<?xml version="1.0"?> <!--*-nxml-*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2013 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'> <refentryinfo> <title>systemd-backlight@.service</title> <productname>systemd</productname> <authorgroup> <author> <contrib>Developer</contrib> <firstname>Lennart</firstname> <surname>Poettering</surname> <email>lennart@poettering.net</email> </author> </authorgroup> </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></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 udev property <option>ID_BACKLIGHT_CLAMP</option> is not set to false value, 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>