Some months ago I burned a Xubuntu distro into a USB drive to use an old barebone computer (BTW I used this link as a guide).
If you use rEFInd to boot multiple operating systems in a Mac you may want to change it’s options. For example the default 20 second timeout, in my opinion too long.
Booting from Mac OS X you’ll have to mount the rEFInd partition. You can see which partition it…
Sometimes the Mac OS X Recovery partition can be seen because it’s mounted automatically on boot. This is usually caused because you moved the operating system to another disk (clone) or because you used an app that changed the disks partitions (rEFInd in my case).