Screen brightness not working

To get working brightness keys, try the following.

Run the command:

sudo -H gedit /etc/default/grub

Change this line

GRUB_CMLINE_LINUX_DEFAULT="quiet splash"

to something like below

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor

Execute sudo update-grub and reboot. See if brightness keys are working.

It is still possible Ubuntu won't remember your brightness settings. So you have to change brightness each time.

Please let us know the result as many Sony users are facing this problem.

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This is for setting brightness manually after doing the above steps.

Try following for paths shown by ls /sys/class/backlight/*/brightness and replace accordingly.

For example, paths will be like:

/sys/class/backlight/acpi_video0/brightness

For the above path Get the maximum brightness:

cat /sys/class/backlight/acpi_video0/max_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 -H 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
exit 0

Also you can try with xdotool

For those who end up here while looking for a solution, I've found the text below from here and this works for my Ubuntu 12.04 64bit.

sudo nano /etc/X11/xorg.conf

This will open your X server configuration (after prompting for your password). You should see a section titled "Device" that looks as follows:

Section "Device"
        Identifier      "Default Device"
        Driver  "nvidia"
        Option  "NoLogo"        "True"
EndSection

Append a line so it appears like this:

Section "Device"
        Identifier      "Default Device"
        Driver  "nvidia"
        Option  "NoLogo"        "True"
        Option "RegistryDwords" "EnableBrightnessControl=1"
EndSection

You will need to restart your graphical server (or reboot) for this change to take effect.

Actually both grub and xorg.conf modifications are needed.

First modify /etc/defaults/grub to add ACPI parameters. The GRUB_CMDLINE_LINUX_DEFAULT line may then look liee:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor"

Update GRUB to apply that change, by running the command:

sudo update-grub

Second, in the file /etc/X11/xorg.conf, find the in Device section and add Option EnableBrightnessControl, so it looks like this:

Section "Device"
     Identifier     "Device0"
     Driver         "nvidia" 
     VendorName     "NVIDIA Corporation" 
     BoardName      "GeForce GT 330M" 
     Option         "RegistryDwords" "EnableBrightnessControl=1"
EndSection

This works for me on Samsung R780 with Nvidia GeForce 330M.