Hard Drive can't unmount
I am stuck with this problem now. Disc will not unmount, no matter what I try.
My disk is fine, so I don't need to repair it, I checked that just encase. I have tried to zero the disk from terminal, says the same can't unmount, and cant unmount it from restore utility. I wanted to boot it up normal, but only got half way then just stay like that. I don't think I have got enough RAM in this one, only 4GB, and I remembered that Logic pro X was on my disk, with all the gear, everything.
This is why I wanted to Erase it, so as I could use from an earlier backup that didn't have all that. it is loaded with an earlier version of Yosemite to what's on Disk as well.
How do I erase this disk?
Any help would be appreciated