NAME
	
systemd.syntax - General syntax of systemd configuration files



INTRODUCTION
	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.

Example 1.

   [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.



QUOTING
	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           │
└─────────────┴────────────────────────────────┘



SEE ALSO
systemd.time(7)

NOTES

XDG Desktop Entry Specification
   https://standards.freedesktop.org/desktop-entry-spec/latest/