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diff --git a/src/grp-system/systemd/systemd.unit.xml b/src/grp-system/systemd/systemd.unit.xml new file mode 100644 index 0000000000..40c4cfd854 --- /dev/null +++ b/src/grp-system/systemd/systemd.unit.xml @@ -0,0 +1,1493 @@ +<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [ +<!ENTITY % entities SYSTEM "custom-entities.ent" > +%entities; +]> + +<!-- + This file is part of systemd. + + Copyright 2010 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +--> + +<refentry id="systemd.unit"> + + <refentryinfo> + <title>systemd.unit</title> + <productname>systemd</productname> + + <authorgroup> + <author> + <contrib>Developer</contrib> + <firstname>Lennart</firstname> + <surname>Poettering</surname> + <email>lennart@poettering.net</email> + </author> + </authorgroup> + </refentryinfo> + + <refmeta> + <refentrytitle>systemd.unit</refentrytitle> + <manvolnum>5</manvolnum> + </refmeta> + + <refnamediv> + <refname>systemd.unit</refname> + <refpurpose>Unit configuration</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <para><filename><replaceable>service</replaceable>.service</filename>, + <filename><replaceable>socket</replaceable>.socket</filename>, + <filename><replaceable>device</replaceable>.device</filename>, + <filename><replaceable>mount</replaceable>.mount</filename>, + <filename><replaceable>automount</replaceable>.automount</filename>, + <filename><replaceable>swap</replaceable>.swap</filename>, + <filename><replaceable>target</replaceable>.target</filename>, + <filename><replaceable>path</replaceable>.path</filename>, + <filename><replaceable>timer</replaceable>.timer</filename>, + <filename><replaceable>slice</replaceable>.slice</filename>, + <filename><replaceable>scope</replaceable>.scope</filename></para> + + <para><literallayout><filename>/etc/systemd/system/*</filename> +<filename>/run/systemd/system/*</filename> +<filename>/usr/lib/systemd/system/*</filename> +<filename>…</filename> + </literallayout></para> + + <para><literallayout><filename>~/.config/systemd/user/*</filename> +<filename>/etc/systemd/user/*</filename> +<filename>$XDG_RUNTIME_DIR/systemd/user/*</filename> +<filename>/run/systemd/user/*</filename> +<filename>~/.local/share/systemd/user/*</filename> +<filename>/usr/lib/systemd/user/*</filename> +<filename>…</filename> + </literallayout></para> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para>A unit configuration file encodes information about a + service, a socket, a device, a mount point, an automount point, a + swap file or partition, a start-up target, a watched file system + path, a timer controlled and supervised by + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + a resource management slice or + a group of externally created processes. 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>This man page lists the common configuration options of all + the unit types. These options need to be configured in the [Unit] + or [Install] sections of the unit files.</para> + + <para>In addition to the generic [Unit] and [Install] sections + described here, each unit may have a type-specific section, e.g. + [Service] for a service unit. See the respective man pages for + more information: + <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> + + <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 unit file incompatible with parsers for the XDG + <filename>.desktop</filename> file format.</para> + + <para>Unit files are loaded from a set of paths determined during + compilation, described in the next section.</para> + + <para>Unit files may contain additional options on top of those + listed here. If systemd encounters an unknown option, it will + write a warning log message but continue loading the unit. If an + option or section name is prefixed with <option>X-</option>, it is + ignored completely by systemd. Options within an ignored section + do not need the prefix. Applications may use this to include + additional information in the unit files.</para> + + <para>Boolean arguments used in unit 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 unit 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>Empty lines and lines starting with <literal>#</literal> or <literal>;</literal> are + ignored. This 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.</para> + + <para>Units can be aliased (have an alternative name), by creating a symlink from the new name + to the existing name in one of the unit search paths. For example, + <filename>systemd-networkd.service</filename> has the alias + <filename>dbus-org.freedesktop.network1.service</filename>, created during installation as the + symlink <filename>/usr/lib/systemd/system/dbus-org.freedesktop.network1.service</filename>. In + addition, unit files may specify aliases through the <varname>Alias=</varname> directive in the + [Install] section; those aliases are only effective when the unit is enabled. When the unit is + enabled, symlinks will be created for those names, and removed when the unit is disabled. For + example, <filename>reboot.target</filename> specifies + <varname>Alias=ctrl-alt-del.target</varname>, so when enabled it will be invoked whenever + CTRL+ALT+DEL is pressed. Alias names may be used in commands like <command>enable</command>, + <command>disable</command>, <command>start</command>, <command>stop</command>, + <command>status</command>, …, and in unit dependency directives <varname>Wants=</varname>, + <varname>Requires=</varname>, <varname>Before=</varname>, <varname>After=</varname>, …, with the + limitation that aliases specified through <varname>Alias=</varname> are only effective when the + unit is enabled. Aliases cannot be used with the <command>preset</command> command.</para> + + <para>Along with a unit file <filename>foo.service</filename>, the directory + <filename>foo.service.wants/</filename> may exist. All unit files symlinked from such a + directory are implicitly added as dependencies of type <varname>Wants=</varname> to the unit. + This is useful to hook units into the start-up of other units, without having to modify their + unit files. For details about the semantics of <varname>Wants=</varname>, see below. The + preferred way to create symlinks in the <filename>.wants/</filename> directory of a unit file is + with the <command>enable</command> command of the + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> + tool which reads information from the [Install] section of unit files (see below). A similar + functionality exists for <varname>Requires=</varname> type dependencies as well, the directory + suffix is <filename>.requires/</filename> in this case.</para> + + <para>Along with a unit file <filename>foo.service</filename>, a "drop-in" directory + <filename>foo.service.d/</filename> may exist. All files with the suffix + <literal>.conf</literal> from this directory will be parsed after the file itself is + parsed. This is useful to alter or add configuration settings for a unit, without having to + modify unit files. Each drop-in file must have appropriate section headers. Note that for + instantiated units, this logic will first look for the instance <literal>.d/</literal> + subdirectory and read its <literal>.conf</literal> files, followed by the template + <literal>.d/</literal> subdirectory and the <literal>.conf</literal> files there. Also note that + settings from the <literal>[Install]</literal> section are not honored in drop-in unit files, + and have no effect.</para> + + <para>In addition to <filename>/etc/systemd/system</filename>, the drop-in <literal>.d</literal> + directories for system services can be placed in <filename>/usr/lib/systemd/system</filename> or + <filename>/run/systemd/system</filename> directories. Drop-in files in <filename>/etc</filename> + take precedence over those in <filename>/run</filename> which in turn take precedence over those + in <filename>/usr/lib</filename>. Drop-in files under any of these directories take precedence + over unit files wherever located.