Acronym for Name Service Switch

The NSS is a glibc mechanism for providing multiple methods of accessing common databases such as the password or hosts database. It is commonly used to provide an interface to both local /etc/passwd (and shadow) files, and a remote authentication mechanism such as NIS or LDAP.

The databases available for configuration within the NSS are:

• aliases: Mail aliases
• ethers: Ethernet numbers,
• group: Groups of users
• hosts: Host names and numbers.
• netgroup: Network wide list of host and users
• networks: Network names and numbers
• protocols: Network protocols
• passwd: User passwords
• rpc: Remote procedure call names and numbers,
• services: Network services
• shadow: Shadow user passwords

Most of these databases are normally only configured for flatfile access: protocols and services, for example, look up only in /etc/protocols and /etc/services. You could serve these from LDAP, or from a DBM file, or from an SQL database, or so on.

See http://www.delorie.com/gnu/docs/glibc/libc_591.html for more information on the glibc NSS