Enable VNC (Desktop Sharing) via Console

Install X11vnc

sudo apt-get install x11vnc

Set a password (as the user used to automaticaly log into the desktopl)

x11vnc -storepasswd

Make X to load X11vnc at startup

echo "x11vnc -display :0 -bg -nopw -noxdamage -forever" > ~/.xsessionrc