/etc/systemd/user-preset/*.preset</filename></para>
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<para><filename>/run/systemd/user-preset/*.preset</filename></para>
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<para><filename>/usr/lib/systemd/user-preset/*.preset</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>Preset files may be used to encode policy which
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units shall be enabled by default and which ones
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shall be disabled. They are read by <command>systemctl
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preset</command> (for more information see
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>)
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which uses this information to enable or disable a
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unit according to preset policy. <command>systemctl
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preset</command> is used by the post install
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scriptlets of RPM packages (or other OS package formats),
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to enable/disable specific units by default on package
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installation, enforcing distribution, spin or
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administrator preset policy. This allows choosing a certain
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set of units to be enabled/disabled even before
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installing the actual package.</para>
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<para>For more information on the preset logic please
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have a look at the <ulink
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url="http://freedesktop.org/wiki/Software/systemd/Preset">Presets</ulink>
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document.</para>
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<para>It is not recommended to ship preset files
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within the respective software packages implementing
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the units, but rather centralize them in a
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distribution or spin default policy, which can be
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amended by administrator policy.</para>
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<para>If no preset files exist, <command>systemctl
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preset</command> will enable all units that are
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installed by default. If this is not desired and all
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units shall rather be disabled it is necessary to ship
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a preset file with a single, catchall
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"<filename>disable *</filename>" line. (See example 1,
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below.)</para>
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</refsect1>
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<refsect1>
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<title>Preset File Format</title>
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<para>The preset files contain a list of
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directives consisting of either the word
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<literal>enable</literal> or
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<literal>disable</literal> followed by a space and a
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unit name (possibly with shell style wildcards),
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separated by newlines. Empty lines and lines whose
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first non-whitespace character is # or ; are
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ignored.</para>
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<para>Two different directives are understood:
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<literal>enable</literal> may be used to enable units
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by default, <literal>disable</literal> to disable
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units by default.</para>
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<para>If multiple lines apply to a unit name, the
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first matching one takes precedence over all
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others.</para>
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<para>Each preset file shall be named in the style of
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<filename><priority>-<program>.conf</filename>.
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Files in <filename>/etc/</filename> override files
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with the same name in <filename>/usr/lib/</filename>
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and <filename>/run/</filename>. Files in
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<filename>/run/</filename> override files with the
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same name in <filename>/usr/lib/</filename>. Packages
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should install their preset files in
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<filename>/usr/lib/</filename>. Files in
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<filename>/etc/</filename> are reserved for the local
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administrator, who may use this logic to override the
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preset files installed by vendor packages. All preset
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files are sorted by their filename in alphabetical
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order, regardless in which of the directories they
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reside, to guarantee that a specific preset file takes
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precedence over another file with an alphabetically
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earlier name, if both files contain lines that apply
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to the same unit names. It is recommended to prefix
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all filenames with two-digit number, to simplify
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ordering.</para>
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<para>If the administrator wants to disable a preset
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file supplied by the vendor, the recommended way is to
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place a symlink to <filename>/dev/null</filename> in
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<filename>/etc/systemd/system-preset/</filename>
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bearing the same filename.</para>
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</refsect1>
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<refsect1>
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<title>Example</title>
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<example>
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<title>Default off example <filename>/usr/lib/systemd/system-preset/99-default.preset</filename>:</title>
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<programlisting>disable *</programlisting>
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</example>
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<para>This disables all units. Due to the filename
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prefix <literal>99-</literal>, it will be read last and
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hence can easily be overridden by spin or
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administrator preset policy or suchlike.</para>
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<example>
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<title>A GNOME spin example <filename>/usr/lib/systemd/system-preset/50-gnome.preset</filename>:</title>
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<programlisting>enable gdm.service
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enable colord.service
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enable accounts-daemon.service
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enable avahi-daemon.*</programlisting>
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</example>
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<para>This enables the three mentioned units, plus all
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<filename>avahi-daemon</filename> regardless of which
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unit type. A file like this could be useful for
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inclusion in a GNOME spin of a distribution. It will
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ensure that the units necessary for GNOME are properly
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enabled as they are installed. It leaves all other
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units untouched, and subject to other (later) preset
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files, for example like the one from the first example
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above.</para>
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<example>
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<title>Administrator policy <filename>/etc/systemd/system-preset/00-lennart.preset</filename>:</title>
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<programlisting>enable httpd.service
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enable sshd.service
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enable postfix.service
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disable *</programlisting>
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</example>
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<para>This enables three specific services and
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disables all others. This is useful for administrators
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to specifically select the units to enable, and
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disable all others. Due to the filename prefix
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<literal>00-</literal> it will be read early and hence
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overrides all other preset policy files.</para>
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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>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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