How to permanently set screen brightness level in Ubuntu 12.04 on Dell Vostro 2420 laptop?

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

cat /sys/class/backlight/acpi_video0/brightness

Then you can take that value and

sudo gedit /etc/rc.local

Right above 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 /sys/class/backlight/acpi_video0/

Install backlight on your system.

Place the command xbacklight -set value in your startup.

It will automatically do the job for you. Hope this helps!