Network Information Service , as the name suggests this is a nameservice, information to the system is provided from a centralized database, which is a source domain wide. Ypservers run "ypserv" and clients run "ypbind" and bind to the ypservers.
 
 

Instead of managing databases of information on each client, data is consolidated on specific database files (dbm), for easier lookup. These databases or dbm files are accessible to each client from its ypserver to which it binds to. And data can be retrieved through a set of " yp" commands.
 
 

You can run "ypwhich" to find out the binding ypserver. And "ypwhich -m", would tell us of all the yp files available to us. They usually include;
 
 

passwd,
 
 

ypmatch froomin passwd ; would return
 
 

froomin:r3gxIjLU0.ZI.:3093:105:Marty Froomin :/home/t/froomin:/bin/tcsh
 
 

hosts,
 
 

ypmatch rattler hosts ; would return
 
 

130.65.88.71    rattler
 
 

hosts.byaddr,
 
 

ypmatch 130.65.88.71 hosts.byaddr ; would return
 
 

130.65.88.71        rattler     #Marty Froomin
 
 

aliases,
 
 

ypmatch froomin aliases ; would return
 
 

marty.froomin
 
 

and ypmatch marty.froomin aliases ; Would return
 
 

froomin@mailhost
 
 

By having ypservers available to a group of buildings, and placing ypslaves (ypslaves are replicas of ypmasters, ypmasters have access to ascii data. And they convert it to data files, and feed them to ypslaves) in strategic locations information can be shared uniformly across the NIS domain.
 
 

The below picture helps in understanding the scheme. Herein is shown a ypslave with 4 interfaces servicing the 37, 61, 67, and the 37 subnets. All clients run ypbind in broadcast mode, and bind to the ypslave available.
 
 
 
 

The power of NIS is understood by analyzing some basic data. Say there are about 8000 users in a domain, and about nearly 25,000 machines which they should be able to log in. The friendly neighborhood "System Administrator" should duplicate the huge password files in all these machines. And update them with changes.

That would be...
 
 

8000 x 25,000 = 200,000 lines of passwd information to maintain.
 
 

With NIS, we can have one copy of the data available to all the clients when and where they need, through transparent "yp" calls. And they can be administered from one place. The same scenario is duplicated for different yp maps, as shown above.
 
 

Note: Now is a good time to familarize yourself with the yp commands. Read man pages for ypmatch, ypcat, ypwhich, ypbind, and nsswitch.conf.

Marty Froomin 6/19/03