chiark / gitweb /
man: improve documentation for StandardOutput= and StandardInput=
[elogind.git] / man / systemd.exec.xml
index e1193d2..cfcf996 100644 (file)
@@ -1,4 +1,3 @@
-<?xml version='1.0'?> <!--*-nxml-*-->
 <?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
         </refnamediv>
 
         <refsynopsisdiv>
-                <para><filename>systemd.service</filename>,
-                <filename>systemd.socket</filename>,
-                <filename>systemd.mount</filename>,
-                <filename>systemd.swap</filename></para>
+                <para><filename><replaceable>service</replaceable>.service</filename>,
+                <filename><replaceable>socket</replaceable>.socket</filename>,
+                <filename><replaceable>mount</replaceable>.mount</filename>,
+                <filename><replaceable>swap</replaceable>.swap</filename></para>
         </refsynopsisdiv>
 
         <refsect1>
                 <title>Description</title>
 
                 <para>Unit configuration files for services, sockets,
-                mount points and swap devices share a subset of
+                mount points, and swap devices share a subset of
                 configuration options which define the execution
                 environment of spawned processes.</para>
 
                 files, and
                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
-                <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                 and
                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                 for more information on the specific unit
                 configuration files. The execution specific
                 configuration options are configured in the [Service],
-                [Socket], [Mount] resp. [Swap] section, depending on the unit
+                [Socket], [Mount], or [Swap] sections, depending on the unit
                 type.</para>
         </refsect1>
 
         <refsect1>
                 <title>Options</title>
 
-                <variablelist>
+                <variablelist class='unit-directives'>
 
                         <varlistentry>
                                 <term><varname>WorkingDirectory=</varname></term>
@@ -90,7 +89,7 @@
                                 <listitem><para>Takes an absolute
                                 directory path. Sets the working
                                 directory for executed processes. If
-                                not set defaults to the root directory
+                                not set, defaults to the root directory
                                 when systemd is running as a system
                                 instance and the respective user's
                                 home directory if run as
                                 directory path. Sets the root
                                 directory for executed processes, with
                                 the
-                                <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
-                                system call. If this is used it must
+                                <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                system call. If this is used, it must
                                 be ensured that the process and all
                                 its auxiliary files are available in
                                 the <function>chroot()</function>
                                 <term><varname>Group=</varname></term>
 
                                 <listitem><para>Sets the Unix user
-                                resp. group the processes are executed
-                                as. Takes a single user resp. group
+                                or group that the processes are executed
+                                as, respectively. Takes a single user or group
                                 name or ID as argument. If no group is
-                                set the default group of the user is
+                                set, the default group of the user is
                                 chosen.</para></listitem>
                         </varlistentry>
 
 
                                 <listitem><para>Sets the supplementary
                                 Unix groups the processes are executed
-                                as. This takes a space separated list
+                                as. This takes a space-separated list
                                 of group names or IDs. This option may
                                 be specified more than once in which
                                 case all listed groups are set as
-                                supplementary groups. This option does
-                                not override but extends the list of
-                                supplementary groups configured in the
-                                system group database for the
+                                supplementary groups. When the empty
+                                string is assigned the list of
+                                supplementary groups is reset, and all
+                                assignments prior to this one will
+                                have no effect. In any way, this
+                                option does not override, but extends
+                                the list of supplementary groups
+                                configured in the system group
+                                database for the
                                 user.</para></listitem>
                         </varlistentry>
 
                                 for this process) and 1000 (to make
                                 killing of this process under memory
                                 pressure very likely). See <ulink
-                                url="http://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
+                                url="https://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
                                 for details.</para></listitem>
                         </varlistentry>
 
 
                                 <listitem><para>Sets the CPU
                                 scheduling priority for executed
-                                processes. Takes an integer between 1
-                                (lowest priority) and 99 (highest
-                                priority). The available priority
+                                processes. The available priority
                                 range depends on the selected CPU
-                                scheduling policy (see above). See
-                                <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
-                                for details.</para></listitem>
+                                scheduling policy (see above). For
+                                real-time scheduling policies an
+                                integer between 1 (lowest priority)
+                                and 99 (highest priority) can be used.
+                                See <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                for details.
+                                </para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <term><varname>CPUSchedulingResetOnFork=</varname></term>
 
