I downloaded latest stable Ubuntu (ubuntu-16.04.3-desktop-amd64.iso image that I double checked for authenticity) and used it to boot my new Win10 system which I wanted to wipe. I followed the instructions, like those at
to unfreeze the drive and wipe it using the
time hdparm --user-master u --security-erase ... /dev/sda3
command. In fact I ran it another time (after resetting the drive password) and running with --security-erase-enhanced option second time (thanks to http://www.stevenmaude.co.uk/posts/securely-erasing-frozen-hard-disks-with-hdparm instructions).
It took almost 2 hours each time to go through the erase process. At the end, no errors were printed out. 0's were shown for various times, like 0 cpu time and 0 system time. Only the elapsed time was showing ~2 hours.
After those two runs, I was still able to open random text and xml files in both Windows and non-Windows directories and look at their contents even though I had not opened them earlier in that same Ubuntu session, so it could not have cached them!
I could no longer boot into Windows - guess that's a good sign :-)
After restarting computer and loading up Ubuntu again, it no longer auto-mounts /dev/sda3 (or anything else resembling a hard drive). fdisk -l shows the drive but that's about it.
Tried loading Paragon bootable CD and it also shows no filesystem.
Any ideas as to what I am missing?
It's almost as if it blew away the entry into the file system but after the two erases it was still able to navigate and find file content in that same session of running Ubuntu. Now I don't seem to be able to see anything because anything I try to run no longer finds starting point for the file system, but I wonder if all the data is still laid out there on disk?!