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Quick HOWTO : Ch30 : Configuring NIS/zh

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Dhyang555讨论 | 贡献2010年2月7日 (日) 20:27的版本 Configuring The NIS Server

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介绍

网络用户信息服务(NIS)使你可以在你的网络中创建账户并在所有的系统共享。这个账户只能在NIS的服务器上创建。NIS客户端从NIS服务器下载需要的用户名和密码数据来验证用户的登录。

NIS的一个优点是用户只需要在NIS服务器上更改他们的密码,而不必在网络上的每个系统上去更改密码。这使得NIS在计算机实验室很流行,使用在一些分布式软件开发项目和组内成员必须共享很多不同的电脑的情况下。


缺点是NIS没有加密登录时发送到客户端的用户名和密码信息,所有用户有访问在存储NIS服务器加密的密码信息的权限。关于NIS安全细节的分析在这本书的前面部分,但是我建议你限制使用NIS在高安全的网络中,或者有权访问非NIS网络是有很高的限制的网络。

轻量级目录访问协议提供了和NIS相似的特性,但是不依靠额外的软件可以支持加密,并且支持客户端可以不依靠从机访问多重网络。因为这个原因,LDAP在这个应用上十分流行。LDAP更所细节的讨论在31章,"Centralized Logins Using LDAP and RADIUS".

方案

为了理解NFS的好处,考虑一个例子。一个学校要为学生建立一个小型计算机实验室。

  • 主要的Linux服务器,bigboy,有很大的磁盘空间,会被同时用作NIS服务器和为实验室的Linux PC提供基于NFS文件系统的服务器。
  • 登录到PC的用户会被分配一个主目录,这个目录在bigboy上而不是在这些PC上。
  • 每个用户的主目录会用NFS自动挂载在用户登录的PC上。
  • 在其它PC实行使用NIS前,实验室的教师会在一个名字为smallfry 的Linux PC 上练习。
  • NIS RPMs 套件会被安装在服务器和客户端;ypserve 和yp-tools 在服务器,ypbind 和 yp-tools 在客户端。

下载安装RPM并不难,将在第六章讨论,"Installing Linux Software". 搜索RPM时,记住文件的名字一般是软件包的名字后面跟着版本号,就像yp-tools-2.8-3.i386.rpm.

实验室教师会做一些研究并且谋划一个实现计划:

  1. 配置bigboy,把它作为一个NFS服务器使它的 /home 目录对Linux工作站是可用的。
  2. 配置smallfry ,把它作为一个可以访问bigbos 的 /home 目录的客户端。
  3. 配置bigboy,把它作为一个NIS服务器。
  4. 在bigboy 上创建一个用户账号(nisuser),这个用户在smallfry 上并不存在。将这个用户转变为NIS用户账号。
  5. 将smallfry 配置为一个NIS客户端。
  6. 测试远程登录,用nisuser 这个用户的账号和密码从bigboy 登录到smallfry 。

你有了方案和计划,该是工作的时候了。

配置NFS 服务器

这里是在这个方案中配置NFS 服务器的步骤

1. 编辑 /etc/exports 文件允许NFS 挂载到 /home 目录,并与读写权限。

/home                   *(rw,sync)

2. 让NFS读取 /etc/exports 文件或的新的入口,用exportfs 命令让/home 在网络上可用。

[root@bigboy tmp]# exportfs -a
[root@bigboy tmp]#

3.保证 nfs, nfslock, 和 portmap 守护进程都在运行并且下次重启后配置为启动.

