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[thirdparty/systemd.git] / man / systemd.exec.xml

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<refentry id="systemd.exec">
        <refentryinfo>
                <title>systemd.exec</title>
                <productname>systemd</productname>

                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>Lennart</firstname>
                                <surname>Poettering</surname>
                                <email>lennart@poettering.net</email>
                        </author>
                </authorgroup>
        </refentryinfo>

        <refmeta>
                <refentrytitle>systemd.exec</refentrytitle>
                <manvolnum>5</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>systemd.exec</refname>
                <refpurpose>systemd execution environment configuration</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <para><filename>systemd.service</filename>,
                <filename>systemd.socket</filename>,
                <filename>systemd.mount</filename>,
                <filename>systemd.swap</filename></para>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para>Unit configuration files for services, sockets,
                mount points and swap devices share a subset of
                configuration options which define the execution
                environment of spawned processes.</para>

                <para>This man page lists the configuration options
                shared by these four unit types. See
                <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                for the common options of all unit configuration
                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>
                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
                type.</para>
        </refsect1>

        <refsect1>
                <title>Options</title>

                <variablelist>

                        <varlistentry>
                                <term><varname>WorkingDirectory=</varname></term>

                                <listitem><para>Takes an absolute
                                directory path. Sets the working
                                directory for executed
                                processes.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>RootDirectory=</varname></term>

                                <listitem><para>Takes an absolute
                                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
                                be ensured that the process and all
                                its auxiliary files are available in
                                the <function>chroot()</function>
                                jail.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>User=</varname></term>
                                <term><varname>Group=</varname></term>

                                <listitem><para>Sets the Unix user
                                resp. group the processes are executed
                                as. Takes a single user resp. group
                                name or ID as argument. If no group is
                                set the default group of the user is
                                chosen.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>SupplementaryGroups=</varname></term>

                                <listitem><para>Sets the supplementary
                                Unix groups the processes are executed
                                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
                                user.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>Nice=</varname></term>

                                <listitem><para>Sets the default nice
                                level (scheduling priority) for
                                executed processes. Takes an integer
                                between -20 (highest priority) and 19
                                (lowest priority). See
                                <citerefentry><refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>OOMScoreAdjust=</varname></term>

                                <listitem><para>Sets the adjustment
                                level for the Out-Of-Memory killer for
                                executed processes. Takes an integer
                                between -1000 (to disable OOM killing
                                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>
                                for details.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>IOSchedulingClass=</varname></term>

                                <listitem><para>Sets the IO scheduling
                                class for executed processes. Takes an
                                integer between 0 and 3 or one of the
                                strings <option>none</option>,
                                <option>realtime</option>,
                                <option>best-effort</option> or
                                <option>idle</option>. See
                                <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>IOSchedulingPriority=</varname></term>

                                <listitem><para>Sets the IO scheduling
                                priority for executed processes. Takes
                                an integer between 0 (highest
                                priority) and 7 (lowest priority). The
                                available priorities depend on the
                                selected IO scheduling class (see
                                above). See
                                <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>CPUSchedulingPolicy=</varname></term>

                                <listitem><para>Sets the CPU
                                scheduling policy for executed
                                processes. Takes one of
                                <option>other</option>,
                                <option>batch</option>,
                                <option>idle</option>,
                                <option>fifo</option> or
                                <option>rr</option>. See
                                <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>CPUSchedulingPriority=</varname></term>

                                <listitem><para>Sets the CPU
                                scheduling priority for executed
                                processes. Takes an integer between 1
                                (lowest priority) and 99 (highest
                                priority). 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>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>CPUSchedulingResetOnFork=</varname></term>

                                <listitem><para>Takes a boolean
                                argument. If true elevated CPU
                                scheduling priorities and policies
                                will be reset when the executed
                                processes fork, and can hence not leak
                                into child processes. See
                                <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details. Defaults to false.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>CPUAffinity=</varname></term>

                                <listitem><para>Controls the CPU
                                affinity of the executed
                                processes. Takes a space-separated
                                list of CPU indexes. See
                                <citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>UMask=</varname></term>

                                <listitem><para>Controls the file mode
                                creation mask. Takes an access mode in
                                octal notation. See
                                <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details. Defaults to
                                0022.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>Environment=</varname></term>

