X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=man%2Fsystemd.unit.xml;h=4f0bd64b121728c488e8ba1747f39348d55b5206;hb=409dee2e44e7dc73d6bf00d782938e4cb4105f5b;hp=f23aad9fa04358db7d33bf94af406fc1582770a2;hpb=bb31a4ac1997c189a344caf554f34c6aabc71aa7;p=elogind.git

diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index f23aad9fa..4f0bd64b1 100644
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -1,6 +1,9 @@
 <?xml version='1.0'?> <!--*-nxml-*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
-        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
+<!ENTITY % entities SYSTEM "custom-entities.ent" >
+%entities;
+]>
 
 <!--
   This file is part of systemd.
@@ -48,16 +51,28 @@
         </refnamediv>
 
         <refsynopsisdiv>
-                <para><filename>systemd.service</filename>,
-                <filename>systemd.socket</filename>,
-                <filename>systemd.device</filename>,
-                <filename>systemd.mount</filename>,
-                <filename>systemd.automount</filename>,
-                <filename>systemd.swap</filename>,
-                <filename>systemd.target</filename>,
-                <filename>systemd.path</filename>,
-                <filename>systemd.timer</filename>,
-                <filename>systemd.snapshot</filename></para>
+                <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>snapshot</replaceable>.snapshot</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>/etc/systemd/user/*</filename>
+<filename>/run/systemd/user/*</filename>
+<filename>/usr/lib/systemd/user/*</filename>
+<filename>...</filename>
+                </literallayout></para>
         </refsynopsisdiv>
 
         <refsect1>
@@ -66,7 +81,7 @@
                 <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 file system path or a timer controlled and
+                target, a file system path, or a timer controlled and
                 supervised by
                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. The
                 syntax is inspired by <ulink
@@ -81,10 +96,25 @@
                 sections of the unit files.</para>
 
                 <para>In addition to the generic [Unit] and [Install]
-                sections described here, each unit should have a
+                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.</para>
+                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.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+                </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
@@ -106,12 +136,14 @@
                 <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: "50" refers to 50
+                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 plus 200
                 milliseconds, i.e. 120200ms. The following time units
-                are understood: s, min, h, d, w, ms, us.</para>
+                are understood: s, min, h, d, w, ms, us. For details
+                see
+                <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 
                 <para>Empty lines and lines starting with # or ; are
                 ignored. This may be used for commenting. Lines ending
@@ -119,47 +151,56 @@
                 line while reading and the backslash is replaced by a
                 space character. This may be used to wrap long lines.</para>
 
-                <para>If a line starts with <option>.include</option>
-                followed by a file name, the specified file will be
-                parsed at this point. Make sure that the file that is
-                included has the appropriate section headers before
-                any directives.</para>
-
                 <para>Along with a unit file
-                <filename>foo.service</filename> a directory
+                <filename>foo.service</filename> the directory
                 <filename>foo.service.wants/</filename> may exist. All
-                units symlinked from such a directory are implicitly
-                added as dependencies of type
+                unit files symlinked from such a directory are
+                implicitly added as dependencies of type
                 <varname>Wanted=</varname> to the unit. This is useful
                 to hook units into the start-up of other units,
-                without having to modify their unit configuration
-                files. For details about the semantics of
-                <varname>Wanted=</varname> see below. The preferred
-                way to create symlinks in the
-                <filename>.wants/</filename> directory of a service is
-                with the <command>enable</command> command of the
+                without having to modify their unit files. For details
+                about the semantics of <varname>Wanted=</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
+                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 directory
+                <filename>foo.service.d/</filename> may exist. All
+                files with the suffix <filename>.conf</filename> from
+                this directory will be parsed after the file itself is
+                parsed. This is useful to alter or add configuration
+                settings to a unit, without having to modify their
+                unit files. Make sure that the file that is included
+                has the appropriate section headers before any
+                directive.</para>
+
+                <para>If a line starts with <option>.include</option>
+                followed by a filename, the specified file will be
+                parsed at this point. Make sure that the file that is
+                included has the appropriate section headers before
+                any directives.</para>
+
                 <para>Note that while systemd offers a flexible
                 dependency system between units it is recommended to
-                use this functionality only sparsely and instead rely
+                use this functionality only sparingly and instead rely
                 on techniques such as bus-based or socket-based
-                activation which makes dependencies implicit, which
-                both results in a simpler and more flexible
-                system.</para>
+                activation which make dependencies implicit, resulting
+                in a both simpler and more flexible system.</para>
 
