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SYSTEMD.SYNTAX(7) systemd.syntax SYSTEMD.SYNTAX(7)
systemd.syntax - General syntax of systemd configuration files
This page describes the basic principles of configuration files
used by systemd(1) and related programs for:
• systemd unit files, see systemd.unit(5), systemd.service(5),
systemd.socket(5), systemd.device(5), systemd.mount(5),
systemd.automount(5), systemd.swap(5), systemd.target(5),
systemd.path(5), systemd.timer(5), systemd.slice(5),
systemd.scope(5)
• link files, see systemd.link(5)
• netdev and network files, see systemd.netdev(5),
systemd.network(5)
• daemon config files, see systemd-system.conf(5),
systemd-user.conf(5), logind.conf(5), journald.conf(5),
journal-remote.conf(5), journal-upload.conf(5),
systemd-sleep.conf(5), timesyncd.conf(5)
• nspawn files, see systemd.nspawn(5)
The syntax is inspired by XDG Desktop Entry Specification[1]
.desktop files, which are in turn inspired by Microsoft Windows
.ini files.
Each file is a plain text file divided into sections, with
configuration entries in the style key=value. Whitespace
immediately before or after the "=" is ignored. Empty lines and
lines starting with "#" or ";" are ignored, which may be used for
commenting.
Lines ending in a backslash are concatenated with the following
line while reading and the backslash is replaced by a space
character. This may be used to wrap long lines. The limit on line
length is very large (currently 1 MB), but it is recommended to
avoid such long lines and use multiple directives, variable
substitution, or other mechanism as appropriate for the given
file type. When a comment line or lines follow a line ending with
a backslash, the comment block is ignored, so the continued line
is concatenated with whatever follows the comment block.
[Section A]
KeyOne=value 1
KeyTwo=value 2
# a comment
[Section B]
Setting="something" "some thing" "..."
KeyTwo=value 2 \
value 2 continued
[Section C]
KeyThree=value 3\
# this line is ignored
; this line is ignored too
value 3 continued
Boolean arguments used in configuration files can be written in
various formats. For positive settings the strings 1, yes, true
and on are equivalent. For negative settings, the strings 0, no,
false and off are equivalent.
Time span values encoded in configuration files can be written in
various formats. A stand-alone number specifies a time in
seconds. If suffixed with a time unit, the unit is honored. A
concatenation of multiple values with units is supported, in
which case the values are added up. Example: "50" refers to 50
seconds; "2min 200ms" refers to 2 minutes and 200 milliseconds,
i.e. 120200 ms. The following time units are understood: "s",
"min", "h", "d", "w", "ms", "us". For details see
systemd.time(7).
Various settings are allowed to be specified more than once, in
which case the interpretation depends on the setting. Often,
multiple settings form a list, and setting to an empty value
"resets", which means that previous assignments are ignored. When
this is allowed, it is mentioned in the description of the
setting. Note that using multiple assignments to the same value
makes the file incompatible with parsers for the XDG .desktop
file format.
For settings where quoting is allowed, the following general
rules apply: double quotes ("...") and single quotes ('...') may
be used to wrap a whole item (the opening quote may appear only
at the beginning or after whitespace that is not quoted, and the
closing quote must be followed by whitespace or the end of line),
in which case everything until the next matching quote becomes
part of the same item. Quotes themselves are removed. C-style
escapes are supported. The table below contains the list of known
escape patterns. Only escape patterns which match the syntax in
the table are allowed; other patterns may be added in the future
and unknown patterns will result in a warning. In particular, any
backslashes should be doubled. Finally, a trailing backslash
("\") may be used to merge lines, as described above. UTF-8 is
accepted, and hence typical unicode characters do not need to be
escaped.
Table 1. Supported escapes
┌──────────────┬─────────────────────────┐
│ Literal │ Actual value │
├──────────────┼─────────────────────────┤
│ "\a" │ bell │
├──────────────┼─────────────────────────┤
│ "\b" │ backspace │
├──────────────┼─────────────────────────┤
│ "\f" │ form feed │
├──────────────┼─────────────────────────┤
│ "\n" │ newline │
├──────────────┼─────────────────────────┤
│ "\r" │ carriage return │
├──────────────┼─────────────────────────┤
│ "\t" │ tab │
├──────────────┼─────────────────────────┤
│ "\v" │ vertical tab │
├──────────────┼─────────────────────────┤
│ "\\" │ backslash │
├──────────────┼─────────────────────────┤
│ "\"" │ double quotation mark │
├──────────────┼─────────────────────────┤
│ "\'" │ single quotation mark │
├──────────────┼─────────────────────────┤
│ "\s" │ space │
├──────────────┼─────────────────────────┤
│ "\xxx" │ character number xx in │
│ │ hexadecimal encoding │
├──────────────┼─────────────────────────┤
│ "\nnn" │ character number nnn in │
│ │ octal encoding │
├──────────────┼─────────────────────────┤
│ "\unnnn" │ unicode code point nnnn │
│ │ in hexadecimal encoding │
├──────────────┼─────────────────────────┤
│ "\Unnnnnnnn" │ unicode code point │
│ │ nnnnnnnn in hexadecimal │
│ │ encoding │
└──────────────┴─────────────────────────┘
systemd.time(7)
1. XDG Desktop Entry Specification
https://standards.freedesktop.org/desktop-entry-spec/latest/
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel SYSTEMD.SYNTAX(7)
Pages that refer to this page: journald.conf(5), journal-remote.conf(5), journal-upload.conf(5), logind.conf(5), oomd.conf(5), systemd.exec(5), systemd.link(5), systemd.netdev(5), systemd.network(5), systemd.nspawn(5), systemd.service(5), systemd-sleep.conf(5), systemd-system.conf(5), systemd.unit(5), timesyncd.conf(5), systemd.index(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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