I have installed Ubuntu 12.04 on Sony Vaio VPCEH18FG but the screen brightness does not change with Fn+F5/F6 keys and
/etc/X11/xorg.conf file is also not found.
How can I solve this problem?
You can create a basic xorg.conf using the X executable itself. As root run:
This will create the file /root/xorg.conf.new, which you can then copy to /etc/X11/xorg.conf:
and edit it according to:
LCD Brightness Control
Once you have installed the proprietary Nvidia drivers as suggested above, you may notice that your brightness control keys do not work properly. This is fixable by editing one's xorg.conf file. Open a terminal window and type the following:
This will open your X server configuration (after prompting for your password). You should see a section titled "Device" that looks as follows:
Append a line so it appears like this:
You will need to restart your graphical server (or reboot) for this change to take effect.