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Date: Tue, 20 Jun 2006 16:43:58 +0100
From: Simon Truss <simon_freebsd_fs@bigblue.demon.co.uk>
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Subject: Re: On-disk format of UFS/UFS2 (for firmware implementation)
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Matt Sealey wrote:
> Hello,
> 
> I was wondering if there is any definitive, authoritative or even just comprehensive
> documentation on the on-disk format (superblock, nodes, file linking, extents..) of
> the UFS and UFS2 filesystems.

You probably are looking for this paper:

A Fast File System for UNIX (1984)
http://citeseer.ist.psu.edu/12920.html

There are several books on BSD of which Kirk McKusick has written some.
I would recommend 'Design and Implementation of xxxBSD'. I have the 
4.3BSD book however there are newer releases and a quick google turned 
up FreeBSD.

Sleuthkit contains code to read many file systems and its code may 
assist in extracting the design of FFS.
http://www.sleuthkit.org/

> We would like to implement it in firmware for booting FreeBSD (and NetBSD and eventually
> Solaris which uses some variant). I have the source code from sys/fs/ufs already but it
> is not the preferred method of implementing filesystem code. It only needs read support
> for now so it shouldn't be that complicated, but...

There has been work on flash file systems for BSD, a quick search may 
turn up something useful.

Simon