On an Ubuntu 14.10 box, I set up vino-server and enabled remote desktop, which allowed me to see the applications currently running as the user sees them.
However, I could not log in if the computer was restarted. Investigating vino-server only came up with the suggestion to enable autologin, which is a little unsafe, IMHO.
So I installed vnc4server and enabled lightdm's VNCServer option with the following config in /etc/lightdm/lightdm.conf:
[VNCServer] enabled=true command=/usr/bin/Xvnc -rfbauth /etc/vncpasswd port=5900 width=1024 height=768 depth=24
This enabled me to vnc into the login screen.
However, if the user then logs into the screen again after me, they can't see what I'm doing on their machine. It seems that lightdm creates different sessions for each user logged in, and does not share.
How do I make it so that I can restart and log in while the user is still sharing their desktop so they can see what I'm doing?