Last-modified: 2 Jul 95
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*** The Linux NIS HOWTO is posted automatically by the Linux
*** HOWTO coordinator, Greg Hankins <gr...@sunsite.unc.edu>. Please
*** direct any comments or questions about this HOWTO to the author,
*** Erwin Embsen <er...@nioz.nl>.
- --- BEGIN Linux NIS HOWTO part 1/1 ---
The Linux NIS(YP)/NIS+/NYS HOWTO
Andrea Dell'Amico, Mitchum DSouza, Erwin Embsen, Peter Eriksson
v0.5, 24 January 1995
1. Glossary of Terms
In this document a lot of acronyms are used. Here are the most
important acronyms and a brief explanation:
DataBase Management, a library of functions which maintain key-
content pairs in a data base.
Dynamically Linked Library, a library linked to an executable
program at run-time.
A name "key" that is used by NIS clients to be able to locate a
suitable NIS server that serves that domainname key. Please note
that this does not necessarily have anything at all to do with
the DNS "domain" (machine name) of the machine(s).
File Transfer Protocol, a protocol used to transfer files
between two computers.
Name services library, a library of name service calls
(getpwnam, getservbyname, etc...) on SVR4 Unixes.
Socket services library, a library for the socket service calls
(socket, bind, listen, etc...) on SVR4 Unixes.
Network Information Service, a service that provides
information, that has to be known throughout the network, to all
machines on the network. There is support for NIS in Linux's
standard libc library, which in the following text is referred
to as "traditional NIS".
Network Information Service (Plus :-), essentially NIS on
steroids. NIS+ is designed by Sun Microsystems Inc. as a
replacement for NIS with better security and better handling of
This is the name of a project and stands for NIS+, YP and Switch
and is managed by Peter Eriksson <p...@lysator.liu.se>. It
contains among other things a complete reimplementation of the
NIS (=YP) code that uses the Name Services Switch functionality
of the NYS library.
Remote Procedure Call. RPC routines allow C programs to make
procedure calls on other machines across the network. When
people talk about RPC they most often mean the SunRPC variant.
YP Yellow Pages(tm), a registered trademark in the UK of British
Transmission Control Protocol/Internet Protocol. It's a data
communication protocol often used on Unix machines.
1.1. Some General Information
The next three lines are quoted from the Sun(tm) System & Network
"NIS was formerly known as Sun Yellow Pages (YP) but
the name Yellow Pages(tm) is a registered trademark
in the United Kingdom of British Telecom plc and may
not be used without permission."
NIS stands for Network Information Service. It's purpose is to provide
information, that has to be known throughout the network, to all
machines on the network. Information likely to be distributed by NIS
o login names/passwords/home directories (/etc/passwd)
o group information (/etc/group)
So, for example, if your password entry is recorded in the NIS passwd
database, you will be able to login on all machines on the net which
have the NIS client programs running.
Sun is a trademark of Sun Microsystems, Inc. licensed to SunSoft, Inc.
More and more, Linux machines are installed as part of a network of
computers. To simplify network administration, most networks (mostly
Sun-based networks) run the Network Information Service. Linux
machines can take full advantage of existing NIS service or provide
NIS service themselves. It can also (with the NYS library) act as a
limited NIS+ client.
This document tries to answer questions about setting up NIS(YP) on
your Linux machine. It does not talk about how to set up NIS+. Don't
forget to read section 5.1, The RPC Portmapper.
2.1. New versions of this document
New versions of this document will be posted periodically (about every
month) to the newsgroups comp.os.linux.announce and
comp.os.linux.misc. The document is archived on a number of Linux FTP
sites, including sunsite.unc.edu in /pub/Linux/docs/HOWTO.
Although this document has been put together to the best of our
knowledge it may, and probably does contain errors. Please read any
README files that are bundled with any of the various pieces of
software described in this document for more detailed and accurate
information. We will attempt to keep this document as error free as
If you have any comments, questions or suggestions please email them
to Erwin Embsen <er...@nioz.nl>. Definitely contact him if you find
errors or obvious omissions.