[root@bigboy tmp]# chkconfig nfslock on
[root@bigboy tmp]# chkconfig nfs on
[root@bigboy tmp]# chkconfig portmap on
[root@bigboy tmp]# service portmap start
Starting portmapper: [  OK  ]
[root@bigboy tmp]# service nfslock start
Starting NFS statd: [  OK  ]
[root@bigboy tmp]# service nfs start
Starting NFS services:  [  OK  ]
Starting NFS quotas: [  OK  ]
Starting NFS daemon: [  OK  ]
Starting NFS mountd: [  OK  ]
[root@bigboy tmp]#

配置完NFS服务器,我们要配置它的客户端,这些会在下面涉及。

配置NFS 客户端

You also need to configure the NFS clients to mount their /home directories on the NFS server. 你需要配置NFS 客户端挂载 /home 目录到NFS 服务器。

These steps archive the /home directory. In a production environment in which the /home directory would be actively used, you'd have to force the users to log off, backup the data, restore it to the NFS server, and then follow the steps below. As this is a lab environment, these prerequisites aren't necessary. 这些步骤会归档 /home 目录。在一个/home目录会经常使用的产品环境中,你不得不强制用户登出,备份数据,并恢复到NFS 服务器,然后按照下面步骤来做。因为这是一个实验室的环境,这些准备并不需要。

1. Make sure the required netfs, nfslock, and portmap daemons are running and configured to start after the next reboot. 1. 保证需要的 netfs, nfslock, 和 portmap守护进程在运行,并且配置为再重启后启动。

[root@smallfry tmp]# chkconfig nfslock on
[root@smallfry tmp]# chkconfig netfs on
[root@smallfry tmp]# chkconfig portmap on
[root@smallfry tmp]# service portmap start
Starting portmapper: [  OK  ]
[root@smallfry tmp]# service netfs start
Mounting other filesystems:  [  OK  ]
[root@smallfry tmp]# service nfslock start
Starting NFS statd: [  OK  ]
[root@smallfry tmp]#

2. Keep a copy of the old /home directory, and create a new directory /home on which you'll mount the NFS server's directory. 2. 保留一个以前/home 目录的副本,在你需要挂在的NFS 服务器的目录上创建一个新的/home目录。

[root@smallfry tmp]# mv /home /home.save
[root@smallfry tmp]# mkdir /home
[root@smallfry tmp]# ll /
...
...
drwxr-xr-x    1 root   root     11 Nov 16 20:22 home
drwxr-xr-x    2 root   root   4096 Jan 24  2003 home.save
...
...
[root@smallfry tmp]#

3. Make sure you can mount bigboy's /home directory on the new /home directory you just created. Unmount it once everything looks correct. 3. 保证你可以挂载bigboy 的/home 目录在你刚刚创建的目录上。卸载这个目录一次看看是否正常。

[root@smallfry tmp]# mount 192.168.1.100:/home /home/
[root@smallfry tmp]# ls /home
ftpinstall  nisuser  quotauser  smallfry  www
[root@smallfry tmp]# umount /home
[root@smallfry tmp]#

4. Start configuring autofs automounting. Edit your /etc/auto.master file to refer to file /etc/auto.home for mounting information whenever the /home directory is accessed. After five minutes, autofs unmounts the directory. 4. 开始配置autofs 来自动挂载。

#/etc/auto.master
/home      /etc/auto.home --timeout 600

5. Edit file /etc/auto.home to do the NFS mount whenever the /home directory is accessed. If the line is too long to view on your screen, you can add a \ character at the end to continue on the next line.

#/etc/auto.home
*   -fstype=nfs,soft,intr,rsize=8192,wsize=8192,nosuid,tcp \
   192.168.1.100:/home:&

6. Start autofs and make sure it starts after the next reboot with the chkconfig command.

[root@smallfry tmp]# chkconfig autofs on
[root@smallfry tmp]# service autofs restart
Stopping automount:[  OK  ]
Starting automount:[  OK  ]
[root@smallfry tmp]#

After doing this, you won't be able to see the contents of the /home directory on bigboy as user root. This is because by default NFS activates the root squash feature, which disables this user from having privileged access to directories on remote NFS servers. You'll be able to test this later after NIS is configured.

Note: This automounter feature doesn't appear to function correctly in my preliminary testing of Fedora Core 3. See Chapter 29, "Remote Disk Access with NFS", for details.

All newly added Linux users will now be assigned a home directory under the new remote /home directory. This scheme will make the users feel their home directories are local, when in reality they are automatically mounted and accessed over your network.

