Yet more power cuts badly affecting external Time Machine drive

Having previously posted about issues with power cuts corrupting Time Machine, it happened again this time, but to the extent that the drive didn't even display in Disk Utility.

I followed the steps here:

diskutil list

So the 2TB drive is clearly there. 

Next step - diskutil unmount /dev/disk2

That didn't work ("disk2 was already unmounted or it has a partitioning scheme so use "diskutil unmountDisk" instead"), had to modify slightly to:

diskutil unmountDisk /dev/disk2

Also didn't work - "Unmount of disk2 failed: at least one volume could not be unmounted"

Therefore referred here and tried instead:

sudo lsof|grep disk2

Running processes were displayed:

fsck_hfs  889            root    4u      CHR                1,7 0x1b0508000      693 /dev/rdisk2s2

fsck_hfs  889            root    5u      CHR                1,7 0x1b0508000      693 /dev/rdisk2s2

So I closed these in Activity Manager

At this point, the Time Machine (albeit greyed out) showed in Disk Utility, so next step is First Aid there.

Having also then tried diskutil mount /dev/disk7s2 and getting the response Volume on disk7s2 timed out waiting to mount

I was about to give up. But then, as a last throw of the dice, I tried connecting to my Ubuntu desktop.

Immediately in Home Folder it showed as a mounted drive! So from there I went to Disk Utility, unmounted the partitions, erased and formatted them and then re-connected to Mac.

A Time Machine backup has now commenced.....