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<refentry id="systemd.resource-control">
  <refentryinfo>
    <title>systemd.resource-control</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.resource-control</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd.resource-control</refname>
    <refpurpose>Resource control unit settings</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para>
      <filename><replaceable>slice</replaceable>.slice</filename>,
      <filename><replaceable>scope</replaceable>.scope</filename>,
      <filename><replaceable>service</replaceable>.service</filename>,
      <filename><replaceable>socket</replaceable>.socket</filename>,
      <filename><replaceable>mount</replaceable>.mount</filename>,
      <filename><replaceable>swap</replaceable>.swap</filename>
    </para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>Unit configuration files for services, slices, scopes,
    sockets, mount points, and swap devices share a subset of
    configuration options for resource control of spawned
    processes. Internally, this relies on the Control Groups
    kernel concept for organizing processes in a hierarchical tree of
    named groups for the purpose of resource management.</para>

    <para>This man page lists the configuration options shared by
    those six 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.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>systemd.scope</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.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    and
    <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for more information on the specific unit configuration files. The
    resource control configuration options are configured in the
    [Slice], [Scope], [Service], [Socket], [Mount], or [Swap]
    sections, depending on the unit type.</para>

    <para>See the <ulink
    url="http://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/">New
    Control Group Interfaces</ulink> for an introduction on how to make
    use of resource control APIs from programs.</para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>Units of the types listed above can have settings
    for resource control configuration:</para>

    <variablelist class='unit-directives'>

      <varlistentry>
        <term><varname>CPUAccounting=</varname></term>

        <listitem>
          <para>Turn on CPU usage accounting for this unit. Takes a
          boolean argument. Note that turning on CPU accounting for
          one unit might also implicitly turn it on for all units
          contained in the same slice and for all its parent slices
          and the units contained therein. The system default for this
          setting maybe controlled with
          <varname>DefaultCPUAccounting=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUShares=<replaceable>weight</replaceable></varname></term>
        <term><varname>StartupCPUShares=<replaceable>weight</replaceable></varname></term>

        <listitem>
          <para>Assign the specified CPU time share weight to the
          processes executed. Those options take an integer value and
          control the <literal>cpu.shares</literal> control group
          attribute, which defaults to 1024. For details about this
          control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.
          The available CPU time is split up among all units within
          one slice relative to their CPU time share weight.</para>

          <para>While <varname>StartupCPUShares=</varname> only
          applies to the startup phase of the system,
          <varname>CPUShares=</varname> applies to normal runtime of
          the system, and if the former is not set also to the startup
          phase. Using <varname>StartupCPUShares=</varname> allows
          prioritizing specific services at boot-up differently than
          during normal runtime.</para>

          <para>Those options imply
          <literal>CPUAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUQuota=</varname></term>

        <listitem>
          <para>Assign the specified CPU time quota to the processes
          executed. Takes a percentage value, suffixed with "%". The
          percentage specifies how much CPU time the unit shall get at
          maximum, relative to the total CPU time available on one
          CPU. Use values &gt; 100% for allotting CPU time on more than
          one CPU. This controls the
          <literal>cpu.cfs_quota_us</literal> control group
          attribute. For details about this control group attribute,
          see <ulink
          url="https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.</para>

          <para>Example: <varname>CPUQuota=20%</varname> ensures that
          the executed processes will never get more than 20% CPU time
          on one CPU.</para>

          <para>Implies <literal>CPUAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MemoryAccounting=</varname></term>

        <listitem>
          <para>Turn on process and kernel memory accounting for this
          unit. Takes a boolean argument. Note that turning on memory
          accounting for one unit might also implicitly turn it on for
          all its parent slices. The system default for this setting
          maybe controlled with
          <varname>DefaultMemoryAccounting=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MemoryLimit=<replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Specify the limit on maximum memory usage of the
          executed processes. The limit specifies how much process and
          kernel memory can be used by tasks in this unit. 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, or Terabytes (with the base 1024),
          respectively. This controls the
          <literal>memory.limit_in_bytes</literal> control group
          attribute. For details about this control group attribute,
          see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroups/memory.txt">memory.txt</ulink>.</para>

          <para>Implies <literal>MemoryAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIOAccounting=</varname></term>

        <listitem>
          <para>Turn on Block IO accounting for this unit. Takes a
          boolean argument. Note that turning on block IO accounting
          for one unit might also implicitly turn it on for all units
          contained in the same slice and all for its parent slices
          and the units contained therein. The system default for this
          setting maybe controlled with
          <varname>DefaultBlockIOAccounting=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIOWeight=<replaceable>weight</replaceable></varname></term>
        <term><varname>StartupBlockIOWeight=<replaceable>weight</replaceable></varname></term>

        <listitem><para>Set the default overall block IO weight for
        the executed processes. Takes a single weight value (between
        10 and 1000) to set the default block IO weight. This controls
        the <literal>blkio.weight</literal> control group attribute,
        which defaults to 1000. For details about this control group
        attribute, see <ulink
        url="https://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.
        The available IO bandwidth is split up among all units within
        one slice relative to their block IO weight.</para>