配置NIS服务器

NFS 只提供网际文件共享。你现在必须在试验室的学生完成工作之前为他们配置好NIS登录验证。NIS服务器的配置并不难,但是需要很多你可能会漏掉的步骤。别担心,我们将深入细致地重温每个环节。 注意: 在早期,NIS被称为黄页。 开发者被迫在一次版权侵害诉讼之后更名。,然而许多与NIS相关的主要程序仍然保持其以yp开头的原始名称。

安装NIS服务器包

NIS客户端需要的所有包是许多Fedora安装的标准部分。服务器的ypserv包不包括在内 。安装该包参考第六章的步骤概述。,"安装Linux软件".

编辑你的/etc/sysconfig/network 文件

你需要在/etc/sysconfig/network文件中增加你想要使用的NIS域。对学校而言,叫做NIS-SCHOOL-NETWORK域。

#/etc/sysconfig/network
NISDOMAIN="NIS-SCHOOL-NETWORK"

编辑你的 /etc/yp.conf 文件

NIS服务器必定也是他自己的客户端, 所以你也需要编辑NIS客户端配置文件/etc/yp.conf 来列出本域的NIS服务器,如服务器本身或本地主机.

# /etc/yp.conf - ypbind 配置文件

启动关键NIS服务器相关守护进程

在 /etc/init.d目录中启动必需的NIS守护进程同时使用chkconfig命令确保在下一次重启后启动他们。

[root@bigboy tmp]# service portmap start
Starting portmapper: [  OK  ]
[root@bigboy tmp]# service yppasswdd start
Starting YP passwd service: [  OK  ]
[root@bigboy tmp]# service ypserv start
Setting NIS domain name NIS-SCHOOL-NETWORK:  [  OK  ]
Starting YP server services: [  OK  ]
[root@bigboy tmp]# 

[root@bigboy tmp]# chkconfig portmap on
[root@bigboy tmp]# chkconfig yppasswdd on
[root@bigboy tmp]# chkconfig ypserv on

表 30.1 列出了守护进程功能的概要。

表 30-1 依赖的NIS服务器守护进程

Daemon Name Purpose
portmap The foundation RPC daemon upon which NIS runs.
yppasswdd Lets users change their passwords on the NIS server from NIS clients
ypserv Main NIS server daemon
ypbind Main NIS client daemon
ypxfrd Used to speed up the transfer of very large NIS maps

继续下一步之前确保他们都在运行。 可以使用rpcinfo命令来完成。

[root@bigboy tmp]# 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
[root@bigboy tmp]#
ypbind 和ypxfrd 守护进程将不会正确启动直到你初始化NIS域之后。在初始化完成之后你需要启动这些守护进程。

初始化你的NIS域

既已确定NIS域名,你必须使用ypinit命令来为该域创建相关验证文件。你将被提示NIS服务器的名称,本例中为bigboy。 在该过程中,所有非特权账户通过NIS自动获得访问权限。

[root@bigboy tmp]# /usr/lib/yp/ypinit -m
在这里,我们不得不建立一个运行NIS服务器的主机列表。 bigboy在NIS服务器的主机列表中 。请继续为其他主机增加名字,每行一个。列表创建完毕,输入<control D>。
        next host to add:  bigboy
        next host to add:

NIS 服务器的当前列表看起来如下:

bigboy
 
Is this correct?  [y/n: y]  y
We need a few minutes to build the databases...
Building /var/yp/NIS-SCHOOL-NETWORK/ypservers...
Running /var/yp/Makefile...
gmake[1]: Entering directory `/var/yp/NIS-SCHOOL-NETWORK'
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/NIS-SCHOOL-NETWORK'
 
bigboy 已经被设置成一个NIS主服务器。
 

现在你在所有的从服务器上能执行 ypinit -s bigboy 。

[root@bigboy tmp]#

注意:' 确保在该步骤之前端口映射已经开启否则将出错,例如:

