Bottom Line: If you’re getting a NO WRITE error on MacOS Mojave when trying to repair a Time Machine sparsebundle, try adding /sbin/fsck_hfs to Full Disk Access.

My Time Machine backup goes to a hard drive connected to my Airport Extreme.

Unfortunately, it’s somewhat common to occasionally get an error messages that goes something like: Time Machine completed a verification of your backups on … Time Machine must create a new backup for you.

The fix for this is posted on numerous blogs, so when I occasionally get this error, I usually just Google the message and follow the instructions.

However, yesterday I tried to run the commands and kept running into an error when you get to the part about using fsck_hfs to actually fix the problem.

The error I kept getting was:

$ sudo /sbin/fsck_hfs -drfy -c 2200m /dev/rdisk2s2
Unable to open block device /dev/disk2s2: Operation not permittedjournal_replay(/dev/disk2s2) returned 1
** /dev/rdisk2s2 (NO WRITE)
Can't open /dev/rdisk2s2: Operation not permitted

I searched around and couldn’t find anything on this except to use sudo diskutil repairVolume /dev/disk2s2 instead of fsck_hfs – which seemed to work, but also seemed agonizingly ~50% in 12 hours, over a wired connection).

Luckily, I’d recently been doing some digging around with the new Full Disk Access permissions in Mojave, so I thought I’d see if that was related.

Sure enough, once I added /sbin/fsck_hfs to System Preferences -> Security & Privacy -> Full Disk Access, I could run the fsck command.

Unfortunately, it looks like my drive is probably failing. Good thing it’s Cyber Monday, I guess.