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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"> | |
0307f791 | 5 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
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6 | <refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'> |
7 | ||
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8 | <refentryinfo> |
9 | <title>systemd-backlight@.service</title> | |
10 | <productname>systemd</productname> | |
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11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>systemd-backlight@.service</refentrytitle> | |
15 | <manvolnum>8</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>systemd-backlight@.service</refname> | |
20 | <refname>systemd-backlight</refname> | |
21 | <refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose> | |
22 | </refnamediv> | |
23 | ||
24 | <refsynopsisdiv> | |
25 | <para><filename>systemd-backlight@.service</filename></para> | |
12b42c76 | 26 | <para><filename>/usr/lib/systemd/systemd-backlight</filename></para> |
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27 | </refsynopsisdiv> |
28 | ||
29 | <refsect1> | |
30 | <title>Description</title> | |
31 | ||
32 | <para><filename>systemd-backlight@.service</filename> is a service | |
33 | that restores the display backlight brightness at early boot and | |
34 | saves it at shutdown. On disk, the backlight brightness is stored | |
35 | in <filename>/var/lib/systemd/backlight/</filename>. During | |
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36 | loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is |
37 | not set to false, the brightness is clamped to a value of at | |
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38 | least 1 or 5% of maximum brightness, whichever is greater. This |
39 | restriction will be removed when the kernel allows user space to | |
40 | reliably set a brightness value which does not turn off the | |
41 | display.</para> | |
42 | </refsect1> | |
43 | ||
44 | <refsect1> | |
45 | <title>Kernel Command Line</title> | |
46 | ||
47 | <para><filename>systemd-backlight</filename> understands the | |
48 | following kernel command line parameter:</para> | |
49 | ||
50 | <variablelist class='kernel-commandline-options'> | |
51 | <varlistentry> | |
52 | <term><varname>systemd.restore_state=</varname></term> | |
53 | ||
54 | <listitem><para>Takes a boolean argument. Defaults to | |
55 | <literal>1</literal>. If <literal>0</literal>, does not | |
56 | restore the backlight settings on boot. However, settings will | |
57 | still be stored on shutdown. </para></listitem> | |
58 | </varlistentry> | |
59 | </variablelist> | |
60 | </refsect1> | |
61 | ||
62 | <refsect1> | |
63 | <title>See Also</title> | |
64 | <para> | |
65 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
66 | </para> | |
67 | </refsect1> | |
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68 | |
69 | </refentry> |