client1 – your local machine that you want to view the server’s full gnome X session on.
server1 – the server that will send its X display through the ssh tunnel, to display on client1.
Type the following from client side.
Xephyr -ac -screen 1024×768 -reset -terminate 2> /dev/null :1 &
DISPLAY=:1.0 ssh -XC root@server1 gnome-session 2>/dev/null