ssh problems when upgrading 5.5 to 6.3

[Christopher Arnold]

Hi all,

i'm trying to remotely upgrade a 5.5 system to 6.3 and have run into an 
issue with userland not matching my kernel. (Yes i know i am a bad guy for 
even trying to do a upgrade remote, but this is a dress rehersal for 
future such scenarios.)

Symptoms:
When trying to ssh to the machine with a 6.3 kernel and a 5.5 userland i 
get:
% ssh machine
Password:
Warning: no access to tty (Bad file descriptor).
Thus no job control in this shell.

And then the motd and after the session is stuck.

I can manage to do "ssh machine csh" i dont get a prompt but are able to 
execute commands. A tail of /var/log/messages reveal:
Sep 26 12:00:36 web sshd[3012]: error: openpty: Invalid argument
Sep 26 12:00:36 web sshd[3015]: error: session_pty_req: session 0 alloc failed

ok lets do a "su" and reboot the machine (I have used nextboot to try the 
new kernel out), but su gives me a "su: Sorry" straight away. Looking in 
messages i see:
Sep 26 11:14:14 web su: in prompt_echo_off(): tcgetattr(): Operation not supported
Sep 26 11:14:14 web su: BAD SU chris to root on tty

Ok, i'm totally aware that this is related to running the wrong userland 
for the wrong kernel. But i still would like to explore this problem a 
bit. Thus these questions:

A) Is this issue related to going directly from 5.5 to 6.3?
That is could i have gotten away without theese problems by upgrading to 
6.0 first and then head on to 6.3?

B) do you thing i would have been able to do an "su" or even login if i 
have had /usr/ports/misc/compat5x installed?

C) Does anyone have a creative way to reboot the machine remote?
You all where waiting for this, wasn't you ;-)
(Or is there a way to get su to survive long enough to do a reebot?)




 	/Chris