I have a monitor Samsung SyncMaster 943B (connected through DVI) to my Raspberry Pi which has a rotatable screen.
Monitor Preferences shows “Monitor Unknown” and the correct Resolution but not the Refreshrate and won’t allow me to change Rotation from Normal. The Monitor icon on the Panel says “Rotation not supported”.
How can I configure the monitor to allow rotation.
For now this is only possible by editing display_rotate line in /boot/config.txt file, and then restarting.
Press Alt+F2 and write
gksu pluma /boot/config.txt
and press enter. It’s gonna ask for your password (so it can get administration rights it needs to edit config files), and after that it will open config.txt file for editing.
Find display_rotate line (line 428 in my case, you can use search) and change the line from:
#display_rotate=0
to
display_rotate=1
0 or 1 or 2 or 3 are for 0, 90, 180, 270 degrees of rotation.
Save the file, restart, see if it works.