units: for all unit settings that take lists, allow the empty string for resetting...

[elogind.git] / man / systemd.unit.xml

diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index 3236bfa7416f07670294827c0984ba6df5df9f6f..953a2897ad488074839bf6f2f90f6bac449ea27e 100644 (file)
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -44,7 +44,7 @@
 
         <refnamediv>
                 <refname>systemd.unit</refname>
 
         <refnamediv>
                 <refname>systemd.unit</refname>

-                <refpurpose>systemd unit configuration files</refpurpose>
+                <refpurpose>Unit configuration</refpurpose>

         </refnamediv>
 
         <refsynopsisdiv>
         </refnamediv>
 
         <refsynopsisdiv>


@@ -75,13 +75,13 @@
                 inspired by Microsoft Windows
                 <filename>.ini</filename> files.</para>
 
                 inspired by Microsoft Windows
                 <filename>.ini</filename> files.</para>
 

-                <para>This man pages lists the common configuration
+                <para>This man page lists the common configuration

                 options of all the unit types. These options need to
                 options of all the unit types. These options need to

-                be configured in the [Unit] resp. [Install]
-                section of the unit files.</para>
+                be configured in the [Unit] or [Install]
+                sections of the unit files.</para>

 
                 <para>In addition to the generic [Unit] and [Install]
 
                 <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>
                 type-specific section, e.g. [Service] for a service
                 unit. See the respective man pages for more
                 information.</para>


@@ -106,12 +106,14 @@
                 <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
                 <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
                 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
 
                 <para>Empty lines and lines starting with # or ; are
                 ignored. This may be used for commenting. Lines ending


@@ -119,32 +121,42 @@
                 line while reading and the backslash is replaced by a
                 space character. This may be used to wrap long lines.</para>
 
                 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
                 <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
                 <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,
                 <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]
                 <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>
 
                 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 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>Note that while systemd offers a flexible
                 dependency system between units it is recommended to
                 use this functionality only sparsely and instead rely
                 <para>Note that while systemd offers a flexible
                 dependency system between units it is recommended to
                 use this functionality only sparsely and instead rely


@@ -186,91 +198,7 @@
                 <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
                 <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>
-
-                <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>This refers to the string before the @, i.e. "getty" in the example above, where "tty3" is the instance name.</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>This is the string between the @ 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 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>
-                      </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 of systemd</entry>
-                        <entry></entry>
-                      </row>
-                      <row>
-                        <entry><literal>%R</literal></entry>
-                        <entry>Parent directory of the root control group path of systemd</entry>
-                        <entry></entry>
-                      </row>
-                      <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>
-                      </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>%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>
-                    </tbody>
-                  </tgroup>
-                </table>
+                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>
 
                 <para>If a unit file is empty (i.e. has the file size
                 0) or is symlinked to <filename>/dev/null</filename>


@@ -284,6 +212,7 @@
                 <ulink
                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
                 Stability Promise</ulink>.</para>
                 <ulink
                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
                 Stability Promise</ulink>.</para>

+

         </refsect1>
 
         <refsect1>
         </refsect1>
 
         <refsect1>


@@ -318,7 +247,20 @@
                                 <literal>man:</literal>. For more
                                 information about the syntax of these
                                 URIs see
                                 <literal>man:</literal>. For more
                                 information about the syntax of these
                                 URIs see

-                                <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
+                                <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>
                         </varlistentry>
 
                         <varlistentry>


@@ -358,7 +300,15 @@
                                 <varname>Requires=</varname> in order
                                 to achieve a system that is more
                                 robust when dealing with failing
                                 <varname>Requires=</varname> in order
                                 to achieve a system that is more
                                 robust when dealing with failing

-                                services.</para></listitem>
+                                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>
                         </varlistentry>
 
                         <varlistentry>


@@ -390,7 +340,7 @@
 
                                 <listitem><para>Similar to
                                 <varname>Requires=</varname>
 
                                 <listitem><para>Similar to
                                 <varname>Requires=</varname>

-                                resp. <varname>RequiresOverridable=</varname>. However,
+                                and <varname>RequiresOverridable=</varname>, respectively. However,

