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