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The network information system, also known as NIS, is a client and server system that is remote procedure call (RPC) based. It allows all machines in the network information system, or NIS domain, to share a common set of configuration files. Remote procedure call enables a computer program to execute a procedure on another machine on the shared network and is a form of inter-process communication. NIS was developed by Sun Microsystems to centralize the administration of Unix® systems and allows NIS client systems to be set up from one location with minimal configuration.
There are two sides to a network information system: servers and clients. Hosts, or machines, on the network can either act as a server or client. Hosts can be clients, slave servers or master servers. Master servers are authoritative name servers that process and respond to input from client servers; slave servers mirror, or make copies of, the output from master servers; and client machines simply receive information from slave or master servers.
NIS environments allow many types of files to be shared, but the most common types are host, group and master password files. In a non-network environment, these types of files would be stored on individual computers and not remotely accessible by multiple computers. In the NIS environment, however, these files are stored on the master server, and the client machine sends a request to retrieve the information. This makes one file accessible by any number of machines, or clients, on the network.
When a shared network is set up, the general goal is to make the network as transparent as possible; for this reason, it is important to keep all user account information synchronized. When data is centrally stored, it can be accessed by users from any machine within the network without having to remember passwords or to physically move data from one machine to the next. When using a network information system, the network administrator only needs to maintain one copy of the information, as it is stored in one location in the network.
Since its development, the network information system has become an industry standard, and all Unix® and Unix-like systems, such as Solaris™, AIX®, HP-UX, and Linux, support the use of network information services. The NIS was originally called Yellow Pages, or YP, but because the phrase Yellow Pages is a registered trademark, Sun Microsystems had to discontinue use of the name. This explains why to this day most of the network information system commands are prefixed with the letters "yp" and why NIS still is referred to as YP by some.