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190 lines
7.6 KiB
XML
190 lines
7.6 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 units shall
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be enabled by default and which ones shall be disabled. They are
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read by <command>systemctl preset</command> (for more information
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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 unit according
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to preset policy. <command>systemctl preset</command> is used by
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the post install scriptlets of RPM packages (or other OS package
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formats), to enable/disable specific units by default on package
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installation, enforcing distribution, spin or administrator preset
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policy. This allows choosing a certain set of units to be
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enabled/disabled even before installing the actual package.</para>
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<para>For more information on the preset logic please have a look
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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 within the
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respective software packages implementing the units, but rather
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centralize them in a distribution or spin default policy, which
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can be 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 installed by
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default. If this is not desired and all units shall rather be
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disabled, it is necessary to ship a preset file with a single,
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catchall "<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 directives consisting of
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either the word <literal>enable</literal> or
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<literal>disable</literal> followed by a space and a unit name
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(possibly with shell style wildcards), separated by newlines.
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Empty lines and lines whose first non-whitespace character is # or
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; are 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 by default,
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<literal>disable</literal> to disable units by default.</para>
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<para>If multiple lines apply to a unit name, the first matching
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one takes precedence over all others.</para>
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<para>Each preset file shall be named in the style of
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<filename><priority>-<policy-name>.preset</filename>. Files
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in <filename>/etc/</filename> override files with the same name in
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<filename>/usr/lib/</filename> and <filename>/run/</filename>.
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Files in <filename>/run/</filename> override files with the same
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name in <filename>/usr/lib/</filename>. Packages should install
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their preset files in <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 preset files
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installed by vendor packages. All preset files are sorted by their
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filename in lexicographic order, regardless of which of the
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directories they reside in. If multiple files specify the same
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unit name, the entry in the file with the lexicographically
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earliest name will be applied. It is recommended to prefix all
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filenames with a two-digit number and a dash, to simplify the
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ordering of the files.</para>
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<para>If the administrator wants to disable a preset file supplied
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by the vendor, the recommended way is to place a symlink to
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<filename>/dev/null</filename> in
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<filename>/etc/systemd/system-preset/</filename> bearing the same
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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 prefix
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<literal>99-</literal>, it will be read last and hence can easily
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be overridden by spin or administrator preset policy or
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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 unit type. A
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file like this could be useful for inclusion in a GNOME spin of a
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distribution. It will ensure that the units necessary for GNOME
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are properly enabled as they are installed. It leaves all other
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units untouched, and subject to other (later) preset files, for
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example like the one from the first example 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 disables all
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others. This is useful for administrators to specifically select
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the units to enable, and disable all others. Due to the filename
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prefix <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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