Replace the “/dev/diskx” with the correct disk number, such as “/dev/disk1”. Lastly, you should type “sudo diskutil unmountDisk force /dev/diskx” line.At this time, you ought to find out the disk that you want to force unmount.

Then, input the “diskutil list” line, which will list out all the disks on the Mac.To begin with, you have to access Terminal application.Moreover, you can also attempt to eradicate this error, forcing unmounting disk by command line. Lastly, select “First Aid” to re-verify the disk or choose “Erase” to format the disk at your will.Next, access Disk Utility from the boot menu.Then, when booting, hold down the “Option” key to select Recovery Partition.At this point, you can try solving it with Recovery Partition. If the error message appears during “First Aid” or formatting a non-boot disk, the above means will not make effects surely. Lastly, just perform the original task on the original disk.After that, go to “First Aid” and verify the disk.Next, in the boot menu, select “Disk Utility”.Then, during booting, you should hold down the “Option” key button to select the attached boot drive.First off, insert the USB boot drive to Mac and reboot.By this means, you can make use of USB boot drive. If this error occurs in that the disk to be modified is the boot drive, the simplest solution is to boot the Mac system from another drive and then run Disk Utility on the disk. Therefore, it is imperative to resolve this error as soon as possible. When this error pops up, not only will the Disk Utility halt suddenly, but also the disk will suffer as well, such as damaged data on this disk, like damaged Outlook file. This error generally results from improper modification of the boot drive, such as partitioning, disk verification or repairing or formatting. However, it still can fail to fix disk issues accompanied with some error messages, such as “Couldn’t Unmount Disk” error.

This article will focus on this error and provide 5 feasible solutions.ĭisk Utility plays an extremely important and good role in solving disk problems on Mac system. “Couldn’t Unmount Disk” error message usually pops up when you try formatting, partitioning, verifying or repairing internal disk by Disk Utility on Mac system.

Partition failed could not unmount disk