I tried many ways to boot Ubuntu on my Mac operating system. I do not have an internal CD drive, but when I tried to install it using the external CD drive (from Apple), the drive does not work. Admittedly, Apple made it clear that you can't do this.
I tried using many tools. I downloaded the AMD64 + Mac edition and copied it to my USB using UNetbootin. It said that it would not boot on Mac, but the instructions on another blog claimed that it has no problems as the iso will handle it. It also instructed to install rEFIt and it worked for him, but it doesn't boot for me. I even tried the terminal method of installing but this didn't work either.
What should I do to boot Ubuntu on my Mac?