man/systemd.syntax.xml

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  10 <refentry id="systemd.syntax">
  11
  12   <refentryinfo>
  13     <title>systemd.syntax</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>systemd.syntax</refentrytitle>
  19     <manvolnum>7</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>systemd.syntax</refname>
  24     <refpurpose>General syntax of systemd configuration files</refpurpose>
  25   </refnamediv>
  26
  27   <refsect1>
  28     <title>Introduction</title>
  29
  30     <para>This page describes the basic principles of configuration files used by
  31     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  32     and related programs for:
  33     <itemizedlist>
  34       <listitem><para>systemd unit files, see
  35       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  36       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  37       <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  38       <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  39       <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  40       <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  41       <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  42       <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  43       <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  44       <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  45       <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  46       <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry></para></listitem>
  47
  48       <listitem><para>daemon config files, see
  49       <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  50       <citerefentry><refentrytitle>systemd-user.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  51       <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  52       <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  53       <citerefentry><refentrytitle>journal-remote.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  54       <citerefentry><refentrytitle>journal-upload.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  55       <citerefentry><refentrytitle>systemd-sleep.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  56       <citerefentry><refentrytitle>timesyncd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  57       </para></listitem>
  58     </itemizedlist>
  59     </para>
  60
  61     <para>The syntax is inspired by
  62     <ulink url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG Desktop Entry Specification</ulink>
  63     <filename>.desktop</filename> files, which are in turn inspired by Microsoft Windows
  64     <filename>.ini</filename> files.
  65     </para>
  66
  67     <para>Each file is a plain text file divided into sections, with configuration entries in the
  68     style <replaceable>key</replaceable>=<replaceable>value</replaceable>.
  69     Empty lines and lines starting with <literal>#</literal> or <literal>;</literal> are
  70     ignored, which may be used for commenting.</para>
  71
  72     <para>Lines ending in a backslash are concatenated with the following line while reading and the
  73     backslash is replaced by a space character. This may be used to wrap long lines. The limit on
  74     line length is very large (currently 1 MB), but it is recommended to avoid such long lines and
  75     use multiple directives, variable substitution, or other mechanism as appropriate for the given
  76     file type.</para>
  77
  78     <example><programlisting>[Section A]
  79 KeyOne=value 1
  80 KeyTwo=value 2
  81
  82 # a comment
  83
  84 [Section B]
  85 Setting="something" "some thing" "…"
  86 KeyTwo=value 2 \
  87        value 2 continued
  88 </programlisting></example>
  89
  90     <para>Various settings are allowed to be specified more than once, in which case the
  91     interpretation depends on the setting. Often, multiple settings form a list, and setting to an
  92     empty value "resets", which means that previous assignments are ignored. When this is allowed,
  93     it is mentioned in the description of the setting. Note that using multiple assignments to the
  94     same value makes the file incompatible with parsers for the XDG <filename>.desktop</filename>
  95     file format.</para>
  96   </refsect1>
  97
  98 </refentry>