4 Solutions to the Error Message “Couldn’t Unmount Disk” When Using Disk Utility on Mac

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October 18, 2021


Undoubtedly, disk utility on Mac can be relied on for any logical issue in Mac hard drives. Though, the “couldn’t unmount disk” may disturb the disk utility while repairing the disk and result in data loss. This error can show up due to modifications of the boot drive. Therefore, we have concluded four solutions for […]

External Hard drive

1. Recovery partition

Taking the case when this error message appears during “first aid” or non-boot disk, you can remove it with a recovery partition. Reboot Mac>while booting press “option” key and select recovery partition> use disk utility from boot menu> select “first aid” or format the disk.

2. Boot disk from another drive

Use a USB boot drive when the error occurs in the drive that has modified the boot drive. You can boot a Mac on another drive which can be a USB drive too. Start with mounting the drive on Mac and reboot it>while booting, hold the “option” key and select “attached boot drive”>in the boot menu, select “Disk utility”>go to “first aid” and check the disk>do the task on the original disk.

3. Command line

Command-line in Mac can also prove to be a helpful solution when you need to eliminate this error. Start with “terminal application”>input “diskutil list” line, and a list of disks on Mac will show up>choose target disk to force unmount>input “sudo diskutil unmountDisk force /dev/disk” with correct disk number.

4. Resort to specialist

When all Mac solutions fail to eradicate the error “couldn’t unmount disk”, get your Mac hard drive recovered by a professional. With professional skill sets and dedicated tools, complicated, hard drive problems can be resolved.


We can not predict when the hard drive can be encountered with errors. To protect your files from Mac hard drive data loss, create updated backup data always to access your files.

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