The Linux NIS(YP)/NIS+/NYS HOWTO: What you need to set up NYS?

6. What you need to set up NYS?

6.1 Determine whether you are a Server, Slave or Client.

To answer this question you have to consider two cases:

Your machine is going to be part of a network with existing NIS servers
You do not have any NIS servers in the network yet

In the first case you have two choices:

Either you relink all client and daemon programs with the NYS library libnsl.so (or statically link them with libnsl.a). This means adding the line:
LIBS=-lnsl
to your Makefile signifing you want to link the Network Services Library. Basically all network deamons and the "login" program need to be recompiled.
Or you can recompile the standard C library libc to include the NYS client library functions into the normal libc library, and then relink all statically linked programs (the dynamically linked programs automatically get the new version of libc). See section 6.5 below for more information about this option.

Similarly like in the case of traditional NIS, if you don't have NIS servers, then you will also need a NIS server program (usually called ypserv) and you have to designate one of the machines in your network as a master NIS server. Again, you might want to set up at least one slave server as well.

6.2 The Software

You need to retrieve and compile the NYS services library libnsl.so. If you don't have the DLL tools installed you may retrieve a precompiled shared, static and stub library from the same site mentioned below. Note, however, that the precompiled version may be (and probably is) older than the latest source code release.

The NYS library (source and precompiled version) can be obtained from:


    Site                Directory                      File Name

    ftp.lysator.liu.se  /pub/NYS/libs                  nys-0.27.4.tar.gz
    ftp.lysator.liu.se  /pub/NYS/binaries/lib          libnsl.so.1.0.a26
 
    ftp.funet.fi        /pub/OS/Linux/BETA/NYS/libs    nys-0.27.4.tar.gz
    ftp.funet.fi        /pub/OS/Linux/BETA/NYS/lib     libnsl.so.1.0.a26

Precompiled "login" and "su" programs may also be fetched from


    Site                Directory                      File Name

    ftp.lysator.liu.se  /pub/NYS/binaries/bin          login
    ftp.lysator.liu.se  /pub/NYS/binaries/bin          su

    ftp.funet.fi        /pub/OS/Linux/BETA/NYS/bin     login
    ftp.funet.fi        /pub/OS/Linux/BETA/NYS/bin     su

Similarly, example configuration files may be retrieved from


    Site                Directory                      File Name

    ftp.lysator.liu.se  /pub/NYS/binaries/etc          *conf
    ftp.funet.fi        /pub/OS/Linux/BETA/NYS/etc     *conf

For compilation of the nsl library, please follow the instructions which come with the software. If you wish to compile the shared DLL library you must have the DLL tools installed in the standard place (/usr/dll). The DLL tools (the package tools-2.11.tar.gz or later) can be obtained from many sites.

6.3 Setting up a NYS Client using NYS

Unlike traditional NIS, there is no setting up required for a NIS client. All that is required is that the NIS configuration file (/etc/yp.conf) points to the correct server(s) for its information. Also, the Name Services Switch configuration file (/etc/nsswitch.conf) must be correctly set up.

Please refer to the examples provided with the source code.

6.4 The nsswitch.conf File

The Network Services switch file /etc/nsswitch.conf determines the order of lookups performed when a certain piece of information is requested, just like the /etc/host.conf file which determines the way host lookups are performed. Again, look at at the example file provided in the source distribution. For example, the line


    hosts: files nis dns

specifies that host lookup functions should first look in the local /etc/hosts file, followed by a NIS lookup and finally thru the domain name service (/etc/resolv.conf and named), at which point if no match is found an error is returned.

6.5 Making your binaries NYS aware

Instead of relinking each binary with the NYS library (libnsl.so), a cleaner solution has been achieved by providing the user with the ability to build a NYS aware libc. This means all you need to do is recompile a new libc and replace your existing /lib/libc.so.x.y.z for all (non-static compiled) programs to be NYS aware.

This merge also gives you the advantage over the traditional NIS implementation in the linux libc in that it allows transparent shadow passwords support (via the /etc/nisswitch.conf file).

Follow the simple steps below to rebuild a NYS aware libc.

Make sure you have the latest DLL tools installed. Refer to the the GCC-FAQ for more info on where to get this.
Get the latest libc sources. (again see GCC-FAQ)
Get the latest nys sources from
ftp.lysator.liu.se:/pub/NYS/libs
and extract it under this libc-linux source directory. The current NYS distribution is "nys-0.27.4.tar.gz".
Do the ./configure as before and first answer "n" to the question
Values correct (y/n) [y] ?
Then go thru all the other questions and the last question will now be
Build a NYS libc from nys-0.27 (y default) ?
answer "y" to this.
Then issue the command
% make

The library generated after compilation is named something like


    libc.so.4.5.26

and placed under the directory jump/libc-nys. To install this library our advise would be copying it to /lib with a name lexiographically greater than the version number it currently has. Just appending the letter "a" should do the trick. For example:


    % cp jump/libc-nys/libc.so.4.5.26 /lib/libc.so.4.5.26a

Alternatively, append "nys" to it so you can quickly identify it. Now run the command


    % ldconfig

which will reset your cache to use the new library. The dynamic linker strategy may be examined with the command "ldconfig -p".

That's basically it. All your programs should now be NYS aware. Please note that usually the program "login" is compiled static and thus cannot access the new NYS functions from the NYS aware libc. You must either recompile "login" without the -static flag, or else statically link it to the libnsl.a library.