</para> + + <!-- Note that we do not document .include here, as we consider it mostly obsolete, and want + people to use .d/ drop-ins instead. --> + + <para>Some unit names reflect paths existing in the file system + namespace. Example: a device unit + <filename>dev-sda.device</filename> refers to a device with the + device node <filename noindex='true'>/dev/sda</filename> in the + file system namespace. If this applies, a special way to escape + the path name is used, so that the result is usable as part of a + filename. Basically, given a path, "/" is replaced by "-", and all + other characters which are not ASCII alphanumerics are replaced by + C-style "\x2d" escapes (except that "_" is never replaced and "." + is only replaced when it would be the first character in the + escaped path). The root directory "/" is encoded as single dash, + while otherwise the initial and ending "/" are removed from all + paths during transformation. This escaping is reversible. Properly + escaped paths can be generated using the + <citerefentry><refentrytitle>systemd-escape</refentrytitle><manvolnum>1</manvolnum></citerefentry> + command.</para> + + <para>Optionally, units may be instantiated from a + template file at runtime. This allows creation of + multiple units from a single configuration file. If + systemd looks for a unit configuration file, it will + first search for the literal unit name in the + file system. If that yields no success and the unit + name contains an <literal>@</literal> character, systemd will look for a + unit template that shares the same name but with the + instance string (i.e. the part between the <literal>@</literal> character + and the suffix) removed. Example: if a service + <filename>getty@tty3.service</filename> is requested + and no file by that name is found, systemd will look + for <filename>getty@.service</filename> and + instantiate a service from that configuration file if + it is found.</para> + + <para>To refer to the instance string from within the + configuration file you may use the special <literal>%i</literal> + specifier in many of the configuration options. See below for + details.</para> + + <para>If a unit file is empty (i.e. has the file size 0) or is + symlinked to <filename>/dev/null</filename>, its configuration + will not be loaded and it appears with a load state of + <literal>masked</literal>, and cannot be activated. Use this as an + effective way to fully disable a unit, making it impossible to + start it even manually.</para> + + <para>The unit file format is covered by the + <ulink + url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface + Stability Promise</ulink>.</para> + + </refsect1> + + <refsect1> + <title>Automatic Dependencies</title> + + <para>Note that while systemd offers a flexible dependency system + between units it is recommended to use this functionality only + sparingly and instead rely on techniques such as bus-based or + socket-based activation which make dependencies implicit, + resulting in a both simpler and more flexible system.</para> + + <para>A number of unit dependencies are automatically established, + depending on unit configuration. On top of that, for units with + <varname>DefaultDependencies=yes</varname> (the default) a couple + of additional dependencies are added. The precise effect of + <varname>DefaultDependencies=yes</varname> depends on the unit + type (see below).</para> + + <para>If <varname>DefaultDependencies=yes</varname> is set, units + that are referenced by other units of type + <filename>.target</filename> via a <varname>Wants=</varname> or + <varname>Requires=</varname> dependency might automatically gain + an <varname>Before=</varname> dependency too. See + <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details.</para> + </refsect1> + + <refsect1> + <title>Unit File Load Path</title> + + <para>Unit files are loaded from a set of paths determined during + compilation, described in the two tables below. Unit files found + in directories listed earlier override files with the same name in + directories lower in the list.</para> + + <para>When the variable <varname>$SYSTEMD_UNIT_PATH</varname> is set, + the contents of this variable overrides the unit load path. If + <varname>$SYSTEMD_UNIT_PATH</varname> ends with an empty component + (<literal>:</literal>), the usual unit load path will be appended + to the contents of the variable.</para> + + <table> + <title> + Load path when running in system mode (<option>--system</option>). + </title> + + <tgroup cols='2'> + <colspec colname='path' /> + <colspec colname='expl' /> + <thead> + <row> + <entry>Path</entry> + <entry>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry><filename>/etc/systemd/system</filename></entry> + <entry>Local configuration</entry> + </row> + <row> + <entry><filename>/run/systemd/system</filename></entry> + <entry>Runtime units</entry> + </row> + <row> + <entry><filename>/usr/lib/systemd/system</filename></entry> + <entry>Units of installed packages</entry> + </row> + </tbody> + </tgroup> + </table> + + <table> + <title> + Load path when running in user mode (<option>--user</option>). + </title> + + <tgroup cols='2'> + <colspec colname='path' /> + <colspec colname='expl' /> + <thead> + <row> + <entry>Path</entry> + <entry>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry><filename>$XDG_CONFIG_HOME/systemd/user</filename></entry> + <entry>User configuration (only used when $XDG_CONFIG_HOME is set)</entry> + </row> + <row> + <entry><filename>$HOME/.config/systemd/user</filename></entry> + <entry>User configuration (only used when $XDG_CONFIG_HOME is not set)</entry> + </row> + <row> + <entry><filename>/etc/systemd/user</filename></entry> + <entry>Local configuration</entry> + </row> + <row> + <entry><filename>$XDG_RUNTIME_DIR/systemd/user</filename></entry> + <entry>Runtime units (only used when $XDG_RUNTIME_DIR is set)</entry> + </row> + <row> + <entry><filename>/run/systemd/user</filename></entry> + <entry>Runtime units</entry> + </row> + <row> + <entry><filename>$XDG_DATA_HOME/systemd/user</filename></entry> + <entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is set)</entry> + </row> + <row> + <entry><filename>$HOME/.local/share/systemd/user</filename></entry> + <entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is not set)</entry> + </row> + <row> + <entry><filename>/usr/lib/systemd/user</filename></entry> + <entry>Units of packages that have been installed system-wide</entry> + </row> + </tbody> + </tgroup> + </table> + + <para>Additional units might be loaded into systemd ("linked") + from directories not on the unit load path. See the + <command>link</command> command for + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. + Also, some units are dynamically created via a + <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>. + </para> + </refsect1> + + <refsect1> + <title>[Unit] Section Options</title> + + <para>The unit file may include a [Unit] section, which carries + generic information about the unit that is not dependent on the + type of unit:</para> + + <variablelist class='unit-directives'> + + <varlistentry> + <term><varname>Description=</varname></term> + <listitem><para>A free-form string describing the unit. This + is intended for use in UIs to show descriptive information + along with the unit name. The description should contain a + name that means something to the end user. <literal>Apache2 + Web Server</literal> is a good example. Bad examples are + <literal>high-performance light-weight HTTP server</literal> + (too generic) or <literal>Apache2</literal> (too specific and + meaningless for people who do not know + Apache).