I am running Ubuntu 12.04 LTS on new Acer Aspire V5. There is no other OS installed. I can not control the brightness of the screen using Fn+left and Fn+right keys. I tried to change brightness from "Brightness and Lock" settings, bit still it does not work. Brightness control bar moves, but brightness does not actually change.

Other people have modified the file /etc/default/grub for other Acer models. But that solution does not work for me.

Any advise will be of much help. Thank you.


If your Acer Aspire V5 uses intel_backlight device instead of acpi_video0, then this set of scripts might provide a solution to you. See if you have intel_backlight device by examining the output of "ls -l /sys/class/backlight". To determine if your notebook responds to brightness commands on the intel_backlight device, start a root shell by executing "sudo -i" and then do this in the root shell:

  1. Determine your maximum brightness:

    cat /sys/class/backlight/intel_backlight/max_brightness

  2. Decrease brightness to a desired value, for example to half of the maximum brightness value (substitute 500 with your value):

    echo 500 > /sys/class/backlight/intel_backlight/brightness

  3. If your brightness has decreased, then use the above set of scripts to fix the problem with your brightness control hotkeys.

Finally, see how many steps you have for brightness control. If you completely decrease or increase brightness in about 5 key presses, then you should make one additional correction to your configs so that you have 10 steps to regulate brightness, as originally designed.

In your root shell, execute:

cat /sys/module/video/parameters/brightness_switch_enabled

If you see 'Y' or '1', run the following command:

echo 'N' > /sys/module/video/parameters/brightness_switch_enabled

Replace 'N' with '0' if you received '1' as an output from the previous command. After that, you should have 10 steps for brightness control instead of 5.


In most computer you can set the brightness by echoing directly in /sys/class/backlight/acpi_video0/brightness in a terminal, e.g.

# echo <value> > /sys/class/backlight/acpi_video0/brightness

where value can vary from 0 to 15. Problem is, you need to run this as root, as the file you will edit is in the /sys/ directory.

  • Thank you for your reply. I ran the command you mentioned as a root. The acceptable values of brightness seem to be 0 to 9. Command runs but it does not have any effect on the brightness. Any further help will be very useful. Thank you. – user184683 Aug 17 '13 at 17:12

I can testify that the answer marked as solution on How to control Brightness on Acer Laptop works with Ubuntu GNOME 13.04 on an Acer Aspire V5-571P with Intel HD4000 graphics, reported as Ivybridge Mobile by Ubuntu's System Settings > Details... but then, I know there are other V5's around so YMMV.

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