                                 <listitem><para>Takes a boolean
-                                argument. If true elevated CPU
+                                argument. If true, elevated CPU
                                 scheduling priorities and policies
                                 will be reset when the executed
                                 processes fork, and can hence not leak
                                 <listitem><para>Controls the CPU
                                 affinity of the executed
                                 processes. Takes a space-separated
-                                list of CPU indexes. See
+                                list of CPU indices. This option may
+                                be specified more than once in which
+                                case the specificed CPU affinity masks
+                                are merged. If the empty string is
+                                assigned, the mask is reset, all
+                                assignments prior to this will have no
+                                effect. See
                                 <citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                 for details.</para></listitem>
                         </varlistentry>
                                 option may be specified more than once
                                 in which case all listed variables
                                 will be set. If the same variable is
-                                set twice the later setting will
-                                override the earlier setting. See
-                                <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
-                                for details.</para></listitem>
+                                set twice, the later setting will
+                                override the earlier setting. If the
+                                empty string is assigned to this
+                                option, the list of environment
+                                variables is reset, all prior
+                                assignments have no effect.
+                                Variable expansion is not performed
+                                inside the strings, however, specifier
+                                expansion is possible. The $ character has
+                                no special meaning.
+                                If you need to assign a value containing spaces
+                                to a variable, use double quotes (")
+                                for the assignment.</para>
+
+                                <para>Example:
+                                <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"</programlisting>
+                                gives three variables <literal>VAR1</literal>,
+                                <literal>VAR2</literal>, <literal>VAR3</literal>
+                                with the values <literal>word1 word2</literal>,
+                                <literal>word3</literal>, <literal>$word 5 6</literal>.
+                                </para>
+
+                                <para>
+                                See
+                                <citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                                for details about environment variables.</para></listitem>
                         </varlistentry>
                         <varlistentry>
                                 <term><varname>EnvironmentFile=</varname></term>
                                 <varname>Environment=</varname> but
                                 reads the environment variables from a
                                 text file. The text file should
-                                contain new-line separated variable
+                                contain new-line-separated variable
                                 assignments. Empty lines and lines
                                 starting with ; or # will be ignored,
-                                which may be used for commenting. The
-                                parser strips leading and
-                                trailing whitespace from the values
+                                which may be used for commenting. A line
+                                ending with a backslash will be concatenated
+                                with the following one, allowing multiline variable
+                                definitions. The parser strips leading
+                                and trailing whitespace from the values
                                 of assignments, unless you use
-                                double quotes (").
-                                The
-                                argument passed should be an absolute
-                                file name, optionally prefixed with
-                                "-", which indicates that if the file
-                                does not exist it won't be read and no
-                                error or warning message is
-                                logged. The files listed with this
+                                double quotes (").</para>
+
+                                <para>The argument passed should be an
+                                absolute filename or wildcard
+                                expression, optionally prefixed with
+                                <literal>-</literal>, which indicates
+                                that if the file does not exist, it
+                                will not be read and no error or warning
+                                message is logged.  This option may be
+                                specified more than once in which case
+                                all specified files are read. If the
+                                empty string is assigned to this
+                                option, the list of file to read is
+                                reset, all prior assignments have no
+                                effect.</para>
+
+                                <para>The files listed with this
                                 directive will be read shortly before
-                                the process is executed. Settings from
-                                these files override settings made
-                                with
+                                the process is executed (more
+                                specifically, after all
+                                processes from a previous unit state
+                                terminated. This means you can
+                                generate these files in one unit
+                                state, and read it with this option in
+                                the next). Settings from these files
+                                override settings made with
                                 <varname>Environment=</varname>. If
                                 the same variable is set twice from
-                                these files the files will be read in
+                                these files, the files will be read in
                                 the order they are specified and the
                                 later setting will override the
-                                earlier setting. </para></listitem>
+                                earlier setting.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <option>tty</option>,
                                 <option>tty-force</option>,
                                 <option>tty-fail</option> or
-                                <option>socket</option>. If
-                                <option>null</option> is selected
-                                standard input will be connected to
+                                <option>socket</option>.</para>
+
+                                <para>If <option>null</option> is
+                                selected, standard input will be
+                                connected to
                                 <filename>/dev/null</filename>,
                                 i.e. all read attempts by the process
-                                will result in immediate EOF. If
-                                <option>tty</option> is selected
-                                standard input is connected to a TTY
-                                (as configured by
+                                will result in immediate EOF.</para>
+
+                                <para>If <option>tty</option> is
+                                selected, standard input is connected
+                                to a TTY (as configured by
                                 <varname>TTYPath=</varname>, see
                                 below) and the executed process
                                 becomes the controlling process of the
                                 terminal. If the terminal is already
-                                being controlled by another process the
-                                executed process waits until the current
-                                controlling process releases the
-                                terminal.
-                                <option>tty-force</option>
-                                is similar to <option>tty</option>,
-                                but the executed process is forcefully
-                                and immediately made the controlling
+                                being controlled by another process,
+                                the executed process waits until the
+                                current controlling process releases
+                                the terminal.</para>
+
+                                <para><option>tty-force</option> is similar
+                                to <option>tty</option>, but the
+                                executed process is forcefully and
+                                immediately made the controlling
                                 process of the terminal, potentially
                                 removing previous controlling
                                 processes from the
-                                terminal. <option>tty-fail</option> is
+                                terminal.</para>
+
+                                <para><option>tty-fail</option> is
                                 similar to <option>tty</option> but if
                                 the terminal already has a controlling
                                 process start-up of the executed
-                                process fails.  The
-                                <option>socket</option> option is only
-                                valid in socket-activated services,
-                                and only when the socket configuration
-                                file (see
+                                process fails.</para>
+
+                                <para>The <option>socket</option>
+                                option is only valid in
+                                socket-activated services, and only
+                                when the socket configuration file
+                                (see
                                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                                 for details) specifies a single socket
-                                only. If this option is set standard
+                                only. If this option is set, standard
                                 input will be connected to the socket
                                 the service was activated from, which
                                 is primarily useful for compatibility
                                 with daemons designed for use with the
                                 traditional
                                 <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
-                                daemon. This setting defaults to
+                                daemon.</para>
+
+                                <para>This setting defaults to
                                 <option>null</option>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
                                 of <option>inherit</option>,
                                 <option>null</option>,
                                 <option>tty</option>,
+                                <option>journal</option>,
                                 <option>syslog</option>,
                                 <option>kmsg</option>,
-                                <option>journal</option>,
+                                <option>journal+console</option>,
                                 <option>syslog+console</option>,
-                                <option>kmsg+console</option>,
-                                <option>journal+console</option> or
-                                <option>socket</option>. If set to
-                                <option>inherit</option> the file
-                                descriptor of standard input is
-                                duplicated for standard output. If set
-                                to <option>null</option> standard
-                                output will be connected to
+                                <option>kmsg+console</option> or
+                                <option>socket</option>.</para>
+
+                                <para><option>inherit</option>
+                                duplicates the file descriptor of
+                                standard input for standard
+                                output.</para>
+
+                                <para><option>null</option> connects
+                                standard output to
                                 <filename>/dev/null</filename>,
                                 i.e. everything written to it will be
-                                lost. If set to <option>tty</option>
-                                standard output will be connected to a
-                                tty (as configured via
+                                lost.</para>
+
+                                <para><option>tty</option> connects
+                                standard output to a tty (as
+                                configured via
                                 <varname>TTYPath=</varname>, see
                                 below). If the TTY is used for output
-                                only the executed process will not
+                                only, the executed process will not
                                 become the controlling process of the
                                 terminal, and will not fail or wait
                                 for other processes to release the
-                                terminal. <option>syslog</option>
-                                connects standard output to the
-                                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
-                                system syslog
-                                service. <option>kmsg</option>
-                                connects it with the kernel log buffer
-                                which is accessible via
-                                <citerefentry><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>. <option>journal</option>
-                                connects it with the journal which is
-                                accessible via
-                                <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
-                                (Note that everything that is written
-                                to syslog or kmsg is implicitly stored
-                                in the journal as well, those options
-                                are hence supersets of this
-                                one). <option>syslog+console</option>,
-                                <option>journal+console</option> and
-                                <option>kmsg+console</option> work
-                                similarly but copy the output to the
-                                system console as
-                                well. <option>socket</option> connects
-                                standard output to a socket from
-                                socket activation, semantics are
-                                similar to the respective option of
-                                <varname>StandardInput=</varname>.
-                                This setting defaults to the value set
-                                with
+                                terminal.</para>
+
+                                <para><option>journal</option>
+                                connects standard output with the
+                                journal which is accessible via
+                                <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
+                                Note that everything that is written
+                                to syslog or kmsg (see below) is
+                                implicitly stored in the journal as
+                                well, the specific two options listed
+                                below are hence supersets of this
+                                one.</para>
+
+                                <para><option>syslog</option> connects
+                                standard output to the <citerefentry
+                                project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                                system syslog service, in addition to
+                                the journal. Note that the journal
+                                daemon is usually configured to
+                                forward everything it receives to
+                                syslog anyway, in which case this
+                                option is no different from
+                                <option>journal</option>.</para>
+
+                                <para><option>kmsg</option> connects
+                                standard output with the kernel log
+                                buffer which is accessible via
+                                <citerefentry
+                                project='man-pages'><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+                                in addition to the journal. The
+                                journal daemon might be configured to
+                                send all logs to kmsg anyway, in which
+                                case this option is no different from
+                                <option>journal</option>.</para>
+
+                                <para><option>journal+console</option>,
+                                <option>syslog+console</option> and
+                                <option>kmsg+console</option> work in
+                                a similar way as the three options
+                                above but copy the output to the
+                                system console as well.</para>
+
+                                <para><option>socket</option> connects
+                                standard output to a socket acquired
+                                via socket activation. The semantics
+                                are similar to the same option of
+                                <varname>StandardInput=</varname>.</para>
+
+                                <para>This setting defaults to the
+                                value set with
                                 <option>DefaultStandardOutput=</option>
                                 in
-                                <citerefentry><refentrytitle>systemd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                                 which defaults to
                                 <option>journal</option>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
                                 <term><varname>StandardError=</varname></term>
                                 <listitem><para>Controls where file
-                                descriptor 2 (STDERR) of the executed
-                                processes is connected to. The
-                                available options are identical to
+                                descriptor 2 (STDERR) of the
+                                executed processes is connected to.
+                                The available options are identical to
                                 those of
                                 <varname>StandardOutput=</varname>,
                                 with one exception: if set to
                                 setting defaults to the value set with
                                 <option>DefaultStandardError=</option>
                                 in
-                                <citerefentry><refentrytitle>systemd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                                 which defaults to
                                 <option>inherit</option>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
                                 <term><varname>TTYPath=</varname></term>
                                 <listitem><para>Sets the terminal
-                                device node to use if standard input,
-                                output or stderr are connected to a
+                                device node to use if standard input, output,
+                                or error are connected to a
                                 TTY (see above). Defaults to
                                 <filename>/dev/console</filename>.</para></listitem>
                         </varlistentry>
                         </varlistentry>
                         <varlistentry>
                                 <term><varname>TTYVTDisallocate=</varname></term>
-                                <listitem><para>If the the terminal
+                                <listitem><para>If the terminal
                                 device specified with
                                 <varname>TTYPath=</varname> is a
-                                virtual console terminal try to
+                                virtual console terminal, try to
                                 deallocate the TTY before and after
                                 execution. This ensures that the
                                 screen and scrollback buffer is
                                 <term><varname>SyslogIdentifier=</varname></term>
                                 <listitem><para>Sets the process name
                                 to prefix log lines sent to syslog or
-                                the kernel log buffer with. If not set
+                                the kernel log buffer with. If not set,
                                 defaults to the process name of the
                                 executed process. This option is only
                                 useful when
                                 <option>local5</option>,
                                 <option>local6</option> or
                                 <option>local7</option>. See
-                                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                                <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                                 for details. This option is only
                                 useful when
                                 <varname>StandardOutput=</varname> or
                                 <option>notice</option>,
                                 <option>info</option>,
                                 <option>debug</option>. See
-                                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                                <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                                 for details. This option is only
                                 useful when
                                 <varname>StandardOutput=</varname> or
                                 argument. If true and
                                 <varname>StandardOutput=</varname> or
                                 <varname>StandardError=</varname> are
-                                set to <option>syslog</option> or
-                                <option>kmsg</option> log lines
+                                set to <option>syslog</option>,
+                                <option>kmsg</option> or
+                                <option>journal</option>, log lines
                                 written by the executed process that
                                 are prefixed with a log level will be
                                 passed on to syslog with this log
                         <varlistentry>
                                 <term><varname>PAMName=</varname></term>
                                 <listitem><para>Sets the PAM service
-                                name to set up a session as. If set
+                                name to set up a session as. If set,
                                 the executed process will be
                                 registered as a PAM session under the
                                 specified service name. This is only
                                 useful in conjunction with the
                                 <varname>User=</varname> setting. If
-                                not set no PAM session will be opened
+                                not set, no PAM session will be opened
                                 for the executed processes. See
-                                <citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                                <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                                 for details.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
-                                <term><varname>TCPWrapName=</varname></term>
-                                <listitem><para>If this is a
-                                socket-activated service this sets the
-                                tcpwrap service name to check the
-                                permission for the current connection
-                                with. This is only useful in
-                                conjunction with socket-activated
-                                services, and stream sockets (TCP) in
-                                particular. It has no effect on other
-                                socket types (e.g. datagram/UDP) and
-                                on processes unrelated to socket-based
-                                activation. If the tcpwrap
-                                verification fails daemon start-up
-                                will fail and the connection is
-                                terminated. See
-                                <citerefentry><refentrytitle>tcpd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
-                                for details. Note that this option may
-                                be used to do access control checks
-                                only. Shell commands and commands
-                                described in
-                                <citerefentry><refentrytitle>hosts_options</refentrytitle><manvolnum>5</manvolnum></citerefentry>
-                                are not supported.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
                                 <term><varname>CapabilityBoundingSet=</varname></term>
 
