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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd.syntax">
<refentryinfo>
<title>systemd.syntax</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>A. U. Thor</contrib>
<firstname>Zbigniew</firstname>
<surname>Jędrzejewski-Szmek</surname>
<email>zbyszek@in.waw.pl</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.syntax</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.syntax</refname>
<refpurpose>General syntax of systemd configuration files</refpurpose>
</refnamediv>
<refsect1>
<title>Introduction</title>
<para>This page describes the basic principles of configuration files used by
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and related programs for:
<itemizedlist>
<listitem><para>systemd unit files, see
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry></para></listitem>
<listitem><para>daemon config files, see
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-user.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>journal-remote.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>journal-upload.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-sleep.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para></listitem>
</itemizedlist>
</para>
<para>The syntax is inspired by
<ulink url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG Desktop Entry Specification</ulink>
<filename>.desktop</filename> files, which are in turn inspired by Microsoft Windows
<filename>.ini</filename> files.
</para>
<para>Each file is a plain text file divided into sections, with configuration entries in the
style <replaceable>key</replaceable>=<replaceable>value</replaceable>.
Empty lines and lines starting with <literal>#</literal> or <literal>;</literal> are
ignored, which may be used for commenting.</para>
<para>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.</para>
<example><programlisting>[Section A]
KeyOne=value 1
KeyTwo=value 2
# a comment
[Section B]
Setting="something" "some thing" "…"
KeyTwo=value 2 \
value 2 continued
</programlisting></example>
<para>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 <filename>.desktop</filename>
file format.</para>
</refsect1>
</refentry>
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