I've installed Ubuntu 12.04 LTS onto an 8gb flash drive just to experiment with Ubuntu.
I installed it with a 64 bit live cd on a macbook pro 4,1 with OSX 10.6.8 and I'm attempting to boot to the usb drive using refit.
At first I got an error saying no
boot drive found, insert bootable drive and press any key to continue.
I synced the partitions through refit's partition utility and now I get error loading operating system.
Note: I'm not trying to have a drive that I can install ubuntu FROM, I'm trying to boot to the usb drive with the operating system installed on it.