</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>Documentation=</varname></term> + <listitem><para>A space-separated list of URIs referencing + documentation for this unit or its configuration. Accepted are + only URIs of the types <literal>http://</literal>, + <literal>https://</literal>, <literal>file:</literal>, + <literal>info:</literal>, <literal>man:</literal>. For more + information about the syntax of these URIs, see <citerefentry + project='man-pages'><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. + The URIs should be listed in order of relevance, starting with + the most relevant. It is a good idea to first reference + documentation that explains what the unit's purpose is, + followed by how it is configured, followed by any other + related documentation. This option may be specified more than + once, in which case the specified list of URIs is merged. If + the empty string is assigned to this option, the list is reset + and all prior assignments will have no + effect.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>Requires=</varname></term> + + <listitem><para>Configures requirement dependencies on other + units. If this unit gets activated, the units listed here will + be activated as well. If one of the other units gets + deactivated or its activation fails, this unit will be + deactivated. This option may be specified more than once or + multiple space-separated units may be specified in one option + in which case requirement dependencies for all listed names + will be created. Note that requirement dependencies do not + influence the order in which services are started or stopped. + This has to be configured independently with the + <varname>After=</varname> or <varname>Before=</varname> + options. If a unit <filename>foo.service</filename> requires a + unit <filename>bar.service</filename> as configured with + <varname>Requires=</varname> and no ordering is configured + with <varname>After=</varname> or <varname>Before=</varname>, + then both units will be started simultaneously and without any + delay between them if <filename>foo.service</filename> is + activated. Often, it is a better choice to use + <varname>Wants=</varname> instead of + <varname>Requires=</varname> in order to achieve a system that + is more robust when dealing with failing services.</para> + + <para>Note that dependencies of this type may also be + configured outside of the unit configuration file by adding a + symlink to a <filename>.requires/</filename> directory + accompanying the unit file. For details, see + above.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>Requisite=</varname></term> + + <listitem><para>Similar to <varname>Requires=</varname>. + However, if the units listed here are not started already, + they will not be started and the transaction will fail + immediately. </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>Wants=</varname></term> + + <listitem><para>A weaker version of + <varname>Requires=</varname>. Units listed in this option will + be started if the configuring unit is. However, if the listed + units fail to start or cannot be added to the transaction, + this has no impact on the validity of the transaction as a + whole. This is the recommended way to hook start-up of one + unit to the start-up of another unit.</para> + + <para>Note that dependencies of this type may also be + configured outside of the unit configuration file by adding + symlinks to a <filename>.wants/</filename> directory + accompanying the unit file. For details, see + above.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>BindsTo=</varname></term> + + <listitem><para>Configures requirement dependencies, very + similar in style to <varname>Requires=</varname>, however in + addition to this behavior, it also declares that this unit is + stopped when any of the units listed suddenly disappears. + Units can suddenly, unexpectedly disappear if a service + terminates on its own choice, a device is unplugged or a mount + point unmounted without involvement of + systemd.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>PartOf=</varname></term> + + <listitem><para>Configures dependencies similar to + <varname>Requires=</varname>, but limited to stopping and + restarting of units. When systemd stops or restarts the units + listed here, the action is propagated to this unit. Note that + this is a one-way dependency — changes to this unit do not + affect the listed units. </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>Conflicts=</varname></term> + + <listitem><para>A space-separated list of unit names. + Configures negative requirement dependencies. If a unit has a + <varname>Conflicts=</varname> setting on another unit, + starting the former will stop the latter and vice versa. Note + that this setting is independent of and orthogonal to the + <varname>After=</varname> and <varname>Before=</varname> + ordering dependencies.</para> + + <para>If a unit A that conflicts with a unit B is scheduled to + be started at the same time as B, the transaction will either + fail (in case both are required part of the transaction) or be + modified to be fixed (in case one or both jobs are not a + required part of the transaction). In the latter case, the job + that is not the required will be removed, or in case both are + not required, the unit that conflicts will be started and the + unit that is conflicted is stopped.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>Before=</varname></term> + <term><varname>After=</varname></term> + + <listitem><para>A space-separated list of unit names. + Configures ordering dependencies between units. If a unit + <filename>foo.service</filename> contains a setting + <option>Before=bar.service</option> and both units are being + started, <filename>bar.service</filename>'s start-up is + delayed until <filename>foo.service</filename> is started up. + Note that this setting is independent of and orthogonal to the + requirement dependencies as configured by + <varname>Requires=</varname>. It is a common pattern to + include a unit name in both the <varname>After=</varname> and + <varname>Requires=</varname> option, in which case the unit + listed will be started before the unit that is configured with + these options. This option may be specified more than once, in + which case ordering dependencies for all listed names are + created. <varname>After=</varname> is the inverse of + <varname>Before=</varname>, i.e. while + <varname>After=</varname> ensures that the configured unit is + started after the listed unit finished starting up, + <varname>Before=</varname> ensures the opposite, i.e. that the + configured unit is fully started up before the listed unit is + started. Note that when two units with an ordering dependency + between them are shut down, the inverse of the start-up order + is applied. i.e. if a unit is configured with + <varname>After=</varname> on another unit, the former is + stopped before the latter if both are shut down. Given two units + with any ordering dependency between them, if one unit is shut + down and the other is started up, the shutdown is ordered + before the start-up. It doesn't matter if the ordering + dependency is <varname>After=</varname> or + <varname>Before=</varname>. It also doesn't matter which of the + two is shut down, as long as one is shut down and the other is + started up. The shutdown is ordered before the start-up in all + cases. If two units have no ordering dependencies between them, + they are shut down or started up simultaneously, and no ordering + takes place. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>OnFailure=</varname></term> + + <listitem><para>A space-separated list of one or more units + that are activated when this unit enters the + <literal>failed</literal> state.