vncserver configuration ?

[stan]

I have an Ubuntu machine that lives behiind a NAT'es firewall. Various
users, who have access to Windows machines only, need to be able to access
this machine,  and log on to it to various accounts.

What I have in mind is setting up VNC on this machine, such that when you
connect, you are presented with a login banner, much like you would get
with XDM.

I can't seem to find any inormation as to how to set this up. Most of the
resources that I am finding talk about setting VNC up so that it presnes
the desktop of an already loged in user. It would be good if this VC
session could support muliple idnependent sesions also.

Sugestions?

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