Learn about NIS server(Network Information System)

is a network naming and administration system for smaller networks that was developed by Sun Microsystems. NIS uses the client/server model and the Remote Procedure Call (RPC) interface for communication between hosts. NIS consists of a server, a library of client programs, and some administrative tools. NIS is often used with the Network File System (NFS). NIS is a Unix-based program. It is more efficient to combine machines into groups that share configuration information. This can be done in various ways.

The most commonly shared files are:

/etc/passwd - User account information

/etc/group - UNIX group definitions

/etc/hosts - Maps hostnames and ip addresses

/etc/services - Lists port numbers for well-known network services

/etc/protocols - Maps text names to protocol numbers

/etc/ethers* - Maps hostnames and ethernet addresses

/etc/aliases - Mail alias definitions, including postmaster

/etc/rpc - Lists id numbers for rpc services

/etc/netgroup - Defines collections of hosts, users and networks

Advantages / Disadvantages of NIS

• NIS is fairly easy to maintain without being aware of the internal data formats, you just edit the same "flat" files, and learn one or two new procedures to go with it. • NIS is a very good way to easily maintain a large number of users and groups across a large number of shared systems. These systems have to be configured similarly. • NIS can consume a lot of network bandwidth since NIS doesn't cache data on client machines. Every lookup causes an exchange of network packets. When a master's maps get updated, every slave server is also updated with the new maps. So it's a tradeoff depending on your setup. • NIS is not secure! Outside hosts can pose as a client of your domain and grab your maps. Once they get your password map, a crack program can be run on it to decrypt passwords, opening your system up. For this reason it is fairly important to pick an obscure domain name, and not something like "cmsc" for say the computer science domain.

NIS commands and daemons

ypserv: NIS server daemon started at boot time by master/slave servers ypbind: NIS client daemon started at boot time by all ypxfr: Downloads current version of a map from master server ypxfrd: Serves requests from ypxfr (runs on master) yppush: Makes slave servers update their map versions makedbm: Builds a ndbm map from a flat file ypmake*: Rebuilds ndbm maps from flat files that have changed (IRIX) ypinit: Configures a host as a master or slave server ypset: Makes ypbind connect to a particular server ypwhich: Finds out which server the current host is using yppoll: Finds out what version of a map a server is using ypcat: Prints the values contained in an NIS map ypmatch: Prints map entries for a specified key yppasswd: Changes a password on the NIS master server ypchfn: Changes GECOS info on the NIS master server ypchsh: Changes a login shell on NIS master server yppasswdd: Server for yppasswd, ypchsh and ypchfn ypupdated: Server for updating NIS maps (managed by inetd)

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