We would like to thank all the people who have contributed (directly
or indirectly) to this document. In alphabetical order:
Andrea Dell'Amico <adel...@di.unipi.it>
Mitchum DSouza <Mitch.Dso...@Dubai.Sun.COM>
Erwin Embsen <er...@nioz.nl>
Byron A Jeff <by...@cc.gatech.edu>
Peter Eriksson <p...@lysator.liu.se>
Theo de Raadt <dera...@fsa.ca> is responsible for the original yp-
clients code. Swen Thuemmler <s...@uni-paderborn.de> ported the yp-
clients code to Linux and also ported the yp-routines in libc (again
based on Theo's work).
3. NIS or NIS+ ?
The choice between NIS and NIS+ is easy - use NIS if you don't have to
use NIS+ or have severe security needs. NIS+ is _much_ more
problematic to administer (it's pretty easy to handle on the client
side, but the server side is horrible). Another problem is that the
support for NIS+ under Linux is still under developement - one major
thing it still lacks is support for data encryption/authentication
which is _the_ major thing why anyone would want to use NIS+...
3.1. Traditional NIS or the NYS library ?
The choice between Traditional NIS or the NIS code in the NYS library
is a choice between laziness and maturity vs. flexibility and love of
The "traditional NIS" code is in the standard C library and has been
around longer and sometimes suffers from it's age and slight
The NIS code in the NYS library, on the other hand requires you either
to recompile and relink all your programs to the libnsl library, or
recompile the libc library to include the libnsl code into the libc
library (or maybe you can go get a precompiled version of libc from
someone who has already done it).
Another difference is that the traditional NIS code has some support
for NIS Netgroups, which the NYS code doesn't (yet). On the other hand
the NYS code allows you to handle Shadow Passwords in a transparent
4. How it works
Within a network there must be at least one machine acting as a NIS
server. You can have multiple NIS servers, each serving different NIS
"domains" - or you can have cooperating NIS servers, where one is said
to be the master NIS server, and all the other are so-called slave NIS
servers (for a certain NIS "domain", that is!) - or you can have a mix
Slave servers only have copies of the NIS databases and receive these
copies from the master NIS server whenever changes are made to the
master's databases. Depending on the number of machines in your
network and the reliability of your network, you might decide to
install one or more slave servers. Whenever a NIS server goes down or
is too slow in responding to requests, a NIS client connected to that
server will try to find one that is up or quicker.
NIS databases are in so-called DBM format, derived from ASCII
databases. For example, the files /etc/passwd and /etc/group can be
directly converted to DBM format using ASCII-to-DBM translation
software ("dbload", it's included with the server software). The
master NIS server should have both, the ASCII databases and the DBM
Slave servers will be notified of any change to the NIS maps, (via
the "yppush" program), and automatically retrieve the necessary
changes in order to synchronize their databases. NIS clients does not
need to do this since they always talks to the NIS server to read the
information stored in it's DBM databases.
The author of the YP clients for linux has informed us that the newest
ypbind (from yp-clients.tar.gz) is able to get the server from a
configuration file - thus no need to broadcast (which is insecure -
due to the fact that anyone may install a NIS server and answer the
5. What do you need to set up NIS?
5.1. The RPC Portmapper
To run any of the software mentioned below you will need to run the
program /usr/sbin/rpc.portmap. Some Linux distributions already have
the code in /etc/rc.d/rc.inet2 to start up this daemon. All you have
to do is comment it out and reboot your Linux machine to activate it.
The RPC portmapper (portmap(8c)) is a server that converts RPC program
numbers into TCP/IP (or UDP/IP) protocol port numbers. It must be
running in order to make RPC calls (which is what the NIS client
software does) to RPC servers (like a NIS server) on that machine.
When an RPC server is started, it will tell portmap what port number
it is listening to, and what RPC program numbers it is prepared to
serve. When a client wishes to make an
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