man/user@.service.xml

   1 <?xml version="1.0"?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="user@.service">
   7   <refentryinfo>
   8     <title>user@.service</title>
   9     <productname>systemd</productname>
  10   </refentryinfo>
  11
  12   <refmeta>
  13     <refentrytitle>user@.service</refentrytitle>
  14     <manvolnum>5</manvolnum>
  15   </refmeta>
  16
  17   <refnamediv>
  18     <refname>user@.service</refname>
  19     <refname>user-runtime-dir@.service</refname>
  20     <refpurpose>System units to manage user processes</refpurpose>
  21   </refnamediv>
  22
  23   <refsynopsisdiv>
  24     <para><filename>user@<replaceable>UID</replaceable>.service</filename></para>
  25     <para><filename>user-runtime-dir@<replaceable>UID</replaceable>.service</filename></para>
  26     <para><filename>user-<replaceable>UID</replaceable>.slice</filename></para>
  27   </refsynopsisdiv>
  28
  29   <refsect1>
  30     <title>Description</title>
  31
  32     <para>The
  33     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  34     system manager (PID 1) starts user manager instances as
  35     <filename>user@<replaceable>UID</replaceable>.service</filename>, where the user's numerical UID
  36     is used as the instance identifier. Each <command>systemd --user</command> instance manages a
  37     hierarchy of its own units. See
  38     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
  39     a discussion of systemd units and
  40     <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  41     for a list of units that form the basis of the unit hierarchies of system and user units.</para>
  42
  43     <para><filename>user@<replaceable>UID</replaceable>.service</filename> is accompanied by the
  44     system unit <filename>user-runtime-dir@<replaceable>UID</replaceable>.service</filename>, which
  45     creates the user's runtime directory
  46     <filename>/run/user/<replaceable>UID</replaceable></filename>, and then removes it when this
  47     unit is stopped.</para>
  48
  49     <para>User processes may be started by the <filename>user@.service</filename> instance, in which
  50     case they will be part of that unit in the system hierarchy. They may also be started elsewhere,
  51     for example by
  52     <citerefentry><refentrytitle>sshd</refentrytitle><manvolnum>8</manvolnum></citerefentry> or a
  53     display manager like <command>gdm</command>, in which case they form a .scope unit (see
  54     <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
  55     Both <filename>user@<replaceable>UID</replaceable>.service</filename> and the scope units are
  56     collected under a <filename>user-<replaceable>UID</replaceable>.slice</filename>.</para>
  57
  58     <para>Individual <filename>user-<replaceable>UID</replaceable>.slice</filename> slices are
  59     collected under <filename>user.slice</filename>, see
  60     <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  61     </para>
  62   </refsect1>
  63
  64   <refsect1>
  65     <title>Controlling resources for logged-in users</title>
  66
  67     <para>Options that control resources available to logged-in users can be configured at a few
  68     different levels. As described in the previous section, <filename>user.slice</filename> contains
  69     processes of all users, so any resource limits on that slice apply to all users together. The
  70     usual way to configure them would be through drop-ins, e.g. <filename
  71     noindex='true'>/etc/systemd/system/user.slice.d/resources.conf</filename>.
