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diff --git a/man/systemd.syntax.xml b/man/systemd.syntax.xml new file mode 100644 index 0000000..1441b2b --- /dev/null +++ b/man/systemd.syntax.xml @@ -0,0 +1,229 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [ +<!ENTITY % entities SYSTEM "custom-entities.ent" > +%entities; +]> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<refentry id="systemd.syntax"> + + <refentryinfo> + <title>systemd.syntax</title> + <productname>systemd</productname> + </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>, + <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry> + </para></listitem> + + <listitem><para>link files, see + <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry> + </para></listitem> + + <listitem><para>netdev and network files, see + <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.network</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="https://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>. Whitespace immediately before or after + the <literal>=</literal> is ignored. 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. 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.</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 + +[Section C] +KeyThree=value 3\ +# this line is ignored +; this line is ignored too + value 3 continued +</programlisting></example> + + <para>Boolean arguments used in configuration files can be written in + various formats. For positive settings the strings + <option>1</option>, <option>yes</option>, <option>true</option> + and <option>on</option> are equivalent. For negative settings, the + strings <option>0</option>, <option>no</option>, + <option>false</option> and <option>off</option> are + equivalent.</para> + + <para>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: <literal>50</literal> refers to 50 seconds; <literal>2min 200ms</literal> refers to + 2 minutes and 200 milliseconds, i.e. 120200 ms. The following time units are understood: + <literal>s</literal>, <literal>min</literal>, <literal>h</literal>, <literal>d</literal>, + <literal>w</literal>, <literal>ms</literal>, <literal>us</literal>. For details see + <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> + + <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> + + <refsect1> + <title>Quoting</title> + + <para>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 (<literal>\</literal>) may be used to merge lines, as described + above. UTF-8 is accepted, and hence typical unicode characters do not need to be escaped.</para> + + <table> + <title>Supported escapes</title> + <tgroup cols='2'> + <colspec colname='escape' /> + <colspec colname='meaning' /> + <thead> + <row> + <entry>Literal</entry> + <entry>Actual value</entry> + </row> + </thead> + <tbody> + <row> + <entry><literal>\a</literal></entry> + <entry>bell</entry> + </row> + <row> + <entry><literal>\b</literal></entry> + <entry>backspace</entry> + </row> + <row> + <entry><literal>\f</literal></entry> + <entry>form feed</entry> + </row> + <row> + <entry><literal>\n</literal></entry> + <entry>newline</entry> + </row> + <row> + <entry><literal>\r</literal></entry> + <entry>carriage return</entry> + </row> + <row> + <entry><literal>\t</literal></entry> + <entry>tab</entry> + </row> + <row> + <entry><literal>\v</literal></entry> + <entry>vertical tab</entry> + </row> + <row> + <entry><literal>\\</literal></entry> + <entry>backslash</entry> + </row> + <row> + <entry><literal>\"</literal></entry> + <entry>double quotation mark</entry> + </row> + <row> + <entry><literal>\'</literal></entry> + <entry>single quotation mark</entry> + </row> + <row> + <entry><literal>\s</literal></entry> + <entry>space</entry> + </row> + <row> + <entry><literal>\x<replaceable>xx</replaceable></literal></entry> + <entry>character number <replaceable>xx</replaceable> in hexadecimal encoding</entry> + </row> + <row> + <entry><literal>\<replaceable>nnn</replaceable></literal></entry> + <entry>character number <replaceable>nnn</replaceable> in octal encoding</entry> + </row> + <row> + <entry><literal>\u<replaceable>nnnn</replaceable></literal></entry> + <entry>unicode code point <replaceable>nnnn</replaceable> in hexadecimal encoding</entry> + </row> + <row> + <entry><literal>\U<replaceable>nnnnnnnn</replaceable></literal></entry> + <entry>unicode code point <replaceable>nnnnnnnn</replaceable> in hexadecimal encoding</entry> + </row> + </tbody> + </tgroup> + </table> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |