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514094f9 | 1 | <?xml version='1.0'?> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
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3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [ |
4 | <!ENTITY % entities SYSTEM "custom-entities.ent" > | |
5 | %entities; | |
6 | ]> | |
db9ecf05 | 7 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
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8 | |
9 | <refentry id="systemd.syntax"> | |
10 | ||
11 | <refentryinfo> | |
12 | <title>systemd.syntax</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>systemd.syntax</refentrytitle> | |
18 | <manvolnum>7</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>systemd.syntax</refname> | |
23 | <refpurpose>General syntax of systemd configuration files</refpurpose> | |
24 | </refnamediv> | |
25 | ||
26 | <refsect1> | |
27 | <title>Introduction</title> | |
28 | ||
29 | <para>This page describes the basic principles of configuration files used by | |
30 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
31 | and related programs for: | |
32 | <itemizedlist> | |
33 | <listitem><para>systemd unit files, see | |
34 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
35 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
36 | <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
37 | <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
38 | <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
39 | <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
40 | <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
41 | <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
42 | <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
43 | <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
44 | <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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45 | <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
46 | <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
47 | </para></listitem> | |
0f943ae4 | 48 | |
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49 | <listitem><para>link files, see |
50 | <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
51 | </para></listitem> | |
52 | ||
53 | <listitem><para>netdev and network files, see | |
54 | <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
55 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
56 | </para></listitem> | |
57 | ||
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58 | <listitem><para>daemon config files, see |
59 | <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
60 | <citerefentry><refentrytitle>systemd-user.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
61 | <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
62 | <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
63 | <citerefentry><refentrytitle>journal-remote.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
64 | <citerefentry><refentrytitle>journal-upload.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
65 | <citerefentry><refentrytitle>systemd-sleep.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
66 | <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
67 | </para></listitem> | |
68 | </itemizedlist> | |
69 | </para> | |
70 | ||
71 | <para>The syntax is inspired by | |
41d6f3bf | 72 | <ulink url="https://standards.freedesktop.org/desktop-entry-spec/latest/">XDG Desktop Entry Specification</ulink> |
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73 | <filename>.desktop</filename> files, which are in turn inspired by Microsoft Windows |
74 | <filename>.ini</filename> files. | |
75 | </para> | |
76 | ||
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77 | <para>Each file is a plain text file divided into sections, with configuration entries in the style |
78 | <replaceable>key</replaceable>=<replaceable>value</replaceable>. Whitespace immediately before or after | |
79 | the <literal>=</literal> is ignored. Empty lines and lines starting with <literal>#</literal> or | |
80 | <literal>;</literal> are ignored, which may be used for commenting.</para> | |
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81 | |
82 | <para>Lines ending in a backslash are concatenated with the following line while reading and the | |
83 | backslash is replaced by a space character. This may be used to wrap long lines. The limit on | |
84 | line length is very large (currently 1 MB), but it is recommended to avoid such long lines and | |
85 | use multiple directives, variable substitution, or other mechanism as appropriate for the given | |
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86 | file type. When a comment line or lines follow a line ending with a backslash, the comment block |
87 | is ignored, so the continued line is concatenated with whatever follows the comment block.</para> | |
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88 | |
89 | <example><programlisting>[Section A] | |
90 | KeyOne=value 1 | |
91 | KeyTwo=value 2 | |
92 | ||
93 | # a comment | |
94 | ||
95 | [Section B] | |
96 | Setting="something" "some thing" "…" | |
97 | KeyTwo=value 2 \ | |
98 | value 2 continued | |
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99 | |
100 | [Section C] | |
e9dd6984 | 101 | KeyThree=value 3\ |
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102 | # this line is ignored |
103 | ; this line is ignored too | |
e9dd6984 | 104 | value 3 continued |
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105 | </programlisting></example> |
106 | ||
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107 | <para>Boolean arguments used in configuration files can be written in |
108 | various formats. For positive settings the strings | |
109 | <option>1</option>, <option>yes</option>, <option>true</option> | |
