Commit 75d67e68 authored by Lennart Poettering's avatar Lennart Poettering
Browse files

man: document preset files

parent ff5d32c8
......@@ -500,7 +500,8 @@ MANPAGES = \
man/systemd-tty-ask-password-agent.1 \
man/systemd-getty-generator.8 \
man/systemd-system-update-generator.8 \
man/systemd-fstab-generator.8
man/systemd-fstab-generator.8 \
man/systemd.preset.5
MANPAGES_ALIAS = \
man/reboot.8 \
......
......@@ -814,12 +814,15 @@
<listitem><para>Reset one or more unit
files, as specified on the command
line, to the defaults configured in a
preset file. This has the same effect
as <command>disable</command> or
line, to the defaults configured in
the preset policy files. This has the
same effect as
<command>disable</command> or
<command>enable</command>, depending
how the unit is listed in the preset
files.</para>
files. For more information on preset
policy see
<citerefentry><refentrytitle>systemd.preset</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
......@@ -1230,7 +1233,8 @@
<citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>
<citerefentry><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.preset</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
......
<?xml version="1.0"?>
<!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2011 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
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-->
<refentry id="systemd.preset">
<refentryinfo>
<title>systemd.preset</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.preset</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.preset</refname>
<refpurpose>Service enablement presets</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>/etc/systemd/system-preset/*.preset</filename></para>
<para><filename>/run/systemd/system-preset/*.preset</filename></para>
<para><filename>/usr/lib/systemd/system-preset/*.preset</filename></para>
<para><filename>/etc/systemd/user-preset/*.preset</filename></para>
<para><filename>/run/systemd/user-preset/*.preset</filename></para>
<para><filename>/usr/lib/systemd/user-preset/*.preset</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>Preset files may be used to encode policy which
services shall be enabled by default and which ones
shall be disabled. They are read by <command>systemctl
preset</command> (for more information see
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>)
which uses this information to enable or disable a
unit according to preset policy. <command>systemctl
preset</command> is used by the post install
scriptlets of RPM packages (or other OS package formats),
to enable/disable specific units by default on package
installation, enforcing distribution, spin or
administrator preset policy. This allows choosing a certain
set of units to be enabled/disabled even before
installing the actual package.</para>
<para>It is not recommended to ship preset files
within the respective software packages implementing
the services, but rather centralize them in a
distribution or spin default policy, which can be
amended by administrator policy.</para>
<para>If no preset files exist, <command>systemctl
preset</command> will enable all units that are
installed by default. If this is not desired and all
units shall rather be disabled it is necessary to ship
a preset file with a single, catchall
"<filename>disable *</filename>" line. (See example 1,
below.)</para>
</refsect1>
<refsect1>
<title>Preset File Format</title>
<para>The preset files contain a list of
directives consisting of either the word
<literal>enable</literal> or
<literal>disable</literal> followed by a space and a
unit name (possibly with shell style wildcards),
separated by newlines. Empty lines and lines whose
first non-whitespace character is # or ; are
ignored.</para>
<para>Two different directives are understood:
<literal>enable</literal> may be used to enable units
by default, <literal>disable</literal> to disable
units by default.</para>
<para>If multiple lines apply to a unit name the
first matching one takes precedence over all
others.</para>
<para>Each preset file shall be named in the style of
<filename>&lt;priority&gt;-&lt;program&gt;.conf</filename>.
Files in <filename>/etc/</filename> override files
with the same name in <filename>/usr/lib/</filename>
and <filename>/run/</filename>. Files in
<filename>/run/</filename> override files with the
same name in <filename>/usr/lib/</filename>. Packages
should install their preset files in
<filename>/usr/lib/</filename>. Files in
<filename>/etc/</filename> are reserved for the local
administrator, who may use this logic to override the
preset files installed by vendor packages. All preset
files are sorted by their filename in alphabetical
order, regardless in which of the directories they
reside, to guarantee that a specific preset file takes
precedence over another file with an alphabetically
earlier name, if both files contain lines that apply
to the same unit names. It is recommended to prefix
all file names with two-digit number, to simplify
ordering.</para>
<para>If the administrator wants to disable a preset
file supplied by the vendor the recommended way is to
place a symlink to <filename>/dev/null</filename> in
<filename>/etc/systemd/system-preset/</filename>
bearing the same file name.</para>
</refsect1>
<refsect1>
<title>Example</title>
<example>
<title>Default off example <filename>/usr/lib/systemd/system-preset/99-default.preset</filename>:</title>
<programlisting>disable *</programlisting>
</example>
<para>This disables all units. Due to the file name
prefix <literal>99-</literal> it will be read last and
hence can easily be overridden by spin or
administrator preset policy or suchlike.</para>
<example>
<title>A GNOME spin example <filename>/usr/lib/systemd/system-preset/50-gnome.preset</filename>:</title>
<programlisting>enable gdm.service
enable colord.service
enable accounts-daemon.service
enable avahi-daemon.*</programlisting>
</example>
<para>This enables the three mentioned units, plus all
<filename>avahi-daemon</filename> regardless of which
unit type. A file like this could be useful for
inclusion in a GNOME spin of a distribution. It will
ensure that the units necessary for GNOME are properly
enabled as they are installed. It leaves all other
units untouched, and subject to other (later) preset
files, for example like the one from the first example
above.</para>
<example>
<title>Administrator policy <filename>/etc/systemd/system-preset/00-lennart.preset</filename>:</title>
<programlisting>enable httpd.service
enable sshd.service
enable postfix.service
disable *</programlisting>
</example>
<para>This enables three specific services and
disables all others. This is useful for administrators
to specifically select the units to enable, and
disable all others. Due to the file name prefix
<literal>00-</literal> it will be read early and hence
overrides all other preset policy files.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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