Fix the Error in Disk Utility for Mac “Couldn’t Unmount Disk”

 "Couldn't Unmount Disk"However, the Disk Utility normally works trouble-free, but an annoying “Couldn’t Unmount Disk” error able to also stop whatever the performed task is right in its ways. Similarly, this is also able to happen during partitioning, disk verification & also repair. And even throughout formatting, & there is normally little to no additional information offered as the way to resolve the issue. Or even what the issue is with regards to the error message or also the application in Mac OS.

Fix the Error in Disk Utility for Mac “Couldn’t Unmount Disk”

Generally the “Couldn’t Unmount Disk” error also emerges simply when the recently start drive is also being modified. Or whether a disk was simply trying to be removed you probably find the delete failed with a could not unmount disk error. However, for the former condition where the start drive is just being modified. Though the simplest solution is to start from another drive & also manage Disk Utility simply from there instead. However, just for the boot drive, it should not matter that version of Mac OS X is also for (assuming 10.7, 10.8, 10.9, 10.10, 10.12, 10.13, 10.14, etc maximum).

Just requirement is that it contains Disk Utility. Though that they all perform. Similarly, then this will permit you to fix the issue, however, of the cause, just by one of two means, the first is a sure-thing in order to fix the problem. Whilst the other just works occasionally. So we will cover both with a little explanation. We will also display you a way to compulsorily unmount a disk just by the command line. However, that approach must be used simply with warning as it is also able to lead to data loss on the drive in a question.

Read: How to Fix the Issue “left or Right AirPods Not Working”?

Fix the Unmount Error with a USB Boot Drive

Alright, this is the suggested method because it always resolves the error. So you will require any Mac OS X boot drive in order to complete this task. So then I used a Mavericks boot installer drive just for this reason. Guys! But others should also work if they are installation drives or only recovery drives. The necessary thing is they are startable & separate from the initial boot disk that stores the installed OS:


  • First of all, you have to Attach the USB boot drive just to the Mac and restart
  • Here you have to hold down the OPTION key just throughout start. So then you have to select the attached boot drive (generally it also has an orange icon at the start menu)
  • Although just at the start menu, you have to select “Disk Utility” (whether using an Installer disk, break down the “Utilities” menu just to access Disk Utility)
  • Now you guys have to head to the “First Aid” & now clarify the disk, then repair whether required
  • Here must perform the real task that threw the “Couldn’t Unmount” error

I also encounter this twice currently, firstly when attempting in order to modify partitions on a drive. Though that also came right along just with a separate “partition failed” error. And again it was triggered simply when striving to format those partitions. Similarly, the above steps also did the trick and each and everything was also functioning again as expected.


However, this is the best instance of why it is very valuable. Just to have a bootable USB thumb drive organize with whatever version of the Mac OS X is also managing on your Macs. Because just without a separate boot drive simply some of these types of errors would be unresolvable. Similarly, such boot drives are pretty straight forward in order to create on your own. Well, guys here are such tips for making boot disks for OS X 10.9, OS X 10.8, & OS X 10.7. Regardless just for previous Macs running old versions of Mac OS X. Generally anything managing OS X 10.6 or also earlier will have a SuperDrive, & hence shipped with also a bootable DVD that able to serve this exact purpose.

Also, read it out: Convert PDF To Word On Mac _4 Ways To Convert

Fix Disk Utility Errors via Mac Recovery Partition

Whether the not able to Unmount Error is also trigger by first support. Or formatting a non-boot partition. So guys then you probably be able in order to fix the error simply by starting from the Recovery partition. Though which is also included with all current versions of Mac OS X. Similarly, this will not work whether the error also triggers simply by attempting in order to modify the boot disk via partitions or also formatting. And you will have to utilize the procedure above with a boot disk rather.

  1. First of all, you have to Restart the Mac holding down the “Option” key & select the Recovery partition
  2. Simply select “Disk Utility” from the start menu
  3. Now head to the “First Aid” in order to verify & repair the disk. Or move to “Erase” to format the disk

Once more, whether the disk just throwing the errors is the exact as the initial boot partition. However, which Recovery is also on, simply the above procedure probably not work in order to resolve the issue. Simply, in that case, you will have to start from a separate USB drive in order to fix the error.

Forcibly Unmount a Disk by Command Line in Mac OS

Although another procedure utilizes the command line in order to force unmount a disk. But this is not the top-suggested option just because of potential for data loss.

Guys the warning must be used simply with this approach. However because forcibly unmounting a disk also able to cause just data loss of the drive being forcibly unmounted. Hence this is just particular whether you plan on formatting & also removing the disk simply to you are forced emitting anyway.

However, simply from the command line of Mac OS, now you have to enter the following string:

diskutil unmountDisk force /Volumes/DRIVENAME

Similarly, now you should replace “DRIVENAME” with the name of the volume you like to unmount. Then hit the RETURN key in order to force the drive to unmount.

Whether that does not work, you are also able to take this a step further:

So you probably also have to target the disk. Just by device identifier just to forcibly unmount it, in that case, you are able to also first search the disk with:

diskutil list

Simply then when you guys search the matching disk just to the identifier (/dev/disk1, /dev/disk2, /dev/disk3, etc). So then you are also able to target the disk in order to unmount as so. For the instance syntax here we will use /dev/disk3 just to forcibly unmount from the command line, & also using sudo that will obtain superuser privileges simply for the task:

sudo diskutil unmountDisk force /dev/disk3

Simply you have to hit return & then enter the admin password. Just to forcibly unmount the disk from the Mac.

When completed you are also able to quit out of Terminal normally.

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Do you have another solution that is also able to resolve the “Couldn’t unmount disk” error message in Disk Utility? If yes so then please share your experiences & also solutions with us. In case of queries or trouble, you can ask us in the comments section below.

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