I have an external USB3 hard disk which used be my Time Machine backup drive.

It is not mounting in Finder, but is showing up if I diskutil list. It sounds like it wants to mount - in fact, it sounds like a drive where there is data being read and written.

If I open Disk Utility with this drive connected, I get the spinner icon and Disk Utility stays a grey window and won't list anything (ever). I have to force quit or reboot to quit it at that point.

I can't fsck_hfs it from terminal under the OS:

Tims-MBP 08:48:50: [~]: fsck_hfs -r /dev/disk3s1 ** /dev/rdisk3s1 (NO WRITE) Can't open /dev/rdisk3s1: Permission denied

but if I reboot into single user mode then it lets me.. the process ticks by and tells me about things like Previous ID in a hard link chain is incorrect, Orphaned file hard link. and Invalid volume free block count. which (after a few hours) it seemed to have a grip on. (probably bits of the time machine backup are corrupt: that's acceptable and expected).

I also thought to plug this into my Windows7 box and mount the drive using HFSExplorer (http://www.catacombae.org/hfsexplorer/ - the mac version doesn't detect or load the drive at all). I'm then able to extract files - so I have a copy of everything EXCEPT the time machine backups. I don't have another drive large enough to make a disk image of the drive (which HFXExplorer can do). So I don't feel like a utility like DiskWarrior is neccesary since I don't know if it can repair the partitions/whatever to make the drive mount again.

I have since bought a new external hard disk and set it up as a new Time Machine backup drive and done a full backup to it. It's part of the backup drive set in case I can get this drive going again.

Is there anything else I should try before I format it again and/or put it in the rubbish bin.

  • Maybe try booting your mac into recovery mode (either internet or local) and use the disk utility to do "First Aid" on the disk. Might fix the permissions problems. Or you may be able to do this from Single User Mode. This github gist might help: gist.github.com/bzerangue/dca8fc2d63309ba2bd9f
    – bret7600
    Commented Oct 22, 2016 at 22:35
  • disk first aid is effectively the same thing as fsck, and I mentioned I did that in single user mode (since in 10.11 is rootless, it's the only way you can)
    – frumbert
    Commented Oct 22, 2016 at 23:34


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