VNC from the Login Screen: accessing the actual Ubuntu X Display shown on the monitor

Issue the following command with elevated rights or as root:

apt-get install x11vnc

 

Create the file /etc/init/x11vnc.conf with your favourite text editor and write this into it:

start on login-session-start
script
x11vnc -xkb -noxrecord -noxfixes -noxdamage -display :0 -auth /var/run/lightdm/root/:0 -forever -bg -o /var/log/x11vnc.log
end script

 

Sources are here and here