Ubuntu 12.10 server && NX && NX Server 3.5

Being the default desktop environment Unity still not supported by NX sessions, Ubuntu 12.10 introduces two different types of GNOME session fallback. The default fallback is named 'GNOME Classic' and neither NX 3.5.0 or NoMachine 4 are able to work with it. It's necessary instead to use the GNOME Classic (No effects) fallback.

The suggested workaround is to install the gnome-session-fallback package either from command line:

$ sudo apt-get install gnome-session-fallback

or by Ubuntu Software Center.

GNOME classic (No effects) will then be made available, and the NX node.cfg (namely /usr/NX/etc/node.cfg) must be modified to have:

#CommandStartGnome "/etc/X11/Xsession gnome-session-fallback"
CommandStartGnome = "/usr/bin/gnome-session --session=gnome-classic"

A drawback of this workaround is that logging out via the 'power' icon is not possible because the menu is empty. To log out, run from a terminal the following command:

$ gnome-session-quit