Make sure to use Time Machine or other third-party services to backup your Mac and protect your files. This becomes especially important whenever you try to fix any disk-related problems, including when you can’t unmount the disk on Mac. We all know that it is recommended to do regular Mac backups. Before Fixing the “Couldn’t Unmount Disk” Error Trying to perform any drive modifications would fail to give you the “couldn’t unmount disk” error message. You are also unable to partition, reformat or erase the disk you are currently booted from. The system won’t allow you to do anything if some other application or process uses the drive. Why is Mac Giving You the “Couldn’t Unmount Disk” ErrorĬan’t unmount disk on Mac usually happens when you try to do some manipulations with the external or internal drive. How to Fix “Couldn’t Unmount Disk” Error on Mac.Before Fixing the “Couldn’t Unmount Disk” Error.Why is Mac Giving You the “Couldn’t Unmount Disk” Error.

Could not unmount disk 69888