starting sysinstall at boot time

[joel at levee-online.org]

Hi,

Something seems magic in freebsd: I am looking for what does start
sysinstall at boot time when I boot from the installation CD.
The only thing related to systinstall is the setting of the init_path variable
in the loader.rc file but it is in comment thus the loader should finish
by launchinig init as usual so what does make it launch sysinstall instead?

I also examined /etc/ttys which is used by init but this file is standard
and I do not find anything that could tell init to start sysinstall instead
of getty!

As you may guess, my goal is to create an customized installation CD in
order to install a network appliance wich embedds freebsd.

Sincerily,
Joel Levee