Linux System - Table 12 > Packages - Table 9 > nss_db

Nss_db is a set of C library extensions which allow Berkeley Databases to be used as a primary source of aliases, ethers, groups, hosts, networks, protocol, users, RPCs, services, and shadow passwords (instead of or in addition to using flat files or NIS). Install nss_db if your flat name service files are too large and lookups are slow.