differential filesystems? (was Re: [plug] Compressed filesystems)

[Bernard Blackham]

On a related topic, has anybody seen or heard of a filesystem that
will load off a read-only device, such as a CD-ROM, but store all
changes in memory? Obviously, it wouldn't have a very long
lifespan, but for short use tools such as rescue disks it would be
very handy if you could simply mount the filesystem off a CD-ROM and
do configuration changes on it, etc, without having to worry about
ramdisks and all the nitty gritty aspects. I haven't seen such a
filesystem around, maybe somebody has? Or should I starting writing
one? :)

Cheers,
Bernard.

-- 
 Bernard Blackham
 bernard at blackham.com.au