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rated 0 times [  4] [ 0]  / answers: 1 / hits: 14517  / 3 Years ago, sun, june 6, 2021, 5:39:22

I have a Dell Inspiron N4010 laptop. My brightness hotkeys are not able increase or decrease the brightness of the screen. And as a matter of fact, I also can not reduce the brightness from the Brightness & Lock menu under System Settings. Any solutions?

EDIT: I think I may have found the reason behind the problem. In the previous versions of Ubuntu there were acpi_video0 and intel_backlight inside the /sys/class/backlight folder. Now in 13.04 there are dell_backlight and intel_backlight in that folder. And the most interesting part, my friend installed 13.04 on his Dell Vostro and in his system's /sys/class/backlight folder there are acpi_video0 and intel_backlight. So the brightness hotkeys are working for him.

More From » 13.04


I have the same model and I had the same problem all the way through 13.04 development until one day before release and then it started working. I filed the bug here: Bug #1105604: Brightness control stopped working

What you can do is to use a manual override that I used throughout development, by modifying /etc/rc.local as follows:

#!/bin/sh -e
# rc.local
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
# In order to enable or disable this script just change the execution
# bits.
# By default this script does nothing.
echo 978 > /sys/class/backlight/intel_backlight/brightness
chmod 777 /sys/class/backlight/intel_backlight/brightness
exit 0

The downside is that you can't change the brightness easily except by manually modifying the file /sys/class/backlight/intel_backlight/brightness

When I did have it working, I used the Fn + brightness keys to check the settings: the lowest setting is 490 and after that it goes up in increments of 488. So these are the default settings for /sys/class/backlight/intel_backlight/brightness:

490 Lowest with backlight on
4882 Brightest

My brightness controls were previously working, but are broken again so I decided to create a script to manage it:

# Dell N4010 brightness control workaround
# Note: add the following to /etc/rc.local
# chmod 777 /sys/class/backlight/intel_backlight/brightness
# For convenience I've assigned the keys Alt-Up and Alt-Down to run this script
# Fine tune the bump parameter as required
# Usage:
# ./ up # bump up brightness
# ./ down # bump down brightness
curr=`cat /sys/class/backlight/intel_backlight/brightness`
if [ "$1" == "up" ]; then
curr=`echo "$curr + $bump" | bc`
curr=`echo "$curr - $bump" | bc`
# Set the brightness to the new level making sure it's always above 30 (minimum usable)
if [ $curr -gt 30 ]; then
echo $curr | tee /sys/class/backlight/intel_backlight/brightness

Note: I added a line in /etc/rc/local to give me authority to the brightness file:

chmod 777 /sys/class/backlight/intel_backlight/brightness

Then I assigned it to the keys Alt+Up and Alt+Down as shown here:

enter image description here

[#31453] Monday, June 7, 2021, 3 Years  [reply] [flag answer]
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