The machine is a fairly standard debian...squashed into an initrd.
It's loaded into the machine with "kvm -kernel ... -initrd ... -append ..."
Then I've executed the attached script, and cleaned up the remainings of it from the memory.
How it was supposed to be solved: (Kudos to Eindbazed for the other way to solve it!)
1. Restore the VM with kvm -m 384 -cpu phenom,vendor=AuthenticAMD -incoming "exec:gzip -d <memdump.gz"
1 and a half: Go to the first VT, you already logged in as root.
2. tcpdump -i eth0 - and see the suspicious IPv6 router solicitations.
3. Try to connect to that ip with ssh (previouslyseenIPv6)%eth0
4. Guess that it was the same machine (ssh key fingerprint should help) - Change the root password with passwd.
5. Read motd
6. cat key/* | (use the tr command from motd, obviously reversing character classes!!) > output
7. vi output
8. :set nowrap
9. Read the ASCII art! It's the flag.