systemd.syntax(7) — Linux manual page

NAME | INTRODUCTION | QUOTING | SEE ALSO | NOTES | COLOPHON

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

NAME         top

       systemd.syntax - General syntax of systemd configuration files

INTRODUCTION         top

       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), systemd.nspawn(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)

       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         top

       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         top

       systemd.time(7)

NOTES         top

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

COLOPHON         top

       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 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-27.)  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
       man-pages@man7.org

systemd 249                                            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)