        <para>While <varname>StartupBlockIOWeight=</varname> only
        applies to the startup phase of the system,
        <varname>BlockIOWeight=</varname> applies to the later runtime
        of the system, and if the former is not set also to the
        startup phase. This allows prioritizing specific services at
        boot-up differently than during runtime.</para>

        <para>Implies
        <literal>BlockIOAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIODeviceWeight=<replaceable>device</replaceable> <replaceable>weight</replaceable></varname></term>

        <listitem>
          <para>Set the per-device overall block IO weight for the
          executed processes. Takes a space-separated pair of a file
          path and a weight value to specify the device specific
          weight value, between 10 and 1000. (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_device</literal> control group
          attribute, which defaults to 1000. Use this option multiple
          times to set weights for multiple devices. For details about
          this control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.</para>

          <para>Implies
          <literal>BlockIOAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIOReadBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>
        <term><varname>BlockIOWriteBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Set the per-device overall block IO bandwidth limit
          for the executed processes. Takes a space-separated pair of
          a file path and a bandwidth value (in bytes per second) to
          specify the device specific bandwidth. The file path may be
          a 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 used. If the bandwidth is suffixed with K, M, G, or T,
          the specified bandwidth is parsed as Kilobytes, Megabytes,
          Gigabytes, or Terabytes, respectively, to the base of
          1000. (Example:
          "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This
          controls the <literal>blkio.read_bps_device</literal> and
          <literal>blkio.write_bps_device</literal> control group
          attributes. Use this option multiple times to set bandwidth
          limits for multiple devices. For details about these control
          group attributes, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.
          </para>

          <para>Implies
          <literal>BlockIOAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>DeviceAllow=</varname></term>

        <listitem>
          <para>Control access to specific device nodes by the
          executed processes. Takes two space-separated strings: a
          device node specifier followed by a combination of
          <constant>r</constant>, <constant>w</constant>,
          <constant>m</constant> to control
          <emphasis>r</emphasis>eading, <emphasis>w</emphasis>riting,
          or creation of the specific device node(s) by the unit
          (<emphasis>m</emphasis>knod), respectively. 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="https://www.kernel.org/doc/Documentation/cgroups/devices.txt">devices.txt</ulink>.</para>

          <para>The device node specifier is either a path to a device
          node in the file system, starting with
          <filename>/dev/</filename>, or a string starting with either
          <literal>char-</literal> or <literal>block-</literal>
          followed by a device group name, as listed in
          <filename>/proc/devices</filename>. The latter is useful to
          whitelist all current and future devices belonging to a
          specific device group at once. The device group is matched
          according to file name globbing rules, you may hence use the
          <literal>*</literal> and <literal>?</literal>
          wildcards. Examples: <filename>/dev/sda5</filename> is a
          path to a device node, referring to an ATA or SCSI block
          device. <literal>char-pts</literal> and
          <literal>char-alsa</literal> are specifiers for all pseudo
          TTYs and all ALSA sound devices,
          respectively. <literal>char-cpu/*</literal> is a specifier
          matching all CPU related device groups.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>DevicePolicy=auto|closed|strict</varname></term>

        <listitem>
          <para>
            Control the policy for allowing device access:
          </para>
          <variablelist>
            <varlistentry>
              <term><option>strict</option></term>
              <listitem>
                <para>means to only allow types of access that are
                explicitly specified.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>closed</option></term>
              <listitem>
                <para>in addition, allows access to standard pseudo
                devices including
                <filename>/dev/null</filename>,
                <filename>/dev/zero</filename>,
                <filename>/dev/full</filename>,
                <filename>/dev/random</filename>, and
                <filename>/dev/urandom</filename>.
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>auto</option></term>
              <listitem>
                <para>
                  in addition, allows access to all devices if no
                  explicit <varname>DeviceAllow=</varname> is present.
                  This is the default.
                </para>
              </listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Slice=</varname></term>

        <listitem>
          <para>The name of the slice unit to place the unit
          in. Defaults to <filename>system.slice</filename> for all
          non-instantiated units of all unit types (except for slice
          units themselves see below). Instance units are by default
          placed in a subslice of <filename>system.slice</filename>
          that is named after the template name.</para>

          <para>This option may be used to arrange systemd units in a
          hierarchy of slices each of which might have resource
          settings applied.</para>

          <para>For units of type slice, the only accepted value for
          this setting is the parent slice. Since the name of a slice
          unit implies the parent slice, it is hence redundant to ever
          set this parameter directly for slice units.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Delegate=</varname></term>

        <listitem>
          <para>Turns on delegation of further resource control
          partitioning to processes of the unit. For unprivileged
          services (i.e. those using the <varname>User=</varname>
          setting) this allows processes to create a subhierarchy
          beneath its control group path. For privileged services and
          scopes this ensures the processes will have all control
          group controllers enabled.</para>
        </listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      The documentation for control groups and specific controllers in the Linux kernel:
      <ulink url="https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>,
      <ulink url="https://www.kernel.org/doc/Documentation/cgroups/cpuacct.txt">cpuacct.txt</ulink>,
      <ulink url="https://www.kernel.org/doc/Documentation/cgroups/memory.txt">memory.txt</ulink>,
      <ulink url="https://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.
    </para>
  </refsect1>
</refentry>