How can I set and limit the resolution in Ubuntu 12 to 640x480 There's not much in the xorg.conf file anymore, so I'm guessing this is no longer the place to do it?
I can't do it using the GUI either because it doesn't show me the 640x480 option.
While setting the resolution the computer is connected to a normal screen but later it will be connected to a screen that only supports 640x480 and doesn't report its supported modes to the computer.
The only thing in my xorg.conf (by default) is this:
Section "Device"
Identifier "Default Device"
Option "NoLogo" "True"
EndSection
Update, in response to Kamil's answer:
I do not have the gdm folder, but I get the idea
However if I execute those commands I get the following
xrandr --newmode "640x480_60.00" 23.75 640 664 720 800 480 483 487 500 -hsync +vsync
xrandr: Failed to get size of gamma for output default
X Error of failed request: BadName (named color or font does not exist)
Major opcode of failed request: 153 (RANDR)
Minor opcode of failed request: 16 (RRCreateMode)
Serial number of failed request: 19
Current serial number in output stream: 19
root@timothy-desktop:~# xrandr --addmode default 640x480_60.00
xrandr: Failed to get size of gamma for output default
root@timothy-desktop:~# xrandr --output default --mode 640x480
xrandr: Failed to get size of gamma for output default
Note that VGA1 is default in my case.