                                <listitem><para>Sets environment
                                variables for executed
                                processes. Takes a space-separated
                                list of variable assignments. This
                                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>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>EnvironmentFile=</varname></term>
                                <listitem><para>Similar to
                                <varname>Environment=</varname> but
                                reads the environment variables from a
                                text file. The text file should
                                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
                                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
                                directive will be read shortly before
                                the process is executed. 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
                                the order they are specified and the
                                later setting will override the
                                earlier setting. </para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>StandardInput=</varname></term>
                                <listitem><para>Controls where file
                                descriptor 0 (STDIN) of the executed
                                processes is connected to. Takes one
                                of <option>null</option>,
                                <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
                                <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
                                <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
                                process of the terminal, potentially
                                removing previous controlling
                                processes from the
                                terminal. <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
                                <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                                for details) specifies a single socket
                                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
                                <option>null</option>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>StandardOutput=</varname></term>
                                <listitem><para>Controls where file
                                descriptor 1 (STDOUT) of the executed
                                processes is connected to. Takes one
                                of <option>inherit</option>,
                                <option>null</option>,
                                <option>tty</option>,
                                <option>syslog</option>,
                                <option>kmsg</option>,
                                <option>journal</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
                                <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
                                <varname>TTYPath=</varname>, see
                                below). If the TTY is used for output
                                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>systemd-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
                                <option>DefaultStandardOutput=</option>
                                in
                                <citerefentry><refentrytitle>systemd.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
                                those of
                                <varname>StandardOutput=</varname>,
                                with one exception: if set to
                                <option>inherit</option> the file
                                descriptor used for standard output is
                                duplicated for standard error. This
                                setting defaults to the value set with
                                <option>DefaultStandardError=</option>
                                in
                                <citerefentry><refentrytitle>systemd.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
                                TTY (see above). Defaults to
                                <filename>/dev/console</filename>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>TTYReset=</varname></term>
                                <listitem><para>Reset the terminal
                                device specified with
                                <varname>TTYPath=</varname> before and
                                after execution. Defaults to
                                <literal>no</literal>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>TTYVHangup=</varname></term>
                                <listitem><para>Disconnect all clients
                                which have opened the terminal device
                                specified with
                                <varname>TTYPath=</varname>
                                before and after execution. Defaults
                                to
                                <literal>no</literal>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>TTYVTDisallocate=</varname></term>
                                <listitem><para>If the the terminal
                                device specified with
                                <varname>TTYPath=</varname> is a
                                virtual console terminal try to
                                deallocate the TTY before and after
                                execution. This ensures that the
                                screen and scrollback buffer is
                                cleared. Defaults to
                                <literal>no</literal>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <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
                                defaults to the process name of the
                                executed process. This option is only
                                useful when
                                <varname>StandardOutput=</varname> or
                                <varname>StandardError=</varname> are
                                set to <option>syslog</option> or
                                <option>kmsg</option>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>SyslogFacility=</varname></term>
                                <listitem><para>Sets the syslog
                                facility to use when logging to
                                syslog. One of <option>kern</option>,
                                <option>user</option>,
                                <option>mail</option>,
                                <option>daemon</option>,
                                <option>auth</option>,
                                <option>syslog</option>,
                                <option>lpr</option>,
                                <option>news</option>,
                                <option>uucp</option>,
                                <option>cron</option>,
                                <option>authpriv</option>,
                                <option>ftp</option>,
                                <option>local0</option>,
                                <option>local1</option>,
                                <option>local2</option>,
                                <option>local3</option>,
                                <option>local4</option>,
                                <option>local5</option>,
                                <option>local6</option> or
                                <option>local7</option>. See
                                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                                for details. This option is only
                                useful when
                                <varname>StandardOutput=</varname> or
                                <varname>StandardError=</varname> are
                                set to <option>syslog</option>.
                                Defaults to
                                <option>daemon</option>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>SyslogLevel=</varname></term>
                                <listitem><para>Default syslog level
                                to use when logging to syslog or the
                                kernel log buffer. One of
                                <option>emerg</option>,
                                <option>alert</option>,
                                <option>crit</option>,
                                <option>err</option>,
                                <option>warning</option>,
                                <option>notice</option>,
                                <option>info</option>,
                                <option>debug</option>. See
                                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                                for details. This option is only
                                useful when
                                <varname>StandardOutput=</varname> or
                                <varname>StandardError=</varname> are
                                set to <option>syslog</option> or
                                <option>kmsg</option>. Note that
                                individual lines output by the daemon
                                might be prefixed with a different log
                                level which can be used to override
                                the default log level specified
                                here. The interpretation of these
                                prefixes may be disabled with
                                <varname>SyslogLevelPrefix=</varname>,
                                see below. For details see
                                <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.

