I was copying a huge file from a USB external drive when it suddenly disappeared from the Finder. I disconnected and connected it back, but the primary partition wouldn't mount. Rebooting the Mac didn't help.
If in the terminal I type
diskutil list
the primary partition disk4s2 does show up.
It does not show up, however, when I type in
df
because the partition is indeed not mounted.
I'm now trying
sudo fsck_hfs -fy /dev/disk4s2
in and the result is
** /dev/rdisk4s2 (NO WRITE)
Can't open /dev/rdisk4s2: Resource busy
I've already tried
diskutil unmountDisk force /dev/disk4s2
and fsck still won't run.
Full disk access is granted to the terminal in security system preferences.
I'm running macOS Ventura on an M1 Max and the drive its andis an USB external 8TB "WD My Book 25EE Media" formatted to Mac OS Extended (Journaled) i.e. HSF+.
Any ideas on how to make it mount?