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

在成功之前,你将不得不删除 /var/yp/NIS-SCHOOL-NETWORK目录同时重启portmap yppasswd, 和ypserv。

Start The ypbind and ypxfrd Daemons

你现在能启动 ypbind 和 the ypxfrd 后台,因为NIS域文件已经创建。

[root@bigboy tmp]# service ypbind start
Binding to the NIS domain: [  OK  ]
Listening for an NIS domain server.
[root@bigboy tmp]# service ypxfrd start
Starting YP map server: [  OK  ]
[root@bigboy tmp]# chkconfig ypbind on
[root@bigboy tmp]# chkconfig ypxfrd on

确保守护进程运行

所有的NIS 后台使用RPC 端口映射同时,也因而,当他们正确运行时能使用rpcinfo命令被列出。

[root@bigboy tmp]# 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
[root@bigboy tmp]#

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@bigboy tmp]# useradd -g users nisuser
[root@bigboy tmp]# passwd nisuser
Changing password for user nisuser.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.
[root@bigboy tmp]# cd /var/yp
[root@bigboy yp]# make
gmake[1]: Entering directory `/var/yp/NIS-SCHOOL-NETWORK'
Updating passwd.byname...
Updating passwd.byuid...
Updating netid.byname...
gmake[1]: Leaving directory `/var/yp/NIS-SCHOOL-NETWORK'
[root@bigboy yp]#

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@bigboy yp]# ypmatch nisuser passwd
nisuser:$1$d6E2i79Q$wp3Eo0Qw9nFD/::504:100::/home/nisuser:/bin/bash
[root@bigboy yp]

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@bigboy yp]# getent passwd nisuser
nisuser:x:504:100::/home/nisuser:/bin/bash
[root@bigboy yp]#

Configuring The NIS Client

Now that the NIS server is configured, it's time to configure the NIS clients. There are a number of related configuration files that you need to edit to get it to work. Take a look at the procedure.

Run authconfig

The authconfig or the authconfig-tui program automatically configures your NIS files after prompting you for the IP address and domain of the NIS server.

[root@smallfry tmp]# authconfig-tui

Once finished, it should create an /etc/yp.conf file that defines, amongst other things, the IP address of the NIS server for a particular domain. It also edits the /etc/sysconfig/network file to define the NIS domain to which the NIS client belongs.

# /etc/yp.conf - ypbind configuration file
domain NIS-SCHOOL-NETWORK server 192.168.1.100

#/etc/sysconfig/network
NISDOMAIN=NIS-SCHOOL-NETWORK

In addition, the authconfig program updates the /etc/nsswitch.conf file that lists the order in which certain data sources should be searched for name lookups, such as those in DNS, LDAP, and NIS. Here you can see where NIS entries were added for the important login files.

#/etc/nsswitch.conf
passwd:     files nis
shadow:     files nis
group:      files nis

Note: You can also locate a sample NIS nsswitch.conf file in the /usr/share/doc/yp-tools* directory.

Start The NIS Client Related Daemons

Start the ypbind NIS client, and portmap daemons in the /etc/init.d directory and use the chkconfig command to ensure they start after the next reboot. Remember to use the rpcinfo command to ensure they are running correctly.

[root@smallfry tmp]# service portmap start
Starting portmapper: [  OK  ]
[root@smallfry tmp]# service ypbind start
Binding to the NIS domain:
Listening for an NIS domain server.
[root@smallfry tmp]#

[root@smallfry tmp]# chkconfig ypbind on
[root@smallfry tmp]# chkconfig portmap on

Note: Remember to use the rpcinfo -p localhost command to make sure they all started correctly.

Verify Name Resolution

As the configuration examples refer to the NIS client and server by their hostnames, you'll have to make sure the names resolve correctly to IP addresses. This can be configured either in DNS, when the hosts reside in the same domain, or more simply by editing the /etc/hosts file on both Linux boxes.

#
# File: /etc/hosts (smallfry)
#
192.168.1.100    bigboy

 
#
# File: /etc/hosts (bigboy)
#
192.168.1.102    smallfry

Test NIS Access To The NIS Server

You can run the ypcat, ypmatch, and getent commands to make sure communication to the server is correct.