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>PropagatesReloadTo=</varname></term> + <term><varname>ReloadPropagatedFrom=</varname></term> + + <listitem><para>A space-separated list of one or more units + where reload requests on this unit will be propagated to, or + reload requests on the other unit will be propagated to this + unit, respectively. Issuing a reload request on a unit will + automatically also enqueue a reload request on all units that + the reload request shall be propagated to via these two + settings.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>JoinsNamespaceOf=</varname></term> + + <listitem><para>For units that start processes (such as + service units), lists one or more other units whose network + and/or temporary file namespace to join. This only applies to + unit types which support the + <varname>PrivateNetwork=</varname> and + <varname>PrivateTmp=</varname> directives (see + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details). If a unit that has this setting set is started, + its processes will see the same <filename>/tmp</filename>, + <filename>/var/tmp</filename> and network namespace as one + listed unit that is started. If multiple listed units are + already started, it is not defined which namespace is joined. + Note that this setting only has an effect if + <varname>PrivateNetwork=</varname> and/or + <varname>PrivateTmp=</varname> is enabled for both the unit + that joins the namespace and the unit whose namespace is + joined.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>RequiresMountsFor=</varname></term> + + <listitem><para>Takes a space-separated list of absolute + paths. Automatically adds dependencies of type + <varname>Requires=</varname> and <varname>After=</varname> for + all mount units required to access the specified path.</para> + + <para>Mount points marked with <option>noauto</option> are not + mounted automatically and will be ignored for the purposes of + this option. If such a mount should be a requirement for this + unit, direct dependencies on the mount units may be added + (<varname>Requires=</varname> and <varname>After=</varname> or + some other combination). </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>OnFailureJobMode=</varname></term> + + <listitem><para>Takes a value of + <literal>fail</literal>, + <literal>replace</literal>, + <literal>replace-irreversibly</literal>, + <literal>isolate</literal>, + <literal>flush</literal>, + <literal>ignore-dependencies</literal> or + <literal>ignore-requirements</literal>. Defaults to + <literal>replace</literal>. Specifies how the units listed in + <varname>OnFailure=</varname> will be enqueued. See + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s + <option>--job-mode=</option> option for details on the + possible values. If this is set to <literal>isolate</literal>, + only a single unit may be listed in + <varname>OnFailure=</varname>..</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>IgnoreOnIsolate=</varname></term> + + <listitem><para>Takes a boolean argument. If + <option>true</option>, this unit will not be stopped when + isolating another unit. Defaults to + <option>false</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>StopWhenUnneeded=</varname></term> + + <listitem><para>Takes a boolean argument. If + <option>true</option>, this unit will be stopped when it is no + longer used. Note that, in order to minimize the work to be + executed, systemd will not stop units by default unless they + are conflicting with other units, or the user explicitly + requested their shut down. If this option is set, a unit will + be automatically cleaned up if no other active unit requires + it. Defaults to <option>false</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>RefuseManualStart=</varname></term> + <term><varname>RefuseManualStop=</varname></term> + + <listitem><para>Takes a boolean argument. If + <option>true</option>, this unit can only be activated or + deactivated indirectly. In this case, explicit start-up or + termination requested by the user is denied, however if it is + started or stopped as a dependency of another unit, start-up + or termination will succeed. This is mostly a safety feature + to ensure that the user does not accidentally activate units + that are not intended to be activated explicitly, and not + accidentally deactivate units that are not intended to be + deactivated. These options default to + <option>false</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>AllowIsolate=</varname></term> + + <listitem><para>Takes a boolean argument. If + <option>true</option>, this unit may be used with the + <command>systemctl isolate</command> command. Otherwise, this + will be refused. It probably is a good idea to leave this + disabled except for target units that shall be used similar to + runlevels in SysV init systems, just as a precaution to avoid + unusable system states. This option defaults to + <option>false</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>DefaultDependencies=</varname></term> + + <listitem><para>Takes a boolean argument. If + <option>true</option>, (the default), a few default + dependencies will implicitly be created for the unit. The + actual dependencies created depend on the unit type. For + example, for service units, these dependencies ensure that the + service is started only after basic system initialization is + completed and is properly terminated on system shutdown. See + the respective man pages for details. Generally, only services + involved with early boot or late shutdown should set this + option to <option>false</option>. It is highly recommended to + leave this option enabled for the majority of common units. If + set to <option>false</option>, this option does not disable + all implicit dependencies, just non-essential + ones.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>JobTimeoutSec=</varname></term> + <term><varname>JobTimeoutAction=</varname></term> + <term><varname>JobTimeoutRebootArgument=</varname></term> + + <listitem><para>When a job for this unit is queued, a time-out may be configured. If this time limit is + reached, the job will be cancelled, the unit however will not change state or even enter the + <literal>failed</literal> mode. This value defaults to <literal>infinity</literal> (job timeouts disabled), + except for device units. NB: this timeout is independent from any unit-specific timeout (for example, the + timeout set with <varname>TimeoutStartSec=</varname> in service units) as the job timeout has no effect on the + unit itself, only on the job that might be pending for it. Or in other words: unit-specific timeouts are useful + to abort unit state changes, and revert them. The job timeout set with this option however is useful to abort + only the job waiting for the unit state to change.</para> + + <para><varname>JobTimeoutAction=</varname> + optionally configures an additional + action to take when the time-out is + hit. It takes the same values as the + per-service + <varname>StartLimitAction=</varname> + setting, see + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details. Defaults to + <option>none</option>. <varname>JobTimeoutRebootArgument=</varname> + configures an optional reboot string + to pass to the + <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry> + system call.