For the past week or so, my Seagate USB 2.0 external 500 GB hard drive would not mount when I plugged it in to my Mac. It showed up in Disk Utility, and when I ran “Repair Disk” in the First Aid tab, it said “Invalid content in Journal” and never actually repaired the problem after running several times. I searched Google and found this page which told me exactly what I needed.
The line of code I executed was this:
/System/Library/Filesystems/hfs.fs/hfs.util -N /dev/disk2s1
where you might need to change “disk2s1″ to something else. If you don’t know whether you need “disk2s1″ or something else, select the problem volume in Disk Utility and do an Apple-I for get info.
Afterwards, I was able to mount the drive, repair it successfully using Disk Utility, then re-enable journaling (select the volume and hit Apple-J in Disk Utility) and repair it again for good measure. Things appear to be working well now.
