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1 | <?xml version="1.0"?> | |
2 | <!--*-nxml-*--> | |
3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | <!-- | |
5 | SPDX-License-Identifier: LGPL-2.1+ | |
6 | ||
7 | This file is part of systemd. | |
8 | ||
9 | Copyright 2011 Lennart Poettering | |
10 | --> | |
11 | <refentry id="systemd.preset"> | |
12 | ||
13 | <refentryinfo> | |
14 | <title>systemd.preset</title> | |
15 | <productname>systemd</productname> | |
16 | ||
17 | <authorgroup> | |
18 | <author> | |
19 | <contrib>Developer</contrib> | |
20 | <firstname>Lennart</firstname> | |
21 | <surname>Poettering</surname> | |
22 | <email>lennart@poettering.net</email> | |
23 | </author> | |
24 | </authorgroup> | |
25 | </refentryinfo> | |
26 | ||
27 | <refmeta> | |
28 | <refentrytitle>systemd.preset</refentrytitle> | |
29 | <manvolnum>5</manvolnum> | |
30 | </refmeta> | |
31 | ||
32 | <refnamediv> | |
33 | <refname>systemd.preset</refname> | |
34 | <refpurpose>Service enablement presets</refpurpose> | |
35 | </refnamediv> | |
36 | ||
37 | <refsynopsisdiv> | |
38 | <para><filename>/etc/systemd/system-preset/*.preset</filename></para> | |
39 | <para><filename>/run/systemd/system-preset/*.preset</filename></para> | |
40 | <para><filename>/usr/lib/systemd/system-preset/*.preset</filename></para> | |
41 | <para><filename>/etc/systemd/user-preset/*.preset</filename></para> | |
42 | <para><filename>/run/systemd/user-preset/*.preset</filename></para> | |
43 | <para><filename>/usr/lib/systemd/user-preset/*.preset</filename></para> | |
44 | </refsynopsisdiv> | |
45 | ||
46 | <refsect1> | |
47 | <title>Description</title> | |
48 | ||
49 | <para>Preset files may be used to encode policy which units shall | |
50 | be enabled by default and which ones shall be disabled. They are | |
51 | read by <command>systemctl preset</command> (for more information | |
52 | see | |
53 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>) | |
54 | which uses this information to enable or disable a unit according | |
55 | to preset policy. <command>systemctl preset</command> is used by | |
56 | the post install scriptlets of RPM packages (or other OS package | |
57 | formats), to enable/disable specific units by default on package | |
58 | installation, enforcing distribution, spin or administrator preset | |
59 | policy. This allows choosing a certain set of units to be | |
60 | enabled/disabled even before installing the actual package.</para> | |
61 | ||
62 | <para>For more information on the preset logic please have a look | |
63 | at the <ulink | |
64 | url="https://www.freedesktop.org/wiki/Software/systemd/Preset">Presets</ulink> | |
65 | document.</para> | |
66 | ||
67 | <para>It is not recommended to ship preset files within the | |
68 | respective software packages implementing the units, but rather | |
69 | centralize them in a distribution or spin default policy, which | |
70 | can be amended by administrator policy.</para> | |
71 | ||
72 | <para>If no preset files exist, <command>systemctl | |
73 | preset</command> will enable all units that are installed by | |
74 | default. If this is not desired and all units shall rather be | |
75 | disabled, it is necessary to ship a preset file with a single, | |
76 | catchall "<filename>disable *</filename>" line. (See example 1, | |
77 | below.)</para> | |
78 | </refsect1> | |
79 | ||
80 | <refsect1> | |
81 | <title>Preset File Format</title> | |
82 | ||
83 | <para>The preset files contain a list of directives consisting of | |
84 | either the word <literal>enable</literal> or | |
85 | <literal>disable</literal> followed by a space and a unit name | |
86 | (possibly with shell style wildcards), separated by newlines. | |
87 | Empty lines and lines whose first non-whitespace character is # or | |
88 | ; are ignored.</para> | |
89 | ||
90 | <para>Presets must refer to the "real" unit file, and not to any aliases. See | |
91 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
92 | for a description of unit aliasing.</para> | |
93 | ||
94 | <para>Two different directives are understood: | |