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>StartLimitIntervalSec=</varname></term> + <term><varname>StartLimitBurst=</varname></term> + + <listitem><para>Configure unit start rate limiting. By default, units which are started more than 5 times + within 10 seconds are not permitted to start any more times until the 10 second interval ends. With these two + options, this rate limiting may be modified. Use <varname>StartLimitIntervalSec=</varname> to configure the + checking interval (defaults to <varname>DefaultStartLimitIntervalSec=</varname> in manager configuration file, + set to 0 to disable any kind of rate limiting). Use <varname>StartLimitBurst=</varname> to configure how many + starts per interval are allowed (defaults to <varname>DefaultStartLimitBurst=</varname> in manager + configuration file). These configuration options are particularly useful in conjunction with the service + setting <varname>Restart=</varname> (see + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>); however, + they apply to all kinds of starts (including manual), not just those triggered by the + <varname>Restart=</varname> logic. Note that units which are configured for <varname>Restart=</varname> and + which reach the start limit are not attempted to be restarted anymore; however, they may still be restarted + manually at a later point, from which point on, the restart logic is again activated. Note that + <command>systemctl reset-failed</command> will cause the restart rate counter for a service to be flushed, + which is useful if the administrator wants to manually start a unit and the start limit interferes with + that. Note that this rate-limiting is enforced after any unit condition checks are executed, and hence unit + activations with failing conditions are not counted by this rate limiting. Slice, target, device and scope + units do not enforce this setting, as they are unit types whose activation may either never fail, or may + succeed only a single time.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>StartLimitAction=</varname></term> + + <listitem><para>Configure the action to take if the rate limit configured with + <varname>StartLimitIntervalSec=</varname> and <varname>StartLimitBurst=</varname> is hit. Takes one of + <option>none</option>, <option>reboot</option>, <option>reboot-force</option>, + <option>reboot-immediate</option>, <option>poweroff</option>, <option>poweroff-force</option> or + <option>poweroff-immediate</option>. If <option>none</option> is set, hitting the rate limit will trigger no + action besides that the start will not be permitted. <option>reboot</option> causes a reboot following the + normal shutdown procedure (i.e. equivalent to <command>systemctl reboot</command>). + <option>reboot-force</option> causes a forced reboot which will terminate all processes forcibly but should + cause no dirty file systems on reboot (i.e. equivalent to <command>systemctl reboot -f</command>) and + <option>reboot-immediate</option> causes immediate execution of the + <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry> system call, which + might result in data loss. Similarly, <option>poweroff</option>, <option>poweroff-force</option>, + <option>poweroff-immediate</option> have the effect of powering down the system with similar + semantics. Defaults to <option>none</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>RebootArgument=</varname></term> + <listitem><para>Configure the optional argument for the + <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry> system call if + <varname>StartLimitAction=</varname> or a service's <varname>FailureAction=</varname> is a reboot action. This + works just like the optional argument to <command>systemctl reboot</command> command.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>ConditionArchitecture=</varname></term> + <term><varname>ConditionVirtualization=</varname></term> + <term><varname>ConditionHost=</varname></term> + <term><varname>ConditionKernelCommandLine=</varname></term> + <term><varname>ConditionSecurity=</varname></term> + <term><varname>ConditionCapability=</varname></term> + <term><varname>ConditionACPower=</varname></term> + <term><varname>ConditionNeedsUpdate=</varname></term> + <term><varname>ConditionFirstBoot=</varname></term> + <term><varname>ConditionPathExists=</varname></term> + <term><varname>ConditionPathExistsGlob=</varname></term> + <term><varname>ConditionPathIsDirectory=</varname></term> + <term><varname>ConditionPathIsSymbolicLink=</varname></term> + <term><varname>ConditionPathIsMountPoint=</varname></term> + <term><varname>ConditionPathIsReadWrite=</varname></term> + <term><varname>ConditionDirectoryNotEmpty=</varname></term> + <term><varname>ConditionFileNotEmpty=</varname></term> + <term><varname>ConditionFileIsExecutable=</varname></term> + + <!-- We do not document ConditionNull= + here, as it is not particularly + useful and probably just + confusing. --> + + <listitem><para>Before starting a unit, verify that the specified condition is true. If it is not true, the + starting of the unit will be (mostly silently) skipped, however all ordering dependencies of it are still + respected. A failing condition will not result in the unit being moved into a failure state. The condition is + checked at the time the queued start job is to be executed. Use condition expressions in order to silently skip + units that do not apply to the local running system, for example because the kernel or runtime environment + doesn't require its functionality. Use the various <varname>AssertArchitecture=</varname>, + <varname>AssertVirtualization=</varname>, … options for a similar mechanism that puts the unit in a failure + state and logs about the failed check (see below).</para> + + <para><varname>ConditionArchitecture=</varname> may be used to + check whether the system is running on a specific + architecture. Takes one of + <varname>x86</varname>, + <varname>x86-64</varname>, + <varname>ppc</varname>, + <varname>ppc-le</varname>, + <varname>ppc64</varname>, + <varname>ppc64-le</varname>, + <varname>ia64</varname>, + <varname>parisc</varname>, + <varname>parisc64</varname>, + <varname>s390</varname>, + <varname>s390x</varname>, + <varname>sparc</varname>, + <varname>sparc64</varname>, + <varname>mips</varname>, + <varname>mips-le</varname>, + <varname>mips64</varname>, + <varname>mips64-le</varname>, + <varname>alpha</varname>, + <varname>arm</varname>, + <varname>arm-be</varname>, + <varname>arm64</varname>, + <varname>arm64-be</varname>, + <varname>sh</varname>, + <varname>sh64</varname>, + <varname>m86k</varname>, + <varname>tilegx</varname>, + <varname>cris</varname> to test + against a specific architecture. The architecture is + determined from the information returned by + <citerefentry project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry> + and is thus subject to + <citerefentry><refentrytitle>personality</refentrytitle><manvolnum>2</manvolnum></citerefentry>. + Note that a <varname>Personality=</varname> setting in the + same unit file has no effect on this condition. A special + architecture name <varname>native</varname> is mapped to the + architecture the system manager itself is compiled for. The + test may be negated by prepending an exclamation mark.</para> + + <para><varname>ConditionVirtualization=</varname> may be used + to check whether the system is executed in a virtualized + environment and optionally test whether it is a specific + implementation. Takes either boolean value to check if being + executed in any virtualized environment, or one of + <varname>vm</varname> and + <varname>container</varname> to test against a generic type of + virtualization solution, or one of + <varname>qemu</varname>, + <varname>kvm</varname>, + <varname>zvm</varname>, + <varname>vmware</varname>, + <varname>microsoft</varname>, + <varname>oracle</varname>, + <varname>xen</varname>, + <varname>bochs</varname>, + <varname>uml</varname>, + <varname>openvz</varname>, + <varname>lxc</varname>, + <varname>lxc-libvirt</varname>, + <varname>systemd-nspawn</varname>, + <varname>docker</varname>, + <varname>rkt</varname> to test + against a specific implementation, or + <varname>private-users</varname> to check whether we are running in a user namespace. See + <citerefentry><refentrytitle>systemd-detect-virt</refentrytitle><manvolnum>1</manvolnum></citerefentry> + for a full list of known virtualization technologies and their + identifiers. If multiple virtualization technologies are + nested, only the innermost is considered. The test may be + negated by prepending an exclamation mark.