Cannot reformat or unmount external that was used for Time Machine 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 &quot;has a partitioning scheme so use 'disk util unmountDisk' instead&quot;
However:
sudo diskutil unmountDisk /dev/disk2
...resulted in &quot;Unmount of disk2 failed: at least one volume could not be unmounted.&quot;
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.
what @salocor meant was as below:


Select &quot;Show All Device&quot; 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.