                                 if a unit listed here is not started
                                 already it will not be started and the
                                 transaction fails
                                 if a unit listed here is not started
                                 already it will not be started and the
                                 transaction fails


@@ -410,7 +360,9 @@
                                 the transaction as a whole. This is
                                 the recommended way to hook start-up
                                 of one unit to the start-up of another
                                 the transaction as a whole. This is
                                 the recommended way to hook start-up
                                 of one unit to the start-up of another

-                                unit. Note that dependencies of this
+                                unit.</para>
+
+                                <para>Note that dependencies of this

                                 type may also be configured outside of
                                 the unit configuration file by
                                 adding a symlink to a
                                 type may also be configured outside of
                                 the unit configuration file by
                                 adding a symlink to a


@@ -425,7 +377,7 @@
                                 <listitem><para>Configures requirement
                                 dependencies, very similar in style to
                                 <varname>Requires=</varname>, however
                                 <listitem><para>Configures requirement
                                 dependencies, very similar in style to
                                 <varname>Requires=</varname>, however

-                                in addition to this behaviour it also
+                                in addition to this behavior it also

                                 declares that this unit is stopped
                                 when any of the units listed suddenly
                                 disappears. Units can suddenly,
                                 declares that this unit is stopped
                                 when any of the units listed suddenly
                                 disappears. Units can suddenly,


@@ -436,6 +388,21 @@
                                 systemd.</para></listitem>
                         </varlistentry>
 
                                 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>
 
                         <varlistentry>
                                 <term><varname>Conflicts=</varname></term>
 


@@ -521,7 +488,7 @@
                                 <varname>Before=</varname>. If two
                                 units have no ordering dependencies
                                 between them they are shut down
                                 <varname>Before=</varname>. If two
                                 units have no ordering dependencies
                                 between them they are shut down

-                                resp. started up simultaneously, and
+                                or started up simultaneously, and

                                 no ordering takes
                                 place. </para></listitem>
                         </varlistentry>
                                 no ordering takes
                                 place. </para></listitem>
                         </varlistentry>


@@ -556,7 +523,7 @@
                                 <term><varname>RequiresMountsFor=</varname></term>
 
                                 <listitem><para>Takes a space
                                 <term><varname>RequiresMountsFor=</varname></term>
 
                                 <listitem><para>Takes a space

-                                separated list of paths. Automatically
+                                separated list of absolute paths. Automatically

                                 adds dependencies of type
                                 <varname>Requires=</varname> and
                                 <varname>After=</varname> for all
                                 adds dependencies of type
                                 <varname>Requires=</varname> and
                                 <varname>After=</varname> for all


@@ -627,13 +594,13 @@
                                 <listitem><para>Takes a boolean
                                 argument. If <option>true</option>
                                 this unit can only be activated
                                 <listitem><para>Takes a boolean
                                 argument. If <option>true</option>
                                 this unit can only be activated

-                                (resp. deactivated) indirectly. In
+                                or deactivated indirectly. In

                                 this case explicit start-up
                                 this case explicit start-up

-                                (resp. termination) requested by the
+                                or termination requested by the

                                 user is denied, however if it is
                                 user is denied, however if it is

-                                started (resp. stopped) as a
+                                started or stopped as a

                                 dependency of another unit, start-up
                                 dependency of another unit, start-up

-                                (resp. termination) will succeed. This
+                                or termination will succeed. This

                                 is mostly a safety feature to ensure
                                 that the user does not accidentally
                                 activate units that are not intended
                                 is mostly a safety feature to ensure
                                 that the user does not accidentally
                                 activate units that are not intended


@@ -725,70 +692,100 @@
                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
                                 <term><varname>ConditionDirectoryNotEmpty=</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>
                                 <term><varname>ConditionKernelCommandLine=</varname></term>
                                 <term><varname>ConditionVirtualization=</varname></term>
                                 <term><varname>ConditionSecurity=</varname></term>
                                 <term><varname>ConditionCapability=</varname></term>
                                 <term><varname>ConditionFileIsExecutable=</varname></term>
                                 <term><varname>ConditionKernelCommandLine=</varname></term>
                                 <term><varname>ConditionVirtualization=</varname></term>
                                 <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
                                 verify that the specified condition is
                                 <term><varname>ConditionNull=</varname></term>
 
