[geekmaster]

Measure twice. Cut once. Cut once again. Fill in the gaps with epoxy?

And despite being SUPER CAREFUL and triple checking, I still dd'd over the partition table on the wrong device. Still trying to recover from that FUBAR. My command history (both root and user) LOOK like I did it right, but the results defy making such conclusions... And worse, the "me too" instructions plastered on the net just make fsck zero out the EXT4 inodes when it deletes all but a handful of (useless) files from the 4TB drive... Making me long for the simplicity of EXT2, eh? And what good is journalling if fsck really wants to delete ALL the files anyway?

EDIT: It just occured to me what went wrong. I was working in a linux VM (on a WINDOWS host). Source drive was USB passed to the VM as a block device. Destination drive was USB passed the VM as a USB device. After copying the beginning of one drive to the other (so later, the Windows EXT IFS driver could SEE the partition table, which was not working on one drive), THEY BOTH HAD THE SAME DRIVE SIGNATURES, which I know from past experience confuses the heck out of Windoze and makes it sometimes write to the WRONG DRIVE. Never mount a pair of cloned drives on Windoze until AFTER altering the drive signature on one of them, And also, never mount a drive on Windoze over USB if it is intended to be used as a data recovery source, because windows writes (and quickly erases) a "readyboost" test file on a drive when you plug it in, and that could eat your lost data for lunch.

EDIT2: I found a backup copy of the first 100mb of the damaged drive. The FIRST attempt at this copy was successful, but changes were not visible (and so was all my lost data) until I rebooted THREE DAYS later. Anyway, I have a copy of the first 100MB from before the damage, the damage was /dev/zero copied to only the first megabyte -- BUT, fsck was run on the damaged drive and deleted millions of files (including the directory structure). Data recovery programs do not find all my archived partition images from various kindles -- instead finding files from INSIDE those partitions; and of course all the filenames are scrambled (with sequence numbers). I have a decades-old collection of hard drives I plan to do data recovery on SOME DAY, but this one is relevant to me at the moment... I am sure it was windows that bit me despite how careful I attempted to do this. In the future, no TWO USB drives passed through to VirtualBox at the same time... Or better, when working with raw drives, get windoze out of the picture completely.

EDIT3: And another thing I did not see before -- the online instructions I used to "fix" the drive used tools that I now see some claim are NOT compatible with my GPT-partitioned disk. Perhaps that is why fsck decided to delete millions on a partition that HAD NO DAMAGE (not the first partition). Only the partition table was damaged until fsck raped my drive (and that was my primary kindle development drive when I was so active here a few years back). Like I said elsewhere, a bad power supply killed many of my backup drives (good reason to archive to DVD I guess).

So yeah, modeling clay and epoxy sound a lot less dangerous at this point...