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Two MonitorsIf you have more than one monitor, you probably might to turn off one of them if it’s simply unnecesary. It’s likely that you simply turn off the monitor pushing the power button, but your computer always put a window, tool rule or message in the monitor off because it don’t have a way to know whether the monitor is off. You surely don’t want to turn off and turn on or plug in and unplug frecuently your data cable to prevent this behavior (it isn’t recommendable).

You can do this simple procedure on Ubuntu systems:

Open Terminal (CTRL + ALT + T) and run:


The output is going to be similar to this, just take note of the strings that looks like a logical name of the display devices, for example: I have three interfaces, and was highlight in red:

Screen 0: minimum 8 x 8, current 2560 x 1024, maximum 32767 x 32767
LVDS1 connected primary 1280×800+1280+224 (normal left inverted right x axis y axis) 331mm x 207mm
1280×800 60.0*+
1024×768 60.0
800×600 60.3 56.2
640×480 59.9
TV1 unknown connection (normal left inverted right x axis y axis)
848×480 59.9 +
640×480 59.9 +
1024×768 59.9
800×600 59.9
VGA1 connected 1280×1024+0+0 (normal left inverted right x axis y axis) 337mm x 270mm
1280×1024 60.0*+ 75.0
1024×768 75.1 75.0 70.1 60.0
832×624 74.6
800×600 72.2 75.0 60.3 56.2
640×480 75.0 72.8 66.7 60.0
720×400 70.1
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

Let’s turn off the monitor, it’s have the name VGA1:

xrandr --output VGA1 --off


If you want to turn on again, just type:

xrandr --output VGA1


xrandr --output VGA1 --auto

If you see the same output in both displays, you can fix it with something like:

xrandr --output VGA1 --auto --right-of LVDS1


Enjoy it and help to protect the environment saving energy !!!