The NIS network information service uses a distributed, replicated database of dbm files (in ASCII form) contained in the /var/yp directory hierarchy on each NIS server. NIS has been replaced by NIS+, the new version of the Network Information Service. See nis+(1). This release only supports the client functionality of NIS, (see ypclnt(3NSL)). The client functions are either supported by the ypserv process running on a machine with an earlier version of SunOS or by the NIS+ server in "YP-compatibility" mode, (see rpc.nisd(1M)).
A dbm database served by the NIS server is called an NIS map. An NIS domain is a subdirectory of /var/yp containing a set of NIS maps on each NIS server.
Standard nicknames are defined in the file /var/yp/nicknames. These names can be used in place of the full map name in the ypmatch and ypcat commands. The command ypcat -x can be used to display the current set of nicknames. The command ypwhich -m can be used to display all the available maps. Each line of the nickname file contains two fields separated by white space. The first field is the nickname and the second field is the name of the map that it expands to. The nickname cannot contain a ".".
The NIS+ server, rpc.nisd, when run in "YP-compatibility mode", can support NIS clients only for the standard NIS maps listed below, provided that it has been set up to serve the corresponding NIS+ tables using nissetup(1M) and nisaddent(1M). The NIS+ server should serve the directory with the same name (case sensitive) as the domainname of the NIS client. NIS+ servers use secure RPC to verify client credentials but the NIS clients do not authenticate their requests using secure RPC. Therefore, NIS clients can look up the information stored by the NIS+ server only if the information has "read" access for an unauthenticated client (i.e. one with "nobody" NIS+ credentials).