                                 <listitem><para>Controls which
                                 capabilities to include in the
                                 capability bounding set for the
                                 executed process. See
-                                <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
-                                for details. Takes a whitespace
-                                separated list of capability names as
-                                read by
-                                <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+                                <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                                for details. Takes a whitespace-separated
+                                list of capability names as read by
+                                <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+                                e.g. <constant>CAP_SYS_ADMIN</constant>,
+                                <constant>CAP_DAC_OVERRIDE</constant>,
+                                <constant>CAP_SYS_PTRACE</constant>.
                                 Capabilities listed will be included
                                 in the bounding set, all others are
                                 removed. If the list of capabilities
-                                is prefixed with ~ all but the listed
-                                capabilities will be included, the
-                                effect of the assignment
-                                inverted. Note that this option also
-                                effects the respective capabilities in
-                                the effective, permitted and
-                                inheritable capability sets, on top of
-                                what <varname>Capabilities=</varname>
-                                does. If this option is not used the
+                                is prefixed with <literal>~</literal>,
+                                all but the listed capabilities will
+                                be included, the effect of the
+                                assignment inverted. Note that this
+                                option also affects the respective
+                                capabilities in the effective,
+                                permitted and inheritable capability
+                                sets, on top of what
+                                <varname>Capabilities=</varname>
+                                does. If this option is not used, the
                                 capability bounding set is not
                                 modified on process execution, hence
                                 no limits on the capabilities of the
-                                process are
-                                enforced.</para></listitem>
+                                process are enforced. This option may
+                                appear more than once in which case
+                                the bounding sets are merged. If the
+                                empty string is assigned to this
+                                option, the bounding set is reset to
+                                the empty capability set, and all
+                                prior settings have no effect. If set
+                                to <literal>~</literal> (without any
+                                further argument), the bounding set is
+                                reset to the full set of available
+                                capabilities, also undoing any
+                                previous settings.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <term><varname>SecureBits=</varname></term>
                                 <listitem><para>Controls the secure
                                 bits set for the executed process. See
-                                <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                                <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                                 for details. Takes a list of strings:
                                 <option>keep-caps</option>,
                                 <option>keep-caps-locked</option>,
                                 <option>no-setuid-fixup</option>,
                                 <option>no-setuid-fixup-locked</option>,
                                 <option>noroot</option> and/or
-                                <option>noroot-locked</option>.
-                                </para></listitem>
+                                <option>noroot-locked</option>. This
+                                option may appear more than once in
+                                which case the secure bits are
+                                ORed. If the empty string is assigned
+                                to this option, the bits are reset to
+                                0.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <term><varname>Capabilities=</varname></term>
                                 <listitem><para>Controls the
-                                <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                                <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                                 set for the executed process. Take a
                                 capability string describing the
                                 effective, permitted and inherited
                                 capability sets as documented in
                                 <citerefentry><refentrytitle>cap_from_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
                                 Note that these capability sets are
-                                usually influenced by the capabilities
+                                usually influenced (and filtered) by the capabilities
                                 attached to the executed file. Due to
                                 that
                                 <varname>CapabilityBoundingSet=</varname>
                         </varlistentry>
 
