4 Replies Latest reply: Sep 26, 2012 5:34 PM by Max Miles
EHUBS Level 1 Level 1 (0 points)

Hi Everyone,


I've just transferred my data to a new computer and now need to erase the hard drive on my old one.. I've tried Disk Utility, increased the security, and tried 'erase' but I keep getting an error message "couldn't unmount disk". I've gone into Partitions and tried deleting the HD there as well but I get the same message. Does anyone know the solution for this? I just want to get the computer securely wiped and would like to keep Lion as the operating system.


Thanks in advance!



Macbook 2GB ram, Mac OS X (10.4.9)
  • Frank Caggiano Level 7 Level 7 (25,695 points)

    You cannot erase the root drive if you are booted off it, you'll need to boot off your install DVD's or else the Lion recovery partition.


    Once you are running off something other then the root drive you will be allowed to erase and partition it.

  • Don Archibald Level 10 Level 10 (101,245 points)

    If you are using the internal drive as the boot volume, you can not erase it. It is impossible to erase the boot volume - the running OS will not suicide.


    If that is the case, the solution is to boot the machine to a different volume - typically an installation disk, but can also be a different hard drive such as an external one. Once you are booted to a volume other than the one you want to erase, you can use Disk Utility to erase that volume.

  • EHUBS Level 1 Level 1 (0 points)

    Hi Frank,


    Thanks for the quikc response. I booted up in the Recovery Disk I believe. I held option at boot up and chose the recovery disk option. Is that the correct method?


    I may have figured out what I was doing wrong. I was clicking on the parent hard drive reading "1 TB WDC WD1001Fals..." Now I've clicked on the next level hard drive "Macintosh HD" and I believe it is working.


    Looks like 5 hours to erase...

  • Max Miles Level 3 Level 3 (630 points)

    I just encountered the same issue in Recovery mode. My question is why are the HDD's represented in two different ways? many times I've erased both, the root or parent representation of the drive, and e drive with a name we've given it. Curious what the nature of this is..