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">
   4 <!--
   5   SPDX-License-Identifier: LGPL-2.1+
   6
   7   Copyright 2013 Lennart Poettering
   8 -->
   9 <refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'>
  10
  11   <refentryinfo>
  12     <title>systemd-backlight@.service</title>
  13     <productname>systemd</productname>
  14
  15     <authorgroup>
  16       <author>
  17         <contrib>Developer</contrib>
  18         <firstname>Lennart</firstname>
  19         <surname>Poettering</surname>
  20         <email>lennart@poettering.net</email>
  21       </author>
  22     </authorgroup>
  23   </refentryinfo>
  24
  25   <refmeta>
  26     <refentrytitle>systemd-backlight@.service</refentrytitle>
  27     <manvolnum>8</manvolnum>
  28   </refmeta>
  29
  30   <refnamediv>
  31     <refname>systemd-backlight@.service</refname>
  32     <refname>systemd-backlight</refname>
  33     <refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose>
  34   </refnamediv>
  35
  36   <refsynopsisdiv>
  37     <para><filename>systemd-backlight@.service</filename></para>
  38     <para><filename>/usr/lib/systemd/systemd-backlight</filename></para>
  39   </refsynopsisdiv>
  40
  41   <refsect1>
  42     <title>Description</title>
  43
  44     <para><filename>systemd-backlight@.service</filename> is a service
  45     that restores the display backlight brightness at early boot and
  46     saves it at shutdown. On disk, the backlight brightness is stored
  47     in <filename>/var/lib/systemd/backlight/</filename>. During
  48     loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is
  49     not set to false, the brightness is clamped to a value of at
  50     least 1 or 5% of maximum brightness, whichever is greater. This
  51     restriction will be removed when the kernel allows user space to
  52     reliably set a brightness value which does not turn off the
  53     display.</para>
  54   </refsect1>
  55
  56   <refsect1>
  57     <title>Kernel Command Line</title>
  58
  59     <para><filename>systemd-backlight</filename> understands the
  60     following kernel command line parameter:</para>
  61
  62     <variablelist class='kernel-commandline-options'>
  63       <varlistentry>
  64         <term><varname>systemd.restore_state=</varname></term>
  65
  66         <listitem><para>Takes a boolean argument. Defaults to
  67         <literal>1</literal>. If <literal>0</literal>, does not
  68         restore the backlight settings on boot. However, settings will
  69         still be stored on shutdown. </para></listitem>
  70       </varlistentry>
  71     </variablelist>
  72   </refsect1>
  73
  74   <refsect1>
  75     <title>See Also</title>
  76     <para>
  77       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  78     </para>
  79   </refsect1>
  80
  81 </refentry>