[root@smallfry tmp]# ypcat passwd
nisuser:$1$Cs2GMe6r$1hohkyG7ALrDLjH1:505:100::/home/nisuser:/bin/bash
quotauser:!!:503:100::/home/quotauser:/bin/bash
ftpinstall:$1$8WjAVtes$SnRh9S1w07sYkFNJwpRKa.:502:100::/:/bin/bash
www:$1$DDCi/OPI$hwiTQ.L0XqYJUk09Bw.pJ/:504:100::/home/www:/bin/bash
smallfry:$1$qHni9dnR$iKDs7gfyt..BS9Lry3DAq.:501:100::/:/bin/bash
[root@smallfry tmp]#

[root@smallfry tmp]# ypmatch nisuser passwd
nisuser:$1$d6E2i79Q$wp3Eo0Qw9nFD/:504:100::/home/nisuser:/bin/bash
[root@smallfry tmp]#

[root@smallfry tmp]# getent passwd nisuser
nisuser:$1$d6E2i79Q$wp3Eo0Qw9nFD/:504:100::/home/nisuser:/bin/bash
[root@smallfry tmp]#

Possible sources of error would include:

  • Incorrect authconfig setup resulting in errors in the /etc/yp.conf, /etc/sysconfig/network and /etc/nsswitch.conf files
  • Failure to run the ypinit command on the NIS server
  • NIS not being started on the NIS server or client.
  • Poor routing between the server and client, or the existence of a firewall that's blocking traffic

Try to eliminate these areas as sources of error and refer to the syslog /var/log/messages file on the client and server for entries that may provide additional clues.

Test Logins via The NIS Server

Once your basic NIS functionality testing is complete, try to test a remote login. Failures in this area could be due to firewalls blocking TELNET or SSH access and the TELNET and SSH server process not being started on the clients.

Logging In Via Telnet

Try logging into the NIS client via telnet if it is enabled

[root@bigboy tmp]# telnet 192.168.1.201
Trying 192.168.1.201...
Connected to 192.168.1.201.
Escape character is '^]'.
Red Hat Linux release 9 (Shrike)
Kernel 2.4.20-6 on an i686
login: nisuser
Password:
Last login: Sun Nov 16 22:03:51 from 192-168-1-100.simiya.com
[nisuser@smallfry nisuser]$

Logging In Via SSH

Try logging into the NIS client via SSH.

[root@bigboy tmp]# ssh -l nisuser 192.168.1.102
[email protected]'s password:
[nisuser@smallfry nisuser]$

In some versions of Linux, the NIS client's SSH daemon doesn't re-read the /etc/nsswitch.conf file you just modified until SSH is restarted. SSH logins, therefore, won't query the NIS server until this is done. Restart SSH on the NIS client.

[root@smallfry root]# service sshd restart
Stopping sshd:[  OK  ]
Starting sshd:[  OK  ]
[root@smallfry root]#

NIS Slave Servers

NIS relies a lot on broadcast traffic to operate, which prevents you from having an NIS server on a different network from the clients. You can avoid this problem on your local subnet by using slave servers that are configured to automatically synchronize their NIS data with that of the single master server.

You can also consider placing multiple NIS servers on a single subnet for the sake of redundancy. To do this, configure the NIS clients to have multiple NIS servers for the domain in the /etc/yp.conf file.

Configuring NIS Slave Servers

In this scenario, you need to add an NIS slave server named nisslave (IP address 192.168.1.254) to the NIS-SCHOOL-NETWORK NIS domain. You also must configure the NIS master server, bigboy, to push its database map information to the slave whenever there is an update. Here are the steps you need.


1. As you're referring to our servers by their hostnames, you'll have to make sure the names resolve correctly to IP addresses. This can be done either in DNS, when the hosts reside in the same domain, or more simply by editing the /etc/hosts files on both servers as seen in Table 30.2.

