Screen rotation

I am unable to set my screen rotation to portrait, can anybody tell me how to do this ? It is even a problem when I turn on the computer.

In the menu with Settings → ARandR you can set the orientation of your desktop.
The configuration can be saved via its menu to ~/.screenlayout/
Content of my config :
xrandr --output DisplayPort-0 --off --output DisplayPort-1 --off --output DisplayPort-2 --off --output DisplayPort-3 --mode 1920x1200 --pos 0x0 --rotate left

Now BIOS and BOOT I don’t see how to rotate. The login screen I can live with that until I know the system better.

Would you consider sharing your desktop when succesful?