Disk Utility Help
How do you get first aid to work properly in disk utility. When I click on my external hard drive it states, "First Aid could not unmount the volume for repair. Please help.
How do you get first aid to work properly in disk utility. When I click on my external hard drive it states, "First Aid could not unmount the volume for repair. Please help.
What is on that drive? Are you started up from that drive or running something besides DU that is using that drive?
Startup in macOS Recovery and use that Disk Utility to Repair your drive(s).
Disk Utility Help