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Configuring NIS Services in Linux

What is NIS?

Network Information Service (NIS) is used for keeping a centralized repository of users, hostnames and other useful information in a computer network. In single server UNIX environments, the list of users and groups is usually kept in a file such as /etc/passwd. Using NIS adds a "global" directory which is used for authenticating users from any host on the network.

Note: In the early days, NIS was called Yellow Pages. The developers had to change the name after a copyright infringement lawsuit, yet many of the key programs associated with NIS have kept their original names beginning with yp.

Getting Started

This tutorial covers mostly RPM based distributions of GNU/Linux such as Red Hat, Fedora, or CentOS. There are also references to Debian based distrbutions such as Ubuntu. For information pertaining to your particular distrbution, please consult your documentation.

Defining the NIS Domain Name

Edit the /etc/sysconfig/network file

In Red Hat-based distributions need to add the NIS domain name we wish to use in the /etc/sysconfig/network file. For this example, we will call the domain "LINUX-NIS".


In Debian based distributions we would edit the /etc/defaultdomain file and simply put in the NIS domain name


Also, in Debian-based distributions, we would edit the /etc/default/nis file and configure this as a Master NIS server


Both Linux distributions have a configuration file for YP. We need to edit our /etc/yp.conf file. NIS servers also need to be NIS clients themselves, so we will have to edit the yp.conf to point this file towards the server itself, or localhost.

# /etc/yp.conf - ypbind configuration file

NIS Server Daemons

The following is a list of NIS server daemons and their functionality. We need to know these individual components in order to troubleshoot NIS issues later on.




The foundation service for RPC


Allows users to change their NIS passwords


NIS server daemon


NIS client daemon


The NIS map transfer daemon

Starting The NIS Server Related Daemons

We now need to start a couple of the NIS daemons in the /etc/init.d directory. In this case we will only be starting the portmapyppasswdd, and ypserv daemons so that we can initialize the NIS domain.

On Red Hat we would issue the following commands:

[root@nis-server1]# /etc/init.d/portmap start
Starting portmapper: [  OK  ]

[root@nis-server1]# /etc/init.d/yppasswdd start
Starting YP passwd service: [  OK  ]

[root@nis-server1]# /etc/init.d/ypserv start
Setting NIS domain name LINUX-NIS:  [  OK  ]
Starting YP server services: [  OK  ]

On Debian we would issue the following commands:

[root@nis-server1]# /etc/init.d/portmap start
Starting portmapper: [  OK  ]

[root@nis-server1]# /etc/init.d/nis start
Setting NIS domainname to: LINUX-NIS
Starting NIS services: ypserv yppasswdd ypxfrd ypbind:  [  OK  ]

Note: The ypxfrd and ypbind daemons start with the all-encompassing nis startup script for Debian. These daemons will time out on starting due to the fact that the NIS domain has not been initialized yet. This is expected. NFS domain initialization is covered in the next section.

With Redhat-based distributions we would use the chkconfig command to configure these daemons to start after every reboot.

[root@nis-server1]# chkconfig portmap on
[root@nis-server1]# chkconfig yppasswdd on
[root@nis-server1]# chkconfig ypserv on

With Debian-based distributions we would simply invoke the update-rc.d command to configure these services to start at boot time

[root@nis-server1]# update-rc.d portmap defaults  [  OK  ]
[root@nis-server1]# update-rc.d nis defaults      [  OK  ]

We need to make sure these daemons are running before continuing to the next step. We can use the rpcinfo command to do this:

[root@nis-server1]# rpcinfo -p localhost
program     vers proto  port
   100000    2   tcp    111  portmapper
   100000    2   udp    111  portmapper
   100009    1   udp    681  yppasswdd
   100004    2   udp    698  ypserv
   100004    1   udp    698  ypserv
   100004    2   tcp    701  ypserv
   100004    1   tcp    701  ypserv

The ypbind and ypxfrd might be listed as running, even though they do not start properly until after the initialization of the NIS domain. If they are running, we will restart these daemons after the domain initialization is completed.

Initializing The NIS Domain

Now that we have decided on the name of the NIS domain, we will have to use the ypinit command to create the associated authentication files for the domain. We will be prompted for the name of the NIS server, which in this case is nis-server.

