Capturing session for remote control from a linux host

Question

Use case:

1. A does something on his box and gots stuck. He asks B (remote) for support.
2. B logs into the session of A, sees all windows, A was seeing and is able to manipulate the GUI.

If A uses Windows it is very convenient to log into a running session e.g. via VNC. But if A uses Linux, AFAIK, this is not possible. Using VNC requires a "vncserver"-session, which is a sepeate session. You could get screen captures from remote by quering the X-server, but you cannot press buttons on the screen.

Is there some workaround for this?

Answer 1

There is x11vnc: "x11vnc allows one to view remotely and interact with real X displays (i.e. a display corresponding to a physical monitor, keyboard, and mouse) with any VNC viewer. It has built-in SSL encryption and authentication, UNIX account and password support, server-side scaling, single port HTTPS and VNC, mDNS service advertising, and TightVNC and UltraVNC file-transfer".

It could be used with existing X11 session, without need to start one under "xvncserver".

Answer 2

Apart from x11vnc (which is indeed really nice) and krfb (which I have no experience with), recent Gnome desktops have the Vino VNC server built-in. IIRC it can be enabled under System->Settings->Desktop Sharing. It has a nice GUI and is well-integrated with Gnome and the system, but AFAIK it uses more CPU time than x11vnc does.