                                Defaults to
                                <option>info</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>SyslogLevelPrefix=</varname></term>
                                <listitem><para>Takes a boolean
                                argument. If true and
                                <varname>StandardOutput=</varname> or
                                <varname>StandardError=</varname> are
                                set to <option>syslog</option> or
                                <option>kmsg</option> log lines
                                written by the executed process that
                                are prefixed with a log level will be
                                passed on to syslog with this log
                                level set but the prefix removed. If
                                set to false, the interpretation of
                                these prefixes is disabled and the
                                logged lines are passed on as-is. For
                                details about this prefixing see
                                <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
                                Defaults to true.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>TimerSlackNSec=</varname></term>
                                <listitem><para>Sets the timer slack
                                in nanoseconds for the executed
                                processes. The timer slack controls the
                                accuracy of wake-ups triggered by
                                timers. See
                                <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for more information. Note that in
                                contrast to most other time span
                                definitions this parameter takes an
                                integer value in nano-seconds and does
                                not understand any other
                                units.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>LimitCPU=</varname></term>
                                <term><varname>LimitFSIZE=</varname></term>
                                <term><varname>LimitDATA=</varname></term>
                                <term><varname>LimitSTACK=</varname></term>
                                <term><varname>LimitCORE=</varname></term>
                                <term><varname>LimitRSS=</varname></term>
                                <term><varname>LimitNOFILE=</varname></term>
                                <term><varname>LimitAS=</varname></term>
                                <term><varname>LimitNPROC=</varname></term>
                                <term><varname>LimitMEMLOCK=</varname></term>
                                <term><varname>LimitLOCKS=</varname></term>
                                <term><varname>LimitSIGPENDING=</varname></term>
                                <term><varname>LimitMSGQUEUE=</varname></term>
                                <term><varname>LimitNICE=</varname></term>
                                <term><varname>LimitRTPRIO=</varname></term>
                                <term><varname>LimitRTTIME=</varname></term>
                                <listitem><para>These settings control
                                various resource limits for executed
                                processes. See
                                <citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                for details. Use the string
                                <varname>infinity</varname> to
                                configure no limit on a specific
                                resource.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>PAMName=</varname></term>
                                <listitem><para>Sets the PAM service
                                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
                                for the executed processes. See
                                <citerefentry><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.</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>.
                                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 does
                                not actually set or unset any
                                capabilities in the effective,
                                permitted or inherited capability
                                sets. That's what
                                <varname>Capabilities=</varname> is
                                for. 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>
                        </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>
                                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>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>Capabilities=</varname></term>
                                <listitem><para>Controls the
                                <citerefentry><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
                                attached to the executed file. Due to
                                that
                                <varname>CapabilityBoundingSet=</varname>
                                is probably the much more useful
                                setting.</para></listitem>
                        </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 bandwith limit for
                                the executed processes. Takes a space
                                separated pair of a file path and a
                                bandwith 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 bandwith is suffixed with K, M,
                                G, or T the specified bandwith 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 bandwith
                                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
                                processes. These options may be used
                                to limit access a process might have
                                to the main file-system
                                hierarchy. Each setting takes a
                                space-separated list of absolute
                                directory paths. Directories listed in
                                <varname>ReadWriteDirectories=</varname>
                                are accessible from within the
                                namespace with the same access rights
                                as from outside. Directories listed in
                                <varname>ReadOnlyDirectories=</varname>
                                are accessible for reading only,
                                writing will be refused even if the
                                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
                                namespace.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>PrivateTmp=</varname></term>

                                <listitem><para>Takes a boolean
                                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
                                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>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>PrivateNetwork=</varname></term>

                                <listitem><para>Takes a boolean
                                argument. If true sets up a new
                                network namespace for the executed
                                processes and configures only the
                                loopback network device
                                <literal>lo</literal> inside it. No
                                other network devices will be
                                available to the executed process.
                                This is useful to securely turn off
                                network access by the executed
                                process. Defaults to
                                false.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>MountFlags=</varname></term>

                                <listitem><para>Takes a mount
                                propagation flag:
                                <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>
                                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>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>UtmpIdentifier=</varname></term>

                                <listitem><para>Takes a a four
                                character identifier string for an
                                utmp/wtmp entry for this service. This
                                should only be set for services such
                                as <command>getty</command>
                                implementations where utmp/wtmp
                                entries must be created and cleared
                                before and after execution. If the
                                configured string is longer than four
                                characters it is truncated and the
                                terminal four characters are
                                used. This setting interprets %I style
                                string replacements. This setting is
                                unset by default, i.e. no utmp/wtmp
                                entries are created or cleaned up for
                                this service.</para></listitem>
                        </varlistentry>

                </variablelist>
        </refsect1>

        <refsect1>
                  <title>See Also</title>
                  <para>
                          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                  </para>
        </refsect1>

</refentry>