                 <para>Some unit names reflect paths existing in the
-                file system name space. Example: a device unit
+                file system namespace. Example: a device unit
                 <filename>dev-sda.device</filename> refers to a device
-                with the device node <filename>/dev/sda</filename> in
+                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 file name. Basically,
+                result is usable as part of a filename. Basically,
                 given a path, "/" is replaced by "-", and all
                 unprintable characters and the "-" are replaced by
                 C-style "\x20" escapes. The root directory "/" is
@@ -173,9 +214,9 @@
                 systemd looks for a unit configuration file it will
                 first search for the literal unit name in the
                 filesystem. If that yields no success and the unit
-                name contains an @ character, systemd will look for a
+                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 @ character
+                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
@@ -186,124 +227,139 @@
                 <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. Other specifiers exist, the
-                full list is:</para>
+                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>Unit 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 higher
+                in the hierarchy override files with the same name
+                lower in the hierarchy, thus allowing overrides.
+                </para>
+
+                <para>When systemd is running in user mode
+                (<option>--user</option>) and the variable
+                <varname>$SYSTEMD_UNIT_PATH</varname> is set, this
+                contents of this variable overrides the unit load
+                path.
+                </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" />
+                  <title>
+                    Load path when running in system mode (<option>--system</option>).
+                  </title>
+
+                  <tgroup cols='2'>
+                    <colspec colname='path' />
+                    <colspec colname='expl' />
                     <thead>
                       <row>
-                        <entry>Specifier</entry>
-                        <entry>Meaning</entry>
-                        <entry>Details</entry>
+                        <entry>Path</entry>
+                        <entry>Description</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></entry>
-                      </row>
-                      <row>
-                        <entry><literal>%p</literal></entry>
-                        <entry>Prefix name</entry>
-                        <entry>This refers to the string before the @, i.e. "getty" in the example above, where "tty3" is the instance name.</entry>
+                        <entry><filename>/run/systemd/generator.early</filename></entry>
+                        <entry>Generated units (early)</entry>
                       </row>
                       <row>
-                        <entry><literal>%P</literal></entry>
-                        <entry>Unescaped prefix name</entry>
-                        <entry></entry>
+                        <entry><filename>/etc/systemd/system</filename></entry>
+                        <entry>Local configuration</entry>
                       </row>
                       <row>
-                        <entry><literal>%i</literal></entry>
-                        <entry>Instance name</entry>
-                        <entry>This is the string between the @ character and the suffix.</entry>
+                        <entry><filename>/run/systemd/systemd</filename></entry>
+                        <entry>Volatile units</entry>
                       </row>
                       <row>
-                        <entry><literal>%I</literal></entry>
-                        <entry>Unescaped instance name</entry>
-                        <entry></entry>
+                        <entry><filename>/run/systemd/generator</filename></entry>
+                        <entry>Generated units (middle)</entry>
                       </row>
                       <row>
-                        <entry><literal>%f</literal></entry>
-                        <entry>Unescaped file name</entry>
-                        <entry>This is either the unescaped instance name (if set) with / prepended (if necessary), or the prefix name similarly prepended with /.</entry>
+                        <entry><filename>/usr/local/lib/systemd/system</filename></entry>
+                        <entry>Units for local packages</entry>
                       </row>
                       <row>
-                        <entry><literal>%c</literal></entry>
-                        <entry>Control group path of the unit</entry>
-                        <entry></entry>
+                        <entry><filename>/usr/lib/systemd/system</filename></entry>
+                        <entry>Units for installed packages</entry>
                       </row>
                       <row>
-                        <entry><literal>%r</literal></entry>
-                        <entry>Root control group path of systemd</entry>
-                        <entry></entry>
+                        <entry><filename>/run/systemd/generator.late</filename></entry>
+                        <entry>Generated units (late)</entry>
                       </row>
+                    </tbody>
+                  </tgroup>
+                </table>
+
+                <table>
+                  <title>
+                    Load path when running in session mode (<option>--user</option>).
+                  </title>
+
+                  <tgroup cols='2'>
+                    <colspec colname='path' />
+                    <colspec colname='expl' />
+                    <thead>
                       <row>
-                        <entry><literal>%R</literal></entry>
-                        <entry>Parent directory of the root control group path of systemd</entry>
-                        <entry></entry>
+                        <entry>Path</entry>
+                        <entry>Description</entry>
                       </row>
+                    </thead>
+                    <tbody>
                       <row>
-                        <entry><literal>%t</literal></entry>
-                        <entry>Runtime socket dir</entry>
-                        <entry>This is either /run (for the system manager) or $XDG_RUNTIME_DIR (for user managers).</entry>
+                        <entry><filename>/tmp/systemd-generator.early.<replaceable>XXXXXX</replaceable></filename></entry>
+                        <entry>Generated units (early)</entry>
                       </row>
                       <row>
-                        <entry><literal>%u</literal></entry>
-                        <entry>User name</entry>
-                        <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
+                        <entry><filename>/etc/systemd/user</filename></entry>
+                        <entry>Local configuration</entry>
                       </row>
                       <row>
-                        <entry><literal>%h</literal></entry>
-                        <entry>User home directory</entry>
-                        <entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
+                        <entry><filename>/run/systemd/user</filename></entry>
+                        <entry>Volatile units</entry>
                       </row>
                       <row>
-                        <entry><literal>%s</literal></entry>
-                        <entry>User shell</entry>
-                        <entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
+                        <entry><filename>/tmp/systemd-generator.<replaceable>XXXXXX</replaceable></filename></entry>
+                        <entry>Generated units (middle)</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>
+                        <entry><filename>/usr/local/lib/systemd/user</filename></entry>
+                        <entry>Units for local packages</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>
+                        <entry><filename>/usr/lib/systemd/user</filename></entry>
+                        <entry>Units for installed packages</entry>
                       </row>
                       <row>
-                        <entry><literal>%H</literal></entry>
-                        <entry>Host name</entry>
-                        <entry>The host name of the running system.</entry>
+                        <entry><filename>/tmp/systemd-generator.late.<replaceable>XXXXXX</replaceable></filename></entry>
+                        <entry>Generated units (late)</entry>
                       </row>
                     </tbody>
                   </tgroup>
                 </table>
 