110 | and <option>on</option> are equivalent. For negative settings, the | |
111 | strings <option>0</option>, <option>no</option>, | |
112 | <option>false</option> and <option>off</option> are | |
113 | equivalent.</para> | |
114 | ||
115 | <para>Time span values encoded in configuration files can be written in various formats. A stand-alone | |
116 | number specifies a time in seconds. If suffixed with a time unit, the unit is honored. A | |
117 | concatenation of multiple values with units is supported, in which case the values are added | |
118 | up. Example: <literal>50</literal> refers to 50 seconds; <literal>2min 200ms</literal> refers to | |
119 | 2 minutes and 200 milliseconds, i.e. 120200 ms. The following time units are understood: | |
120 | <literal>s</literal>, <literal>min</literal>, <literal>h</literal>, <literal>d</literal>, | |
121 | <literal>w</literal>, <literal>ms</literal>, <literal>us</literal>. For details see | |
122 | <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> | |
123 | ||
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124 | <para>Various settings are allowed to be specified more than once, in which case the |
125 | interpretation depends on the setting. Often, multiple settings form a list, and setting to an | |
126 | empty value "resets", which means that previous assignments are ignored. When this is allowed, | |
127 | it is mentioned in the description of the setting. Note that using multiple assignments to the | |
128 | same value makes the file incompatible with parsers for the XDG <filename>.desktop</filename> | |
129 | file format.</para> | |
130 | </refsect1> | |
131 | ||
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132 | <refsect1> |
133 | <title>Quoting</title> | |
134 | ||
135 | <para>For settings where quoting is allowed, the following general rules apply: double quotes ("…") and | |
136 | single quotes ('…') may be used to wrap a whole item (the opening quote may appear only at the beginning | |
137 | or after whitespace that is not quoted, and the closing quote must be followed by whitespace or the end | |
138 | of line), in which case everything until the next matching quote becomes part of the same item. Quotes | |
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139 | themselves are removed. C-style escapes are supported. The table below contains the list of known escape |
140 | patterns. Only escape patterns which match the syntax in the table are allowed; other patterns may be | |
141 | added in the future and unknown patterns will result in a warning. In particular, any backslashes should | |
142 | be doubled. Finally, a trailing backslash (<literal>\</literal>) may be used to merge lines, as described | |
143 | above. UTF-8 is accepted, and hence typical unicode characters do not need to be escaped.</para> | |
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144 | |
145 | <table> | |
1447d87a | 146 | <title>Supported escapes</title> |
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147 | <tgroup cols='2'> |
148 | <colspec colname='escape' /> | |
149 | <colspec colname='meaning' /> | |
150 | <thead> | |
151 | <row> | |
152 | <entry>Literal</entry> | |
153 | <entry>Actual value</entry> | |
154 | </row> | |
155 | </thead> | |
156 | <tbody> | |
157 | <row> | |
158 | <entry><literal>\a</literal></entry> | |
159 | <entry>bell</entry> | |
160 | </row> | |
161 | <row> | |
162 | <entry><literal>\b</literal></entry> | |
163 | <entry>backspace</entry> | |
164 | </row> | |
165 | <row> | |
166 | <entry><literal>\f</literal></entry> | |
167 | <entry>form feed</entry> | |
168 | </row> | |
169 | <row> | |
170 | <entry><literal>\n</literal></entry> | |
171 | <entry>newline</entry> | |
172 | </row> | |
173 | <row> | |
174 | <entry><literal>\r</literal></entry> | |
175 | <entry>carriage return</entry> | |
176 | </row> | |
177 | <row> | |
178 | <entry><literal>\t</literal></entry> | |
179 | <entry>tab</entry> | |
180 | </row> | |
181 | <row> | |
182 | <entry><literal>\v</literal></entry> | |
183 | <entry>vertical tab</entry> | |
184 | </row> | |
185 | <row> | |
186 | <entry><literal>\\</literal></entry> | |
187 | <entry>backslash</entry> | |
188 | </row> | |
189 | <row> | |
190 | <entry><literal>\"</literal></entry> | |
191 | <entry>double quotation mark</entry> | |
192 | </row> | |
193 | <row> | |
194 | <entry><literal>\'</literal></entry> | |
195 | <entry>single quotation mark</entry> | |
196 | </row> | |
197 | <row> | |
198 | <entry><literal>\s</literal></entry> | |
199 | <entry>space</entry> | |
200 | </row> | |
201 | <row> | |
202 | <entry><literal>\x<replaceable>xx</replaceable></literal></entry> | |
203 | <entry>character number <replaceable>xx</replaceable> in hexadecimal encoding</entry> | |
204 | </row> | |
205 | <row> | |
206 | <entry><literal>\<replaceable>nnn</replaceable></literal></entry> | |
207 | <entry>character number <replaceable>nnn</replaceable> in octal encoding</entry> | |
208 | </row> | |
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209 | <row> |
210 | <entry><literal>\u<replaceable>nnnn</replaceable></literal></entry> | |
211 | <entry>unicode code point <replaceable>nnnn</replaceable> in hexadecimal encoding</entry> | |
212 | </row> | |
213 | <row> | |
214 | <entry><literal>\U<replaceable>nnnnnnnn</replaceable></literal></entry> | |
215 | <entry>unicode code point <replaceable>nnnnnnnn</replaceable> in hexadecimal encoding</entry> | |
216 | </row> | |
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217 | </tbody> |
218 | </tgroup> | |
219 | </table> | |
220 | </refsect1> | |
221 | ||
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222 | <refsect1> |
223 | <title>See Also</title> | |
224 | <para> | |
225 | <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
226 | </para> | |
227 | </refsect1> | |
228 | ||
0f943ae4 | 229 | </refentry> |