Repairing a disk
Repair Disk fixes the filesystem — after taking an instant, free backup you can go back to.
On this page 3 sections
Repair Disk… fixes whatever the filesystem check finds. It asks first — "Repair this instance's disk?" — and explains what happens next.
What it does#
- Takes a backup. An instant copy of the whole disk, made with an APFS clone: it appears immediately and costs no space on your Mac until the disk starts to differ from it.
- Repairs.
e2fsckfixes everything it can. - Reports what happened.
The same prerequisites as Checking a disk apply: shut down, no hibernated session, e2fsprogs installed.
Results#
| Result | Means |
|---|---|
| Problems found and fixed | Done. The backup is kept until you discard it. |
| Problems fixed | Fixed, and e2fsck wants a restart before the disk is used — starting the instance now is that restart. |
| Some problems couldn't be fixed | It fixed what it safely could. What's left needs a closer look; the backup is kept. |
| The check didn't run | Nothing was repaired. The reason follows. |
The backup#
After a repair, the Disk section shows "A copy of the disk from before the last repair is kept." with two buttons:
- Restore… — puts the old disk back. It asks first: "Put the old disk back?" — anything written to the disk since that repair is lost.
- Discard — deletes the backup. Do this once you're happy the repaired disk is fine.
The backup sits beside the disk image, with .pre-repair on the end of its name. If one already exists when you repair again, MSL keeps the existing one instead of replacing it — so it's always from before the first repair since you last discarded.