man/runlevel.xml

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