From the Crack 4.1 docs:
In a similar vein, when a Crack run terminates normally, it writes out to
the feedback file all encrypted passwords that it has NOT succeeding in
cracking. Crack will then ignore all of these passwords next time you run it.
This functionality does not seem to exist in 5.0 and I found no mention
of it being removed or how you might gain this functionality. Has this
truly been removed? This was very handy, can it be simulated?
Wayne E. Beech
University of Kentucky Computing Center
Senior Systems Programmer