how to boot a file different from /unix ?

[doelz at urz.unibas.ch]

Hi, 

I am playing with my operating system in order to fix a problem I have with 
IP5 on high load. The lboot -t nicely produces a new kernel, asks whether
I want to reconfigure the system upon startup, and is apparently o.k.

The only thing which puzzles me is that I am getting in trouble 
with the panic messages if I accidentially did something wrong.
The machine dies, and hangs, without RESET being active... I 
need to power off the machine in order to get the PROM prompt.  
I then load the inst, spawn a sh and rename my save file to /root/unix
in order to be able to boot. 

Question: In early versions of PROM, there was a hint how to boot a 
different file than /unix on the system disk. I didn't find that info 
somewhere now in the current documentation (3.3). 
How to boot a file other than /unix ? 

Merci 
Reinhard