Remote X

Everything we have looked at so far has been about command-line remoting, with no mention so far of how to bring up a graphical user interface. There are two ways of doing this in Linux: the X Display Manager Control Protocol (XDMCP) and Virtual Network Computing (VNC). The former is specific to X Windows and is very tightly integrated with the rest of the graphical system but is also very insecure. VNC is more modern and very widespread but insecure in some implementations. Both are being used with Ubuntu, so we will cover both here.

XDMCP

Unless you have Ubuntu configured to log in a specific user automatically, you will be familiar with the user login screen that appears at bootup. What you are seeing is the Gnome Display Manager (GDM), which runs your X sessions, checks passwords, and so forth. What you are doing is logging in to the local machine because that is the default configuration.