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