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1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
12b42c76 | 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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4 | <!-- |
5 | This file is part of systemd. | |
6 | ||
7 | Copyright 2013 Lennart Poettering | |
8 | ||
9 | systemd is free software; you can redistribute it and/or modify it | |
10 | under the terms of the GNU Lesser General Public License as published by | |
11 | the Free Software Foundation; either version 2.1 of the License, or | |
12 | (at your option) any later version. | |
13 | ||
14 | systemd is distributed in the hope that it will be useful, but | |
15 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | Lesser General Public License for more details. | |
18 | ||
19 | You should have received a copy of the GNU Lesser General Public License | |
20 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
21 | --> | |
22 | <refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'> | |
23 | ||
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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> | |
12b42c76 | 51 | <para><filename>/usr/lib/systemd/systemd-backlight</filename></para> |
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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 | |
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61 | loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is |
62 | not set to false, the brightness is clamped to a value of at | |
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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> | |
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93 | |
94 | </refentry> |