Linux Applications

What Are Linux NIS and NIS+

NIS and NIS+ share as many differences as they share similarities. These programs, commonly known as Network Information Service and Network Information Service Plus, deliver a simple network lookup and check of processes and databases.

NIS is formally known as Sun Yellow Pages and provides information that the entire network should know. Notably, NIS and NIS+ provide the following information:

  • Login passwords, names, or home directories (e.g. /etc/password)
  • Group information (e.g. /etc/group)
  • IP numbers and hostnames (e.g. /etc/hosts)

This article will explain how NIS and NIS plus work. The article will also highlight the key differences and similarities between the two frameworks. Finally, you will learn when to go with NIS and when to consider using NIS+.

What is NIS?

Network information system, NIS, is a naming and administration mechanism used by administrators of smaller networks. NIS stands out as a distributed database that allows users to maintain the right and consistent configuration of files within a network.

Developed by Sun Microsystems, NIS also allows users to access system files from anywhere. It is part of the robust Network File System or NFS and features an array of daemons and commands for various other services, including NIS and NFS. Notable NIS components include servers, clients, NIS maps, and a NIS domain.

The NIS Syntax is as shown below:

What is NIS+?

Also developed by Sun Microsystems, NIS+ is a directory service used by system administrators to store shared credentials in the form of NIS+ tables. It is a replacement of NIS which is older and more basic.

This network information service provides a central place where network administrators can store client credentials where everyone can access. The service is ideal for storing machine addresses, mail information, security information, network details, Ethernet information, and other shared client credentials. It comes with a set of commands to help administer the name space.

NIS vs. NIS+ Comparison

NIS and NIS+ share more than their name—they share a common objective. However, they also have an array of differences. Notably, Network Information Service Plus (NIS+) is an enhanced version of the original Network Information Service. It implies that it has new features and different terminology for similar concepts.

The below table summarizes the difference between NIS and NIS+.

Comparison Table Between NIS and NIS+

It features the flat domains and has no hierarchy. It features the hierarchical domains and stores the data in different namespace levels.
It allows the use of similar machine names and user names. The machine and user cannot share a name. Besides, you cannot have a dot (.) in either of the names.
All names and commands are pretty case-sensitive. The commands and names are not case-sensitive.
Does not use any authentication. Uses DES authentication.
Uses two-column tables to store data. Uses multi-column tables to store data.
The client has only one choice of network information source. The client has a range of network information sources to choose from including DNS, NIS, NIS+, or any local /etc. file.
Features a maximum size of 1024 bites, a limitation applying to all the NIS map files. There are no size limitations.
Does not support the encrypted and secure RPC. Supports the secure and encrypted RPC.
It uses RPC Version 2. It uses RPC version 3.
Will often delay the updates for batch propagation. It propagates incremental updates instantly.

NIS and NIS+ Domain Structure

Notably, unlike most versions of original protocols, NIS+ does not improve NIS. Instead, it works as its replacement. NIS aims to address the network administration requirements of relatively small client-server requirements. Thus, it is more suitable for environments with a few hundred clients, trusted users, and a few multipurpose servers.

But you will need NIS+ for large, modern and complex client-server network administrations. It comes with more autonomy. It will conveniently handle networks with up to 10,000 multivendor clients and up to 100 specialized servers located worldwide. The domain hierarchy is similar to that of DNS. However, it is more developed and able to store information about users, workstations, and network services.

NIS+ features interoperability characteristics that allow you to upgrade from NIS. It also allows continued interaction with DNS as initially provided by NIS. The nispopulate command allows NIS compatibility if you intend to move from NIS to NIS Plus.

An example file of NIS is:

An example of a NIS+ file is:

How NIS Works

You must have a single machine within your network acting as a NIS server for NIS to work. However, you can still have multiple NIS servers, with each server serving a different NIS domain.

You can also utilize cooperating servers where one machine will act as a master server while the rest will be NIS slave servers. In such an arrangement, slave servers will only have NIS database copies and will receive and implement changes from the master server.

The main reason for having one or more slave servers in your systems is to maintain the uptime of your network throughout. Thus, client machines can check through any fast or reliable slave servers whenever a master server is down or too slow.

How NIS+ Works

NIS+ works by supporting authentication and data encryption—and it does this over a secure and reliable RPC. Thus, this is a better security tool than NIS.

The naming model here leverages a tree structure, with each node in the tree directly corresponding to a NIS+ object. The design has up to six trees, including table, link, directory, group, entry, and private.

The root directory forms the basis of the NIS+ namespace. The two special directories include the groups_dir and the org_dir. The groups_dir is responsible for access control since it has NIS+ group objects. On the other hand, the org_dir contains administration tables such as hosts, passwd, and mail_aliases.


Now, choosing between NIS and NIS+ is not a hard choice. Consider NIS+ if you have serious security needs within your networks. Although it is slightly easy to administer, it will remarkably secure your systems. On the other hand, NIS is generally an administration protocol. It is pretty easy to minister but lacks security measures.

About the author

Kennedy Brian

Brian is a computer scientist with a bias for software development, programming, and technical content development. He has been in the profession since 2015. He reads novels, jogs, or plays table tennis whenever not on gadgets. He is an expert in Python, SQL, Java, and data and network security.