Repair a disk error in recovery
by RUSSELL CAPLAN
Once you have run First Aid on the Data volume, select the container higher up and run it on that to complete any repairs.
Q When I ran Disk Utility on my Mac’s Data volume, it reported an error, but couldn’t repair it. How can I fix that?
A This can occur when you ask Disk Utility to repair your current Data volume, as it and its container can’t be unmounted while your Mac is still running from its volumes. Repairs to the active Data volume are generally best performed in recovery mode, which does allow those volumes and their whole container to be unmounted while repair takes place. Start your Mac up in recovery mode, make your way to Disk Utility, then select the Data volume on the left. Click First Aid and let that run to completion. That may return the same warnings, and a recommendation to run First Aid on the container for repair. To do that, Show All Devices in the View tool and select the container on the left, such as Container disk3. Click First Aid again and let that finish.