Sidebar: Sun Network Information System (NIS)

NIS is a way of making simple databases available to every computer on a network. The original of the database resides as a text file on the master NIS server. Each database is converted into one or more "maps" (lookup tables) having a single key. The NIS server responds to queries and supplies the appropriate entries. The process is generally transparent to user programs.

The most familiar of the traditional databases is /etc/passwd. This database appears to NIS clients as two NIS maps, passwd.byname and passwd.byuid, with the key of user name and user ID, respectively. The user command ypmatch passwd.byname johnlees returns the entry in the passwd.byname map having the key johnlees.

The probe script makes use of the NIS netgroup maps. The netgroup database is optional in the sense that nothing depends on it by default. It can be used to group machines (or users) for the purpose of granting access to various system and network resources. We use the netgroup database as a way of grouping our computers into a number of different labs, or domains, each having one or more managers responsible for its system administration.

Following is a much abbreviated (the real one has over 600 lines) version of our master /etc/netgroup file showing the scheme we use to organize machines into labs.

cps             lab1 lab2...
lab1            lab1_server lab1_client
lab1_server     (server1.cps.msu.edu,-,)\
(server2.cps.msu.edu,-,)
lab1_client     lab1_next lab1_sparc
lab1_next       (client1.cps.msu.edu,-,)\
(client2.cps.msu.edu,-,)
lab1_sparc      lab1_sun4 lab1_sun4c lab1_sun4m
lab1_sun4       (client3.cps.msu.edu,-,)\
(client4.cps.msu.edu,-,)
lab1_sun4c      (client5.cps.msu.edu,-,)\
(client6.cps.msu.edu,-,)
lab1_sun4m      (client7.cps.msu.edu,-,)\
(client8.cps.msu.edu,-,)