This library provide the capability to have all classical
users definitions in a PostgreSQL server instead than in the
old plain text files in /etc passwd,group,shadow.

All is done without any trick or something like, simply
connecting to the nss (Name Service Switch) facility
offered by the libc (2.x) as nis and nisplus already did.

All without recompiling or touching any application
configurations. Just compile and install nss_postgresql
library and set up a PostgreSQL server.