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 "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.

Solution 1:

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

Solution 2:

what @salocor meant was as below:

• 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.