Client: Ubuntu 11.10 64-Bit
Server: VirtualBox Ubuntu 11.10 64-Bit
I would like to start a gnome-session/lightdm-session, but it doesn't work. Even though I'm able to start single programs like Gedit.
Does I have to make specific changes to be able to use a gnome-session through ssh? As far as I have seen in the online tutorials I've read, all you need is:
ssh -X username@ip gnome-session
I think you are confusing two things:
X11 forwarding requires you to connect with the -X (or -Y) switch. (Unless specified in your local ssh_config or remote sshd_config). As you've experienced this will allow you to run almost all programs that require X but as separate application (remember you can background them immediately when invoking the program with a n '&' behind it.
You seem to want something akin to a 'remote desktop'. Application along those lines are FreeNX or NeatX by google. Apparently in 11.10, it is now easier to use x2go (see here for some installation instructions).
All of these remote-desktop setups require a bit more setting up. For instance you need a suitable client on the connecting side. But on the other hand, they are generally better than VNC and they are much quicker than running X11 over ssh due to some funky compression. Good luck.