man/systemd-backlight@.service.xml

   1 <?xml version="1.0"?>
   2 <!--*-nxml-*-->
   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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   5   This file is part of systemd.
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   7   Copyright 2013 Lennart Poettering
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  22 <refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'>
  23
  24         <refentryinfo>
  25                 <title>systemd-backlight@.service</title>
  26                 <productname>systemd</productname>
  27
  28                 <authorgroup>
  29                         <author>
  30                                 <contrib>Developer</contrib>
  31                                 <firstname>Lennart</firstname>
  32                                 <surname>Poettering</surname>
  33                                 <email>lennart@poettering.net</email>
  34                         </author>
  35                 </authorgroup>
  36         </refentryinfo>
  37
  38         <refmeta>
  39                 <refentrytitle>systemd-backlight@.service</refentrytitle>
  40                 <manvolnum>8</manvolnum>
  41         </refmeta>
  42
  43         <refnamediv>
  44                 <refname>systemd-backlight@.service</refname>
  45                 <refname>systemd-backlight</refname>
  46                 <refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose>
  47         </refnamediv>
  48
  49         <refsynopsisdiv>
  50                 <para><filename>systemd-backlight@.service</filename></para>
  51                 <para><filename>/usr/lib/systemd/systemd-backlight</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para><filename>systemd-backlight@.service</filename>
  58                 is a service that restores the display backlight
  59                 brightness at early boot and saves it at shutdown. On
  60                 disk, the backlight brightness is stored in
  61                 <filename>/var/lib/systemd/backlight/</filename>. During
  62                 loading, if udev property
  63                 <option>ID_BACKLIGHT_CLAMP</option> is not set to
  64                 false value, the brightness is clamped to a value of
  65                 at least 1 or 5% of maximum brightness, whichever is
  66                 greater. This restriction will be removed when the
  67                 kernel allows user space to reliably set a brightness
  68                 value which does not turn off the display.</para>
  69         </refsect1>
  70
  71         <refsect1>
  72                 <title>Kernel Command Line</title>
  73
  74                 <para><filename>systemd-backlight</filename> understands
  75                 the following kernel command line parameter:</para>
  76
  77                 <variablelist class='kernel-commandline-options'>
  78                         <varlistentry>
  79                                 <term><varname>systemd.restore_state=</varname></term>
  80
  81                                 <listitem><para>Takes a boolean
  82                                 argument. Defaults to
  83                                 <literal>1</literal>. If
  84                                 <literal>0</literal>, does not restore
  85                                 the backlight settings on boot. However,
  86                                 settings will still be stored on shutdown.
  87                                 </para></listitem>
  88                         </varlistentry>
  89                 </variablelist>
  90         </refsect1>
  91
  92         <refsect1>
  93                 <title>See Also</title>
  94                 <para>
  95                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  96                 </para>
  97         </refsect1>
  98
  99 </refentry>