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1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
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3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
4 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
0307f791 | 5 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
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6 | <refentry id="systemd.preset"> |
7 | ||
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8 | <refentryinfo> |
9 | <title>systemd.preset</title> | |
10 | <productname>systemd</productname> | |
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11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>systemd.preset</refentrytitle> | |
15 | <manvolnum>5</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>systemd.preset</refname> | |
20 | <refpurpose>Service enablement presets</refpurpose> | |
21 | </refnamediv> | |
22 | ||
23 | <refsynopsisdiv> | |
12b42c76 | 24 | <para><filename>/etc/systemd/system-preset/*.preset</filename></para> |
798d3a52 | 25 | <para><filename>/run/systemd/system-preset/*.preset</filename></para> |
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26 | <para><filename>/usr/lib/systemd/system-preset/*.preset</filename></para> |
27 | <para><filename>/etc/systemd/user-preset/*.preset</filename></para> | |
798d3a52 | 28 | <para><filename>/run/systemd/user-preset/*.preset</filename></para> |
12b42c76 | 29 | <para><filename>/usr/lib/systemd/user-preset/*.preset</filename></para> |
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30 | </refsynopsisdiv> |
31 | ||
32 | <refsect1> | |
33 | <title>Description</title> | |
34 | ||
35 | <para>Preset files may be used to encode policy which units shall | |
36 | be enabled by default and which ones shall be disabled. They are | |
37 | read by <command>systemctl preset</command> (for more information | |
38 | see | |
39 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>) | |
40 | which uses this information to enable or disable a unit according | |
41 | to preset policy. <command>systemctl preset</command> is used by | |
42 | the post install scriptlets of RPM packages (or other OS package | |
43 | formats), to enable/disable specific units by default on package | |
44 | installation, enforcing distribution, spin or administrator preset | |
45 | policy. This allows choosing a certain set of units to be | |
46 | enabled/disabled even before installing the actual package.</para> | |
47 | ||
48 | <para>For more information on the preset logic please have a look | |
49 | at the <ulink | |
28a0ad81 | 50 | url="https://www.freedesktop.org/wiki/Software/systemd/Preset">Presets</ulink> |
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51 | document.</para> |
52 | ||
53 | <para>It is not recommended to ship preset files within the | |
54 | respective software packages implementing the units, but rather | |
55 | centralize them in a distribution or spin default policy, which | |
56 | can be amended by administrator policy.</para> | |
57 | ||
58 | <para>If no preset files exist, <command>systemctl | |
59 | preset</command> will enable all units that are installed by | |
60 | default. If this is not desired and all units shall rather be | |
61 | disabled, it is necessary to ship a preset file with a single, | |
62 | catchall "<filename>disable *</filename>" line. (See example 1, | |
63 | below.)</para> | |
64 | </refsect1> | |
65 | ||
66 | <refsect1> | |
67 | <title>Preset File Format</title> | |
68 | ||
69 | <para>The preset files contain a list of directives consisting of | |
70 | either the word <literal>enable</literal> or | |
71 | <literal>disable</literal> followed by a space and a unit name | |
72 | (possibly with shell style wildcards), separated by newlines. | |
73 | Empty lines and lines whose first non-whitespace character is # or | |
74 | ; are ignored.</para> | |
75 | ||
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76 | <para>Presets must refer to the "real" unit file, and not to any aliases. See |
77 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
78 | for a description of unit aliasing.</para> | |
79 | ||
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80 | <para>Two different directives are understood: |
81 | <literal>enable</literal> may be used to enable units by default, | |
82 | <literal>disable</literal> to disable units by default.</para> | |
83 | ||
84 | <para>If multiple lines apply to a unit name, the first matching | |
85 | one takes precedence over all others.</para> | |
86 | ||
87 | <para>Each preset file shall be named in the style of | |
9e0d90f9 | 88 | <filename><priority>-<policy-name>.preset</filename>. Files |
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89 | in <filename>/etc/</filename> override files with the same name in |
90 | <filename>/usr/lib/</filename> and <filename>/run/</filename>. | |
91 | Files in <filename>/run/</filename> override files with the same | |
92 | name in <filename>/usr/lib/</filename>. Packages should install | |
93 | their preset files in <filename>/usr/lib/</filename>. Files in | |
94 | <filename>/etc/</filename> are reserved for the local | |
95 | administrator, who may use this logic to override the preset files | |
96 | installed by vendor packages. All preset files are sorted by their | |
97 | filename in lexicographic order, regardless of which of the | |
98 | directories they reside in. If multiple files specify the same | |
99 | unit name, the entry in the file with the lexicographically | |
100 | earliest name will be applied. It is recommended to prefix all | |
101 | filenames with a two-digit number and a dash, to simplify the | |
102 | ordering of the files.</para> | |
103 | ||
104 | <para>If the administrator wants to disable a preset file supplied | |
105 | by the vendor, the recommended way is to place a symlink to | |
106 | <filename>/dev/null</filename> in | |
12b42c76 | 107 | <filename>/etc/systemd/system-preset/</filename> bearing the same |
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108 | filename.</para> |
109 | </refsect1> | |
110 | ||
111 | <refsect1> | |
1655cdee | 112 | <title>Examples</title> |
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113 | |
114 | <example> | |
1655cdee | 115 | <title>Default to off</title> |
798d3a52 | 116 | |
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117 | <programlisting># /usr/lib/systemd/system-preset/99-default.preset |
118 | ||
119 | disable *</programlisting> | |
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120 | </example> |
121 | ||
122 | <para>This disables all units. Due to the filename prefix | |
123 | <literal>99-</literal>, it will be read last and hence can easily | |
1655cdee | 124 | be overridden by spin or administrator preset policy.</para> |
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125 | |
126 | <example> | |
1655cdee | 127 | <title>A GNOME spin</title> |
798d3a52 | 128 | |
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129 | <programlisting># /usr/lib/systemd/system-preset/50-gnome.preset |
130 | ||
131 | enable gdm.service | |
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132 | enable colord.service |
133 | enable accounts-daemon.service | |
134 | enable avahi-daemon.*</programlisting> | |
135 | ||
798d3a52 | 136 | </example> |
75d67e68 | 137 | |
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138 | <para>This enables the three mentioned units, plus all |
139 | <filename>avahi-daemon</filename> regardless of which unit type. A | |
140 | file like this could be useful for inclusion in a GNOME spin of a | |
141 | distribution. It will ensure that the units necessary for GNOME | |
142 | are properly enabled as they are installed. It leaves all other | |
143 | units untouched, and subject to other (later) preset files, for | |
144 | example like the one from the first example above.</para> | |
75d67e68 | 145 | |
798d3a52 | 146 | <example> |
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147 | <title>Administrator policy</title> |
148 | ||
149 | <programlisting># /etc/systemd/system-preset/00-lennart.preset | |
75d67e68 | 150 | |
1655cdee | 151 | enable httpd.service |
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152 | enable sshd.service |
153 | enable postfix.service | |
154 | disable *</programlisting> | |
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155 | </example> |
156 | ||
157 | <para>This enables three specific services and disables all | |
158 | others. This is useful for administrators to specifically select | |
159 | the units to enable, and disable all others. Due to the filename | |
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160 | prefix <literal>00-</literal> it will be read early and |
161 | override all other preset policy files.</para> | |
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162 | </refsect1> |
163 | ||
164 | <refsect1> | |
165 | <title>See Also</title> | |
166 | <para> | |
167 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
168 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
169 | <citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
170 | </para> | |
171 | </refsect1> | |
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172 | |
173 | </refentry> |