I have this external (USB) drive that can't seem to be disconnected correctly. Whenever I eject the drive, it won't disappear from Disk Utility. Afterwards when the drive gets re-connected again, it cannot be mounted. At this stage, I would need to reboot the Mac to get the drive to mount again.

Disk Utility Screenshot

Ejecting from the Terminal via diskutil eject /dev/disk2 returns a Disk /dev/disk2 ejected message and unmounts the disk. However the disk still shows up both in Disk Utility and diskutil list.

Furthermore even after the USB cable is disconnected, the disk still shows in both Disk Utility lists — GUI and command line.

How can I solve this?

OS: macOS Mojave 10.14.1 (18B75)

  • What happens if you issue the command in Terminal: diskutil eject disk2? – Allan Nov 5 '18 at 13:45
  • @Allan Question updated with new information. – adib Nov 5 '18 at 14:18
  • Then, if you issue the command diskutil unmountDisk disk2? (you may need to use sudo, but try without first). – Allan Nov 5 '18 at 14:19

Weird as it is, this seems to be the solution:

  1. Remove the disk from Time Machine's list of backup destination drives.
  2. Remove file tmbootpicker.efi from the drive's root directory.
  3. Remove file /var/db/volinfo.database
  4. After restarting and able to mount the drive again, re-add the drive to Time Machine.

Ejecting the drive seems to work now — it finally disappears from Disk Utility's list after the USB cable is unplugged.

  • Worked perfectly, thanks! – SomeDude Jan 3 '20 at 19:25

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