                         <varlistentry>
-                                <term><varname>ControlGroup=</varname></term>
-
-                                <listitem><para>Controls the control
-                                groups the executed processes shall be
-                                made members of. Takes a
-                                space-separated list of cgroup
-                                identifiers. A cgroup identifier has a
-                                format like
-                                <filename>cpu:/foo/bar</filename>,
-                                where "cpu" identifies the kernel
-                                control group controller used, and
-                                <filename>/foo/bar</filename> is the
-                                control group path. The controller
-                                name and ":" may be omitted in which
-                                case the named systemd control group
-                                hierarchy is implied. Alternatively,
-                                the path and ":" may be omitted, in
-                                which case the default control group
-                                path for this unit is implied. This
-                                option may be used to place executed
-                                processes in arbitrary groups in
-                                arbitrary hierarchies -- which can be
-                                configured externally with additional
-                                execution limits. By default systemd
-                                will place all executed processes in
-                                separate per-unit control groups
-                                (named after the unit) in the systemd
-                                named hierarchy. Since every process
-                                can be in one group per hierarchy only
-                                overriding the control group path in
-                                the named systemd hierarchy will
-                                disable automatic placement in the
-                                default group. This option is
-                                primarily intended to place executed
-                                processes in specific paths in
-                                specific kernel controller
-                                hierarchies. It is however not
-                                recommended to manipulate the service
-                                control group path in the systemd
-                                named hierarchy. For details about
-                                control groups see <ulink
-                                url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>ControlGroupModify=</varname></term>
-                                <listitem><para>Takes a boolean
-                                argument. If true, the control groups
-                                created for this unit will be owned by
-                                the user specified with
-                                <varname>User=</varname> (and the
-                                appropriate group), and he/she can create
-                                subgroups as well as add processes to
-                                the group.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>ControlGroupPersistent=</varname></term>
-                                <listitem><para>Takes a boolean
-                                argument. If true, the control groups
-                                created for this unit will be marked
-                                to be persistent, i.e. systemd will
-                                not remove them when stopping the
-                                unit. The default is false, meaning
-                                that the control groups will be
-                                removed when the unit is stopped. For
-                                details about the semantics of this
-                                logic see <ulink
-                                url="http://www.freedesktop.org/wiki/Software/systemd/PaxControlGroups">PaxControlGroups</ulink>.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>ControlGroupAttribute=</varname></term>
-
-                                <listitem><para>Set a specific control
-                                group attribute for executed
-                                processes, and (if needed) add the the
-                                executed processes to a cgroup in the
-                                hierarchy of the controller the
-                                attribute belongs to. Takes two
-                                space-separated arguments: the
-                                attribute name (syntax is
-                                <literal>cpu.shares</literal> where
-                                <literal>cpu</literal> refers to a
-                                specific controller and
-                                <literal>shares</literal> to the
-                                attribute name), and the attribute
-                                value. Example:
-                                <literal>ControlGroupAttribute=cpu.shares
-                                512</literal>. If this option is used
-                                for an attribute that belongs to a
-                                kernel controller hierarchy the unit
-                                is not already configured to be added
-                                to (for example via the
-                                <literal>ControlGroup=</literal>
-                                option) then the unit will be added to
-                                the controller and the default unit
-                                cgroup path is implied. Thus, using
-                                <varname>ControlGroupAttribute=</varname>
-                                is in most case sufficient to make use
-                                of control group enforcements,
-                                explicit
-                                <varname>ControlGroup=</varname> are
-                                only necessary in case the implied
-                                default control group path for a
-                                service is not desirable. For details
-                                about control group attributes see
-                                <ulink
-                                url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>. This
-                                option may appear more than once, in
-                                order to set multiple control group
-                                attributes.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>CPUShares=</varname></term>
-
-                                <listitem><para>Assign the specified
-                                overall CPU time shares to the
-                                processes executed. Takes an integer
-                                value. This controls the
-                                <literal>cpu.shares</literal> control
-                                group attribute, which defaults to
-                                1024. For details about this control
-                                group attribute see <ulink
-                                url="http://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>MemoryLimit=</varname></term>
-                                <term><varname>MemorySoftLimit=</varname></term>
-
-                                <listitem><para>Limit the overall memory usage
-                                of the executed processes to a certain
-                                size. Takes a memory size in bytes. If
-                                the value is suffixed with K, M, G or
-                                T the specified memory size is parsed
-                                as Kilobytes, Megabytes, Gigabytes,
-                                resp. Terabytes (to the base
-                                1024). This controls the
-                                <literal>memory.limit_in_bytes</literal>
-                                and
-                                <literal>memory.soft_limit_in_bytes</literal>
-                                control group attributes. For details
-                                about these control group attributes
-                                see <ulink
-                                url="http://www.kernel.org/doc/Documentation/cgroups/memory.txt">memory.txt</ulink>.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>DeviceAllow=</varname></term>
-                                <term><varname>DeviceDeny=</varname></term>
-
-                                <listitem><para>Control access to
-                                specific device nodes by the executed processes. Takes two
-                                space separated strings: a device node
-                                path (such as
-                                <filename>/dev/null</filename>)
-                                followed by a combination of r, w, m
-                                to control reading, writing resp.
-                                creating of the specific device node
-                                by the unit. This controls the
-                                <literal>devices.allow</literal>
-                                and
-                                <literal>devices.deny</literal>
-                                control group attributes. For details
-                                about these control group attributes
-                                see <ulink
-                                url="http://www.kernel.org/doc/Documentation/cgroups/devices.txt">devices.txt</ulink>.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>BlockIOWeight=</varname></term>
-
-                                <listitem><para>Set the default or
-                                per-device overall block IO weight
-                                value for the executed
-                                processes. Takes either a single
-                                weight value (between 10 and 1000) to
-                                set the default block IO weight, or a
-                                space separated pair of a file path
-                                and a weight value to specify the
-                                device specific weight value (Example:
-                                "/dev/sda 500"). The file path may be
-                                specified as path to a block device
-                                node or as any other file in which
-                                case the backing block device of the
-                                file system of the file is
-                                determined. This controls the
-                                <literal>blkio.weight</literal> and
-                                <literal>blkio.weight_device</literal>
-                                control group attributes, which
-                                default to 1000. Use this option
-                                multiple times to set weights for
-                                multiple devices. For details about
-                                these control group attributes see
-                                <ulink
-                                url="http://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
-                                <term><varname>BlockIOReadBandwidth=</varname></term>
-                                <term><varname>BlockIOWriteBandwidth=</varname></term>
-
-                                <listitem><para>Set the per-device
-                                overall block IO bandwidth limit for
-                                the executed processes. Takes a space
-                                separated pair of a file path and a
-                                bandwidth value (in bytes per second)
-                                to specify the device specific
-                                bandwidth. The file path may be
-                                specified as path to a block device
-                                node or as any other file in which
-                                case the backing block device of the
-                                file system of the file is determined.
-                                If the bandwidth is suffixed with K, M,
-                                G, or T the specified bandwidth is
-                                parsed as Kilobytes, Megabytes,
-                                Gigabytes, resp. Terabytes (Example:
-                                "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0
-                                5M"). This controls the
-                                <literal>blkio.read_bps_device</literal>
-                                and
-                                <literal>blkio.write_bps_device</literal>
-                                control group attributes. Use this
-                                option multiple times to set bandwidth
-                                limits for multiple devices. For
-                                details about these control group
-                                attributes see <ulink
-                                url="http://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.</para></listitem>
-                        </varlistentry>
-
-                        <varlistentry>
                                 <term><varname>ReadWriteDirectories=</varname></term>
                                 <term><varname>ReadOnlyDirectories=</varname></term>
                                 <term><varname>InaccessibleDirectories=</varname></term>
 
