man/systemd.slice.xml

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   6   SPDX-License-Identifier: LGPL-2.1+
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   8   This file is part of systemd.
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  10   Copyright 2013 Zbigniew Jędrzejewski-Szmek
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  12
  13 <refentry id="systemd.slice">
  14   <refentryinfo>
  15     <title>systemd.slice</title>
  16     <productname>systemd</productname>
  17
  18     <authorgroup>
  19       <author>
  20         <contrib>Developer</contrib>
  21         <firstname>Lennart</firstname>
  22         <surname>Poettering</surname>
  23         <email>lennart@poettering.net</email>
  24       </author>
  25     </authorgroup>
  26   </refentryinfo>
  27
  28   <refmeta>
  29     <refentrytitle>systemd.slice</refentrytitle>
  30     <manvolnum>5</manvolnum>
  31   </refmeta>
  32
  33   <refnamediv>
  34     <refname>systemd.slice</refname>
  35     <refpurpose>Slice unit configuration</refpurpose>
  36   </refnamediv>
  37
  38   <refsynopsisdiv>
  39     <para><filename><replaceable>slice</replaceable>.slice</filename></para>
  40   </refsynopsisdiv>
  41
  42   <refsect1>
  43     <title>Description</title>
  44
  45     <para>A unit configuration file whose name ends in <literal>.slice</literal> encodes information about a slice
  46     unit. A slice unit is a concept for hierarchically managing resources of a group of processes. This management is
  47     performed by creating a node in the Linux Control Group (cgroup) tree. Units that manage processes (primarily scope
  48     and service units) may be assigned to a specific slice. For each slice, certain resource limits may be set that
  49     apply to all processes of all units contained in that slice. Slices are organized hierarchically in a tree. The
  50     name of the slice encodes the location in the tree. The name consists of a dash-separated series of names, which
  51     describes the path to the slice from the root slice. The root slice is named <filename>-.slice</filename>. Example:
  52     <filename>foo-bar.slice</filename> is a slice that is located within <filename>foo.slice</filename>, which in turn
  53     is located in the root slice <filename>-.slice</filename>.
  54     </para>
  55
  56     <para>Note that slice units cannot be templated, nor is possible to add multiple names to a slice unit by creating
  57     additional symlinks to its unit file.</para>
  58
  59     <para>By default, service and scope units are placed in
  60     <filename>system.slice</filename>, virtual machines and containers
  61     registered with
  62     <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  63     are found in <filename>machine.slice</filename>, and user sessions
  64     handled by
  65     <citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  66     in <filename>user.slice</filename>. See
  67     <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  68     for more information.</para>
  69
  70     <para>See
  71     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  72     for the common options of all unit configuration
  73     files. The common configuration items are configured
  74     in the generic [Unit] and [Install] sections. The
  75     slice specific configuration options are configured in
  76     the [Slice] section. Currently, only generic resource control settings
  77     as described in
  78     <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> are allowed.
  79     </para>
  80
  81     <para>See the <ulink
  82     url="https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/">New
  83     Control Group Interfaces</ulink> for an introduction on how to make
  84     use of slice units from programs.</para>
  85   </refsect1>
  86
  87   <refsect1>
  88     <title>Automatic Dependencies</title>
  89
  90     <refsect2>
  91       <title>Implicit Dependencies</title>
  92
  93       <para>The following dependencies are implicitly added:</para>
  94
  95       <itemizedlist>
  96         <listitem><para>Slice units automatically gain dependencies of type
  97         <varname>After=</varname> and <varname>Requires=</varname> on
  98         their immediate parent slice unit.</para></listitem>
  99       </itemizedlist>
 100     </refsect2>
 101
 102     <refsect2>
 103       <title>Default Dependencies</title>
 104
 105       <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para>
 106
 107       <itemizedlist>
 108         <listitem><para>Slice units will automatically have dependencies of type <varname>Conflicts=</varname> and
 109         <varname>Before=</varname> on
 110         <filename>shutdown.target</filename>. These ensure that slice units are removed prior to system shutdown.
 111         Only slice units involved with late system shutdown should disable
 112         <varname>DefaultDependencies=</varname> option.</para></listitem>
 113       </itemizedlist>
 114     </refsect2>
 115   </refsect1>
 116
 117   <refsect1>
 118     <title>See Also</title>
 119     <para>
 120       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 121       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 122       <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 123       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 124       <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 127     </para>
 128   </refsect1>
 129
 130 </refentry>