use virtualbox:
http://www.virtualbox.org/
there's no need to install it from command line - simply open Synaptic package manager (in administration tools menu) to search for it and install it!
Virtualbox is very good, I use it with my windows 7 machine and it can deal with vmware machines too. That way, virtual machines that I created with vmware can be opened with it!
Hope this helps ;-p