-                <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>
+                <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>.
+                </para>
         </refsect1>
 
         <refsect1>
@@ -313,7 +369,7 @@
                 carries generic information about the unit that is not
                 dependent on the type of unit:</para>
 
-                <variablelist>
+                <variablelist class='unit-directives'>
 
                         <varlistentry>
                                 <term><varname>Description=</varname></term>
@@ -326,7 +382,7 @@
 
                         <varlistentry>
                                 <term><varname>Documentation=</varname></term>
-                                <listitem><para>A space separated list
+                                <listitem><para>A space-separated list
                                 of URIs referencing documentation for
                                 this unit or its
                                 configuration. Accepted are only URIs
@@ -337,8 +393,21 @@
                                 <literal>info:</literal>,
                                 <literal>man:</literal>. For more
                                 information about the syntax of these
-                                URIs see
-                                <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
+                                URIs, see
+                                <citerefentry><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>
@@ -577,7 +646,7 @@
                                 <listitem><para>Lists one or more
                                 units that are activated when this
                                 unit enters the
-                                '<literal>failed</literal>'
+                                <literal>failed</literal>
                                 state.</para></listitem>
                         </varlistentry>
 
@@ -600,8 +669,8 @@
                         <varlistentry>
                                 <term><varname>RequiresMountsFor=</varname></term>
 
-                                <listitem><para>Takes a space
-                                separated list of absolute paths. Automatically
+                                <listitem><para>Takes a space-separated
+                                list of absolute paths. Automatically
                                 adds dependencies of type
                                 <varname>Requires=</varname> and
                                 <varname>After=</varname> for all
@@ -728,7 +797,7 @@
                                 highly recommended to leave this
                                 option enabled for the majority of
                                 common units. If set to
-                                <option>false</option> this option
+                                <option>false</option>, this option
                                 does not disable all implicit
                                 dependencies, just non-essential
                                 ones.</para></listitem>
@@ -743,7 +812,7 @@
                                 time. 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>'
+                                enter the <literal>failed</literal>
                                 mode. This value defaults to 0 (job
                                 timeouts disabled), except for device
                                 units. NB: this timeout is independent
@@ -777,6 +846,7 @@
                                 <term><varname>ConditionSecurity=</varname></term>
                                 <term><varname>ConditionCapability=</varname></term>
                                 <term><varname>ConditionHost=</varname></term>
+                                <term><varname>ConditionACPower=</varname></term>
                                 <term><varname>ConditionNull=</varname></term>
 
                                 <listitem><para>Before starting a unit
@@ -801,7 +871,7 @@
                                 to
                                 <varname>ConditionPathExists=</varname>
                                 is prefixed with an exclamation mark
-                                ('!'), the test is negated, and the unit
+                                (<literal>!</literal>), the test is negated, and the unit
                                 is only started if the path does not
                                 exist.</para>
 