-                                <listitem><para>Sets up a new
-                                file-system name space for executed
+                                <listitem><para>Sets up a new file
+                                system namespace for executed
                                 processes. These options may be used
                                 to limit access a process might have
-                                to the main file-system
+                                to the main file system
                                 hierarchy. Each setting takes a
                                 space-separated list of absolute
                                 directory paths. Directories listed in
                                 usual file access controls would
                                 permit this. Directories listed in
                                 <varname>InaccessibleDirectories=</varname>
-                                will be made inaccessible for processes
-                                inside the namespace. Note that
-                                restricting access with these options
-                                does not extend to submounts of a
-                                directory. You must list submounts
-                                separately in these settings to
-                                ensure the same limited access. These
-                                options may be specified more than
-                                once in which case all directories
-                                listed will have limited access from
-                                within the
+                                will be made inaccessible for
+                                processes inside the namespace. Note
+                                that restricting access with these
+                                options does not extend to submounts
+                                of a directory that are created later
+                                on. These options may be specified
+                                more than once in which case all
+                                directories listed will have limited
+                                access from within the namespace. If
+                                the empty string is assigned to this
+                                option, the specific list is reset,
+                                and all prior assignments have no
+                                effect.</para>
+                                <para>Paths in
+                                <varname>ReadOnlyDirectories=</varname>
+                                and
+                                <varname>InaccessibleDirectories=</varname>
+                                may be prefixed with
+                                <literal>-</literal>, in which case
+                                they will be ignored when they do not
+                                exist. Note that using this
+                                setting will disconnect propagation of
+                                mounts from the service to the host
+                                (propagation in the opposite direction
+                                continues to work). This means that
+                                this setting may not be used for
+                                services which shall be able to
+                                install mount points in the main mount
                                 namespace.</para></listitem>
                         </varlistentry>
 
                                 <term><varname>PrivateTmp=</varname></term>
 
                                 <listitem><para>Takes a boolean
-                                argument. If true sets up a new file
+                                argument. If true, sets up a new file
                                 system namespace for the executed
-                                processes and mounts a private
-                                <filename>/tmp</filename> directory
-                                inside it, that is not shared by
-                                processes outside of the
+                                processes and mounts private
+                                <filename>/tmp</filename> and
+                                <filename>/var/tmp</filename>
+                                directories inside it that is not
+                                shared by processes outside of the
                                 namespace. This is useful to secure
                                 access to temporary files of the
                                 process, but makes sharing between
                                 processes via
-                                <filename>/tmp</filename>
-                                impossible. Defaults to
-                                false.</para></listitem>
+                                <filename>/tmp</filename> or
+                                <filename>/var/tmp</filename>
+                                impossible. If this is enabled, all
+                                temporary files created by a service
+                                in these directories will be removed
+                                after the service is stopped. Defaults
+                                to false. It is possible to run two or
+                                more units within the same private
+                                <filename>/tmp</filename> and
+                                <filename>/var/tmp</filename>
+                                namespace by using the
+                                <varname>JoinsNamespaceOf=</varname>
+                                directive, see
+                                <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                                for details. Note that using this
+                                setting will disconnect propagation of
+                                mounts from the service to the host
+                                (propagation in the opposite direction
+                                continues to work). This means that
+                                this setting may not be used for
+                                services which shall be able to install
+                                mount points in the main mount
+                                namespace.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>PrivateDevices=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument. If true, sets up a new /dev
+                                namespace for the executed processes
+                                and only adds API pseudo devices such
+                                as <filename>/dev/null</filename>,
+                                <filename>/dev/zero</filename> or
+                                <filename>/dev/random</filename> (as
+                                well as the pseudo TTY subsystem) to
+                                it, but no physical devices such as
+                                <filename>/dev/sda</filename>. This is
+                                useful to securely turn off physical
+                                device access by the executed
+                                process. Defaults to false. Enabling
+                                this option will also remove
+                                <constant>CAP_MKNOD</constant> from
+                                the capability bounding set for the
+                                unit (see above), and set
+                                <varname>DevicePolicy=closed</varname>
+                                (see
+                                <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                                for details). Note that using this
+                                setting will disconnect propagation of
+                                mounts from the service to the host
+                                (propagation in the opposite direction
+                                continues to work). This means that
+                                this setting may not be used for
+                                services which shall be able to
+                                install mount points in the main mount
+                                namespace.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <term><varname>PrivateNetwork=</varname></term>
 