[root@nis-server1]# /usr/lib/yp/ypinit -m 

At this point, we have to construct a list of the hosts which will run NIS servers. nis-server1 is in the list of NIS server hosts. We must continue to add the names for the other hosts, one per line. When we are done with the list, simply type "a".

next host to add:  nis-server1
next host to add:
The current list of NIS servers looks like this:
Is this correct?  [y/n: y]  y
We need a few minutes to build the databases...
Building /var/yp/LINUX-NIS/ypservers...
Running /var/yp/Makefile...
gmake[1]: Entering directory `/var/yp/LINUX-NIS'
Updating passwd.byname...
Updating passwd.byuid...
Updating group.byname...
Updating group.bygid...
Updating hosts.byname...
Updating hosts.byaddr...
Updating rpc.byname...
Updating rpc.bynumber...
Updating services.byname...
Updating services.byservicename...
Updating netid.byname...
Updating protocols.bynumber...
Updating protocols.byname...
Updating mail.aliases...
gmake[1]: Leaving directory `/var/yp/LINUX-NIS'
nis-server1 has been set up as a NIS master server.

Now we can run ypinit -s nis-server1 on all slave servers (If we have any slave servers).

Note: Make sure portmap is running before trying this step or you'll get errors, such as:

failed to send 'clear' to local ypserv: RPC: Port mapper failureUpdating group.bygid... 

You will have to delete the /var/yp/LINUX-NIS directory and restart portmap, yppasswd, and ypserv before you'll be able to do this again successfully.

Start The ypbind and ypxfrd Daemons

On Redhat, you can now start the ypbind and the ypxfrd daemons because the NIS domain had been initialized and the files have been created.

[root@nis-server1]# /etc/init.d/ypbind start
Binding to the NIS domain: [  OK  ]
Listening for an NIS domain server.
[root@nis-server1]# /etc/init.d/ypxfrd start
Starting YP map server: [  OK  ]
[root@nis-server1]# chkconfig ypbind on
[root@nis-server1]# chkconfig ypxfrd on

On Debian, you would simply restart the /etc/init.d/nis service:

[root@nis-server1]# /etc/init.d/nis restart
Starting NIS services: ypserv yppasswdd ypxfrd ypbind

Verify The Daemons Are Running

All the NIS daemons use RPC port mapping and, therefore, are listed using the rpcinfo command when they are running correctly.

[root@nis-server1]# rpcinfo -p localhost
    program vers proto   port
    100000    2   tcp    111  portmapper
    100000    2   udp    111  portmapper
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100021    1   udp   1024  nlockmgr
    100021    3   udp   1024  nlockmgr
    100021    4   udp   1024  nlockmgr
    100004    2   udp    784  ypserv
    100004    1   udp    784  ypserv
    100004    2   tcp    787  ypserv
    100004    1   tcp    787  ypserv
    100009    1   udp    798  yppasswdd
 600100069    1   udp    850  fypxfrd
 600100069    1   tcp    852  fypxfrd
    100007    2   udp    924  ypbind
    100007    1   udp    924  ypbind
    100007    2   tcp    927  ypbind
    100007    1   tcp    927  ypbind

Adding New NIS Users

New NIS users can be created by logging into the NIS server and creating the new user account. In this case, you'll create a user account called nisuser and give it a new password.

Once this is complete, you then have to update the NIS domain's authentication files by executing the make command in the /var/yp directory.

This procedure makes all NIS-enabled, nonprivileged accounts become automatically accessible via NIS, not just newly created ones. It also exports all the user's characteristics stored in the /etc/passwd and /etc/group files, such as the login shell, the user's group, and home directory.

[root@nis-server1]# useradd -g users nisuser
[root@nis-server1]# passwd nisuser
Changing password for user nisuser.
New password: ********
Retype new password: ********
passwd: all authentication tokens updated successfully.

[root@nis-server1]# cd /var/yp
[root@nis-server1]# make
gmake[1]: Entering directory `/var/yp/LINUX-NIS'
Updating passwd.byname...
Updating passwd.byuid...
Updating netid.byname...
gmake[1]: Leaving directory `/var/yp/LINUX-NIS'

You can check to see if the user's authentication information has been updated by using the ypmatch command, which should return the user's encrypted password string.

[root@nis-server1]# ypmatch nisuser passwd

You can also use the getent command, which has similar syntax. Unlike ypmatchgetent doesn't provide an encrypted password when run on an NIS server, it just provides the user's entry in the /etc/passwd file. On a NIS client, the results are identical with both showing the encrypted password.

[root@nis-server1]# getent passwd nisuser

From here you should be up and going with your new NIS domain. Have fun.