I want to backup my Mac partition, including the OS, so that I can use the backup to restore my hard drive to its current state I want to dual-boot Ubuntu (14.04) of my Mac running OS X 10.10.3. I want to make sure that I can use my backup to fix any issues I might have dual-booting. I have a bootable USB with Ubuntu on it, and a partition on my internal hard drive to install it on, but I want to back up that Mac partition, including the OS, so that I can use that to get everything back to how it is now, no matter what error happens during dual-booting.

What is the best way to do that?
Simply connect external hdd with enough storage and use Time Machine application (which is included in OS X)

Here's tutorial from Apple