Sometimes I have to use a MacBook Air (2,1) at work. I'd like to be able to have an Ubuntu USB stick with persistent storage space for it, that does not require any modification of the machine's internal drive. So, that I can work in my normal (K)Ubuntu environment on the Machine and save stuff onto the stick. I don't want to install rEFIt or anything, since I am not to the only other of this machine. How can I achieve this?
I know that there is a Grub 2 version that supports EFI, which should do the trick in principle, but what are the necessary steps to get it working? Are there alternatives to this?