The native screen-size detection doesn’t work for dual-head installations. To let X11 handle both screens as one large display, find the section
Screen in the
/etc/X11/xorg.conf and add the following lines:
SubSection "Display" Virtual 2560 1024 EndSubSection
This is for two 1280×1024 displays side-by-side (1280+1280 = 2560). Now you can use
xrandr to set displays.
Shows all available displays. Usually it will show the devices
LVDS. To change the output of the external display to be left of the internal LCD panel, use something like
xrandr --output VGA-0 --left-of LVDS
You might also have to use System → Preferences → Screen Resolution to configure the location of the displays.
Fix screen order
Under Intrepid, it often happens to me that my screenorder is wrong after login. This is shown by a mirrored output on the left display, but the system thinks that there’s a left workspace. On rare occassions, I even have the wrong order (i.e. if I move the mouse to the right on the right workspace, it appears on the left display’s workspace.) This is quickly fixed by switching the order around:
#!/bin/sh echo Switching position of displays xrandr --output VGA-0 --right-of LVDS echo Switching off ext. display xrandr --output VGA-0 --off echo Switching back to normal xrandr --output VGA-0 --mode 1280x1024 --rate 75 --left-of LVDS
After calling the script, my displays are showing the correct workspaces.
To configure dual-head system-wide (for Desktop computers), there is a great manual at UbuntuForums.
xrandr -qto get the output device’s names (for me it was
- open the
/etc/X11/xorg.confin your favorite editor
- find the section
Deviceand add 2 lines so that it looks like this:
Identifier "Configured Video Device"
Option "monitor-VGA-0" "right"
Option "monitor-DVI-0" "left"
- The device names have to be prefixed with
monitor-. The names after that are for you to choose.
- find the
Monitorsection and change the identifier to one of the names. (e.g.
- add another
Monitorsection below and change the identifier to the other name. (
left) Also add the line
Option "LeftOf" "right"in between.
- now the both monitor sections should look like this:
Option "LeftOf" "right"
- find the
Screensection and add the following line to define the default display.
- add a
SubSection "Display"and the
Virtualline as with the per-user configuration
- save the file and restart X