</para> + + <para><varname>ConditionHost=</varname> may be used to match + against the hostname or machine ID of the host. This either + takes a hostname string (optionally with shell style globs) + which is tested against the locally set hostname as returned + by + <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>, + or a machine ID formatted as string (see + <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>). + The test may be negated by prepending an exclamation + mark.</para> + + <para><varname>ConditionKernelCommandLine=</varname> may be + used to check whether a specific kernel command line option is + set (or if prefixed with the exclamation mark unset). The + argument must either be a single word, or an assignment (i.e. + two words, separated <literal>=</literal>). In the former case + the kernel command line is searched for the word appearing as + is, or as left hand side of an assignment. In the latter case, + the exact assignment is looked for with right and left hand + side matching.</para> + + <para><varname>ConditionSecurity=</varname> may be used to + check whether the given security module is enabled on the + system. Currently, the recognized values are + <varname>selinux</varname>, + <varname>apparmor</varname>, + <varname>ima</varname>, + <varname>smack</varname> and + <varname>audit</varname>. The test may be negated by + prepending an exclamation mark.</para> + + <para><varname>ConditionCapability=</varname> may be used to + check whether the given capability exists in the capability + bounding set of the service manager (i.e. this does not check + whether capability is actually available in the permitted or + effective sets, see + <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry> + for details). Pass a capability name such as + <literal>CAP_MKNOD</literal>, possibly prefixed with an + exclamation mark to negate the check.</para> + + <para><varname>ConditionACPower=</varname> may be used to + check whether the system has AC power, or is exclusively + battery powered at the time of activation of the unit. This + takes a boolean argument. If set to <varname>true</varname>, + the condition will hold only if at least one AC connector of + the system is connected to a power source, or if no AC + connectors are known. Conversely, if set to + <varname>false</varname>, the condition will hold only if + there is at least one AC connector known and all AC connectors + are disconnected from a power source.</para> + + <para><varname>ConditionNeedsUpdate=</varname> takes one of + <filename>/var</filename> or <filename>/etc</filename> as + argument, possibly prefixed with a <literal>!</literal> (for + inverting the condition). This condition may be used to + conditionalize units on whether the specified directory + requires an update because <filename>/usr</filename>'s + modification time is newer than the stamp file + <filename>.updated</filename> in the specified directory. This + is useful to implement offline updates of the vendor operating + system resources in <filename>/usr</filename> that require + updating of <filename>/etc</filename> or + <filename>/var</filename> on the next following boot. Units + making use of this condition should order themselves before + <citerefentry><refentrytitle>systemd-update-done.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + to make sure they run before the stamp file's modification + time gets reset indicating a completed update.</para> + + <para><varname>ConditionFirstBoot=</varname> takes a boolean + argument. This condition may be used to conditionalize units + on whether the system is booting up with an unpopulated + <filename>/etc</filename> directory. This may be used to + populate <filename>/etc</filename> on the first boot after + factory reset, or when a new system instances boots up for the + first time.</para> + + <para>With <varname>ConditionPathExists=</varname> a file + existence condition is checked before a unit is started. If + the specified absolute path name does not exist, the condition + will fail. If the absolute path name passed to + <varname>ConditionPathExists=</varname> is prefixed with an + exclamation mark (<literal>!</literal>), the test is negated, + and the unit is only started if the path does not + exist.</para> + + <para><varname>ConditionPathExistsGlob=</varname> is similar + to <varname>ConditionPathExists=</varname>, but checks for the + existence of at least one file or directory matching the + specified globbing pattern.</para> + + <para><varname>ConditionPathIsDirectory=</varname> is similar + to <varname>ConditionPathExists=</varname> but verifies + whether a certain path exists and is a directory.</para> + + <para><varname>ConditionPathIsSymbolicLink=</varname> is + similar to <varname>ConditionPathExists=</varname> but + verifies whether a certain path exists and is a symbolic + link.</para> + + <para><varname>ConditionPathIsMountPoint=</varname> is similar + to <varname>ConditionPathExists=</varname> but verifies + whether a certain path exists and is a mount point.</para> + + <para><varname>ConditionPathIsReadWrite=</varname> is similar + to <varname>ConditionPathExists=</varname> but verifies + whether the underlying file system is readable and writable + (i.e. not mounted read-only).</para> + + <para><varname>ConditionDirectoryNotEmpty=</varname> is + similar to <varname>ConditionPathExists=</varname> but + verifies whether a certain path exists and is a non-empty + directory.</para> + + <para><varname>ConditionFileNotEmpty=</varname> is similar to + <varname>ConditionPathExists=</varname> but verifies whether a + certain path exists and refers to a regular file with a + non-zero size.</para> + + <para><varname>ConditionFileIsExecutable=</varname> is similar + to <varname>ConditionPathExists=</varname> but verifies + whether a certain path exists, is a regular file and marked + executable.</para> + + <para>If multiple conditions are specified, the unit will be + executed if all of them apply (i.e. a logical AND is applied). + Condition checks can be prefixed with a pipe symbol (|) in + which case a condition becomes a triggering condition. If at + least one triggering condition is defined for a unit, then the + unit will be executed if at least one of the triggering + conditions apply and all of the non-triggering conditions. If + you prefix an argument with the pipe symbol and an exclamation + mark, the pipe symbol must be passed first, the exclamation + second. Except for + <varname>ConditionPathIsSymbolicLink=</varname>, all path + checks follow symlinks. If any of these options is assigned + the empty string, the list of conditions is reset completely, + all previous condition settings (of any kind) will have no + effect.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>AssertArchitecture=</varname></term> + <term><varname>AssertVirtualization=</varname></term> + <term><varname>AssertHost=</varname></term> + <term><varname>AssertKernelCommandLine=</varname></term> + <term><varname>AssertSecurity=</varname></term> + <term><varname>AssertCapability=</varname></term> + <term><varname>AssertACPower=</varname></term> + <term><varname>AssertNeedsUpdate=</varname></term> + <term><varname>AssertFirstBoot=</varname></term> + <term><varname>AssertPathExists=</varname></term> + <term><varname>AssertPathExistsGlob=</varname></term> + <term><varname>AssertPathIsDirectory=</varname></term> + <term><varname>AssertPathIsSymbolicLink=</varname></term> + <term><varname>AssertPathIsMountPoint=</varname></term> + <term><varname>AssertPathIsReadWrite=</varname></term> + <term><varname>AssertDirectoryNotEmpty=</varname></term> + <term><varname>AssertFileNotEmpty=</varname></term> + <term><varname>AssertFileIsExecutable=</varname></term> + + <listitem><para>Similar to the <varname>ConditionArchitecture=</varname>, + <varname>ConditionVirtualization=</varname>, …, condition settings described above, these settings add + assertion checks to the start-up of the unit. However, unlike the conditions settings, any assertion setting + that is not met results in failure of the start job (which means this is logged loudly). Use assertion + expressions for units that cannot operate when specific requirements are not met, and when this is something + the administrator or user should look into.