I need to wipe my Mac Mini and reinstall OS X. Booting into recovery mode (holding command+option+R), I try to erase the disk in Disk Utility but it says it cannot unmount the disk or gets stuck on "Unmounting disk" with an infinite loading progress bar.
I have also tried booting into the recovery partition by holding down option at launch, but the same applies.
Best Answer
Way by Terminal..
Use
diskutil list
in a Terminal instance to list all volumes and find yours.Then do
hdiutil eject disk?
Replace the ? with your disk number, making sure you are not trying to eject the main hard drive :) It is probably called "Disk1"
Here is a Sample when I insert a USB stick and run
diskutil list
disk0 is my hard drive and I can NOT eject that one
disk1 is the USB and I cam eject it.