Scripting bsdinstall

[Gleb Popov]

Hello.

I'm trying to write my own installerconfig script to perform [almost]
unattended install, but facing some problems:

- Script examples in `man bsdinstall` use some variables (PARTITIONS and
nonInteractive) that aren't documented in the man. Where do I find all
supported variables?
- How do I setup networking on target machine? Examples propose running
sysrc ifconfig_em0=DHCP, but how do I know interface name?
- Same question goes for target drive. In most cases it is ada0, but how do
I dynamically find it out?