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>SourcePath=</varname></term> + <listitem><para>A path to a configuration file this unit has + been generated from. This is primarily useful for + implementation of generator tools that convert configuration + from an external configuration file format into native unit + files. This functionality should not be used in normal + units.</para></listitem> + </varlistentry> + + </variablelist> + + </refsect1> + + <refsect1> + <title>[Install] Section Options</title> + + <para>Unit files may include an <literal>[Install]</literal> section, which carries installation information for + the unit. This section is not interpreted by + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> during runtime; it is + used by the <command>enable</command> and <command>disable</command> commands of the + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> tool during + installation of a unit. Note that settings in the <literal>[Install]</literal> section may not appear in + <filename>.d/*.conf</filename> unit file drop-ins (see above).</para> + + <variablelist class='unit-directives'> + <varlistentry> + <term><varname>Alias=</varname></term> + + <listitem><para>A space-separated list of additional names this unit shall be installed under. The names listed + here must have the same suffix (i.e. type) as the unit file name. This option may be specified more than once, + in which case all listed names are used. At installation time, <command>systemctl enable</command> will create + symlinks from these names to the unit filename. Note that not all unit types support such alias names, and this + setting is not supported for them. Specifically, mount, slice, swap, and automount units do not support + aliasing.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>WantedBy=</varname></term> + <term><varname>RequiredBy=</varname></term> + + <listitem><para>This option may be used more than once, or a + space-separated list of unit names may be given. A symbolic + link is created in the <filename>.wants/</filename> or + <filename>.requires/</filename> directory of each of the + listed units when this unit is installed by <command>systemctl + enable</command>. This has the effect that a dependency of + type <varname>Wants=</varname> or <varname>Requires=</varname> + is added from the listed unit to the current unit. The primary + result is that the current unit will be started when the + listed unit is started. See the description of + <varname>Wants=</varname> and <varname>Requires=</varname> in + the [Unit] section for details.</para> + + <para><command>WantedBy=foo.service</command> in a service + <filename>bar.service</filename> is mostly equivalent to + <command>Alias=foo.service.wants/bar.service</command> in the + same file. In case of template units, <command>systemctl + enable</command> must be called with an instance name, and + this instance will be added to the + <filename>.wants/</filename> or + <filename>.requires/</filename> list of the listed unit. E.g. + <command>WantedBy=getty.target</command> in a service + <filename>getty@.service</filename> will result in + <command>systemctl enable getty@tty2.service</command> + creating a + <filename>getty.target.wants/getty@tty2.service</filename> + link to <filename>getty@.service</filename>. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>Also=</varname></term> + + <listitem><para>Additional units to install/deinstall when + this unit is installed/deinstalled. If the user requests + installation/deinstallation of a unit with this option + configured, <command>systemctl enable</command> and + <command>systemctl disable</command> will automatically + install/uninstall units listed in this option as well.</para> + + <para>This option may be used more than once, or a + space-separated list of unit names may be + given.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>DefaultInstance=</varname></term> + + <listitem><para>In template unit files, this specifies for + which instance the unit shall be enabled if the template is + enabled without any explicitly set instance. This option has + no effect in non-template unit files. The specified string + must be usable as instance identifier.</para></listitem> + </varlistentry> + </variablelist> + + <para>The following specifiers are interpreted in the Install + section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v. For their meaning + see the next section. + </para> + </refsect1> + + <refsect1> + <title>Specifiers</title> + + <para>Many settings resolve specifiers which may be used to write + generic unit files referring to runtime or unit parameters that + are replaced when the unit files are loaded. The following + specifiers are understood:</para> + + <table> + <title>Specifiers available in unit files</title> + <tgroup cols='3' align='left' colsep='1' rowsep='1'> + <colspec colname="spec" /> + <colspec colname="mean" /> + <colspec colname="detail" /> + <thead> + <row> + <entry>Specifier</entry> + <entry>Meaning</entry> + <entry>Details</entry> + </row> + </thead> + <tbody> + <row> + <entry><literal>%n</literal></entry> + <entry>Full unit name</entry> + <entry></entry> + </row> + <row> + <entry><literal>%N</literal></entry> + <entry>Unescaped full unit name</entry> + <entry>Same as <literal>%n</literal>, but with escaping undone</entry> + </row> + <row> + <entry><literal>%p</literal></entry> + <entry>Prefix name</entry> + <entry>For instantiated units, this refers to the string before the <literal>@</literal> character of the unit name. For non-instantiated units, this refers to the name of the unit with the type suffix removed.</entry> + </row> + <row> + <entry><literal>%P</literal></entry> + <entry>Unescaped prefix name</entry> + <entry>Same as <literal>%p</literal>, but with escaping undone</entry> + </row> + <row> + <entry><literal>%i</literal></entry> + <entry>Instance name</entry> + <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix of the unit name.</entry> + </row> + <row> + <entry><literal>%I</literal></entry> + <entry>Unescaped instance name</entry> + <entry>Same as <literal>%i</literal>, but with escaping undone</entry> + </row> + <row> + <entry><literal>%f</literal></entry> + <entry>Unescaped filename</entry> + <entry>This is either the unescaped instance name (if applicable) with <filename>/</filename> prepended (if applicable), or the unescaped prefix name prepended with <filename>/</filename>.</entry> + </row> + <row> + <entry><literal>%c</literal></entry> + <entry>Control group path of the unit</entry> + <entry>This path does not include the <filename>/sys/fs/cgroup/systemd/</filename> prefix.</entry> + </row> + <row> + <entry><literal>%r</literal></entry> + <entry>Control group path of the slice the unit is placed in</entry> + <entry>This usually maps to the parent control group path of <literal>%c</literal>.</entry> + </row> + <row> + <entry><literal>%R</literal></entry> + <entry>Root control group path below which slices and units are placed</entry> + <entry>For system instances, this resolves to <filename>/</filename>, except in containers, where this maps to the container's root control group path.