Unix (Cygwin) whatis: returns all commands as "nothing appropriate"

I ran into a similar issue using the 64-bit Red Hat Cygwin installation.

In my case, /usr/sbin/makewhatis did not exist. Running man and a command worked, but neither apropos nor whatis returned anything other than "nothing appropriate".

After searching for a missing package and binging a bunch, I Read The Friendly Manual page for man and found out about mandb.

Running mandb solved my problem.

From the Cygwin FAQ:

Why doesn't man -k (or apropos) work?

Before you can use man -k or apropos, you must create the whatis database. Just run the command

mandb

(it may take a minute to complete).

(Note: It used to say /usr/sbin/makewhatis instead of mandb in older versions of that FAQ.)

Run sudo mandb once

Not sure if this helps, but when I ran mandb, I got this (over several attempts).

mandb    
0 man subdirectories contained newer manual pages.
0 manual pages were added.
0 stray cats were added.
0 old database entries were purged.

However,

sudo mandb
75 man subdirectories contained newer manual pages.
7235 manual pages were added.
0 stray cats were added.
0 old database entries were purged.

worked for real.