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