@@ -870,7 +940,7 @@
                                 exclamation mark unset). The argument
                                 must either be a single word, or an
                                 assignment (i.e. two words, separated
-                                '='). In the former
+                                <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
@@ -913,8 +983,11 @@
                                 <para><varname>ConditionSecurity=</varname>
                                 may be used to check whether the given
                                 security module is enabled on the
-                                system.  Currently the only recognized
-                                value is <varname>selinux</varname>.
+                                system. Currently the recognized values
+                                values are <varname>selinux</varname>,
+                                <varname>apparmor</varname>,
+                                <varname>ima</varname> and
+                                <varname>smack</varname>.
                                 The test may be negated by prepending
                                 an exclamation
                                 mark.</para>
@@ -934,11 +1007,11 @@
 
                                 <para><varname>ConditionHost=</varname>
                                 may be used to match against the
-                                host name or machine ID of the
-                                host. This either takes a host name
+                                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 host name as returned by
+                                locally set hostname as returned by
                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
                                 or a machine ID formatted as string
                                 (see
@@ -946,6 +1019,23 @@
                                 The test may be negated by prepending
                                 an exclamation mark.</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>Finally,
                                 <varname>ConditionNull=</varname> may
                                 be used to add a constant condition
@@ -972,8 +1062,12 @@
                                 pipe symbol must be passed first, the
                                 exclamation second. Except for
                                 <varname>ConditionPathIsSymbolicLink=</varname>,
-                                all path checks follow
-                                symlinks.</para></listitem>
+                                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>
@@ -1000,7 +1094,7 @@
                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                 tool during installation of a unit:</para>
 
-                <variablelist>
+                <variablelist class='unit-directives'>
                         <varlistentry>
                                 <term><varname>Alias=</varname></term>
 
@@ -1014,7 +1108,7 @@
                                 time,
                                 <command>systemctl enable</command>
                                 will create symlinks from these names
-                                to the unit file name.</para></listitem>
+                                to the unit filename.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
@@ -1040,17 +1134,145 @@
                                 <term><varname>Also=</varname></term>
 
                                 <listitem><para>Additional units to
-                                install when this unit is
-                                installed. If the user requests
-                                installation of a unit with this
-                                option configured,
+                                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>
-                                will automatically install units
-                                listed in this option as
+                                and <command>systemctl
+                                disable</command> will automatically
+                                install/uninstall units listed in this option as
                                 well.</para></listitem>
                         </varlistentry>
                 </variablelist>
 
+                <para>The following specifiers are interpreted in the
+                Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b.
+                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></entry>
+                      </row>
+                      <row>
+                        <entry><literal>%p</literal></entry>
+                        <entry>Prefix name</entry>
+                        <entry>For instantiated units this refers to the string before the @. For non-instantiated units this refers to 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></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.</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%I</literal></entry>
+                        <entry>Unescaped instance name</entry>
+                        <entry></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 prefix name similarly prepended with <filename>/</filename>.</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%c</literal></entry>
+                        <entry>Control group path of the unit</entry>
+                        <entry></entry>
+                      </row>
+                      <row>
+                        <entry><literal>%r</literal></entry>
+                        <entry>Root control group path where units are placed.</entry>
+                        <entry>For system instances this usually resolves to <filename>/system</filename>, except in containers, where the path might be prefixed with the container's root control group.</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%R</literal></entry>
+                        <entry>Parent directory of the control group path where units are placed.</entry>
+                        <entry>For system instances this usually resolves to <filename>/</filename>, except in containers, where this resolves to the container's root directory. This specifier is particularly useful in the <varname>ControlGroup=</varname> setting (see <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%t</literal></entry>
+                        <entry>Runtime socket dir</entry>
+                        <entry>This is either <filename>/run</filename> (for the system manager) or <literal>$XDG_RUNTIME_DIR</literal> (for user managers).</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%u</literal></entry>
+                        <entry>User name</entry>
+                        <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%U</literal></entry>
+                        <entry>User UID</entry>
+                        <entry>This is the UID of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%h</literal></entry>
+                        <entry>User home directory</entry>
+                        <entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%s</literal></entry>
+                        <entry>User shell</entry>
+                        <entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd instance.  If the user is <literal>root</literal> (UID equal to 0), the shell configured in account database is ignored and <filename>/bin/sh</filename> is always used.</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.</entry>
+                      </row>
+                      <row>
+                        <entry><literal>%%</literal></entry>
+                        <entry>Escaped %</entry>
+                        <entry>Single percent sign.</entry>
+                      </row>
+                    </tbody>
+                  </tgroup>
+                </table>
         </refsect1>
 
         <refsect1>
@@ -1069,7 +1291,9 @@
                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
-                        <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                        <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                 </para>
         </refsect1>