disk erase failed could not unmount disk

If the OS X is denying you to format, erase and repair the Mac hard drive or a volume due to the Couldn’t Unmount Disk’ Error then use Stellar Partition Manager to format the hard drive with Mac OS X Extended Journaled file system. Formatting the hard drive or partition scheme will recreate a new HFS file structure on the hard drive, which will be free from cryptic errors. Further, the Stellar Partition Manager utility will allow the user to create, resize, add partitions on the hard drive with HFS, HFS+, FAT or NTFS file systems. Note: Stellar Partition Manager is compatible with OS X 10.6 – macOS Sierra 10.12. This is the most recommended method to repair the error.

The USB boot drive is attached to the Mac, and the system is rebooted.īut, the important point to remember is that the installer or the recovery drive must reside in the drive, separate from the primary boot disk with the installed OS on it.Īny OS X boot drive is needed to complete the task.

The OPTION key is held during the booting and then the attached boot drive is selected.

Disk Utility is accessed through the Boot menu.

It is the Utilities Menu for the Installer Disk

Verification of the Disk is done with the “First Aid.”.

The original task which was halted due to the above error was performed again.

The above steps offer a resolution of the problem.

The errors could have been unresolvable without a boot drive.

Disk erase failed could not unmount disk