New port: sysutils/nss_ndb BerkeleyDB-based nsswitch backend for passwd & groups

This project consists of a NSS module (nss_ndb.so.1) and a CLI
utility (makendb) that enables big passwd & group files to be
handled efficiently via BTree BerkeleyDB databases.

To activate and use this you must (after installation):

1. Manually add a symbolic link:
   
   /usr/lib/nss_ndb.so.1 -> /path/to/lib/nss_ndb.so.1.<version>

2. Populate the databases in /var/db/nss_ndb via "makendb" (or some other tool).

3. Activate it in /etc/nsswitch.conf:
   
   passwd: files ndb group: files ndb

WWW: https://github.com/ptrrkssn/nss_ndb

PR: 247211
Submitted by: Peter Eriksson <pen@lysator.liu.se>