I have a toshiba laptop with ubuntu 12.04 on it and I've connected it to an external display but I don't want to mirror the displays nor make it stretch on both I just want it show up on my external display only !! Any help ?
If you go to System Settings > Displays, you will see two different displays: one will be your laptop, and one will be your external monitor.
Select the laptop monitor, and flip the switch to 'off.' Then select the external monitor and make sure the switch is set to 'on.' Afterwards, click on the 'Apply' button and verify that only your external monitor is now displaying.
Run (in terminal)
Find out which connected output you want to disable (in this example we disable LVDS1) and then:
Example output of