Ubuntu’s system requirements say it requires at least 5 GB of space, but something like 20 GB is much more reasonable. How much space you want for Linux is up to you. Shrink the current Mac OS X partition to make space for your Linux system. RELATED: Beginner Geek: Hard Disk Partitions Explained Select your Mac’s hard drive in the list on the left and select Partition on the right. From within Mac OS X, press Command + Space, type Disk Utility, and press Enter to open the Disk Utility. You’ll now need to resize your Mac OS X system partition to make room for your Linux distribution of choice. You should see the rEFInd boot manager screen. Shut down your Mac - a full shut down, not a restart - and boot it back up again.
