I have an external drive that is basically unusable. It’s just for backups, and I have redundant backups, so I don’t care about losing the data, I just want to completely format it and get it working again. (I highly doubt it is a physical issue with the drive)

This is basically the state the drive is in now:

  • The drive has two partitions
  • One partition will mount, but cannot be unmounted, even forcing through Terminal
  • The other partition will never mount
  • Whenever the drive is connected, Disk Utility will stop working
  • What OS? I had a drive that would kill Disk Utility on Yosemite unless I connected it at or just after boot. El Capitan never exhibited the same issue. Maybe have a look at this apple.stackexchange.com/a/205866/85275 [from para 7, bear in mind that user wanted to hide 2 boot drives from each other, so modify the method for a single drive] to persuade Finder not to auto-mount it
    – Tetsujin
    Jul 17, 2016 at 6:20
  • @Tetsujin El Capitan
    – Ryan
    Jul 17, 2016 at 13:37
  • This would help other people. Mind if I undelete it and +1 the question?
    – bmike
    Jul 18, 2016 at 1:41

1 Answer 1


I managed to get the drive to respond and unmount by killing the process fsck_hfs

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