After upgrading to Ubuntu 14.04 I found that I could not increase screen brightness. I'm using a Samsung NC110 netbook. Initially the function key to modify brightness did not respond at all. After implementation of the first part of the fix, the key came alive and the brightness bar could be modified. Yet at maximum brightness indicated the screen still remained very dull. The 2nd part of the fix cures that problem, at least for this type of machine.

First part of the fix was copied and modified in line with my experience from following post:

How to control Brightness

1. Open a terminal (Ctrl + Alt + T).
2. Then type sudo nano /etc/default/grub. It will ask for your password. Type it in. Around the 11th line, there will be something like: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash".

3. Change it to: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor"

4. Save the file by Ctrl+O followed by Ctrl+X.

5. Then run sudo update-grub in the terminal.

6. Reboot and see if backlight adjustment works.

Then I needed to modify the rc.local file. Therefore read below fix to understand the procedure:

problem with adjusting brightness Ubuntu 14.04

In my case I had 2 folders listed under /sys/class/backlight which were:

intel_backlight samsung

I realized that the samsung folder is governing. I had to modify the check for max brightness to:

cat /sys/class/backlight/samsung/max_brightness

In my case the max value obtained is 8. Besides putting this into rc.local, I also had to uncomment the first line to get this working.

My rc.local under /etc/ now looks as follows:

    !/bin/sh -e
    #
    # rc.local
    #
    # This script is executed at the end of each multiuser runlevel.
    # Make sure that the script will "exit 0" on success or any other
    # value on error.
    #
    # In order to enable or disable this script just change the execution
    # bits.
    #
    # By default this script does nothing.
    echo 8 > /sys/class/backlight/samsung/brightness
    exit 0

Now I can modify brightness on my netbook and also can get the screen up to its maximum brightness. Hope this is helpful.