To get working brightness key. try following
press Alt+f2 , execute
gksudo gedit /etc/default/grub
Change this line
to something like below
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
Open a terminal by Alt+ctrl +T, Execute
sudo update-grub and reboot . See if brightness keys are working.
If the above is not working set a fixed value for brightness. To do so,
Open a terminal by pressing Alt+ctrl+T.
ls /sys/class/backlight/*/brightness, copy the outputs to a separate text file
The possibility is there will be two paths,try the following for each path and replace accordingly
example paths will be like
Run following commands in terminal,
- For the above path Get the maximum brightness:
Try a lower value to set the brightness, say output is 16 so I will try with half of it
echo 8 | sudo tee /sys/class/backlight/acpi_video0/brightness
If this works, make this happen in each login automatically by doing the following
sudo gedit /etc/rc.local
Enter this line just before
exit 0. It should look like
echo YOUR_VALUE_HERE > /sys/class/backlight/acpi_video0/brightness
Also you can try with xdotool