On-disk format of UFS/UFS2 (for firmware implementation)

[Eric Anderson]

Matt Sealey wrote:
>> You probably are looking for this paper:
>>
>> A Fast File System for UNIX (1984)
>> http://citeseer.ist.psu.edu/12920.html
> 
> We have this implemented already in the firmware.
> 
> However this does not help reading UFS2 (64-bit numbers, extents etc.
> and myriad other things to look out for).

I like the "Design and Implementation of the FreeBSD 5.2..." book.  It 
covers what you need, plus more that you won't need.  The best 
documentation is the .h files I think, but you aren't interested in those.

>> Sleuthkit contains code to read many file systems and its 
>> code may assist in extracting the design of FFS.
>> http://www.sleuthkit.org/
>>
>> There has been work on flash file systems for BSD, a quick 
>> search may turn up something useful.
> 
> Why a flash filesystem?

For different reasons - mostly for embedded systems builders who use a 
real OS (like FreeBSD) but want to make their flash last a while.


> Our OpenFirmware has disk support, it pushes them into the device
> tree and you can load/boot any file on any supported filesystem (this
> includes IDE, SCSI, USB disks..)
> 
> We just want to parse and use UFS filesystems, i.e. the modern ones
> that OpenBSD (UFS) and FreeBSD and NetBSD (UFS2) use. FFS isn't the
> same thing, as I am told by hundreds of articles... at least there are
> some differences which I have found hard to find the documentation on.
> 
> In theory we should be able to implement the entire gamut in one
> filesystem support package, the same way the Linux ufs driver does,
> by adapting the "1984 FFS" driver.
> 
> For that we need to know what we are doing.. :)
> 
> The Sleuthkit guy seems to have written a book which may be very
> useful to us (if we order it..) http://www.digital-evidence.org/fsfa/
> and this is more like what we are looking for. Source code as
> documentation is really the last resort when it comes to supporting
> things as it makes for very hard and expensive work.
> 


Eric


-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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