                                 <listitem><para>Takes a boolean
-                                argument. If true sets up a new
+                                argument. If true, sets up a new
                                 network namespace for the executed
                                 processes and configures only the
                                 loopback network device
                                 available to the executed process.
                                 This is useful to securely turn off
                                 network access by the executed
-                                process. Defaults to
-                                false.</para></listitem>
+                                process. Defaults to false. It is
+                                possible to run two or more units
+                                within the same private network
+                                namespace by using the
+                                <varname>JoinsNamespaceOf=</varname>
+                                directive, see
+                                <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                                for details. Note that this option
+                                will disconnect all socket families
+                                from the host, this includes
+                                AF_NETLINK and AF_UNIX. The latter has
+                                the effect that AF_UNIX sockets in the
+                                abstract socket namespace will become
+                                unavailable to the processes (however,
+                                those located in the file system will
+                                continue to be
+                                accessible).</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>ProtectSystem=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument or
+                                <literal>full</literal>. If true,
+                                mounts the <filename>/usr</filename>
+                                directory read-only for processes
+                                invoked by this unit. If set to
+                                <literal>full</literal>, the
+                                <filename>/etc</filename> directory is mounted
+                                read-only, too. This setting ensures
+                                that any modification of the vendor
+                                supplied operating system (and
+                                optionally its configuration) is
+                                prohibited for the service. It is
+                                recommended to enable this setting for
+                                all long-running services, unless they
+                                are involved with system updates or
+                                need to modify the operating system in
+                                other ways. Note however that
+                                processes retaining the CAP_SYS_ADMIN
+                                capability can undo the effect of this
+                                setting. This setting is hence
+                                particularly useful for daemons which
+                                have this capability removed, for
+                                example with
+                                <varname>CapabilityBoundingSet=</varname>. Defaults
+                                to off.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>ProtectHome=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument or
+                                <literal>read-only</literal>. If true,
+                                the directories
+                                <filename>/home</filename> and
+                                <filename>/run/user</filename> are
+                                made inaccessible and empty for
+                                processes invoked by this unit. If set
+                                to <literal>read-only</literal>, the
+                                two directores are made read-only
+                                instead. It is recommended to enable
+                                this setting for all long-running
+                                services (in particular network-facing
+                                ones), to ensure they cannot get access
+                                to private user data, unless the
+                                services actually require access to
+                                the user's private data. Note however
+                                that processes retaining the
+                                CAP_SYS_ADMIN capability can undo the
+                                effect of this setting. This setting
+                                is hence particularly useful for
+                                daemons which have this capability
+                                removed, for example with
+                                <varname>CapabilityBoundingSet=</varname>. Defaults
+                                to off.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <option>shared</option>,
                                 <option>slave</option> or
                                 <option>private</option>, which
-                                control whether namespaces set up with
-                                <varname>ReadWriteDirectories=</varname>,
-                                <varname>ReadOnlyDirectories=</varname>
-                                and
-                                <varname>InaccessibleDirectories=</varname>
-                                receive or propagate new mounts
-                                from/to the main namespace. See
-                                <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                                control whether mounts in the file
+                                system namespace set up for this
+                                unit's processes will receive or
+                                propagate mounts or unmounts. See
+                                <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                 for details. Defaults to
-                                <option>shared</option>, i.e. the new
-                                namespace will both receive new mount
-                                points from the main namespace as well
-                                as propagate new mounts to
-                                it.</para></listitem>
+                                <option>shared</option>. Use
+                                <option>shared</option> to ensure that
+                                mounts and unmounts are propagated
+                                from the host to the container and
+                                vice versa. Use <option>slave</option>
+                                to run processes so that none of their
+                                mounts and unmounts will propagate to
+                                the host. Use <option>private</option>
+                                to also ensure that no mounts and
+                                unmounts from the host will propagate
+                                into the unit processes'
+                                namespace. Note that
+                                <option>slave</option> means that file
+                                systems mounted on the host might stay
+                                mounted continously in the unit's
+                                namespace, and thus keep the device
+                                busy. Note that the file system
+                                namespace related options
+                                (<varname>PrivateTmp=</varname>,
+                                <varname>PrivateDevices=</varname>,
+                                <varname>ProtectSystem=</varname>,
+                                <varname>ProtectHome=</varname>,
+                                <varname>ReadOnlyDirectories=</varname>,
+                                <varname>InaccessibleDirectories=</varname>
+                                and
+                                <varname>ReadWriteDirectories=</varname>)
+                                require that mount and unmount
+                                propagation from the unit's file
+                                system namespace is disabled, and
+                                hence downgrade
+                                <option>shared</option> to
+                                <option>slave</option>.
+                                </para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <term><varname>UtmpIdentifier=</varname></term>
 
-                                <listitem><para>Takes a four
+                                <listitem><para>Takes a four
                                 character identifier string for an
                                 utmp/wtmp entry for this service. This
                                 should only be set for services such
                                 entries must be created and cleared
                                 before and after execution. If the
                                 configured string is longer than four
-                                characters it is truncated and the
+                                characters, it is truncated and the
                                 terminal four characters are
                                 used. This setting interprets %I style
                                 string replacements. This setting is
                         </varlistentry>
 
