systemd.exec.xml 74.9 KB
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<?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">

<!--
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
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  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
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  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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  Lesser General Public License for more details.
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  You should have received a copy of the GNU Lesser General Public License
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  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<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>
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                <refpurpose>Execution environment configuration</refpurpose>
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        </refnamediv>

        <refsynopsisdiv>
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                <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>
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        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

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                <para>Unit configuration files for services, sockets,
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                mount points and swap devices share a subset of
                configuration options which define the execution
                environment of spawned processes.</para>
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                <para>This man page lists the configuration options
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                shared by these four unit types. See
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                <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                for the common options of all unit configuration
                files, and
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                <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>
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                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],
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                [Socket], [Mount], or [Swap] sections, depending on the unit
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                type.</para>
        </refsect1>

        <refsect1>
                <title>Options</title>

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                <variablelist class='unit-directives'>
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                        <varlistentry>
                                <term><varname>WorkingDirectory=</varname></term>

                                <listitem><para>Takes an absolute
                                directory path. Sets the working
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                                directory for executed processes. If
                                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
                                user.</para></listitem>
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                        </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
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                                or group that the processes are executed
                                as, respectively. Takes a single user or group
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                                name or ID as argument. If no group is
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                                set, the default group of the user is
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                                chosen.</para></listitem>
                        </varlistentry>

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

                                <listitem><para>Sets the supplementary
                                Unix groups the processes are executed
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                                as. This takes a space separated list
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                                of group names or IDs. This option may
                                be specified more than once in which
                                case all listed groups are set as
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                                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
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                                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>
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                                <term><varname>OOMScoreAdjust=</varname></term>
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                                <listitem><para>Sets the adjustment
                                level for the Out-Of-Memory killer for
                                executed processes. Takes an integer
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                                between -1000 (to disable OOM killing
                                for this process) and 1000 (to make
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                                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
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                                processes. The available priority
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                                range depends on the selected CPU
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                                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>
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                        </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
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                                processes. Takes a space-separated
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                                list of CPU indexes. 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
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                                <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
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                                0022.</para></listitem>
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                        </varlistentry>

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

                                <listitem><para>Sets environment
                                variables for executed
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                                processes. Takes a space-separated
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                                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
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                                override the earlier setting. If the
                                empty string is assigned to this
                                option the list of environment
                                variables is reset, all prior
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                                assignments have no effect.
                                Variable expansion is not performed
                                inside the strings, and $ 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>.
                                </para>

                                <para>
                                See
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                                <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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                                for details about environment variables.</para></listitem>
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                        </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
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                                contain new-line separated variable
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                                assignments. Empty lines and lines
                                starting with ; or # will be ignored,
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                                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
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                                of assignments, unless you use
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                                double quotes (").</para>

                                <para>The argument passed should be an
                                absolute file name or wildcard
                                expression, optionally prefixed with
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                                "-", which indicates that if the file
                                does not exist it won't be read and no
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                                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
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                                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
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                                earlier setting.</para></listitem>
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                        </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
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                                being controlled by another process the
                                executed process waits until the current
                                controlling process releases the
                                terminal.
                                <option>tty-force</option>
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                                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>,
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                                <option>kmsg</option>,
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                                <option>journal</option>,
                                <option>syslog+console</option>,
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                                <option>kmsg+console</option>,
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                                <option>journal+console</option> or
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                                <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>
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                                system syslog
                                service. <option>kmsg</option>
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                                connects it with the kernel log buffer
                                which is accessible via
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                                <citerefentry><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>. <option>journal</option>
                                connects it with the journal which is
                                accessible via
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                                <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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                                (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
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                                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
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                                similar to the respective option of
                                <varname>StandardInput=</varname>.
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                                This setting defaults to the value set
                                with
                                <option>DefaultStandardOutput=</option>
                                in
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                                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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                                which defaults to
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                                <option>journal</option>.</para></listitem>
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                        </varlistentry>
                        <varlistentry>
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                                <term><varname>StandardError=</varname></term>
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                                <listitem><para>Controls where file
                                descriptor 2 (STDERR) of the executed
                                processes is connected to. The
                                available options are identical to
                                those of
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                                <varname>StandardOutput=</varname>,
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                                with one exception: if set to
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                                <option>inherit</option> the file
                                descriptor used for standard output is
                                duplicated for standard error. This
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                                setting defaults to the value set with
                                <option>DefaultStandardError=</option>
                                in
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                                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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                                which defaults to
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                                <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>
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                        <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>
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                                <listitem><para>If the terminal
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                                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>
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                        <varlistentry>
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                                <term><varname>SyslogIdentifier=</varname></term>
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                                <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
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                                <varname>SyslogLevelPrefix=</varname>,
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                                see below. For details see
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                                <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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                                Defaults to
                                <option>info</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
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                                <term><varname>SyslogLevelPrefix=</varname></term>
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                                <listitem><para>Takes a boolean
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                                argument. If true and
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                                <varname>StandardOutput=</varname> or
                                <varname>StandardError=</varname> are
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                                set to <option>syslog</option>,
                                <option>kmsg</option> or
                                <option>journal</option>, log lines
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                                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
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                                set to false, the interpretation of
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                                these prefixes is disabled and the
                                logged lines are passed on as-is. For
                                details about this prefixing see
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                                <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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                                Defaults to true.</para></listitem>
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                        </varlistentry>

