Trying to reformat a drive that was used for an employee's Time Machine and Data storage. It is a partitioned drive. Disk Utility failed to unmount the Data partition and reported the TM partition was OK, but I can't eject either without issues:

See attached. I've tried: sudo diskutil eraseDisk JHFS+ Reformat /dev/disk2 ...which resulted in an error -69888: Couldn't unmount disk.

Also tried: sudo diskutil unmount force /dev/disk2 ...which resulted in an error that it was already unmounted or "has a partitioning scheme so use 'disk util unmountDisk' instead"

However: sudo diskutil unmountDisk /dev/disk2 ...resulted in "Unmount of disk2 failed: at least one volume could not be unmounted."

When I try to reboot, the desktop icons disappear, the reboot never finishes and I end up forcing a shutdown via the power button. I've done all of the above several times.

Any ideas for untrashing this 2TB Seagate drive? Using a MacBook Pro with High Sierra. (Drive originally formatted/used on an High Sierra Mac.) Also tried an iMac which refused to mount it. terminalerrors

  • You can force unmount of the drive by using umount -f /dev/disk2s2. – Joy Jin Dec 10 '20 at 8:20

Try going to Disk Utility then press View in the menu bar and "Show All Devices". In the side bar in Disk Utility you should now see something like "2TB Seagate Drive" or something like that. Try formatting that to format the entire drive.

You can also try following this article to format it if you have a Windows computer. It has saved my drives many times

  • Thanks, Salocor. Same result as trying to format the disk via the terminal; it can't unmount the Seagate device. "Couldn't unmount disk. Operation failed..." – Wendi Dec 1 '20 at 18:30
  • Strange... Have you tried first aid on the disk? – Salocor Dec 1 '20 at 18:48
  • Yep. It reports the Time Machine partition checks out fine. The Data partition reports "Volume could not be unmounted. Restoring the original state found as mounted. Unable to unmount volume for repair. Operation failed..." If I run First Aid on the entire drive, it appears to finish without error (Operation successful) but the Disk Utiity shows the Data partition with 19.24 GB used, and it will not Erase. Attempting to double-click on the Data volume on the desktop results in a Finder pinwheel and I end up forcing a shutdown via power button. (Relaunching Finder does not work either.) – Wendi Dec 1 '20 at 19:06
  • Wow. That is really strange. Do you have a Windows computer you could try using to format it? – Salocor Dec 1 '20 at 19:08
  • Yes, I tried plugging it into a Windows 10 laptop; it doesn't see it. I'm not a Windows person, though, so there may be a workaround that I'm not familiar with. – Wendi Dec 1 '20 at 19:12

what @salocor meant was as below:

enter image description here

  • Select "Show All Device" from the view tab
  • Select the drive that you'd like to erase
  • Select Erase - MacOS Journaled with GUID Partition
  • Try and see if it works.
  • Exactly! Thanks! – Salocor Dec 1 '20 at 18:49

Here's the solution I found, thanks to direction from Salocor. Basically had to use a Windows PC to erase the drive via the command prompt. Windows was able to ignore whatever messed-up Mac leftovers were on the drive. Once it was clean, I plugged it back into the Mac and was prompted to "initialize". And that was that.


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