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1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
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3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
4 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
db9ecf05 | 5 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
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6 | <refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT' |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
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9 | <refentryinfo> |
10 | <title>systemd-backlight@.service</title> | |
11 | <productname>systemd</productname> | |
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12 | </refentryinfo> |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>systemd-backlight@.service</refentrytitle> | |
16 | <manvolnum>8</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>systemd-backlight@.service</refname> | |
21 | <refname>systemd-backlight</refname> | |
22 | <refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose> | |
23 | </refnamediv> | |
24 | ||
25 | <refsynopsisdiv> | |
26 | <para><filename>systemd-backlight@.service</filename></para> | |
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27 | <para><filename>/usr/lib/systemd/systemd-backlight</filename> save [backlight|leds]:DEVICE</para> |
28 | <para><filename>/usr/lib/systemd/systemd-backlight</filename> load [backlight|leds]:DEVICE</para> | |
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29 | </refsynopsisdiv> |
30 | ||
31 | <refsect1> | |
32 | <title>Description</title> | |
33 | ||
34 | <para><filename>systemd-backlight@.service</filename> is a service | |
35 | that restores the display backlight brightness at early boot and | |
36 | saves it at shutdown. On disk, the backlight brightness is stored | |
37 | in <filename>/var/lib/systemd/backlight/</filename>. During | |
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38 | loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is |
39 | not set to false, the brightness is clamped to a value of at | |
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40 | least 1 or 5% of maximum brightness, whichever is greater. This |
41 | restriction will be removed when the kernel allows user space to | |
42 | reliably set a brightness value which does not turn off the | |
43 | display.</para> | |
44 | </refsect1> | |
45 | ||
46 | <refsect1> | |
47 | <title>Kernel Command Line</title> | |
48 | ||
49 | <para><filename>systemd-backlight</filename> understands the | |
50 | following kernel command line parameter:</para> | |
51 | ||
52 | <variablelist class='kernel-commandline-options'> | |
53 | <varlistentry> | |
54 | <term><varname>systemd.restore_state=</varname></term> | |
55 | ||
56 | <listitem><para>Takes a boolean argument. Defaults to | |
57 | <literal>1</literal>. If <literal>0</literal>, does not | |
58 | restore the backlight settings on boot. However, settings will | |
59 | still be stored on shutdown. </para></listitem> | |
60 | </varlistentry> | |
61 | </variablelist> | |
62 | </refsect1> | |
63 | ||
64 | <refsect1> | |
65 | <title>See Also</title> | |
66 | <para> | |
67 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
68 | </para> | |
69 | </refsect1> | |
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70 | |
71 | </refentry> |