Thanks Joseph & Doug, I really should have mentioned I was referring only to the build OS.

I'm using Xen as a host, and according to the gitian documentation I found, only KVM and VirtualBox are known to work. Could this be a massive job to configure?

Also, Ubuntu is a strange choice for build machine, why something office/consumer focused and not Debian? (i.e. developer focused) Everything added to 14.04 that isn't present in it's Wheezy base is unnecessary, as well as a potential source of trouble. Why Ubuntu, there seems to be no compelling reason at all. Or is there something I'm glossing over?