*BSD News Article 84797


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From: Darren Bordelon <darren@wdc.net>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Embedded FreeBSD
Date: Tue, 17 Dec 1996 17:11:28 -0800
Organization: WDC
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Hi,

We would like to try and use FreeBSD in an embedded system, but
we are not sure about the feasibility of certain methods one might
use to achieve this. After we get some ideas, and get a working
system, we will post our experiences.

First, we would like to have about 4megs of ram. What are the best
methods of minimizing kernel usage? Of course, we will not be using
most of the normal daemons. Also, we would be removing all of the
device drivers that we don't need. Are there other ways to further
decrease system usage?

On the booting issue, can Freebsd be made into some sort of a system
image, whereby a small boot loader program could put it from rom into
ram, and then jump to the right instruction in the kernel? If so, what
are the initialization concerns?

There would be 0 swap. Is this going to be a problem?

We would like to have the the file system in flash ram at some address
beyond the normal ram memory. Can the kernel be configured, perhaps with
the ram disk driver, to use such a memory space for a ram disk, or would
a completely new device driver be needed in this situation?

We would not need most of the stuff under /etc. What is required, if
anything, by the kernel in this dir?

We could also use a rom floppy to boot, would this make things much
easier? Are there other ways that we might used to "boot" the system?

What other issues might we need to consider, and what other methods
might 
be useful in embedding FreeBSD? Any pointers, thoughts, musings, etc. on
this subject will be greatly appreciated. Again, we will post a
compilation of suggestions, techniques, and our own successes once we
have
gotten an embedded FreeBSD working.

Darren
darren@wdc.net