1SYSTEMD.SYNTAX(7)               systemd.syntax               SYSTEMD.SYNTAX(7)
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NAME

6       systemd.syntax - General syntax of systemd configuration files
7

INTRODUCTION

9       This page describes the basic principles of configuration files used by
10       systemd(1) and related programs for:
11
12       •   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), systemd.nspawn(5)
17
18       •   link files, see systemd.link(5)
19
20       •   netdev and network files, see systemd.netdev(5), systemd.network(5)
21
22       •   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
27       The syntax is inspired by XDG Desktop Entry Specification[1] .desktop
28       files, which are in turn inspired by Microsoft Windows .ini files.
29
30       Each file is a plain text file divided into sections, with
31       configuration entries in the style key=value. Whitespace immediately
32       before or after the "=" is ignored. Empty lines and lines starting with
33       "#" or ";" are ignored, which may be used for commenting.
34
35       Lines ending in a backslash are concatenated with the following line
36       while reading and the backslash is replaced by a space character. This
37       may be used to wrap long lines. The limit on line length is very large
38       (currently 1 MB), but it is recommended to avoid such long lines and
39       use multiple directives, variable substitution, or other mechanism as
40       appropriate for the given file type. When a comment line or lines
41       follow a line ending with a backslash, the comment block is ignored, so
42       the continued line is concatenated with whatever follows the comment
43       block.
44
45       Example 1.
46
47           [Section A]
48           KeyOne=value 1
49           KeyTwo=value 2
50
51           # a comment
52
53           [Section B]
54           Setting="something" "some thing" "..."
55           KeyTwo=value 2 \
56                  value 2 continued
57
58           [Section C]
59           KeyThree=value 3\
60           # this line is ignored
61           ; this line is ignored too
62                  value 3 continued
63
64       Boolean arguments used in configuration files can be written in various
65       formats. For positive settings the strings 1, yes, true and on are
66       equivalent. For negative settings, the strings 0, no, false and off are
67       equivalent.
68
69       Time span values encoded in configuration files can be written in
70       various formats. A stand-alone number specifies a time in seconds. If
71       suffixed with a time unit, the unit is honored. A concatenation of
72       multiple values with units is supported, in which case the values are
73       added up. Example: "50" refers to 50 seconds; "2min 200ms" refers to 2
74       minutes and 200 milliseconds, i.e. 120200 ms. The following time units
75       are understood: "s", "min", "h", "d", "w", "ms", "us". For details see
76       systemd.time(7).
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78       Various settings are allowed to be specified more than once, in which
79       case the interpretation depends on the setting. Often, multiple
80       settings form a list, and setting to an empty value "resets", which
81       means that previous assignments are ignored. When this is allowed, it
82       is mentioned in the description of the setting. Note that using
83       multiple assignments to the same value makes the file incompatible with
84       parsers for the XDG .desktop file format.
85

QUOTING

87       For settings where quoting is allowed, the following general rules
88       apply: double quotes ("...") and single quotes ('...') may be used to
89       wrap a whole item (the opening quote may appear only at the beginning
90       or after whitespace that is not quoted, and the closing quote must be
91       followed by whitespace or the end of line), in which case everything
92       until the next matching quote becomes part of the same item. Quotes
93       themselves are removed. C-style escapes are supported. The table below
94       contains the list of known escape patterns. Only escape patterns which
95       match the syntax in the table are allowed; other patterns may be added
96       in the future and unknown patterns will result in a warning. In
97       particular, any backslashes should be doubled. Finally, a trailing
98       backslash ("\") may be used to merge lines, as described above. UTF-8
99       is accepted, and hence typical unicode characters do not need to be
100       escaped.
101
102       Table 1. Supported escapes
103       ┌─────────────┬────────────────────────────┐
104Literal      Actual value               
105       ├─────────────┼────────────────────────────┤
106       │"\a"         │ bell                       │
107       ├─────────────┼────────────────────────────┤
108       │"\b"         │ backspace                  │
109       ├─────────────┼────────────────────────────┤
110       │"\f"         │ form feed                  │
111       ├─────────────┼────────────────────────────┤
112       │"\n"         │ newline                    │
113       ├─────────────┼────────────────────────────┤
114       │"\r"         │ carriage return            │
115       ├─────────────┼────────────────────────────┤
116       │"\t"         │ tab                        │
117       ├─────────────┼────────────────────────────┤
118       │"\v"         │ vertical tab               │
119       ├─────────────┼────────────────────────────┤
120       │"\\"         │ backslash                  │
121       ├─────────────┼────────────────────────────┤
122       │"\""         │ double quotation mark      │
123       ├─────────────┼────────────────────────────┤
124       │"\'"         │ single quotation mark      │
125       ├─────────────┼────────────────────────────┤
126       │"\s"         │ space                      │
127       ├─────────────┼────────────────────────────┤
128       │"\xxx"       │ character number xx in     │
129       │             │ hexadecimal encoding       │
130       ├─────────────┼────────────────────────────┤
131       │"\nnn"       │ character number nnn in    │
132       │             │ octal encoding             │
133       ├─────────────┼────────────────────────────┤
134       │"\unnnn"     │ unicode code point nnnn in │
135       │             │ hexadecimal encoding       │
136       ├─────────────┼────────────────────────────┤
137       │"\Unnnnnnnn" │ unicode code point         │
138       │             │ nnnnnnnn in hexadecimal    │
139       │             │ encoding                   │
140       └─────────────┴────────────────────────────┘
141

SEE ALSO

143       systemd.time(7)
144

NOTES

146        1. XDG Desktop Entry Specification
147           http://standards.freedesktop.org/desktop-entry-spec/latest/
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151systemd 250                                                  SYSTEMD.SYNTAX(7)
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