man/runlevel.xml

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