The Problem I met is how to install ubuntu in a very tricky enviornment: My computer is a Macbook Pro (bought in 2013). My OS now is Mac OS and a windows 7 in bootcamp. Since my Mac Pro only have 256 GB hard disk space, I have to install it in external disk. I buy another USB3.0 Portable Hard Disk, which has 500GB space.
So, I want to install Ubuntu(12.04) into this external USB hard disk.
Please give me some hints how to do it. And give me a way to boot it. (whatever method to boot)
(I don't want to install it on any virtual machine.)