It is easy to dual boot Ubuntu on Mac. There might be some problems with the bootloader, but it can be overcome easily. Here are the steps to install and dual boot Ubuntu on Mac.
If you’ve dual-booted Windows and Linux, you might notice that Grub always defaults to the first entry of the bootup list. Here’s how to set Grub to save the last selected entry.
If you have previously dual-booted your OS X with Ubuntu, and you have upgraded to Yosemite, you will lose the dual boot. Here is the solution to fix the dual-boot issue.
If you want to try out OS X Yosemite, but don’t want to overwrite the existing installation, here is how to dual-boot OS X Yosemite and Mavericks on your Mac.