Table 30-2 NIS Master / Slave /etc/hosts Files

Master (Bigboy) Slave (Nisslave)
#
# File: /etc/hosts (Bigboy)
#
192.168.1.254    nisslave
#
# File: /etc/hosts (Nisslave)
#
192.168.1.100    bigboy


2. Configure the NIS slave as a NIS client of itself in the /etc/yp.conf file, and configure the NIS domain in the /etc/sysconfig/network file as seen in Table 30.3.

Table 30-3 NIS Master / Slave /etc/yp.conf Files

/etc/yp.conf /etc/sysconfig/network
#
# File: /etc/yp.conf (Bigboy)
#
ypserver 127.0.0.1
#
# File: /etc/sysconfig/network
#
NISDOMAIN="NIS-SCHOOL-NETWORK"


3. On the slave server, run ypbind so the slave can query the master server.

[root@nisslave tmp]# service portmap start
Starting portmapper: [  OK  ]
[root@nisslave tmp]# service ypbind start
Binding to the NIS domain:
Listening for an NIS domain server.
[root@nisslave tmp]#
 
[root@nisslave tmp]# chkconfig portmap on
[root@nisslave tmp]# chkconfig ypbind on

4. Optimize database map transfers by the NIS map transfer daemon, which should the started on both the master and slave.

[root@nisslave tmp]# service ypxfrd start
Starting YP map server: [  OK  ]
[root@nisslave tmp]#
[root@nisslave tmp]# chkconfig ypxfrd on
 
[root@bigboy tmp]# service ypxfrd start
Starting YP map server: [  OK  ]
[root@bigboy tmp]#
[root@bigboy tmp]# chkconfig ypxfrd on

5. Do a simple database query of the master from the slave using the ypwhich command with the -m (master) switch. You should get a listing of all the tables.

[root@nisslave tmp]# ypwhich -m
mail.aliases bigboy
group.bygid bigboy
passwd.byuid bigboy
rpc.bynumber bigboy
...
...
[root@nisslave tmp]#

6. Do an initial database download to the slave from the master with the ypinit command using the -s switch for a slave-type operation and specifying server bigboy as the master from which the data is to be obtained. You should see "Trying ypxfrd - success" messages. If the messages say "Trying ypxfrd - not running," then start ypxfrd on both servers.

[root@nisslave tmp]# /usr/lib/yp/ypinit -s bigboy
We will need a few minutes to copy the data from bigboy.
Transferring services.byservicename...
Trying ypxfrd ... success
 
Transferring group.byname...
Trying ypxfrd ... success
...
...
 
nisslave's NIS data base has been set up.
If there were warnings, please figure out what went wrong, and fix it.
 
At this point, make sure that /etc/passwd and /etc/group have
been edited so that when the NIS is activated, the data bases you
have just created will be used, instead of the /etc ASCII files.
[root@nisslave tmp]#

If your database is corrupt or your /etc/hosts files are incorrect, you'll get map enumeration errors as shown. Use the make command again to rebuild your database on the master when necessary.

[root@nisslave tmp]# /usr/lib/yp/ypinit -s bigboy
Can't enumerate maps from bigboy. Please check that it is running.
[root@nisslave tmp]#

7. Now that the data has been successfully downloaded, it's time to make the slave server serve NIS clients with ypserv.

[root@nisslave tmp]# service ypserv start
Starting YP server services:
[root@nisslave tmp]#
[root@nisslave tmp]# chkconfig ypxfrd on
 

8. Log on to the master server. Add the slave server to the master server's database map by editing the /var/yp/ypservers file on the master.

[root@bigboy yp]# cd /tmp
[root@bigboy tmp]# cd /var/yp/
[root@bigboy yp]# vi ypservers

Add nisslave to the file.

#
# File: /var/yp/ypservers
#
bigboy
nisslave
 

9. The make file in the /var/yp directory defines how the NIS server will build the database map and how the master will relate to the NIS slave. Make a copy of the master's make file for safekeeping.

[root@bigboy yp]# cp Makefile Makefile.old
 

10. Edit the make file to allow the master to push maps to the slave.

#
# File: /var/vp/Makefile
#
 
#
# Allow the master to do database pushes to the slave
#
NOPUSH=false
 

11. Use the make command to rebuild the database. The make command automatically pushes database updates to the servers listed in the /var/yp/servers file.

