If the DISPLAY variable is set on the client side, the server will create a dummy X server and set DISPLAY accordingly. Any connections to the dummy X server will be forwarded through the secure channel, and will be made to the real X server from the client side. An arbitrary number of X programs can be started during the session, and starting them does not require anything special from the user.

	the user must not manually set DISPLAY, because then it would connect directly to the real display instead of going through the encrypted channel).

$ ssh -l user sunshine
>echo $DISPLAY
sunshine:10.0

— the 10 instead of 0, the dummy X

>xterm &

— works fine