  72     </para>
  73
  74     <para>The processes of a single user are collected under
  75     <filename>user-<replaceable>UID</replaceable>.slice</filename>. Resource limits for that user
  76     can be configured through drop-ins for that unit, e.g. <filename
  77     noindex='true'>/etc/systemd/system/user-1000.slice.d/resources.conf</filename>. If the limits
  78     should apply to all users instead, they may be configured through drop-ins for the truncated
  79     unit name, <filename>user-.slice</filename>. For example, configuration in <filename
  80     noindex='true'>/etc/systemd/system/user-.slice.d/resources.conf</filename> is included in all
  81     <filename>user-<replaceable>UID</replaceable>.slice</filename> units, see
  82     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  83     for a discussion of the drop-in mechanism.</para>
  84
  85     <para>When a user logs in and a .scope unit is created for the session (see previous section),
  86     the creation of the scope may be managed through
  87     <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  88     This PAM module communicates with
  89     <citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  90     to create the session scope and provide access to hardware resources. Resource limits for the
  91     scope may be configured through the PAM module configuration, see
  92     <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  93     Configuring them through the normal unit configuration is also possible, but since
  94     the name of the slice unit is generally unpredictable, this is less useful.</para>
  95
  96     <para>In general any resources that apply to units may be set for
  97     <filename>user@<replaceable>UID</replaceable>.service</filename> and the slice
  98     units discussed above, see
  99     <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 100     for an overview.</para>
 101   </refsect1>
 102
 103   <refsect1>
 104     <title>Examples</title>
 105     <example>
 106       <title>Hierarchy of control groups with two logged in users</title>
 107
 108       <programlisting>$ systemd-cgls
 109 Control group /:
 110 -.slice
 111 ├─user.slice
 112 │ ├─user-1000.slice
 113 │ │ ├─user@1000.service
 114 │ │ │ ├─pulseaudio.service
 115 │ │ │ │ └─2386 /usr/bin/pulseaudio --daemonize=no
 116 │ │ │ └─gnome-terminal-server.service
 117 │ │ │   └─init.scope
 118 │ │ │     ├─ 4127 /usr/libexec/gnome-terminal-server
 119 │ │ │     └─ 4198 zsh
 120 │ │ …
 121 │ │ └─session-4.scope
 122 │ │   ├─ 1264 gdm-session-worker [pam/gdm-password]
 123 │ │   ├─ 2339 /usr/bin/gnome-shell
 124 │ │   …
 125 │ │ ├─session-19.scope
 126 │ │   ├─6497 sshd: zbyszek [priv]
 127 │ │   ├─6502 sshd: zbyszek@pts/6
 128 │ │   ├─6509 -zsh
 129 │ │   └─6602 systemd-cgls --no-pager
 130 │ …
 131 │ └─user-1001.slice
 132 │   ├─session-20.scope
 133 │   │ ├─6675 sshd: guest [priv]
 134 │   │ ├─6708 sshd: guest@pts/6
 135 │   │ └─6717 -bash
 136 │   └─user@1001.service
 137 │     ├─init.scope
 138 │     │ ├─6680 /usr/lib/systemd/systemd --user
 139 │     │ └─6688 (sd-pam)
 140 │     └─sleep.service
 141 │       └─6706 /usr/bin/sleep 30
 142 …</programlisting>
 143       <para>User with UID 1000 is logged in using <command>gdm</command> (<filename
 144       noindex='true'>session-4.scope</filename>) and
 145       <citerefentry><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 146       (<filename noindex='true'>session-19.scope</filename>), and also has a user manager instance
 147       running (<filename noindex='true'>user@1000.service</filename>).  User with UID 1001 is logged
 148       in using <command>ssh</command> (<filename noindex='true'>session-20.scope</filename>) and
 149       also has a user manager instance running (<filename
 150       noindex='true'>user@1001.service</filename>).  Those are all (leaf) system units, and form
 151       part of the slice hierarchy, with <filename noindex='true'>user-1000.slice</filename> and
 152       <filename noindex='true'>user-1001.slice</filename> below <filename
 153       noindex='true'>user.slice</filename>.  User units are visible below the
 154       <filename>user@.service</filename> instances (<filename
 155       noindex='true'>pulseaudio.service</filename>, <filename
 156       noindex='true'>gnome-terminal-server.service</filename>, <filename
 157       noindex='true'>init.scope</filename>, <filename noindex='true'>sleep.service</filename>).
 158       </para>
 159     </example>
 160
 161     <example>
 162       <title>Default user resource limits</title>
 163
 164       <programlisting>$ systemctl cat user-1000.slice
 165 # /usr/lib/systemd/system/user-.slice.d/10-defaults.conf
 166 # …
 167 [Unit]
 168 Description=User Slice of UID %j
 169 After=systemd-user-sessions.service
 170
 171 [Slice]
 172 TasksMax=33%</programlisting>
 173      <para>The <filename>user-<replaceable>UID</replaceable>.slice</filename> units by default don't
 174      have a unit file. The resource limits are set through a drop-in, which can be easily replaced
 175      or extended following standard drop-in mechanisms discussed in the first section.</para>
 176     </example>
 177   </refsect1>
 178
 179   <refsect1>
 180     <title>See Also</title>
 181     <para>
 182       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 183       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 184       <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 185       <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 186       <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 187       <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 188       <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 189     </para>
 190   </refsect1>
 191 </refentry>