man/systemd-backlight@.service.xml

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   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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   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> is a service
  58     that restores the display backlight brightness at early boot and
  59     saves it at shutdown. On disk, the backlight brightness is stored
  60     in <filename>/var/lib/systemd/backlight/</filename>. During
  61     loading, if udev property <option>ID_BACKLIGHT_CLAMP</option> is
  62     not set to false value, the brightness is clamped to a value of at
  63     least 1 or 5% of maximum brightness, whichever is greater. This
  64     restriction will be removed when the kernel allows user space to
  65     reliably set a brightness value which does not turn off the
  66     display.</para>
  67   </refsect1>
  68
  69   <refsect1>
  70     <title>Kernel Command Line</title>
  71
  72     <para><filename>systemd-backlight</filename> understands the
  73     following kernel command line parameter:</para>
  74
  75     <variablelist class='kernel-commandline-options'>
  76       <varlistentry>
  77         <term><varname>systemd.restore_state=</varname></term>
  78
  79         <listitem><para>Takes a boolean argument. Defaults to
  80         <literal>1</literal>. If <literal>0</literal>, does not
  81         restore the backlight settings on boot. However, settings will
  82         still be stored on shutdown. </para></listitem>
  83       </varlistentry>
  84     </variablelist>
  85   </refsect1>
  86
  87   <refsect1>
  88     <title>See Also</title>
  89     <para>
  90       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  91     </para>
  92   </refsect1>
  93
  94 </refentry>