Name Service Switch
The Name Service Switch (NSS) is a feature found in the standard C library of various Unix-like operating systems that connects a computer with a variety of sources of common configuration databases and name resolution mechanisms. These sources include local operating system files (such as /etc/passwd, /etc/group, and /etc/hosts), the Domain Name System (DNS), the Network Information Service (NIS, NIS+), and LDAP. == nsswitch.conf == A system administrator usually configures the operating system's name services using the file /etc/nsswitch.conf.