Cannot adjust brightness?

edit

hi

i had the same problem with acer aspire too. simply go to /etc/default/grub.cfg as root in the GRUB_CMDLINE_LINUX= (............) paste these lines in the end , within the inverted commas

quiet splash pcie_aspm=force acpi_osi=Linux acpi_backlight=vendor

and run grub2-mkconfig -o /boot/grub2/grub.cfg

changes take place at reboot

all answer are ok, but if you use LXDE this solution isn't work ( i don't know , but not work)

try with xblacklight

install xblacklight

dnf -y install xblacklight

set brightness in porcent

xbacklight -set X%

set brightness for +

xbacklight -inc 20

set brightness for -

xbacklight -dec 20

good luck !

For Lenovo T61 users following steps are useful: Install xbacklight, then to dim the screen: xbacklight -set 40 (replace 40 with the level of brightness that suits you). Hope this helps. You can also check Lenovo Thinkpad T61 Manual for detailed help.

On my ASUS UX303LB, I couldn't get the Fn+F5 and Fn+F6 keys to work with any of the kernel parameters suggested. The keys don't even generate events if I check with xev.

As a work-around, I added the file /etc/sudoers.d/backlight with:

ALL ALL = (ALL) NOPASSWD: /usr/bin/tee /sys/class/backlight/intel_backlight/brightness

and created the following shortcuts in keyboard settings:

• Name: Brightness +
  Command: bash -c 'sudo tee /sys/class/backlight/intel_backlight/brightness <<<$(( $(cat /sys/class/backlight/intel_backlight/brightness) + 15 ))'
  Accelerator: Super+F6
• Name: Brightness -
  Command: bash -c 'sudo tee /sys/class/backlight/intel_backlight/brightness <<<$(( $(cat /sys/class/backlight/intel_backlight/brightness) - 15 ))'
  Accelerator: Super+F5

I now can use F5 and F6 together with the Windows key to adjust brightness.

None of these answers (or the other answers I found online) worked for me. Instead I was able to fix this issue on my Lenovo T430 running Fedora 23 XFCE with this (somewhat ugly) workaround.

Make sure xbacklight is installed (sudo dnf install xbacklight) and ensure that xbacklight actually changes your brightness.

Then manually map the key commands (Settings Manager -> Keyboard -> Application Shortcuts) for brightness to the xbacklight command. For example, I mapped "/usr/bin/xbacklight -dec 10" to "Fn+F8" and that allows the key combination to decrease brightness as it was intended to do.

Then reboot and the brightness keys should work!

I hope that helps! :)

Via the link above note the "update" at the bottom of the piece for anyone Linux 3.13 above. The original fix would hang my system at boot. The new command video.use_native_backlight=1 worked first time and I can now dim my screen. Happy days :-)

For the records, i had also the same issue and i've created long time ago a quick bash script. It is NOT complete from programming point of view. Please feel free to make it better or just use it (it requires root privileges).

#!/bin/bash 

# Date: 01.07.12
# Author: alampropoul@gmail.com
# Acer Aspire 5742G Brightness Emergency Correction
# Version : 1.0

currentvalue=`cat /sys/class/backlight/intel_backlight/brightness`
CHOICE='Please enter your choice'
LIST="Brighter Darker END"
select CHOICE in $LIST
do
if [ $CHOICE = "Brighter" ] &> /dev/null
then
currentvalue=`cat /sys/class/backlight/intel_backlight/brightness`
echo $currentvalue
let "currentvalue+=100"
echo $currentvalue > /sys/class/backlight/intel_backlight/brightness
elif [ $CHOICE = "Darker" ] && [ "$currentvalue" -gt 101 ]
then
currentvalue=`cat /sys/class/backlight/intel_backlight/brightness`
echo $currentvalue
echo $currentvalue
let "currentvalue-=100"
echo $currentvalue > /sys/class/backlight/intel_backlight/brightness
elif [ $CHOICE = "END" ] &> /dev/null
then
exit 0
fi
done
#END
#[1;5D

I don't know why it doesn't with mine either, to echo an answer from elsewhere about manually changing it:

there is /sys/class/backlight which will have directories for backlight hardware. In them will be a "brightness" and "max_brightness" entries.

echo (whatever was in max_brightness) >brightness will go to the top, but for example if max is 10, echoing 5 > brightness will be half brightness, if max is 250, echoing 125 will be half brightness.

This worked for me running Fedora 25 on ThinkPad X200

1. Install xbacklight

   dnf install xbacklight

2. Open grub file for edit

   gedit /etc/default/grub

3. Append acpi_backlight=vendor to GRUB_CMDLINE_LINUX=

   EXAMPLE:

   GRUB_CMDLINE_LINUX="rd.lvm.lv=fedora/swap rd.lvm.lv=fedora/root nomodeset rhgb quiet"
   GRUB_CMDLINE_LINUX="rd.lvm.lv=fedora/swap rd.lvm.lv=fedora/root nomodeset rhgb quiet acpi_backlight=vendor"

4. SAVE

5. Rebuild Grub:

   sudo grub2-mkconfig -o /boot/grub2/grub.cfg