this isn't supported by the backtrack team. You'd be better off getting these programs via the ubuntu universe or multiverse repository for stuff like chntpw, medusa, john, ophcrack, aircrack-ng etc.
you could add the repos to your ubuntu install but you'll run into loads of problems as bt4 is based on 8.10 intrepid so dependency hell and slightly different packages made for different systems, there's an faq thread about this in the faq forum, i think



