Il mio HD esterno non è montato e non può essere riparato da Utility Disco. Tuttavia, non riesco nemmeno a cancellare il disco:
$ diskutil list disk2
/dev/disk2
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *4.0 TB disk2
1: EFI EFI 314.6 MB disk2s1
2: Apple_HFS Everest 4.0 TB disk2s2
$ diskutil repairVolume /dev/disk2s2
Started file system repair on disk2s2 Everest
Updating boot support partitions for the volume as required
Error: -69673: Unable to unmount volume for repair
$ diskutil eraseDisk JHFS+ Everest /dev/disk2
Started erase on disk2
Unmounting disk
Error: -69888: Couldn't unmount disk