The name service switch is a configurable selection service that enables an administrator to specify which name information service or source to use for each type of network information. The services are called a database. The name service switch is used by client applications that call any of the getXbyY() interfaces, such as the following.
Each system has its own configuration in an SMF repository. Each property defined in the name service switch identifies a particular database, such as a host, password, or group. The value assigned to each property lists one or more sources from which to request the information. Sometimes, these values include guidance or options. The guidance might include how many retries to a service should be attempted, what timeout to apply, or what to do if the service fails.
The name service switch also controls DNS forwarding for clients as described in Chapter 3, Managing Domain Name System. DNS forwarding grants Internet access to clients.