From running First Aid in Recovery to repairing disk permissions, we've got the answers on how to use First Aid to repair the disk on your Mac.
How to Run First Aid with Disk Utility - iFixit Repair Guide
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Run First Aid from Recovery Repair a Mac Disk in Recovery Mode - MiniTool
Disk First Aid - Macintosh Repository
How to Run First Aid with Disk Utility - iFixit Repair Guide
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How to repair Mac disk errors in macOS Recovery Mode