                                 <listitem><para>Before starting a unit
                                 verify that the specified condition is

-                                true. With
+                                true. If it is not true the starting
+                                of the unit will be 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.</para>
+
+                                <para>With

                                 <varname>ConditionPathExists=</varname>
                                 <varname>ConditionPathExists=</varname>

-                                a file existence condition can be
+                                a file existence condition is

                                 checked before a unit is started. If
                                 the specified absolute path name does
                                 checked before a unit is started. If
                                 the specified absolute path name does

-                                not exist, startup of a unit will not
-                                actually happen, however the unit is
-                                still useful for ordering purposes in
-                                this case. The condition is checked at
-                                the time the queued start job is to be
-                                executed. If the absolute path name
-                                passed to
+                                not exist the condition will
+                                fail. If the absolute path name passed
+                                to

                                 <varname>ConditionPathExists=</varname>
                                 is prefixed with an exclamation mark
                                 <varname>ConditionPathExists=</varname>
                                 is prefixed with an exclamation mark

-                                (!), the test is negated, and the unit
+                                ('!'), the test is negated, and the unit

                                 is only started if the path does not
                                 is only started if the path does not

-                                exist.
-                                <varname>ConditionPathExistsGlob=</varname>
-                                works in a similar way, but checks for
-                                the existence of at least one file or
-                                directory matching the specified
-                                globbing
-                                pattern. <varname>ConditionPathIsDirectory=</varname>
+                                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
                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path
                                 exists and is a

-                                directory. <varname>ConditionPathIsSymbolicLink=</varname>
+                                directory.</para>
+
+                                <para><varname>ConditionPathIsSymbolicLink=</varname>

                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path
                                 exists and is a symbolic
                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path
                                 exists and is a symbolic

-                                link. <varname>ConditionPathIsMountPoint=</varname>
+                                link.</para>
+
+                                <para><varname>ConditionPathIsMountPoint=</varname>

                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path
                                 exists and is a mount
                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path
                                 exists and is a mount

-                                point. <varname>ConditionPathIsReadWrite=</varname>
+                                point.</para>
+
+                                <para><varname>ConditionPathIsReadWrite=</varname>

                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether the underlying
                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether the underlying

-                                file system is read and writable
+                                file system is readable and writable

                                 (i.e. not mounted
                                 (i.e. not mounted

-                                read-only). <varname>ConditionFileIsExecutable=</varname>
+                                read-only).</para>
+
+                                <para><varname>ConditionDirectoryNotEmpty=</varname>

                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path
                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path

-                                exists, is a regular file and marked
-                                executable.
-                                <varname>ConditionDirectoryNotEmpty=</varname>
+                                exists and is a non-empty
+                                directory.</para>
+
+                                <para><varname>ConditionFileNotEmpty=</varname>

                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path
                                 is similar to
                                 <varname>ConditionPathExists=</varname>
                                 but verifies whether a certain path

-                                exists and is a non-empty
-                                directory. Similarly
+                                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>Similar,

                                 <varname>ConditionKernelCommandLine=</varname>
                                 may be used to check whether a
                                 specific kernel command line option is
                                 <varname>ConditionKernelCommandLine=</varname>
                                 may be used to check whether a
                                 specific kernel command line option is


@@ -796,14 +793,16 @@
                                 exclamation mark unset). The argument
                                 must either be a single word, or an
                                 assignment (i.e. two words, separated
                                 exclamation mark unset). The argument
                                 must either be a single word, or an
                                 assignment (i.e. two words, separated

-                                by the equality sign). In the former
+                                '='). 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
                                 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. <varname>ConditionVirtualization=</varname>
+                                matching.</para>
+
+                                <para><varname>ConditionVirtualization=</varname>

                                 may be used to check whether the
                                 system is executed in a virtualized
                                 environment and optionally test
                                 may be used to check whether the
                                 system is executed in a virtualized
                                 environment and optionally test


