summaryrefslogtreecommitdiff
path: root/man/systemd-backlight@.service.xml
blob: 8c7c2c105b28a231d9aa43dc7a26565738f8992d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
<?xml version="1.0"?>
<!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
  SPDX-License-Identifier: LGPL-2.1+

  This file is part of systemd.

  Copyright 2013 Lennart Poettering
-->
<refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'>

  <refentryinfo>
    <title>systemd-backlight@.service</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-backlight@.service</refentrytitle>
    <manvolnum>8</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-backlight@.service</refname>
    <refname>systemd-backlight</refname>
    <refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>systemd-backlight@.service</filename></para>
    <para><filename>/usr/lib/systemd/systemd-backlight</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><filename>systemd-backlight@.service</filename> is a service
    that restores the display backlight brightness at early boot and
    saves it at shutdown. On disk, the backlight brightness is stored
    in <filename>/var/lib/systemd/backlight/</filename>. During
    loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is
    not set to false, the brightness is clamped to a value of at
    least 1 or 5% of maximum brightness, whichever is greater. This
    restriction will be removed when the kernel allows user space to
    reliably set a brightness value which does not turn off the
    display.</para>
  </refsect1>

  <refsect1>
    <title>Kernel Command Line</title>

    <para><filename>systemd-backlight</filename> understands the
    following kernel command line parameter:</para>

    <variablelist class='kernel-commandline-options'>
      <varlistentry>
        <term><varname>systemd.restore_state=</varname></term>

        <listitem><para>Takes a boolean argument. Defaults to
        <literal>1</literal>. If <literal>0</literal>, does not
        restore the backlight settings on boot. However, settings will
        still be stored on shutdown. </para></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>