What does [NOTFOUND=return] in nsswitch.conf mean?

Type "man nsswitch.conf" for more info. There is too much
detail to summarize here. Briefly, [NOTFOUND=return] means
that the name service whose entry it follows should be
considered authoritative (so that if it's up and it says such a
name doesn't exist, believe it and return instead of continuing
to hunt for an answer).