On Ubuntu 12.04 LTS on a Dell Vostro 2420 laptop, each time I start Ubuntu, the screen brightness is set to the maximum level, which gives a high glare. (I have recently installed Ubuntu on the laptop, but did not change any default settings related to brightness, IIRC.) I am currently lowering the brightness manually each time after starting, using the System Settings icon on the left of the screen. Looking for a permanent way to set it to a lower value.
After you set the brightness to your desired level open up a terminal and check what the brightness is set to by using
Then you can take that value and
sudo gedit /etc/rc.local
exit 0 add
echo your_value_here > /sys/class/backlight/acpi_video0/brightness
and then save the file. This will permanently set the brightness to your value as rc.local is executed at each reboot.
Note: This only works if you have a file named brightness in
@bigbash after setting the brightness to a desired set value i am typing this command, /sys/class/backlight/acpi_video0/brightness, did the way u have suggested but it is not working.One more thing what ever value i set for brightness from settings after putting the above command always i am getting the same value i.e 15.