I have upgraded to ubuntu 18.04 LTS the display brightness controls are not working. It appears that the brightness is in its lowest level and I am not able to change display brightness at all. It was working on 16.04 LTS. My laptop uses Intel Graphics card.
I have tried to solve that by creating the file /usr/share/X11/xorg.conf.d/20-intel.conf with the following content. It worked the first time, but after one reboot it remains back to the previous problem.
Section "Device"
Identifier "card0"
Driver "intel"
Option "Backlight" "intel_backlight"
BusID "PCI:0:2:0"
EndSection
What can I do?