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.
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.
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 ypserver 127.0.0.1
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.
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 portmap, yppasswdd, 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.
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: nis-server1 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: 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: 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.
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
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
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: Entering directory `/var/yp/LINUX-NIS' Updating passwd.byname... Updating passwd.byuid... Updating netid.byname... gmake: 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 nisuser:$1$d6E2i79Q$wp3Eo0Qw9nFD/::504:100::/home/nisuser:/bin/bash
You can also use the getent command, which has similar syntax. Unlike ypmatch, getent 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 nisuser:x:504:100::/home/nisuser:/bin/bash
From here you should be up and going with your new NIS domain. Have fun.
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