1SYSTEMD.SYNTAX(7) systemd.syntax SYSTEMD.SYNTAX(7)
2
6 systemd.syntax - General syntax of systemd configuration files
7
9 This page describes the basic principles of configuration files used by
10 systemd(1) and related programs for:
11 • systemd unit files, see systemd.unit(5), systemd.service(5),
13 systemd.socket(5), systemd.device(5), systemd.mount(5),
14 systemd.automount(5), systemd.swap(5), systemd.target(5),
15 systemd.path(5), systemd.timer(5), systemd.slice(5),
16 systemd.scope(5)
17 • link files, see systemd.link(5)
19 • netdev and network files, see systemd.netdev(5), systemd.network(5)
21 • daemon config files, see systemd-system.conf(5), systemd-
23 user.conf(5), logind.conf(5), journald.conf(5), journal-
24 remote.conf(5), journal-upload.conf(5), systemd-sleep.conf(5),
25 timesyncd.conf(5)
26 • nspawn files, see systemd.nspawn(5)
28 The syntax is inspired by XDG Desktop Entry Specification[1] .desktop
30 files, which are in turn inspired by Microsoft Windows .ini files.
31 Each file is a plain text file divided into sections, with
33 configuration entries in the style key=value. Whitespace immediately
34 before or after the "=" is ignored. Empty lines and lines starting with
35 "#" or ";" are ignored, which may be used for commenting.
36 Lines ending in a backslash are concatenated with the following line
38 while reading and the backslash is replaced by a space character. This
39 may be used to wrap long lines. The limit on line length is very large
40 (currently 1 MB), but it is recommended to avoid such long lines and
41 use multiple directives, variable substitution, or other mechanism as
42 appropriate for the given file type. When a comment line or lines
43 follow a line ending with a backslash, the comment block is ignored, so
44 the continued line is concatenated with whatever follows the comment
45 block.
46 Example 1.
48 [Section A]
50 KeyOne=value 1
51 KeyTwo=value 2
52 # a comment
54 [Section B]
56 Setting="something" "some thing" "..."
57 KeyTwo=value 2 \
58 value 2 continued
59 [Section C]
61 KeyThree=value 3\
62 # this line is ignored
63 ; this line is ignored too
64 value 3 continued
65 Boolean arguments used in configuration files can be written in various
67 formats. For positive settings the strings 1, yes, true and on are
68 equivalent. For negative settings, the strings 0, no, false and off are
69 equivalent.
70 Time span values encoded in configuration files can be written in
72 various formats. A stand-alone number specifies a time in seconds. If
73 suffixed with a time unit, the unit is honored. A concatenation of
74 multiple values with units is supported, in which case the values are
75 added up. Example: "50" refers to 50 seconds; "2min 200ms" refers to 2
76 minutes and 200 milliseconds, i.e. 120200 ms. The following time units
77 are understood: "s", "min", "h", "d", "w", "ms", "us". For details see
78 systemd.time(7).
79 Various settings are allowed to be specified more than once, in which
81 case the interpretation depends on the setting. Often, multiple
82 settings form a list, and setting to an empty value "resets", which
83 means that previous assignments are ignored. When this is allowed, it
84 is mentioned in the description of the setting. Note that using
85 multiple assignments to the same value makes the file incompatible with
86 parsers for the XDG .desktop file format.
87
89 For settings where quoting is allowed, the following general rules
90 apply: double quotes ("...") and single quotes ('...') may be used to
91 wrap a whole item (the opening quote may appear only at the beginning
92 or after whitespace that is not quoted, and the closing quote must be
93 followed by whitespace or the end of line), in which case everything
94 until the next matching quote becomes part of the same item. Quotes
95 themselves are removed. C-style escapes are supported. The table below
96 contains the list of known escape patterns. Only escape patterns which
97 match the syntax in the table are allowed; other patterns may be added
98 in the future and unknown patterns will result in a warning. In
99 particular, any backslashes should be doubled. Finally, a trailing
100 backslash ("\") may be used to merge lines, as described above. UTF-8
101 is accepted, and hence typical unicode characters do not need to be
102 escaped.
103 Table 1. Supported escapes
105 ┌─────────────┬────────────────────────────┐
106 │Literal │ Actual value │
107 ├─────────────┼────────────────────────────┤
108 │"\a" │ bell │
109 ├─────────────┼────────────────────────────┤
110 │"\b" │ backspace │
111 ├─────────────┼────────────────────────────┤
112 │"\f" │ form feed │
113 ├─────────────┼────────────────────────────┤
114 │"\n" │ newline │
115 ├─────────────┼────────────────────────────┤
116 │"\r" │ carriage return │
117 ├─────────────┼────────────────────────────┤
118 │"\t" │ tab │
119 ├─────────────┼────────────────────────────┤
120 │"\v" │ vertical tab │
121 ├─────────────┼────────────────────────────┤
122 │"\\" │ backslash │
123 ├─────────────┼────────────────────────────┤
124 │"\"" │ double quotation mark │
125 ├─────────────┼────────────────────────────┤
126 │"\'" │ single quotation mark │
127 ├─────────────┼────────────────────────────┤
128 │"\s" │ space │
129 ├─────────────┼────────────────────────────┤
130 │"\xxx" │ character number xx in │
131 │ │ hexadecimal encoding │
132 ├─────────────┼────────────────────────────┤
133 │"\nnn" │ character number nnn in │
134 │ │ octal encoding │
135 ├─────────────┼────────────────────────────┤
136 │"\unnnn" │ unicode code point nnnn in │
137 │ │ hexadecimal encoding │
138 ├─────────────┼────────────────────────────┤
139 │"\Unnnnnnnn" │ unicode code point │
140 │ │ nnnnnnnn in hexadecimal │
141 │ │ encoding │
142 └─────────────┴────────────────────────────┘
143
145 systemd.time(7)
146
148 1. XDG Desktop Entry Specification
149 https://standards.freedesktop.org/desktop-entry-spec/latest/
150systemd 253 SYSTEMD.SYNTAX(7)