Normally disk utility can be accessed smoothly but sometimes disk utility could not unmount disk error would impede several tasks. This problem mainly appears when repairing, partitioning, accomplishing disk verification and formatting of disk once in a while. Though disk utility is the great built in facility which is mostly by Mac users. Unfortunately by someway there might problem occur in it. And disk utility could not unmount disk is such an issue which usually come across when there is modification done in the boot drive. So for resolving this problem one can try to boot through another drive. Thereafter run the disk utility from that drive.
- Firstly establish attachment of USB boot drive with Mac then reboot.
- Now hold down OPTION keys while booting, thereafter choose attached boot drive.
- Then select “Disk Utility” from boot menu.
- Move to “First Aid” and then verify disk, you can repair it if required.
Hopefully, now disk utility could not unmount disk error could be resolved this way. In case of data inaccessibility one should immediately consider data recovery that can be accomplished either-way. Firstly by latest disk backup if ever created before using Time Machine. Else Mac Data Recovery Software must be used.