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I installed ubuntu 12.04 on my old laptop with SiS671 video card and its working fine with 1280x800 screen resolution. I also connected my external monitor and its working too but I want to turn off laptop's monitor and I can't find any references to external monitor.

When I try to access System Config > Monitors it only shows "laptop" monitor.

typing Xrandr on terminal results:

xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 480, current 1280 x 800, maximum 1280 x 800
default connected 1280x800+0+0 0mm x 0mm
   1280x800       60.0* 
   1024x768       75.0     70.0     60.0  
   800x600        75.0     72.0     60.0     56.0  
   640x480        75.0     73.0     60.0  

How can I turn my laptop monitor OFF and use ONLY the external monitor? thanks...

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I really don;t know how you can solve it. Have you tried looking through the laptop keys and seeing if there is a fn key option to turn off the screen? Tried re-running detect monitors option? Restarting?

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Yep... Fn+F4, detect monitors, Restarting... Nothing works... – user80182 Jul 30 '12 at 19:06

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