Using Ubuntu Linux/Introduction for Mac users
Believe it or not Mac is based on a UNIX-like core called Darwin. UNIX is what Richard Stallman, the founder of the Free Software Foundation, based the GNU tools on; these tools eventually became the GNU/Linux operating system.
Mac OS X is much more like Ubuntu Linux than Windows, so a lot of users won't find it too hard to get used to Ubuntu. Many of the Mac OS terminal commands, such as cp, mv, ls, and so on will also work in a Linux terminal since they use the SAME TERMINAL: bash.