How to Rotate an External Display in Linux

This information was gathered for an Ubuntu 10.04 machine, but should be relevant to any xorg.con file

To make the external display rotate, open the /etc/X11/Xorg.conf file in your favorite editor.

Go to the “Monitor” section (to the monitor you want to rotate and add the following lines at the end of the section:

Option "RandRotate" "on"
Option "Rotate" "CCW"

Use CCW for Counter Clockwise, and use CW for Clockwise.

When you are finished, safe the file and restart the X server (or just reboot your computer).