</entry> + </row> + <row> + <entry><literal>%t</literal></entry> + <entry>Runtime directory</entry> + <entry>This is either <filename>/run</filename> (for the system manager) or the path <literal>$XDG_RUNTIME_DIR</literal> resolves to (for user managers).</entry> + </row> + <row> + <entry><literal>%u</literal></entry> + <entry>User name</entry> + <entry>This is the name of the user running the service manager instance. In case of the system manager this resolves to <literal>root</literal>.</entry> + </row> + <row> + <entry><literal>%U</literal></entry> + <entry>User UID</entry> + <entry>This is the numeric UID of the user running the service manager instance. In case of the system manager this resolves to <literal>0</literal>.</entry> + </row> + <row> + <entry><literal>%h</literal></entry> + <entry>User home directory</entry> + <entry>This is the home directory of the user running the service manager instance. In case of the system manager this resolves to <literal>/root</literal>.</entry> + </row> + <row> + <entry><literal>%s</literal></entry> + <entry>User shell</entry> + <entry>This is the shell of the user running the service manager instance. In case of the system manager this resolves to <literal>/bin/sh</literal>.</entry> + </row> + <row> + <entry><literal>%m</literal></entry> + <entry>Machine ID</entry> + <entry>The machine ID of the running system, formatted as string. See <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.</entry> + </row> + <row> + <entry><literal>%b</literal></entry> + <entry>Boot ID</entry> + <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry> + </row> + <row> + <entry><literal>%H</literal></entry> + <entry>Host name</entry> + <entry>The hostname of the running system at the point in time the unit configuration is loaded.</entry> + </row> + <row> + <entry><literal>%v</literal></entry> + <entry>Kernel release</entry> + <entry>Identical to <command>uname -r</command> output</entry> + </row> + <row> + <entry><literal>%%</literal></entry> + <entry>Single percent sign</entry> + <entry>Use <literal>%%</literal> in place of <literal>%</literal> to specify a single percent sign.</entry> + </row> + </tbody> + </tgroup> + </table> + + <para>Please note that specifiers <literal>%U</literal>, + <literal>%h</literal>, <literal>%s</literal> are mostly useless + when systemd is running in system mode. PID 1 cannot query the + user account database for information, so the specifiers only work + as shortcuts for things which are already specified in a different + way in the unit file. They are fully functional when systemd is + running in <option>--user</option> mode.</para> + </refsect1> + + <refsect1> + <title>Examples</title> + + <example> + <title>Allowing units to be enabled</title> + + <para>The following snippet (highlighted) allows a unit (e.g. + <filename>foo.service</filename>) to be enabled via + <command>systemctl enable</command>:</para> + + <programlisting>[Unit] +Description=Foo + +[Service] +ExecStart=/usr/sbin/foo-daemon + +<emphasis>[Install]</emphasis> +<emphasis>WantedBy=multi-user.target</emphasis></programlisting> + + <para>After running <command>systemctl enable</command>, a + symlink + <filename>/etc/systemd/system/multi-user.target.wants/foo.service</filename> + linking to the actual unit will be created. It tells systemd to + pull in the unit when starting + <filename>multi-user.target</filename>. The inverse + <command>systemctl disable</command> will remove that symlink + again.</para> + </example> + + <example> + <title>Overriding vendor settings</title> + + <para>There are two methods of overriding vendor settings in + unit files: copying the unit file from + <filename>/usr/lib/systemd/system</filename> to + <filename>/etc/systemd/system</filename> and modifying the + chosen settings. Alternatively, one can create a directory named + <filename><replaceable>unit</replaceable>.d/</filename> within + <filename>/etc/systemd/system</filename> and place a drop-in + file <filename><replaceable>name</replaceable>.conf</filename> + there that only changes the specific settings one is interested + in. Note that multiple such drop-in files are read if + present.</para> + + <para>The advantage of the first method is that one easily + overrides the complete unit, the vendor unit is not parsed at + all anymore. It has the disadvantage that improvements to the + unit file by the vendor are not automatically incorporated on + updates.</para> + + <para>The advantage of the second method is that one only + overrides the settings one specifically wants, where updates to + the unit by the vendor automatically apply. This has the + disadvantage that some future updates by the vendor might be + incompatible with the local changes.</para> + + <para>Note that for drop-in files, if one wants to remove + entries from a setting that is parsed as a list (and is not a + dependency), such as <varname>ConditionPathExists=</varname> (or + e.g. <varname>ExecStart=</varname> in service units), one needs + to first clear the list before re-adding all entries except the + one that is to be removed. See below for an example.</para> + + <para>This also applies for user instances of systemd, but with + different locations for the unit files. See the section on unit + load paths for further details.</para> + + <para>Suppose there is a vendor-supplied unit + <filename>/usr/lib/systemd/system/httpd.service</filename> with + the following contents:</para> + + <programlisting>[Unit] +Description=Some HTTP server +After=remote-fs.target sqldb.service +Requires=sqldb.service +AssertPathExists=/srv/webserver + +[Service] +Type=notify +ExecStart=/usr/sbin/some-fancy-httpd-server +Nice=5 + +[Install] +WantedBy=multi-user.target</programlisting> + + <para>Now one wants to change some settings as an administrator: + firstly, in the local setup, <filename>/srv/webserver</filename> + might not exist, because the HTTP server is configured to use + <filename>/srv/www</filename> instead. Secondly, the local + configuration makes the HTTP server also depend on a memory + cache service, <filename>memcached.service</filename>, that + should be pulled in (<varname>Requires=</varname>) and also be + ordered appropriately (<varname>After=</varname>). Thirdly, in + order to harden the service a bit more, the administrator would + like to set the <varname>PrivateTmp=</varname> setting (see + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details). And lastly, the administrator would like to reset + the niceness of the service to its default value of 0.</para> + + <para>The first possibility is to copy the unit file to + <filename>/etc/systemd/system/httpd.service</filename> and + change the chosen settings:</para> + + <programlisting>[Unit] +Description=Some HTTP server +After=remote-fs.target sqldb.service <emphasis>memcached.service</emphasis> +Requires=sqldb.service <emphasis>memcached.service</emphasis> +AssertPathExists=<emphasis>/srv/www</emphasis> + +[Service] +Type=notify +ExecStart=/usr/sbin/some-fancy-httpd-server +<emphasis>Nice=0</emphasis> +<emphasis>PrivateTmp=yes</emphasis> + +[Install] +WantedBy=multi-user.target</programlisting> + + <para>Alternatively, the administrator could create a drop-in + file + <filename>/etc/systemd/system/httpd.service.d/local.conf</filename> + with the following contents:</para> + + <programlisting>[Unit] +After=memcached.service +Requires=memcached.service +# Reset all assertions and then re-add the condition we want +AssertPathExists= +AssertPathExists=/srv/www + +[Service] +Nice=0 +PrivateTmp=yes</programlisting> + + <para>Note that dependencies (<varname>After=</varname>, etc.) + cannot be reset to an empty list, so dependencies can only be + added in drop-ins. If you want to remove dependencies, you have + to override the entire unit.</para> + + </example> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</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.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |