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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"> |
38e19f93 | 4 | <!-- |
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5 | SPDX-License-Identifier: LGPL-2.1+ |
6 | ||
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7 | This file is part of systemd. |
8 | ||
9 | Copyright 2013 Lennart Poettering | |
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10 | --> |
11 | <refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'> | |
12 | ||
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13 | <refentryinfo> |
14 | <title>systemd-backlight@.service</title> | |
15 | <productname>systemd</productname> | |
16 | ||
17 | <authorgroup> | |
18 | <author> | |
19 | <contrib>Developer</contrib> | |
20 | <firstname>Lennart</firstname> | |
21 | <surname>Poettering</surname> | |
22 | <email>lennart@poettering.net</email> | |
23 | </author> | |
24 | </authorgroup> | |
25 | </refentryinfo> | |
26 | ||
27 | <refmeta> | |
28 | <refentrytitle>systemd-backlight@.service</refentrytitle> | |
29 | <manvolnum>8</manvolnum> | |
30 | </refmeta> | |
31 | ||
32 | <refnamediv> | |
33 | <refname>systemd-backlight@.service</refname> | |
34 | <refname>systemd-backlight</refname> | |
35 | <refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose> | |
36 | </refnamediv> | |
37 | ||
38 | <refsynopsisdiv> | |
39 | <para><filename>systemd-backlight@.service</filename></para> | |
12b42c76 | 40 | <para><filename>/usr/lib/systemd/systemd-backlight</filename></para> |
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41 | </refsynopsisdiv> |
42 | ||
43 | <refsect1> | |
44 | <title>Description</title> | |
45 | ||
46 | <para><filename>systemd-backlight@.service</filename> is a service | |
47 | that restores the display backlight brightness at early boot and | |
48 | saves it at shutdown. On disk, the backlight brightness is stored | |
49 | in <filename>/var/lib/systemd/backlight/</filename>. During | |
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50 | loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is |
51 | not set to false, the brightness is clamped to a value of at | |
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52 | least 1 or 5% of maximum brightness, whichever is greater. This |
53 | restriction will be removed when the kernel allows user space to | |
54 | reliably set a brightness value which does not turn off the | |
55 | display.</para> | |
56 | </refsect1> | |
57 | ||
58 | <refsect1> | |
59 | <title>Kernel Command Line</title> | |
60 | ||
61 | <para><filename>systemd-backlight</filename> understands the | |
62 | following kernel command line parameter:</para> | |
63 | ||
64 | <variablelist class='kernel-commandline-options'> | |
65 | <varlistentry> | |
66 | <term><varname>systemd.restore_state=</varname></term> | |
67 | ||
68 | <listitem><para>Takes a boolean argument. Defaults to | |
69 | <literal>1</literal>. If <literal>0</literal>, does not | |
70 | restore the backlight settings on boot. However, settings will | |
71 | still be stored on shutdown. </para></listitem> | |
72 | </varlistentry> | |
73 | </variablelist> | |
74 | </refsect1> | |
75 | ||
76 | <refsect1> | |
77 | <title>See Also</title> | |
78 | <para> | |
79 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
80 | </para> | |
81 | </refsect1> | |
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82 | |
83 | </refentry> |