95 | <literal>enable</literal> may be used to enable units by default, | |
96 | <literal>disable</literal> to disable units by default.</para> | |
97 | ||
98 | <para>If multiple lines apply to a unit name, the first matching | |
99 | one takes precedence over all others.</para> | |
100 | ||
101 | <para>Each preset file shall be named in the style of | |
102 | <filename><priority>-<policy-name>.preset</filename>. Files | |
103 | in <filename>/etc/</filename> override files with the same name in | |
104 | <filename>/usr/lib/</filename> and <filename>/run/</filename>. | |
105 | Files in <filename>/run/</filename> override files with the same | |
106 | name in <filename>/usr/lib/</filename>. Packages should install | |
107 | their preset files in <filename>/usr/lib/</filename>. Files in | |
108 | <filename>/etc/</filename> are reserved for the local | |
109 | administrator, who may use this logic to override the preset files | |
110 | installed by vendor packages. All preset files are sorted by their | |
111 | filename in lexicographic order, regardless of which of the | |
112 | directories they reside in. If multiple files specify the same | |
113 | unit name, the entry in the file with the lexicographically | |
114 | earliest name will be applied. It is recommended to prefix all | |
115 | filenames with a two-digit number and a dash, to simplify the | |
116 | ordering of the files.</para> | |
117 | ||
118 | <para>If the administrator wants to disable a preset file supplied | |
119 | by the vendor, the recommended way is to place a symlink to | |
120 | <filename>/dev/null</filename> in | |
121 | <filename>/etc/systemd/system-preset/</filename> bearing the same | |
122 | filename.</para> | |
123 | </refsect1> | |
124 | ||
125 | <refsect1> | |
126 | <title>Examples</title> | |
127 | ||
128 | <example> | |
129 | <title>Default to off</title> | |
130 | ||
131 | <programlisting># /usr/lib/systemd/system-preset/99-default.preset | |
132 | ||
133 | disable *</programlisting> | |
134 | </example> | |
135 | ||
136 | <para>This disables all units. Due to the filename prefix | |
137 | <literal>99-</literal>, it will be read last and hence can easily | |
138 | be overridden by spin or administrator preset policy.</para> | |
139 | ||
140 | <example> | |
141 | <title>A GNOME spin</title> | |
142 | ||
143 | <programlisting># /usr/lib/systemd/system-preset/50-gnome.preset | |
144 | ||
145 | enable gdm.service | |
146 | enable colord.service | |
147 | enable accounts-daemon.service | |
148 | enable avahi-daemon.*</programlisting> | |
149 | ||
150 | </example> | |
151 | ||
152 | <para>This enables the three mentioned units, plus all | |
153 | <filename>avahi-daemon</filename> regardless of which unit type. A | |
154 | file like this could be useful for inclusion in a GNOME spin of a | |
155 | distribution. It will ensure that the units necessary for GNOME | |
156 | are properly enabled as they are installed. It leaves all other | |
157 | units untouched, and subject to other (later) preset files, for | |
158 | example like the one from the first example above.</para> | |
159 | ||
160 | <example> | |
161 | <title>Administrator policy</title> | |
162 | ||
163 | <programlisting># /etc/systemd/system-preset/00-lennart.preset | |
164 | ||
165 | enable httpd.service | |
166 | enable sshd.service | |
167 | enable postfix.service | |
168 | disable *</programlisting> | |
169 | </example> | |
170 | ||
171 | <para>This enables three specific services and disables all | |
172 | others. This is useful for administrators to specifically select | |
173 | the units to enable, and disable all others. Due to the filename | |
174 | prefix <literal>00-</literal> it will be read early and | |
175 | override all other preset policy files.</para> | |
176 | </refsect1> | |
177 | ||
178 | <refsect1> | |
179 | <title>See Also</title> | |
180 | <para> | |
181 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
182 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
183 | <citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
184 | </para> | |
185 | </refsect1> | |
186 | ||
187 | </refentry> |