The description of Disk Utility’s First Aid command therefore appears incorrect. if there are snapshots on the volume, these are checked individually.However, if it can’t, try unmounting the volume before running First Aid, and mounting it manually again afterwards.įile system objects which are checked on each volume include: When run on a mounted volume (not its container), Disk Utility is usually happy to unmount that volume before performing its checks, then re-mount the volume at the end. If you manually unmount all the volumes in a container and run First Aid on that, or select a volume and run First Aid on that instead of its container, then each volume undergoes a full check on its file system., using the command If you try checking a container on an external APFS disk without ejecting all its volumes, First Aid usually returns an error code -69566 because it can’t apparently unmount the volumes itself. Unmounting its volume(s) make no difference to that, but leaves its container and volumes unchecked. Run First Aid on an external APFS disk and the same checks are made as on an HFS+ disk, covering the partition map and EFI partition. As those require the volume(s) to be unmounted, this is discouraged when running in normal mode, and better performed in Recovery mode. If you want to check the container or volumes on it, you have to select each individually then click First Aid. Run First Aid on your APFS boot disk and the same checks are made as on an HFS+ disk, including the partition map and EFI partition. On completion of any repairs, the volume is mounted again. Is then run on each available volume, which checks its HFS+ file system in full. Run First Aid on an HFS+ volume and the volume is first unmounted, and the command

Other volumes on that disk aren’t checked at all. Core Storage Physical Volume partitions.Miscellaneous features including loader spaces and booter partitions.Run First Aid on an HFS+ disk and the following are checked: If you run First Aid on a volume, Disk Utility verifies all the contents of that volume only.”

“If you run First Aid on a disk, Disk Utility checks the partition maps on the disk and performs some additional checks, and then checks each volume.

Read Disk Utility’s Help book, and you might wonder why there’s any need for this article. The version that I’m using is 19.0 (1704), as supplied with macOS Catalina 10.15.7. In this article, I look at one of Disk Utility’s most essential features, First Aid, and how it works on different disk formats (HFS+ and APFS). This vital tool had been evolving steadily to accommodate the quirks of Apple’s new file system APFS, through a period of turbulence during which some features haven’t worked right, and others have just been puzzling. Recent versions of Disk Utility have changed.

Mac os disk utility first aid fial