Disk Utility First Aid failed: “File system check exit code is 8”

What the message says

When First Aid fails you see a log ending in lines like File system check exit code is 8, Operation failed… or The underlying task reported failure on exit. The check tools behind First Aid (fsck_apfs, fsck_hfs, fsck_exfat, fsck_msdos) return a nonzero exit status when they can’t fully repair the volume, and 8 is the code users commonly see when it fails. Apple doesn’t document each code in its Disk Utility guide, which only says that Disk Utility can’t find or fix every problem and that if a disk is about to fail you should back up and replace it (Apple).

In plain terms, the volume has damage that the checker either can’t fix or doesn’t dare to. Typical triggers: an unclean eject, a drive with bad sectors, a damaged partition map, or a drive that is starting to fail.

Why you shouldn’t just retry

First Aid’s repair pass writes to the drive. A partial or failed repair can leave the volume in a worse state than before, and on a drive with failing sectors every pass adds wear. If the files are irreplaceable, the order is: look, copy, verify, then repair.

Safe checks that only look

1. Note the identifier. In Terminal, diskutil list prints every disk. Find yours, for example disk4.
2. Check the connection. Different cable, different port, direct to the Mac. A flaky connection can make First Aid fail on a healthy drive. Rule that out before blaming the file system.
3. Check for hardware warnings. Spinning drive: listen. Clicking, ticking or repeated spin-ups mean stop, power down and see the next section. In Disk Utility, SMART status (if the drive reports it) appears in the info panel.
4. Verify, don’t repair: diskutil verifyVolume disk4s2 reads and reports without fixing. Compare with what First Aid said.
5. Try mounting read-only: diskutil mount readOnly disk4s2. If this works, copy everything out in Finder before doing anything else.

Get your files off with Retrova

If the volume won’t mount, Retrova can still read it directly. It opens the drive read-only and never repairs, mounts or formats it.

1. Plug the drive in and open Retrova. On the home screen choose A drive won’t open. Retrova lists every drive and partition it can see, with the file system it detected.
2. Pick the drive or partition. macOS asks for your administrator password at this point, because reading a disk directly needs it. Retrova only uses it to read.
3. Browse and choose what you want back. If the file system is readable you see your original folders and file names, and you can preview photos, videos, PDFs and text before copying.
4. Choose a destination on a different drive with enough free space. Retrova never saves onto the drive it is reading.
5. Copy, then Verify. Files are written as temporary parts and renamed only when complete. When it finishes, run Verify to compare every copy with the original, byte for byte.

If what you see in Retrova looks incomplete, or the file system is too damaged to list, run Deep scan:

If no file system is recognised, or the one it finds is too damaged to list files, run Deep scan from I deleted something. Deep scan ignores the file system and searches the raw drive for the start of 72 known file types (photos including camera RAW, videos, audio, documents, archives, mail files and more). It only recovers files that were stored in one piece, and the original names and folders are lost: finds come back sorted by type with new names.

If the drive is failing

If First Aid took a long time, errors appeared at specific points, the drive disconnects, or it makes unusual sounds, don’t browse it. Make one full image first, which copies the healthy data first and returns to the damaged areas later, then recover from the image. See Image a failing drive on Mac or Windows and Recover files from a failing hard drive: image it first. If it clicks or grinds, stop and contact a professional data recovery lab.

After your files are safe

Verify the copy (How to check a copy is perfect: verify files byte for byte). Then, in Disk Utility, erase the drive and choose a format (APFS for a Mac-only drive, exFAT for a Mac and Windows drive). If it keeps failing after being erased, retire it.

What Retrova can’t do: it can’t undelete files with their names on APFS, ext or other file systems (only NTFS, FAT and exFAT), can’t open an encrypted drive without its password or recovery key, can’t open the startup disk of a T2 or Apple silicon Mac away from that Mac, doesn’t handle RAID sets or phones, and can’t fix a drive with physical damage. Retrova’s builds aren’t signed or notarised yet, so macOS and Windows will show a warning the first time you open it.

What not to do

Questions

Sources

• Apple: Repair a Mac storage device with Disk Utility

Related guides

• “Could not mount”: com.apple.DiskManagement.disenter errorErrors 0, 49153 and 49218: gentle steps, then a read-only copy.
• Recover files from an APFS drive that macOS won’t mountFirst Aid failed and the volume stays greyed out? Read the APFS structures directly.
• Image a failing drive on Mac or WindowsA GUI way to copy a dying drive once, and when to stop.
• How to check a copy is perfect: verify files byte for byteCopies fail silently. Check recovered files against the original.