I tried:
1) Adding init=/bin/sh to reset from single user mode. I am seeing some messages on my little CRT monitor but are too small to see what is actually going on. Plugged in a usb keyboard and nothing happens, tried typing nothing at all.
2) root/diepi, dietpi/dietpi once again nothing works
3) Mounted the sd card on another system, tried to edit /etc/shadow but it looks like nothing standard is in there like "root