The:
Code:
root:x:0:0:root:/tmp/root:/bin/sh
indicates that root has a password set in /etc/shadow.
But as you said, you did that yourself.
So we don't know what the Amazon image had in it.
Personally, I think you are still running the "diags" operating system, not the "main" operating system.
It is the only thing that I can think of which would make your findings reasonable.
Over your serial connection, try entering these commands:
mkdir /tmp/main
mount /dev/mmcblk0p1 /tmp/main
If your in 'main' I would expect you to get a 'device busy' sort of message.
If your in 'diags' it will just mount the 'main' partition at /tmp/main
and/or
do a:
cd /
df .
The 'main' file system is much bigger than the 'diags' file system.