problems with dump(8)

[utzoo!henry]

I can't speak for the 4BSD version of dump, but two independent analyses
that I know about (one mine) have concluded that using V6 or V7 dump(8) 
on a live filesystem is not safe, period.  physics!gill's problem sounds
like the first one we found:  going in through the /dev entries for a file
system bypasses all that nice machinery that makes sure everybody always
has a consistent view of things like inodes and indirect blocks.