The nsswitch.conf file specifies how the nsdispatch(3) (name-service switch dispatcher) routines in the C library should operate.
The configuration file controls how a process looks up various databases containing information regarding hosts, users (passwords), groups, etc. Each database comes from a source (such as local files, DNS, and NIS), and the order to look up the sources is specified in nsswitch.conf.
Each entry in nsswitch.conf consists of a database name, and a space separated list of sources. Each source can have an optional trailing criterion that determines whether the next listed source is used, or the search terminates at the current source. Each criterion consists of one or more status codes, and actions to take if that status code occurs.
The following sources are implemented: