  The Linux NIS(YP)/NYS/NIS+ HOWTO
  Thorsten Kukuk
  v1.0, 9 March 1999

  This document describes how to configure Linux as NIS(YP) or NIS+
  client and how to install as NIS server.
  ______________________________________________________________________

  Table of Contents



  1. Introduction

     1.1 New Versions of this Document
     1.2 Disclaimer
     1.3 Feedback and Corrections
     1.4 Acknowledgements

  2. Glossary and General Information

     2.1 Glossary of Terms
     2.2 Some General Information

  3. NIS, NYS or NIS+ ?

     3.1 libc 4/5 with traditional NIS or NYS ?
     3.2 glibc 2 and NIS/NIS+
     3.3 NIS or NIS+ ?

  4. How it works

     4.1 How NIS works
     4.2 How NIS+ works

  5. The RPC Portmapper

  6. What do you need to set up NIS?

     6.1 Determine whether you are a Server, Slave or Client.
     6.2 The Software
     6.3 The ypbind daemon
     6.4 Setting up a NIS Client using Traditional NIS
     6.5 Setting up a NIS Client using NYS
     6.6 Setting up a NIS Client using glibc 2.x
     6.7 The nsswitch.conf File
     6.8 Shadow Passwords with NIS
        6.8.1 Linux
        6.8.2 Solaris
        6.8.3 PAM

  7. What do you need to set up NIS+ ?

     7.1 The Software
     7.2 Setting up a NIS+ client
     7.3 NIS+, keylogin, login and PAM
     7.4 The nsswitch.conf File

  8. Setting up a NIS Server

     8.1 The Server Program ypserv
     8.2 The Server Program yps
     8.3 The Program rpc.ypxfrd
     8.4 The Program rpc.yppasswdd

  9. Verifying the NIS/NYS Installation

  10. Common Problems and Troubleshooting NIS

  11. Frequently Asked Questions



  ______________________________________________________________________



  1.  Introduction

  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. Linux machines can also act as full NIS+
  clients, this support is in beta stage.

  This document tries to answer questions about setting up NIS(YP) and
  NIS+ on your Linux machine. Don't forget to read the section ``The RPC
  Portmapper''.

  The NIS-Howto is edited and maintained by



               Thorsten Kukuk, <kukuk@suse.de>



  The primary source of the information for the initial NIS-Howto was
  from:



       Andrea Dell'Amico       <adellam@ZIA.ms.it>
       Mitchum DSouza          <Mitch.DSouza@NetComm.IE>
       Erwin Embsen            <erwin@nioz.nl>
       Peter Eriksson          <peter@ifm.liu.se>



  who we should thank for writing the first versions of this document.


  1.1.  New Versions of this Document

  You can always view the latest version of this document on the World
  Wide Web via the URL http://www.suse.de/~kukuk/linux/HOWTO/NIS-
  HOWTO.html <http://www.suse.de/~kukuk/linux/HOWTO/NIS-HOWTO.html>.

  New versions of this document will also be uploaded to various Linux
  WWW and FTP sites, including the LDP home page.

  Links to translations of this document could be found at
  http://www.suse.de/~kukuk/linux/nis-howto.html
  <http://www.suse.de/~kukuk/linux/nis-howto.html>.

  1.2.  Disclaimer

  Although this document has been put together to the best of my
  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. I will attempt to keep this document as error free as
  possible.


  1.3.  Feedback and Corrections

  If you have questions or comments about this document, please feel
  free to mail Thorsten Kukuk, at kukuk@suse.de. I welcome any
  suggestions or criticisms. If you find a mistake with this document,
  please let me know so I can correct it in the next version. Thanks.

  Please do not mail me questions about special problems with your Linux
  Distribution! I don't know every Linux Distribution. But I will try to
  add every solution you send me.


  1.4.  Acknowledgements

  We would like to thank all the people who have contributed (directly
  or indirectly) to this document. In alphabetical order:



       Byron A Jeff            <byron@cc.gatech.edu>
       Markus Rex              <msrex@suse.de>
       Miquel van Smoorenburg  <miquels@cistron.nl>



  Theo de Raadt is responsible for the original yp-clients code.  Swen
  Thuemmler ported the yp-clients code to Linux and also ported the yp-
  routines in libc (again based on Theo's work).  Thorsten Kukuk has
  written the NIS(YP) and NIS+ routines for GNU libc 2.x from scratch.


  2.  Glossary and General Information

  2.1.  Glossary of Terms

  In this document a lot of acronyms are used. Here are the most
  important acronyms and a brief explanation:


     DBM
        DataBase Management, a library of functions which maintain key-
        content pairs in a data base.


     DLL
        Dynamically Linked Library, a library linked to an executable
        program at run-time.


     domainname
        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).


     FTP
        File Transfer Protocol, a protocol used to transfer files
        between two computers.


     libnsl
        Name services library, a library of name service calls
        (getpwnam, getservbyname, etc...) on SVR4 Unixes. GNU libc uses
        this for the NIS (YP) and NIS+ functions.


     libsocket
        Socket services library, a library for the socket service calls
        (socket, bind, listen, etc...) on SVR4 Unixes.
     NIS
        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".


     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
        _large_ installations.


     NYS
        This is the name of a project and stands for NIS+, YP and Switch
        and is managed by Peter Eriksson <peter@ifm.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.


     NSS
        Name Service Switch. The /etc/nsswitch.conf file determines the
        order of lookups performed when a certain piece of information
        is requested.


     RPC
        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 Sun RPC variant.


     YP Yellow Pages(tm), a registered trademark in the UK of British
        Telecom plc.


     TCP-IP
        Transmission Control Protocol/Internet Protocol. It is the data
        communication protocol most often used on Unix machines.



  2.2.  Some General Information

  The next four lines are quoted from the Sun(tm) System & Network
  Administration Manual:



           "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. Its 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
  is:


  o  login names/passwords/home directories (/etc/passwd)

  o  group information (/etc/group)

  If, for example, your password entry is recorded in the NIS passwd
  database, you will be able to login on all machines on the network
  which have the NIS client programs running.

  Sun is a trademark of Sun Microsystems, Inc. licensed to SunSoft, Inc.



  3.  NIS, NYS or NIS+ ?

  3.1.  libc 4/5 with traditional NIS or NYS ?

  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 adventure.

  The "traditional NIS" code is in the standard C library and has been
  around longer and sometimes suffers from its age and slight
  inflexibility.

  The NIS code in the NYS library requires you to recompile the libc
  library to include the NYS code into it (or maybe you can 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. On the other hand the
  NYS code allows you to handle Shadow Passwords in a transparent way.
  The "traditonal NIS" code doesn't support Shadow Passwords over NIS.


  3.2.  glibc 2 and NIS/NIS+

  Forgot all this if you use the new GNU C Library 2.x (aka libc6). It
  has real NSS (name switch service) support, which makes it very
  flexible, and contains support for the following NIS/NIS+ maps:
  aliases, ethers, group, hosts, netgroups, networks, protocols,
  publickey, passwd, rpc, services and shadow. The GNU C Library has no
  problems with shadow passwords over NIS.


  3.3.  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 - you need
  the latest glibc 2.1.  There is an unsupported port of the glibc NIS+
  support for libc5 as dropin replacement.



  4.  How it works

  4.1.  How NIS 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 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 of
  them...
  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 faster.

  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 ("makedbm", included with the server software). The master
  NIS server should have both, the ASCII databases and the DBM
  databases.

  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 do not
  need to do this since they always talk to the NIS server to read the
  information stored in it's DBM databases.

  Old ypbind versions do a broadcast to find a running NIS server.  This
  is insecure, due the fact that anyone may install a NIS server and
  answer the broadcast queries. Newer Versions of ypbind (ypbind-3.3 or
  ypbind-mt) are able to get the server from a configuration file - thus
  no need to broadcast.


  4.2.  How NIS+ works

  NIS+ is a new version of the network information nameservice from Sun.
  The biggest difference between NIS and NIS+ is that NIS+ has support
  for data encryption and authentication over secure RPC.

  The  naming  model of NIS+ is based upon a tree structure. Each node
  in the tree corresponds to an NIS+ object, from which we have six
  types: directory, entry, group, link, table and private.

  The NIS+ directory that forms the root of the NIS+ namespace is called
  the root directory. There are two special NIS+ directories: org_dir
  and groups_dir. The org_dir directory consists of all administration
  tables, such as passwd, hosts, and mail_aliases. The groups_dir
  directory consists of NIS+ group objects which are used for access
  control. The collection of org_dir, groups_dir and their parent
  directory is referred to as an NIS+ domain.


  5.  The RPC Portmapper

  To run any of the software mentioned below you will need to run the
  program /usr/sbin/portmap. Some Linux distributions already have the
  code in the /sbin/init.d/ or /etc/rc.d/ files to start up this daemon.
  All you have to do is to activate it and reboot your Linux machine.
  Read your Linux Distribution Documentation how to do this.

  The RPC portmapper (portmap(8)) 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/NIS+ client
  software does) to RPC servers (like a NIS or 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 RPC call to a
  given program number, it will first contact portmap on the server
  machine to determine the port number where RPC packets should be sent.


  Normally, standard RPC servers are started by inetd(8), so portmap
  must be running before inetd is started.

  For secure RPC, the portmapper needs the Time service. Make sure, that
  the Time service is enabled in /etc/inetd.conf on all hosts:


       #
       # Time service is used for clock syncronization.
       #
       time    stream  tcp     nowait  root    internal
       time    dgram   udp     wait    root    internal



  IMPORTANT: Don't forget to restart inetd after changes on its
  configuration file !



  6.  What do you need to set up NIS?

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

  To answer this question you have to consider two cases:


  1. Your machine is going to be part of a network with existing NIS
     servers

  2. You do not have any NIS servers in the network yet

  In the first case, you only need the client programs (ypbind, ypwhich,
  ypcat, yppoll, ypmatch). The most important program is ypbind. This
  program must be running at all times, which means, it should always
  appear in the list of processes. It is a daemon process and needs to
  be started from the system's startup file (eg. /etc/init.d/nis,
  /sbin/init.d/ypclient, /etc/rc.d/init.d/ypbind, /etc/rc.local).  As
  soon as ypbind is running your system has become a NIS client.

  In the second case, if you don't have NIS servers, then you will also
  need a NIS server program (usually called ypserv). Section ``Setting
  up a NIS Server''  describes how to set up a NIS server on your Linux
  machine using the "ypserv" implementation by Peter Eriksson and
  Thorsten Kukuk.  Note that from version 0.14 this implementation
  supports the master-slave concept talked about in section 4.1.

  There is also another free NIS server available, called "yps", written
  by Tobias Reber in Germany which does support the master-slave
  concept, but has other limitations and isn't supported since a long
  time.



  6.2.  The Software

  The system library "/usr/lib/libc.a" (version 4.4.2 and better) or the
  shared library "/lib/libc.so.x" contain all necessary system calls to
  succesfully compile the NIS client and server software. For the GNU C
  Library 2 (glibc 2.x), you also need /lib/libnsl.so.1.

  Some people reported that NIS only works with "/usr/lib/libc.a"
  version 4.5.21 and better so if you want to play it safe don't use
  older libc's.  The NIS client software can be obtained from:

         Site                  Directory                        File Name

         ftp.kernel.org        /pub/linux/utils/net/NIS         yp-tools-2.2.tar.gz
         ftp.kernel.org        /pub/linux/utils/net/NIS         ypbind-mt-1.4.tar.gz
         ftp.kernel.org        /pub/linux/utils/net/NIS         ypbind-3.3.tar.gz
         ftp.kernel.org        /pub/linux/utils/net/NIS         ypbind-3.3-glibc5.diff.gz
         ftp.uni-paderborn.de  /linux/local/yp                  yp-clients-2.2.tar.gz



  Once you obtained the software, please follow the instructions which
  come with the software. yp-clients 2.2 are for use with libc4 and
  libc5 until 5.4.20. libc 5.4.21 and glibc 2.x needs yp-tools 1.4.1 or
  later.  The new yp-tools 2.2 should work with every Linux libc. Since
  there was a bug in the NIS code, you shouldn't use libc 5.4.21-5.4.35.
  Use libc 5.4.36 or later instead, or the most YP programs will not
  work.  ypbind 3.3 will work with all libraries, too. If you use gcc
  2.8.x or greater, egcs or glibc 2.x, you should add the
  ypbind-3.3-glibc5.diff patch to ypbind 3.3. Please never use the
  ypbind from yp-clients 2.2.  ypbind-mt is a new, multithreaded daemon.
  It needs a Linux 2.2 kernel, and glibc 2.1 or later.


  6.3.  The ypbind daemon

  After you have succesfully compiled the software you are now ready to
  install it. A suitable place for the ypbind daemon is the directory
  /usr/sbin. Some people may tell you that you don't need ypbind on a
  system with NYS. This is wrong. ypwhich and ypcat need it always.

  You must do this as root of course. The other binaries (ypwhich,
  ypcat, yppasswd, yppoll, ypmatch) should go in a directory accessible
  by all users, normally /usr/bin.

  Newer ypbind versions have a configuration file called /etc/yp.conf.
  You can hardcode a NIS server there - for more info see the manual
  page for ypbind(8).  You also need this file for NYS.  An example:


         ypserver voyager
         ypserver defiant
         ypserver ds9



  If the system cam resolv the hostnames without NIS, you may use the
  name, otherwise you have to use the IP address. ypbind 3.3 has a bug
  and will only use the last entry (ypserver ds9 in the example). All
  other entries are ignored. ypbind-mt handle this correct and uses that
  one, which answerd at first.

  It might be a good idea to test ypbind before  incorporating it in the
  startup files. To test ypbind do the following:


  o  Make sure you have your YP-domain name set. If it is not set then
     issue the command:



                   /bin/domainname nis.domain



  where nis.domain should be some string _NOT_ normally associated with
  the DNS-domain name of your machine! The reason for this is that it
  makes it a little harder for external crackers to retreive the pass-
  word database from your NIS servers. If you don't know what the NIS
  domain name is on your network, ask your system/network administrator.

  o  Start up "/usr/sbin/portmap" if it is not already running.

  o  Create the directory "/var/yp" if it does not exist.

  o  Start up "/usr/sbin/ypbind"

  o  Use the command "rpcinfo -p localhost" to check if ypbind was able
     to register its service with the portmapper. The output should look
     like:



              program vers proto   port
               100000    2   tcp    111  portmapper
               100000    2   udp    111  portmapper
               100007    2   udp    637  ypbind
               100007    2   tcp    639  ypbind



  or



              program vers proto   port
               100000    2   tcp    111  portmapper
               100000    2   udp    111  portmapper
               100007    2   udp    758  ypbind
               100007    1   udp    758  ypbind
               100007    2   tcp    761  ypbind
               100007    1   tcp    761  ypbind



  Depending on the ypbind version you are using.

  o  You may also run "rpcinfo -u localhost ypbind". This command should
     produce something like:



               program 100007 version 2 ready and waiting



  or



          program 100007 version 1 ready and waiting
          program 100007 version 2 ready and waiting



  The output depends on the ypbind version you have installed.  Impor-
  tant is only the "version 2" message.

  At this point you should be able to use NIS client programs like
  ypcat, etc...  For example, "ypcat passwd.byname" will give you the
  entire NIS password database.

  IMPORTANT: If you skipped the test procedure then make sure you have
  set the domain name, and created the directory



           /var/yp



  This directory MUST exist for ypbind to start up succesfully.

  To check if the domainname is set correct, use the /bin/ypdomainname
  from yp-tools 2.2. It uses the yp_get_default_domain() function which
  is more restrict. It doesn't allow for example the "(none)"
  domainname, which is the default under Linux and makes a lot of
  problems.

  If the test worked you may now want to change your startupd files so
  that ypbind will be started at boot time and your system will act as a
  NIS client. Make sure that the domainname will be set before you start
  ypbind.

  Well, that's it. Reboot the machine and watch the boot messages to see
  if ypbind is actually started.



  6.4.  Setting up a NIS Client using Traditional NIS

  For host lookups you must set (or add) "nis" to the lookup order line
  in your /etc/host.conf file. Please read the manpage "resolv+.8" for
  more details.

  Add the following line to /etc/passwd on your NIS clients:



       +::::::



  You can also use the + and - characters to include/exclude or change
  users. If you want to exclude the user guest just add -guest to your
  /etc/passwd file.  You want to use a different shell (e.g. ksh) for
  the user "linux"?  No problem, just add "+linux::::::/bin/ksh"
  (without the quotes) to your /etc/passwd. Fields that you don't want
  to change have to be left empty. You could also use Netgroups for user
  control.

  For example, to allow login-access only to miquels, dth and ed, and
  all members of the sysadmin netgroup, but to have the account data of
  all other users available use:



             +miquels:::::::
             +ed:::::::
             +dth:::::::
             +@sysadmins:::::::
             -ftp
             +:*::::::/etc/NoShell



  Note that in Linux you can also override the password field, as we did
  in this example. We also remove the login "ftp", so it isn't known any
  longer, and anonymous ftp will not work.

  The netgroup would look like


       sysadmins (-,software,) (-,kukuk,)



  IMPORTANT: The netgroup  feature is implemented starting from libc
  4.5.26.  If you have a version of libc earlier than 4.5.26, every user
  in the NIS password database can access your linux machine if you run
  "ypbind" !



  6.5.  Setting up a NIS Client using NYS

  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.

  You should install ypbind. It isn't needed by the libc, but the
  NIS(YP) tools need it.

  If you wish to use the include/exclude user feature
  (+/-guest/+@admins), you have to use "passwd: compat" and "group:
  compat" in nsswitch.conf.  Note that there is no "shadow: compat"! You
  have to use "shadow: files nis" in this case.

  The NYS sources are part of the libc 5 sources. When run configure,
  say the first time "NO" to the "Values correct" question, then say
  "YES" to "Build a NYS libc from nys".


  6.6.  Setting up a NIS Client using glibc 2.x

  The glibc uses "traditional NIS", so you need to start ypbind. The
  Name Services Switch configuration file (/etc/nsswitch.conf) must be
  correctly set up. If you use the compat mode for passwd, shadow or
  group, you have to add the "+" at the end of this files and you can
  use the include/exclude user feature. The configuration is excatly the
  same as under Solaris 2.x.



  6.7.  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. 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 through the
  domain name service (/etc/resolv.conf and named), at which point if no
  match is found an error is returned. This file must be readable for
  every user! You can find more information in the man-page nsswitch.5
  or nsswitch.conf.5.

  A good /etc/nsswitch.conf file for NIS is:



  #
  # /etc/nsswitch.conf
  #
  # An example Name Service Switch config file. This file should be
  # sorted with the most-used services at the beginning.
  #
  # The entry '[NOTFOUND=return]' means that the search for an
  # entry should stop if the search in the previous entry turned
  # up nothing. Note that if the search failed due to some other reason
  # (like no NIS server responding) then the search continues with the
  # next entry.
  #
  # Legal entries are:
  #
  #       nisplus                 Use NIS+ (NIS version 3)
  #       nis                     Use NIS (NIS version 2), also called YP
  #       dns                     Use DNS (Domain Name Service)
  #       files                   Use the local files
  #       db                      Use the /var/db databases
  #       [NOTFOUND=return]       Stop searching if not found so far
  #

  passwd:     compat
  group:      compat
  # For libc5, you must use shadow: files nis
  shadow:     compat

  passwd_compat: nis
  group_compat: nis
  shadow_compat: nis

  hosts:      nis files dns

  services:   nis [NOTFOUND=return] files
  networks:   nis [NOTFOUND=return] files
  protocols:  nis [NOTFOUND=return] files
  rpc:        nis [NOTFOUND=return] files
  ethers:     nis [NOTFOUND=return] files
  netmasks:   nis [NOTFOUND=return] files
  netgroup:   nis
  bootparams: nis [NOTFOUND=return] files
  publickey:  nis [NOTFOUND=return] files
  automount:  files
  aliases:    nis [NOTFOUND=return] files



  passwd_compat, group_compat and shadow_compat are only supported by
  glibc 2.x.  If there are no shadow rules in /etc/nsswitch.conf, glibc
  will use the passwd rule for lookups. There are some more lookup
  module for glibc like hesoid.  For more information, read the glibc
  documentation.


  6.8.  Shadow Passwords with NIS

  Shadow passwords over NIS are always a bad idea. You loose the
  security, which shadow gives you, and it is supported by only some few
  Linux C Libraries. A good way to avoid shadow passwords over NIS is,
  to put only the local system users in /etc/shadow. Remove the NIS user
  entries from the shadow database, and put the password back in passwd.
  So you can use shadow for the root login, and normal passwd for NIS
  user. This has the advantage that it will work with every NIS client.


  6.8.1.  Linux

  The only Linux libc which supports shadow passwords over NIS, is the
  GNU C Library 2.x. Linux libc5 has no support for it. Linux libc5
  compiled with NYS enabled has some code for it. But this code is badly
  broken in some cases and doesn't work with all correct shadow entries.


  6.8.2.  Solaris

  Solaris does not support shadow passwords over NIS.


  6.8.3.  PAM

  PAM does not support Shadow passwords over NIS, especially
  pam_pwdb/libpwdb. This is a big problem for RedHat 5.x users. If you
  have glibc and PAM, you need to change the /etc/pam.d/* entries.
  Replace all pam_pwdb rules through pam_unix_* modules. Due a bug in
  the pam_unix_auth.so module this will not always work.

  An example /etc/pam.d/login file looks like:



       #%PAM-1.0
       auth       required     /lib/security/pam_securetty.so
       auth       required     /lib/security/pam_unix_auth.so
       auth       required     /lib/security/pam_nologin.so
       account    required     /lib/security/pam_unix_acct.so
       password   required     /lib/security/pam_unix_passwd.so
       session    required     /lib/security/pam_unix_session.so



  For auth you need to use the pam_unix_auth.so module, for account the
  pam_unix_acct.so, for password the pam_unix_passwd.so and for session
  the pam_unix_session.so module.


  7.  What do you need to set up NIS+ ?

  7.1.  The Software

  The Linux NIS+ client code was developed for the GNU C library 2.
  There is also a port for Linux libc5, since most commercial
  Applications are linked against this library, and you cannot recompile
  them for using glibc. There are problems with libc5 and NIS+: static
  programs cannot be linked with it, and programs compiled with this
  library will not work with other libc5 versions.


  You need to retrieve and compile the GNU C Library 2.1 for Intel based
  platforms, or GNU C Library 2.1.1 for 64bit platforms.  As base System
  you need a glibc based Distribution like Debian 2.x, RedHat 5.x or
  SuSE Linux 6.x.

  For every distribution, you need to recompile the gcc/g++ compiler,
  libstdc++ and ncures. For Redhat, you need to make a lot of changes of
  the PAM configuration. For SuSE Linux 6.0, you need to recompile the
  shadow package.

  The NIS+ client software can be obtained from:


    Site             Directory                     File Name

    ftp.funet.fi     /pub/gnu/funet                libc-*, glibc-crypt-*,
                                                   glibc-linuxthreads-*
    ftp.kernel.org   /pub/linux/utils/net/NIS+     nis-utils-19990223.tar.gz
    ftp.kernel.org   /pub/linux/utils/net/NIS+     pam_keylogin-1.2.tar.gz



  Distributions based on glibc can be fetched from:


         Site                   Directory

         ftp.debian.org         /pub/debian/dists/slink
         ftp.redhat.com         /pub/redhat/redhat-5.2
         ftp.suse.de            /pub/SuSE-Linux/6.0



  For compilation of the GNU C Library please follow the instructions
  which come with the software. You cam find the patched libc5, based on
  NYS, and the sources as drop in replacement for the standart libc5 at:



         Site               Directory                  File Name

         ftp.kernel.org     /pub/linux/utils/net/NIS+  libc-5.4.44-nsl-0.4.10.tar.gz



  You should also have a look at
  http://www.suse.de/~kukuk/linux/nisplus.html
  <http://www.suse.de/~kukuk/linux/nisplus.html> for more information
  and the latest sources.


  7.2.  Setting up a NIS+ client

  IMPORTANT: For setting up a NIS+ client read your Solaris NIS+ docs
  what to do on the server side! This document only describes what to do
  on the client side!

  After installing the new libc and nis-tools, create the credentials
  for the new client on the NIS+ server. Make sure portmap is running.
  Then check if your Linux PC has the same time as the NIS+ Server. For
  secure RPC, you have only a small window from about 3 minutes, in
  which the credentials are valid. A good idea is to run xntpd on every
  host. After this, run



       domainname nisplus.domain.
       nisinit -c -H <NIS+ server>



  to initialize the cold start file. Read the nisinit man page for more
  options. Make sure that the domainname will always be set after a
  reboot.  If you don't know what the NIS+ domain name is on your
  network, ask your system/network administrator.
  Now you should change your /etc/nsswitch.conf file. Make sure that the
  only service after publickey is nisplus ("publickey: nisplus"), and
  nothing else!

  Then start keyserv and make sure, that it will always be started as
  first daemon after portmap at boot time. Run


       keylogin -r



  to store the root secretkey on your system. (I hope you have added the
  publickey for the new host on the NIS+ Server?).

  "niscat passwd.org_dir" should now show you all entries in the passwd
  database.



  7.3.  NIS+, keylogin, login and PAM

  When the user logs in, he need to set his secretkey to keyserv. This
  is done by calling "keylogin". The login from the shadow package will
  do this for the user, if it was compiled against glibc 2.1. For a PAM
  aware login, you have to install pam_keylogin-1.2.tar.gz and change
  the /etc/pam.d/login file to use pam_unix_auth, not pwdb, which
  doesn't support NIS+. An example:



       #%PAM-1.0
       auth       required     /lib/security/pam_securetty.so
       auth       required     /lib/security/pam_keylogin.so
       auth       required     /lib/security/pam_unix_auth.so
       auth       required     /lib/security/pam_nologin.so
       account    required     /lib/security/pam_unix_acct.so
       password   required     /lib/security/pam_unix_passwd.so
       session    required     /lib/security/pam_unix_session.so



  7.4.  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. For example, the line



           hosts: files nisplus dns



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


  A good /etc/nsswitch.conf file for NIS+ is:


       #
       # /etc/nsswitch.conf
       #
       # An example Name Service Switch config file. This file should be
       # sorted with the most-used services at the beginning.
       #
       # The entry '[NOTFOUND=return]' means that the search for an
       # entry should stop if the search in the previous entry turned
       # up nothing. Note that if the search failed due to some other reason
       # (like no NIS server responding) then the search continues with the
       # next entry.
       #
       # Legal entries are:
       #
       #       nisplus                 Use NIS+ (NIS version 3)
       #       nis                     Use NIS (NIS version 2), also called YP
       #       dns                     Use DNS (Domain Name Service)
       #       files                   Use the local files
       #       db                      Use the /var/db databases
       #       [NOTFOUND=return]       Stop searching if not found so far
       #

       passwd:     compat
       # for libc5: passwd: files nisplus
       group:      compat
       # for libc5: group: files nisplus
       shadow:     compat
       # for libc5: shadow: files nisplus

       passwd_compat: nisplus
       group_compat:  nisplus
       shadow_compat: nisplus

       hosts:      nisplus files dns

       services:   nisplus [NOTFOUND=return] files
       networks:   nisplus [NOTFOUND=return] files
       protocols:  nisplus [NOTFOUND=return] files
       rpc:        nisplus [NOTFOUND=return] files
       ethers:     nisplus [NOTFOUND=return] files
       netmasks:   nisplus [NOTFOUND=return] files
       netgroup:   nisplus
       bootparams: nisplus [NOTFOUND=return] files
       publickey:  nisplus
       automount:  files
       aliases:    nisplus [NOTFOUND=return] files



  8.  Setting up a NIS Server

  8.1.  The Server Program ypserv

  This document only describes how to set up the "ypserv" NIS server.

  The NIS server software can be found on:


         Site               Directory                    File Name

         ftp.kernel.org     /pub/linux/utils/net/NIS     ypserv-1.3.6.tar.gz



  You could also look at http://www.suse.de/~kukuk/linux/nis.html
  <http://www.suse.de/~kukuk/linux/nis.html> for more information.

  The server setup is the same for both traditional NIS and NYS.

  Compile the software to generate the ypserv and makedbm programs. You
  can configure ypserv to use the securenets file or the tcp_wrappers.
  The tcp_wrapper is much more flexible, but a lot of people have big
  problems with it. And some configuration files for tcp_wrappers may
  cause a memory leak. If you have problems with ypserv compiled for
  tcp_wrapper, recompile it using the securenets file.  ypserv --version
  tells you, which version you have.

  If you run your server as master, determine what files you require to
  be available via NIS and then add or remove the appropriate entries to
  the "all" rule in /var/yp/Makefile. You always should look at the
  Makefile and edit the Options at the beginning of the file.

  There was one big change between ypserv 1.1 and ypserv 1.2. Since
  version 1.2, the file handles are cached. This means you have to call
  makedbm always with the -c option if you create new maps. Make sure,
  you are using the new /var/yp/Makefile from ypserv 1.2 or later, or
  add the -c flag to makedbm in the Makefile. If you don't do that,
  ypserv will continue to use the old maps, and not the updated one.

  Now edit /var/yp/securenets and /etc/ypserv.conf.  For more
  information, read the ypserv(8) and ypserv.conf(5) manual pages.

  Make sure the portmapper (portmap(8)) is running, and start the server
  ypserv. The command



           % rpcinfo -u localhost ypserv



  should output something like



           program 100004 version 1 ready and waiting
           program 100004 version 2 ready and waiting



  The "version 1" line could be missing, depending on the ypserv version
  and configuration you are using. It is only necessary if you have old
  SunOS 4.x clients.

  Now generate the NIS (YP) database. On the master, run



           % /usr/lib/yp/ypinit -m


  On a slave make sure that ypwhich -m works. This means, that your
  slave must be configured as NIS client before you could run


           % /usr/lib/yp/ypinit -s masterhost



  to install the host as NIS slave.


  That's it, your server is up and running.

  If you have bigger problems, you could start ypserv and ypbind in
  debug mode on different xterms. The debug output should show you what
  goes wrong.

  If you need to update a map, run make in the /var/yp directory on the
  NIS master. This will update a map if the source file is newer, and
  push the files to the slave servers. Please don't use ypinit for
  updating a map.

  You might want to edit root's crontab *on the slave* server and add
  the following lines:



             20 *    * * *    /usr/lib/yp/ypxfr_1perhour
             40 6    * * *    /usr/lib/yp/ypxfr_1perday
             55 6,18 * * *    /usr/lib/yp/ypxfr_2perday



  This will ensure that most NIS maps are kept up-to-date, even if an
  update is missed because the slave was down at the time the update was
  done on the master.

  You can add a slave at every time later. At first, make sure that the
  new slave server has permissions to contact the NIS master. Then run


           % /usr/lib/yp/ypinit -s masterhost



  on the new slave. On the master server, add the new slave server name
  to /var/yp/ypservers and run make in /var/yp to update the map.


  If you want to restrict access for users to your NIS server, you'll
  have to setup the NIS server as a client as well by running ypbind and
  adding the plus-entries to /etc/passwd _halfway_ the password file.
  The library functions will ignore all normal entries after the first
  NIS entry, and will get the rest of the info through NIS. This way the
  NIS access rules are maintained. An example:



       root:x:0:0:root:/root:/bin/bash
       daemon:*:1:1:daemon:/usr/sbin:
       bin:*:2:2:bin:/bin:
       sys:*:3:3:sys:/dev:
       sync:*:4:100:sync:/bin:/bin/sync
       games:*:5:100:games:/usr/games:
       man:*:6:100:man:/var/catman:
       lp:*:7:7:lp:/var/spool/lpd:
       mail:*:8:8:mail:/var/spool/mail:
       news:*:9:9:news:/var/spool/news:
       uucp:*:10:50:uucp:/var/spool/uucp:
       nobody:*:65534:65534:noone at all,,,,:/dev/null:
       +miquels::::::
       +:*:::::/etc/NoShell
       [ All normal users AFTER this line! ]
       tester:*:299:10:Just a test account:/tmp:
       miquels:1234567890123:101:10:Miquel van Smoorenburg:/home/miquels:/bin/zsh



  Thus the user "tester" will exist, but have a shell of /etc/NoShell.
  miquels will have normal access.

  Alternatively, you could edit the /var/yp/Makefile file and set NIS to
  use another source password file. On large systems the NIS password
  and group files are usually stored in /etc/yp/. If you do this the
  normal tools to administrate the password file such as passwd, chfn,
  adduser will not work anymore and you need special homemade tools for
  this.

  However, yppasswd, ypchsh and ypchfn will work of course.


  8.2.  The Server Program yps

  To set up the "yps" NIS server please refer to the previous paragraph.
  The "yps" server setup is similar, _but_ not exactly the same so
  beware if you try to apply the "ypserv" instructions to "yps"!  "yps"
  is not supported by any author, and contains some security leaks.  You
  really shouldn't use it !

  The "yps" NIS server software can be found on:



         Site                  Directory                   File Name

         ftp.lysator.liu.se    /pub/NYS/servers            yps-0.21.tar.gz
         ftp.kernel.org        /pub/linux/utils/net/NIS    yps-0.21.tar.gz



  8.3.  The Program rpc.ypxfrd

  rpc.ypxfrd is used for speed up the transfer of very large NIS  maps
  from a NIS master to NIS slave servers. If a NIS slave server receives
  a message that there is  a  new map,  it  will  start  ypxfr  for
  transfering the new map.  ypxfr will read the contents of  a  map
  from  the  master server  using the yp_all() function. This process
  can take several minutes when there are very large maps which  have to
  store by the database library.


  The  rpc.ypxfrd  server  speeds up the transfer process by allowing
  NIS slave  servers  to  simply  copy  the  master server's  map  files
  rather  than building their own from scratch.  rpc.ypxfrd uses an RPC-
  based file transfer  protocol, so that there is no need for building a
  new map.


  rpc.ypxfrd can be started by inetd. But since it starts very slow, it
  should be started with ypserv. You need to start rpc.ypxfrd only on
  the NIS master server.


  8.4.  The Program rpc.yppasswdd

  Whenever users change their passwords, the NIS password database and
  probably other NIS databases, which depend on the NIS password
  database, should be updated.  The program "rpc.yppasswdd" is a server
  that handles password changes and makes sure that the NIS information
  will be updated accordingly. rpc.yppasswdd is now integrated in
  ypserv. You don't need the older, separate yppasswd-0.9.tar.gz or
  yppasswd-0.10.tar.gz, and you shouldn't use them any longer. The
  rpc.yppasswdd in ypserv 1.3.2 has full shadow support. yppasswd is now
  part of yp-tools-2.2.tar.gz.

  You need to start rpc.yppasswdd only on the NIS master server. By
  default, users are not allowed to change their full name or the login
  shell.  You can allow this with the -e chfn or -e chsh option.

  If your passwd and shadow files are not in another directory then
  /etc, you need to add the -D option. For example, if you have put all
  source files in /etc/yp and wish to allow the user to change his
  shell, you need to start rpc.yppasswdd with the following parameters:



          rpc.yppasswdd -D /etc/yp -e chsh



  or



          rpc.yppasswdd -s /etc/yp/shadow -p /etc/yp/passwd -e chsh



  There is nothing more to do. You just need to make sure, that
  rpc.yppasswdd uses the same files as /var/yp/Makefile.  Errors will be
  logged using syslog.


  9.  Verifying the NIS/NYS Installation

  If everything is fine (as it should be), you should be able to verify
  your installation with a few simple commands. Assuming, for example,
  your passwd file is being supplied by NIS, the command



           % ypcat passwd



  should give you the contents of your NIS passwd file. The command



           % ypmatch userid passwd



  (where userid is the login name of an arbitrary user) should give you
  the user's entry in the NIS passwd file. The "ypcat" and "ypmatch"
  programs should be included with your distribution of traditional NIS
  or NYS.

  If a user cannot log in, run the following program on the client:


       #include <stdio.h>
       #include <pwd.h>
       #include <sys/types.h>

       int
       main(int argc, char *argv[])
       {
         struct passwd *pwd;

         if(argc != 2)
           {
             fprintf(stderr,"Usage: getwpnam username\n");
             exit(1);
           }

         pwd=getpwnam(argv[1]);

         if(pwd != NULL)
           {
             printf("name.....: [%s]\n",pwd->pw_name);
             printf("password.: [%s]\n",pwd->pw_passwd);
             printf("user id..: [%d]\n", pwd->pw_uid);
             printf("group id.: [%d]\n",pwd->pw_gid);
             printf("gecos....: [%s]\n",pwd->pw_gecos);
             printf("directory: [%s]\n",pwd->pw_dir);
             printf("shell....: [%s]\n",pwd->pw_shell);
           }
         else
           fprintf(stderr,"User \"%s\" not found!\n",argv[1]);

         exit(0);
       }



  Running this program with the username as parameter will print all the
  information the getpwnam function gives back for this user. This
  should show you which entry is incorrect. The most common problem is,
  that the password field is overwritten with a "*".

  GNU C Library 2.1 (glibc 2.1) comes with a tool called getent. Use
  this program instead the above on such a system. You could try:


          getent passwd



  or


          getent passwd login



  10.  Common Problems and Troubleshooting NIS

  Here are some common problems reported by various users:


  1. The libraries for 4.5.19 are broken. NIS won't work with it.

  2. If you upgrade the libraries from 4.5.19 to 4.5.24 then the su
     command breaks. You need to get the su command from the slackware
     1.2.0 distribution. Incidentally that's where you can get the
     updated libraries.

  3. When a NIS server goes down and comes up again ypbind starts
     complaining with messages like:


              yp_match: clnt_call:
                          RPC: Unable to receive; errno = Connection refused



  and logins are refused for those who are registered in the NIS
  database. Try to login as root and kill ypbind and start it up again.
  An update to ypbind 3.3 or higher should also help.

  4. After upgrading the libc to a version greater then 5.4.20, the YP
     tools will not work any longer. You need yp-tools 1.2 or later for
     libc >= 5.4.21 and glibc 2.x. For earlier libc version you need yp-
     clients 2.2. yp-tools 2.x should work for all libraries.

  5. In libc 5.4.21 - 5.4.35 yp_maplist is broken, you need 5.4.36 or
     later, or some YP programs like ypwhich will segfault.

  6. libc 5 with traditional NIS doesn't support shadow passwords over
     NIS.  You need libc5 + NYS or glibc 2.x.

  7. ypcat shadow doesn't show the shadow map. This is correct, the name
     of the shadow map is shadow.byname, not shadow.

  8. Solaris doesn't use always privileged ports. So don't use password
     mangling if you have a Solaris client.



  11.  Frequently Asked Questions

  Most of your questions should be answered by now. If there are still
  questions unanswered you might want to post a message to



           comp.os.linux.networking