@@ -813,7 +812,7 @@
                                 any virtualized environment, or one of
                                 <varname>vm</varname> and
                                 <varname>container</varname> to test
                                 any virtualized environment, or one of
                                 <varname>vm</varname> and
                                 <varname>container</varname> to test

-                                against a specific type of
+                                against a generic type of

                                 virtualization solution, or one of
                                 <varname>qemu</varname>,
                                 <varname>kvm</varname>,
                                 virtualization solution, or one of
                                 <varname>qemu</varname>,
                                 <varname>kvm</varname>,


@@ -832,15 +831,18 @@
                                 virtualization technologies are nested
                                 only the innermost is considered. The
                                 test may be negated by prepending an
                                 virtualization technologies are nested
                                 only the innermost is considered. The
                                 test may be negated by prepending an

-                                exclamation mark.
-                                <varname>ConditionSecurity=</varname>
+                                exclamation mark.</para>
+
+                                <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>.
                                 The test may be negated by prepending
                                 an exclamation
                                 may be used to check whether the given
                                 security module is enabled on the
                                 system.  Currently the only recognized
                                 value is <varname>selinux</varname>.
                                 The test may be negated by prepending
                                 an exclamation

-                                mark. <varname>ConditionCapability=</varname>
+                                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
                                 may be used to check whether the given
                                 capability exists in the capability
                                 bounding set of the service manager


@@ -851,14 +853,49 @@
                                 for details). Pass a capability name
                                 such as <literal>CAP_MKNOD</literal>,
                                 possibly prefixed with an exclamation
                                 for details). Pass a capability name
                                 such as <literal>CAP_MKNOD</literal>,
                                 possibly prefixed with an exclamation

-                                mark to negate the check. Finally,
+                                mark to negate the check.</para>
+
+                                <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
+                                string (optionally with shell style
+                                globs) which is tested against the
+                                locally set host name 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>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
                                 check value to the unit. It takes a
                                 boolean argument. If set to
                                 <varname>false</varname> the condition
                                 will always fail, otherwise
                                 <varname>ConditionNull=</varname> may
                                 be used to add a constant condition
                                 check value to the unit. It takes a
                                 boolean argument. If set to
                                 <varname>false</varname> the condition
                                 will always fail, otherwise

-                                succeed. If multiple conditions are
+                                succeed.</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
                                 specified the unit will be executed if
                                 all of them apply (i.e. a logical AND
                                 is applied). Condition checks can be


@@ -875,8 +912,12 @@
                                 pipe symbol must be passed first, the
                                 exclamation second. Except for
                                 <varname>ConditionPathIsSymbolicLink=</varname>,
                                 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>
                         </varlistentry>
 
                         <varlistentry>


@@ -926,8 +967,8 @@
 
                                 <listitem><para>Installs a symlink in
                                 the <filename>.wants/</filename>
 
                                 <listitem><para>Installs a symlink in
                                 the <filename>.wants/</filename>

-                                resp. <filename>.requires/</filename>
-                                subdirectory for a unit. This has the
+                                or <filename>.requires/</filename>
+                                subdirectory for a unit, respectively. This has the

                                 effect that when the listed unit name
                                 is activated the unit listing it is
                                 activated
                                 effect that when the listed unit name
                                 is activated the unit listing it is
                                 activated


@@ -956,6 +997,124 @@
 
         </refsect1>
 
 
         </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 @ 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 file name</entry>
+                        <entry>This is either the unescaped instance name (if applicable) with / prepended (if applicable), or the prefix name similarly prepended with /.</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 of systemd</entry>
+                        <entry></entry>
+                      </row>
+                      <row>
+                        <entry><literal>%R</literal></entry>
+                        <entry>Parent directory of the root control group path of systemd</entry>
+                        <entry></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.</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 host name of the running system.</entry>
+                      </row>
+                    </tbody>
+                  </tgroup>
+                </table>
+        </refsect1>
+

         <refsect1>
                 <title>See Also</title>
                 <para>
         <refsect1>
                 <title>See Also</title>
                 <para>


@@ -972,7 +1131,9 @@
                         <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>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>
 
                 </para>
         </refsect1>