                        <varlistentry>
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                                <term><varname>TimerSlackNSec=</varname></term>
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                                <listitem><para>Sets the timer slack
                                in nanoseconds for the executed
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                                processes. The timer slack controls
                                the accuracy of wake-ups triggered by
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                                timers. See
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                                <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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                                for more information. Note that in
                                contrast to most other time span
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                                definitions this parameter takes an
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                                integer value in nano-seconds if no
                                unit is specified. The usual time
                                units are understood
                                too.</para></listitem>
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                        </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>
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                                for details. Use the string
                                <varname>infinity</varname> to
                                configure no limit on a specific
                                resource.</para></listitem>
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                        </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
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                                socket types (e.g. datagram/UDP) and
                                on processes unrelated to socket-based
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                                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>
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                                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>
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                        </varlistentry>

                        <varlistentry>
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                                <term><varname>CapabilityBoundingSet=</varname></term>

                                <listitem><para>Controls which
                                capabilities to include in the
                                capability bounding set for the
                                executed process. See
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                                <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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                                for details. Takes a whitespace
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                                separated list of capability names as
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                                read by
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                                <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                                e.g. <literal>CAP_SYS_ADMIN
                                CAP_DAC_OVERRIDE
                                CAP_SYS_PTRACE</literal>.
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                                Capabilities listed will be included
                                in the bounding set, all others are
                                removed. If the list of capabilities
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                                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>
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                                does. If this option is not used the
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                                capability bounding set is not
                                modified on process execution, hence
                                no limits on the capabilities of the
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                                process are enforced. This option may
                                appear more than once in which case
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                                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>
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                        </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>,
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                                <option>noroot</option> and/or
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                                <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>
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                        </varlistentry>

                        <varlistentry>
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                                <term><varname>Capabilities=</varname></term>
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                                <listitem><para>Controls the
                                <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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                                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>
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                        </varlistentry>

                        <varlistentry>
                                <term><varname>ControlGroup=</varname></term>

                                <listitem><para>Controls the control
                                groups the executed processes shall be
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                                made members of. Takes a
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                                space-separated list of cgroup
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                                identifiers. A cgroup identifier is
                                formatted like
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                                <filename>cpu:/foo/bar</filename>,
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                                where "cpu" indicates the kernel
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                                control group controller used, and
                                <filename>/foo/bar</filename> is the
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                                control group path. The controller
                                name and ":" may be omitted in which
                                case the named systemd control group
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                                hierarchy is implied. Alternatively,
                                the path and ":" may be omitted, in
                                which case the default control group
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                                path for this unit is implied.</para>

                                <para>This option may be used to place
                                executed processes in arbitrary groups
                                in arbitrary hierarchies -- which may
                                then be externally configured 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. This option is primarily
                                intended to place executed processes
                                in specific paths in specific kernel
                                controller hierarchies. It is not
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                                recommended to manipulate the service
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                                control group path in the private
                                systemd named hierarchy
                                (i.e. <literal>name=systemd</literal>),
                                and doing this might result in
                                undefined behaviour. For details about
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                                control groups see <ulink
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                                url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.</para>

                                <para>This option may appear more than
                                once, in which case the list of
                                control group assignments is
                                merged. If the same hierarchy gets two
                                different paths assigned only the
                                later setting will take effect. If the
                                empty string is assigned to this
                                option the list of control group
                                assignments is reset, all previous
                                assignments will have no
                                effect.</para>

                                <para>Note that the list of control
                                group assignments of a unit is
                                extended implicitly based on the
                                settings of
                                <varname>DefaultControllers=</varname>
                                of
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                                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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                                but a unit's
                                <varname>ControlGroup=</varname>
                                setting for a specific controller
                                takes precedence.</para></listitem>
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                        </varlistentry>

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                        <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>

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                        <varlistentry>
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                                <term><varname>ControlGroupPersistent=</varname></term>
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                                <listitem><para>Takes a boolean
                                argument. If true, the control groups
                                created for this unit will be marked
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                                to be persistent, i.e. systemd will
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                                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>

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                        <varlistentry>
                                <term><varname>ControlGroupAttribute=</varname></term>

                                <listitem><para>Set a specific control
                                group attribute for executed
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                                processes, and (if needed) add the
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                                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>
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                                is in most cases sufficient to make
                                use of control group enforcements,
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                                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
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                                attributes. If this option is used
                                multiple times for the same cgroup
                                attribute only the later setting takes
                                effect. If the empty string is
                                assigned to this option the list of
                                attributes is reset, all previous
                                cgroup attribute settings have no
                                effect, including those done with
                                <varname>CPUShares=</varname>,
                                <varname>MemoryLimit=</varname>,
                                <varname>MemorySoftLimit</varname>,
                                <varname>DeviceAllow=</varname>,
                                <varname>DeviceDeny=</varname>,
                                <varname>BlockIOWeight=</varname>,
                                <varname>BlockIOReadBandwidth=</varname>,
                                <varname>BlockIOWriteBandwidth=</varname>.
                                </para></listitem>
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                        </varlistentry>

                        <varlistentry>
                                <term><varname>CPUShares=</varname></term>

                                <listitem><para>Assign the specified
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                                overall CPU time shares to the
                                processes executed. Takes an integer
                                value. This controls the
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                                <literal>cpu.shares</literal> control
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                                group attribute, which defaults to
                                1024. For details about this control
                                group attribute see <ulink
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                                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
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                                as Kilobytes, Megabytes, Gigabytes,
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                                or Terabytes (to the base
                                1024), respectively. This controls the
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                                <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
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                                to control reading, writing, or
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                                creating of the specific device node
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                                by the unit, respectively. This controls the
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                                <literal>devices.allow</literal>
                                and
                                <literal>devices.deny</literal>
                                control group attributes. For details
                                about these control group attributes
                                see <ulink
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