The name service switch configuration file contains the preferred order in which name services will be contacted for name resolution by the filer. For each map, the name services to be used and the lookup order is specified in this file. Currently three name services are supported. They are local files in the /etc directory, NIS and DNS. The maps or "databases" that are supported are hosts, passwd, shadows, group and netgroups. Each line has the form:
map: order of name services
For example:
hosts: files nis dns
passwd: files nis
When trying to resolve a name, the services are contacted one by one, as per the order specified, until the name is successfully resolved. A name resolution failure occurs when no service can successfully resolve the name. When enumerating a map, enumeration happens over all the services specified for the map.