>My bias is towards using Linux in firewalls. Working from an install
>kit or rescue disk you can build a quite spiffy firewall that boots
>and runs totally from a floppy disk. It works out to be pretty easy
>to yank code out of the C runtime libraries, and you don't need a
>shell, network daemons, or sendmail to run a firewall. Or even a disk
>drive beyond the floppy you boot from.
You can even run Linux with / and /usr on a CDROM.
RedHat sells a 'live' filesystem Linux CDROM that you can run a fairly
generic configuration off of -- though you would likely want to look at
what they have done and custom 'burn' your own for firewall use.
A "write disabled" Zip, Jaz or Syquest cartridge should also be good
(anyone run one under Linux drivers?).