71 lines
2.5 KiB
XML
71 lines
2.5 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'>
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<refentryinfo>
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<title>systemd-backlight@.service</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-backlight@.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-backlight@.service</refname>
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<refname>systemd-backlight</refname>
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<refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-backlight@.service</filename></para>
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<para><filename>/usr/lib/systemd/systemd-backlight</filename> save [backlight|leds]:DEVICE</para>
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<para><filename>/usr/lib/systemd/systemd-backlight</filename> load [backlight|leds]:DEVICE</para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-backlight@.service</filename> is a service
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that restores the display backlight brightness at early boot and
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saves it at shutdown. On disk, the backlight brightness is stored
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in <filename>/var/lib/systemd/backlight/</filename>. During
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loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is
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not set to false, the brightness is clamped to a value of at
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least 1 or 5% of maximum brightness, whichever is greater. This
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restriction will be removed when the kernel allows user space to
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reliably set a brightness value which does not turn off the
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display.</para>
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</refsect1>
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<refsect1>
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<title>Kernel Command Line</title>
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<para><filename>systemd-backlight</filename> understands the
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following kernel command line parameter:</para>
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<variablelist class='kernel-commandline-options'>
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<varlistentry>
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<term><varname>systemd.restore_state=</varname></term>
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<listitem><para>Takes a boolean argument. Defaults to
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<literal>1</literal>. If <literal>0</literal>, does not
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restore the backlight settings on boot. However, settings will
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still be stored on shutdown. </para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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