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