                         <varlistentry>
+                                <term><varname>SELinuxContext=</varname></term>
+
+                                <listitem><para>Set the SELinux
+                                security context of the executed
+                                process. If set, this will override
+                                the automated domain
+                                transition. However, the policy still
+                                needs to autorize the transition. This
+                                directive is ignored if SELinux is
+                                disabled. If prefixed by
+                                <literal>-</literal>, all errors will
+                                be ignored. See
+                                <citerefentry><refentrytitle>setexeccon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                                for details.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>AppArmorProfile=</varname></term>
+
+                                <listitem><para>Takes a profile name as argument.
+                                The process executed by the unit will switch to
+                                this profile when started. Profiles must already
+                                be loaded in the kernel, or the unit will fail.
+                                This result in a non operation if AppArmor is not
+                                enabled. If prefixed by <literal>-</literal>, all errors
+                                will be ignored.
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
                                 <term><varname>IgnoreSIGPIPE=</varname></term>
 
                                 <listitem><para>Takes a boolean
-                                argument. If true causes SIGPIPE to be
+                                argument. If true, causes <constant>SIGPIPE</constant> to be
                                 ignored in the executed
-                                process. Defaults to true, since
-                                SIGPIPE generally is useful only in
+                                process. Defaults to true because
+                                <constant>SIGPIPE</constant> generally is useful only in
                                 shell pipelines.</para></listitem>
                         </varlistentry>
 
                                 <term><varname>NoNewPrivileges=</varname></term>
 
                                 <listitem><para>Takes a boolean
-                                argument. If true ensures that the
+                                argument. If true, ensures that the
                                 service process and all its children
                                 can never gain new privileges. This
                                 option is more powerful than the respective
                         <varlistentry>
                                 <term><varname>SystemCallFilter=</varname></term>
 
-                                <listitem><para>Takes a space
-                                separated list of system call
-                                names. If this setting is used all
+                                <listitem><para>Takes a
+                                space-separated list of system call
+                                names. If this setting is used, all
                                 system calls executed by the unit
-                                process except for the listed ones
+                                processes except for the listed ones
                                 will result in immediate process
-                                termination with the SIGSYS signal
+                                termination with the
+                                <constant>SIGSYS</constant> signal
                                 (whitelisting). If the first character
-                                of the list is <literal>~</literal>
+                                of the list is <literal>~</literal>,
                                 the effect is inverted: only the
                                 listed system calls will result in
                                 immediate process termination
-                                (blacklisting). If this option is used
+                                (blacklisting). If running in user
+                                mode and this option is used,
                                 <varname>NoNewPrivileges=yes</varname>
-                                is implied. This feature makes use of
-                                the Secure Computing Mode 2 interfaces
-                                of the kernel ('seccomp filtering')
-                                and is useful for enforcing a minimal
+                                is implied. This feature makes use of the
+                                Secure Computing Mode 2 interfaces of
+                                the kernel ('seccomp filtering') and
+                                is useful for enforcing a minimal
                                 sandboxing environment. Note that the
                                 <function>execve</function>,
                                 <function>rt_sigreturn</function>,
                                 <function>sigreturn</function>,
                                 <function>exit_group</function>,
                                 <function>exit</function> system calls
-                                are implicitly whitelisted and don't
-                                need to be listed
-                                explicitly.</para></listitem>
+                                are implicitly whitelisted and do not
+                                need to be listed explicitly. This
+                                option may be specified more than once
+                                in which case the filter masks are
+                                merged. If the empty string is
+                                assigned, the filter is reset, all
+                                prior assignments will have no
+                                effect.</para>
+
+                                <para>If you specify both types of
+                                this option (i.e. whitelisting and
+                                blacklisting), the first encountered
+                                will take precedence and will dictate
+                                the default action (termination or
+                                approval of a system call). Then the
+                                next occurrences of this option will
+                                add or delete the listed system calls
+                                from the set of the filtered system
+                                calls, depending of its type and the
+                                default action. (For example, if you have started
+                                with a whitelisting of
+                                <function>read</function> and
+                                <function>write</function>, and right
+                                after it add a blacklisting of
+                                <function>write</function>, then
+                                <function>write</function> will be
+                                removed from the set.)
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>SystemCallErrorNumber=</varname></term>
+
+                                <listitem><para>Takes an
+                                <literal>errno</literal> error number
+                                name to return when the system call
+                                filter configured with
+                                <varname>SystemCallFilter=</varname>
+                                is triggered, instead of terminating
+                                the process immediately. Takes an
+                                error name such as
+                                <constant>EPERM</constant>,
+                                <constant>EACCES</constant> or
+                                <constant>EUCLEAN</constant>. When this
+                                setting is not used, or when the empty
+                                string is assigned, the process will be
+                                terminated immediately when the filter
+                                is triggered.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>SystemCallArchitectures=</varname></term>
+
+                                <listitem><para>Takes a space
+                                separated list of architecture
+                                identifiers to include in the system
+                                call filter. The known architecture
+                                identifiers are
+                                <constant>x86</constant>,
+                                <constant>x86-64</constant>,
+                                <constant>x32</constant>,
+                                <constant>arm</constant> as well as
+                                the special identifier
+                                <constant>native</constant>. Only
+                                system calls of the specified
+                                architectures will be permitted to
+                                processes of this unit. This is an
+                                effective way to disable compatibility
+                                with non-native architectures for
+                                processes, for example to prohibit
+                                execution of 32-bit x86 binaries on
+                                64-bit x86-64 systems. The special
+                                <constant>native</constant> identifier
+                                implicitly maps to the native
+                                architecture of the system (or more
+                                strictly: to the architecture the
+                                system manager is compiled for). If
+                                running in user mode and this option
+                                is used,
+                                <varname>NoNewPrivileges=yes</varname>
+                                is implied. Note that setting this
+                                option to a non-empty list implies
+                                that <constant>native</constant> is
+                                included too. By default, this option
+                                is set to the empty list, i.e. no
+                                architecture system call filtering is
+                                applied.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>RestrictAddressFamilies=</varname></term>
+
+                                <listitem><para>Restricts the set of
+                                socket address families accessible to
+                                the processes of this unit. Takes a
+                                space-separated list of address family
+                                names to whitelist, such as
+                                <constant>AF_UNIX</constant>,
+                                <constant>AF_INET</constant> or
+                                <constant>AF_INET6</constant>. When
+                                prefixed with <constant>~</constant>
+                                the listed address families will be
+                                applied as blacklist, otherwise as
+                                whitelist. Note that this restricts
+                                access to the
+                                <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                system call only. Sockets passed into
+                                the process by other means (for
+                                example, by using socket activation
+                                with socket units, see
+                                <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
+                                are unaffected. Also, sockets created
+                                with <function>socketpair()</function>
+                                (which creates connected AF_UNIX
+                                sockets only) are unaffected. Note
+                                that this option has no effect on
+                                32-bit x86 and is ignored (but works
+                                correctly on x86-64). If running in user
+                                mode and this option is used,
+                                <varname>NoNewPrivileges=yes</varname>
+                                is implied. By default, no
+                                restriction applies, all address
+                                families are accessible to
+                                processes. If assigned the empty
+                                string, any previous list changes are
+                                undone.</para>
+
+                                <para>Use this option to limit
+                                exposure of processes to remote
+                                systems, in particular via exotic
+                                network protocols. Note that in most
+                                cases, the local
+                                <constant>AF_UNIX</constant> address
+                                family should be included in the
+                                configured whitelist as it is
+                                frequently used for local
+                                communication, including for
+                                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                logging.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>Personality=</varname></term>
+
+                                <listitem><para>Controls which
+                                kernel architecture
+                                <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                shall report, when invoked by unit
+                                processes. Takes one of
+                                <constant>x86</constant> and
+                                <constant>x86-64</constant>. This is
+                                useful when running 32-bit services on
+                                a 64-bit host system. If not specified,
+                                the personality is left unmodified and
+                                thus reflects the personality of the
+                                host system's
+                                kernel.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>RuntimeDirectory=</varname></term>
+                                <term><varname>RuntimeDirectoryMode=</varname></term>
+
+                                <listitem><para>Takes a list of
+                                directory names. If set, one or more
+                                directories by the specified names
+                                will be created below
+                                <filename>/run</filename> (for system
+                                services) or below
+                                <varname>$XDG_RUNTIME_DIR</varname>
+                                (for user services) when the unit is
+                                started, and removed when the unit is
+                                stopped. The directories will have the
+                                access mode specified in
+                                <varname>RuntimeDirectoryMode=</varname>,
+                                and will be owned by the user and
+                                group specified in
+                                <varname>User=</varname> and
+                                <varname>Group=</varname>. Use this to
+                                manage one or more runtime directories
+                                of the unit and bind their lifetime to
+                                the daemon runtime. The specified
+                                directory names must be relative, and
+                                may not include a
+                                <literal>/</literal>, i.e. must refer
+                                to simple directories to create or
+                                remove. This is particularly useful
+                                for unprivileged daemons that cannot
+                                create runtime directories in
+                                <filename>/run</filename> due to lack
+                                of privileges, and to make sure the
+                                runtime directory is cleaned up
+                                automatically after use. For runtime
+                                directories that require more complex
+                                or different configuration or lifetime
+                                guarantees, please consider using
+                                <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
                         </varlistentry>
 
