man/runlevel.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2010 Lennart Poettering
  11 -->
  12
  13 <refentry id="runlevel"
  14     xmlns:xi="http://www.w3.org/2001/XInclude"
  15     conditional="ENABLE_UTMP">
  16
  17   <refentryinfo>
  18     <title>runlevel</title>
  19     <productname>systemd</productname>
  20
  21     <authorgroup>
  22       <author>
  23         <contrib>Developer</contrib>
  24         <firstname>Lennart</firstname>
  25         <surname>Poettering</surname>
  26         <email>lennart@poettering.net</email>
  27       </author>
  28     </authorgroup>
  29   </refentryinfo>
  30
  31   <refmeta>
  32     <refentrytitle>runlevel</refentrytitle>
  33     <manvolnum>8</manvolnum>
  34   </refmeta>
  35
  36   <refnamediv>
  37     <refname>runlevel</refname>
  38     <refpurpose>Print previous and current SysV runlevel</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <cmdsynopsis>
  43       <command>runlevel</command>
  44       <arg choice="opt" rep="repeat">options</arg>
  45     </cmdsynopsis>
  46   </refsynopsisdiv>
  47
  48   <refsect1>
  49     <title>Overview</title>
  50
  51     <para>"Runlevels" are an obsolete way to start and stop groups of
  52     services used in SysV init. systemd provides a compatibility layer
  53     that maps runlevels to targets, and associated binaries like
  54     <command>runlevel</command>. Nevertheless, only one runlevel can
  55     be "active" at a given time, while systemd can activate multiple
  56     targets concurrently, so the mapping to runlevels is confusing
  57     and only approximate. Runlevels should not be used in new code,
  58     and are mostly useful as a shorthand way to refer the matching
  59     systemd targets in kernel boot parameters.</para>
  60
  61     <table>
  62       <title>Mapping between runlevels and systemd targets</title>
  63       <tgroup cols='2' align='left' colsep='1' rowsep='1'>
  64         <colspec colname="runlevel" />
  65         <colspec colname="target" />
  66         <thead>
  67           <row>
  68             <entry>Runlevel</entry>
  69             <entry>Target</entry>
  70           </row>
  71         </thead>
  72         <tbody>
  73           <row>
  74             <entry>0</entry>
  75             <entry><filename>poweroff.target</filename></entry>
  76           </row>
  77           <row>
  78             <entry>1</entry>
  79             <entry><filename>rescue.target</filename></entry>
  80           </row>
  81           <row>
  82             <entry>2, 3, 4</entry>
  83             <entry><filename>multi-user.target</filename></entry>
  84           </row>
  85           <row>
  86             <entry>5</entry>
  87             <entry><filename>graphical.target</filename></entry>
  88           </row>
  89           <row>
  90             <entry>6</entry>
  91             <entry><filename>reboot.target</filename></entry>
  92           </row>
  93         </tbody>
  94       </tgroup>
  95     </table>
  96   </refsect1>
  97
  98   <refsect1>
  99     <title>Description</title>
 100
 101     <para><command>runlevel</command> prints the previous and current
 102     SysV runlevel if they are known.</para>
 103
 104     <para>The two runlevel characters are separated by a single space
 105     character. If a runlevel cannot be determined, N is printed
 106     instead. If neither can be determined, the word "unknown" is
 107     printed.</para>
 108
 109     <para>Unless overridden in the environment, this will check the
 110     utmp database for recent runlevel changes.</para>
 111   </refsect1>
 112
 113   <refsect1>
 114     <title>Options</title>
 115
 116     <para>The following option is understood:</para>
 117
 118     <variablelist>
 119       <varlistentry>
 120         <term><option>--help</option></term>
 121
 122         <xi:include href="standard-options.xml" xpointer="help-text" />
 123       </varlistentry>
 124     </variablelist>
 125
 126   </refsect1>
 127
 128   <refsect1>
 129     <title>Exit status</title>
 130
 131     <para>If one or both runlevels could be determined, 0 is returned,
 132     a non-zero failure code otherwise.</para>
 133
 134   </refsect1>
 135
 136   <refsect1>
 137     <title>Environment</title>
 138
 139     <variablelist class='environment-variables'>
 140       <varlistentry>
 141         <term><varname>$RUNLEVEL</varname></term>
 142
 143         <listitem><para>If <varname>$RUNLEVEL</varname> is set,
 144         <command>runlevel</command> will print this value as current
 145         runlevel and ignore utmp.</para></listitem>
 146       </varlistentry>
 147
 148       <varlistentry>
 149         <term><varname>$PREVLEVEL</varname></term>
 150
 151         <listitem><para>If <varname>$PREVLEVEL</varname> is set,
 152         <command>runlevel</command> will print this value as previous
 153         runlevel and ignore utmp.</para></listitem>
 154       </varlistentry>
 155     </variablelist>
 156   </refsect1>
 157
 158   <refsect1>
 159     <title>Files</title>
 160
 161     <variablelist>
 162       <varlistentry>
 163         <term><filename>/run/utmp</filename></term>
 164
 165         <listitem><para>The utmp database <command>runlevel</command> reads the previous and current runlevel
 166         from.</para></listitem>
 167       </varlistentry>
 168     </variablelist>
 169   </refsect1>
 170
 171   <refsect1>
 172     <title>See Also</title>
 173     <para>
 174       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 175       <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 176       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 177     </para>
 178   </refsect1>
 179
 180 </refentry>