                 </variablelist>
         </refsect1>
 
         <refsect1>
+                <title>Environment variables in spawned processes</title>
+
+                <para>Processes started by the system are executed in
+                a clean environment in which select variables
+                listed below are set. System processes started by systemd
+                do not inherit variables from PID 1, but processes
+                started by user systemd instances inherit all
+                environment variables from the user systemd instance.
+                </para>
+
+                <variablelist class='environment-variables'>
+                        <varlistentry>
+                                <term><varname>$PATH</varname></term>
+
+                                <listitem><para>Colon-separated list
+                                of directiories to use when launching
+                                executables. Systemd uses a fixed
+                                value of
+                                <filename>/usr/local/sbin</filename>:<filename>/usr/local/bin</filename>:<filename>/usr/sbin</filename>:<filename>/usr/bin</filename>:<filename>/sbin</filename>:<filename>/bin</filename>.
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$LANG</varname></term>
+
+                                <listitem><para>Locale. Can be set in
+                                <citerefentry><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                                or on the kernel command line (see
+                                <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                                and
+                                <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$USER</varname></term>
+                                <term><varname>$LOGNAME</varname></term>
+                                <term><varname>$HOME</varname></term>
+                                <term><varname>$SHELL</varname></term>
+
+                                <listitem><para>User name (twice), home
+                                directory, and the login shell.
+                                The variables are set for the units that
+                                have <varname>User=</varname> set,
+                                which includes user
+                                <command>systemd</command> instances.
+                                See
+                                <citerefentry><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$XDG_RUNTIME_DIR</varname></term>
+
+                                <listitem><para>The directory for volatile
+                                state. Set for the user <command>systemd</command>
+                                instance, and also in user sessions.
+                                See
+                                <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$XDG_SESSION_ID</varname></term>
+                                <term><varname>$XDG_SEAT</varname></term>
+                                <term><varname>$XDG_VTNR</varname></term>
+
+                                <listitem><para>The identifier of the
+                                session, the seat name, and
+                                virtual terminal of the session. Set
+                                by
+                                <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                                for login sessions.
+                                <varname>$XDG_SEAT</varname> and
+                                <varname>$XDG_VTNR</varname> will
+                                only be set when attached to a seat and a
+                                tty.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$MAINPID</varname></term>
+
+                                <listitem><para>The PID of the units
+                                main process if it is known. This is
+                                only set for control processes as
+                                invoked by
+                                <varname>ExecReload=</varname> and
+                                similar.  </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$MANAGERPID</varname></term>
+
+                                <listitem><para>The PID of the user
+                                <command>systemd</command> instance,
+                                set for processes spawned by it.
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$LISTEN_FDS</varname></term>
+                                <term><varname>$LISTEN_PID</varname></term>
+
+                                <listitem><para>Information about file
+                                descriptors passed to a service for
+                                socket activation.  See
+                                <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>$TERM</varname></term>
+
+                                <listitem><para>Terminal type, set
+                                only for units connected to a terminal
+                                (<varname>StandardInput=tty</varname>,
+                                <varname>StandardOutput=tty</varname>,
+                                or
+                                <varname>StandardError=tty</varname>).
+                                See
+                                <citerefentry project='man-pages'><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+                                </para></listitem>
+                        </varlistentry>
+                </variablelist>
+
+                <para>Additional variables may be configured by the
+                following means: for processes spawned in specific
+                units, use the <varname>Environment=</varname> and
+                <varname>EnvironmentFile=</varname> options above; to
+                specify variables globally, use
+                <varname>DefaultEnvironment=</varname> (see
+                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
+                or the kernel option
+                <varname>systemd.setenv=</varname> (see
+                <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Additional
+                variables may also be set through PAM,
+                cf. <citerefentry project='man-pages'><refentrytitle>pam_env</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
+        </refsect1>
+
+        <refsect1>
                   <title>See Also</title>
                   <para>
                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
-                          <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                          <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                          <citerefentry project='man-pages'><refentrytitle>exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                   </para>
         </refsect1>