[root@bigboy yp]# make
gmake[1]: Entering directory `/var/yp/NIS-SCHOOL-NETWORK'
Updating ypservers...
YPPUSH: gethostbyname(): Success
YPPUSH: using not FQDN name
gmake[1]: Leaving directory `/var/yp/NIS-SCHOOL-NETWORK'
gmake[1]: Entering directory `/var/yp/NIS-SCHOOL-NETWORK'
Updating netid.byname...
YPPUSH: gethostbyname(): Success
YPPUSH: using not FQDN name
gmake[1]: Leaving directory `/var/yp/NIS-SCHOOL-NETWORK'
[root@bigboy yp]#

12. On the slave server, create a cron file in the /etc/crond.d directory, in this case named nis_sync, that will run periodic database downloads from the master server. This helps to ensure that the slave servers have current databases even if they miss updates from the master in the event the school goes offline for maintenance. Restart the cron daemon so that the configuration in this file becomes active.

[root@nisslave yp]# vi /etc/cron.d/nis_sync
 
#
# File: /etc/cron.d/nis_sync
#
20 *    * * *    /usr/lib/yp/ypxfr_1perhour
40 6    * * *    /usr/lib/yp/ypxfr_1perday
55 6,18 * * *    /usr/lib/yp/ypxfr_2perday
 
[root@nisslave yp]# service crond restart

That's a lot of work but it's still not over. There is one final configuration step that needs to be done on the NIS clients before you're finished.

Configuring NIS Clients With Slaves

Edit the /etc/yp.conf file on all the clients to include nisslave, and restart ypbind.

#
# File: /etc/yp.conf (Smallfry)
#
domain NIS-SCHOOL-NETWORK server 192.168.1.100
domain NIS-SCHOOL-NETWORK server 192.168.1.254

 
[root@smallfry tmp]# service ypbind restart
Shutting down NIS services: [  OK  ]
Binding to the NIS domain: [  OK  ]
Listening for an NIS domain server..
[root@smallfry tmp]#

Changing Your NIS Passwords

You should also test to make sure your users can change their NIS passwords from the NIS clients with the yppasswd command. The process is different whether there is only a single NIS master or a master-slave server relationship.

When There Is Only An NIS Master

When there is only a single NIS server, password changes can be made only on the NIS server using the yppasswd command.

Users Changing Their Own Passwords

Users can change their passwords by logging into the NIS server and issuing the yppasswd command.

[nisuser@bigboy nisuser]$ yppasswd
Changing NIS account information for nisuser on bigboy.my-site.com.
Please enter old password:
Changing NIS password for nisuser on bigboy.my-site.com.
Please enter new password:
Please retype new password:
 
The NIS password has been changed on bigboy.my-site.com.
 
[nisuser@bigboy nisuser]$

User "Root" Changing Passwords

The root user can change other users' passwords issuing the yppasswd command with the -p switch that specifies the username that needs the change.

[root@bigboy tmp]# yppasswd -p nisuser
Changing NIS account information for nisuser on bigboy.my-site.com.
Please enter root password:
Changing NIS password for nisuser on bigboy.my-site.com.
Please enter new password:
Please retype new password:
 
The NIS password has been changed on bigboy.my-site.com.

[root@bigboy tmp]#

When There Is A NIS Master / Slave Pair

With an NIS master and slave pair configuration, passwords can be changed on the NIS clients or the NIS slave, but not on the NIS master.

Possible Password Errors

There are a number of unexpected errors you may find when changing passwords - errors that have nothing to do with bad typing.

Segmentation Faults

Running the yppasswd command on the wrong client or server depending on your NIS master and slave configuration can cause segmentation fault errors. (Make sure you follow the chapter's guidelines for password changes!) Here are some sample password change failures on an NIS client with only one NIS master server.

[nisuser@smallfry nisuser]$ yppasswd
Segmentation fault
[nisuser@smallfry nisuser]$
 
[root@smallfry root]# yppasswd -p nisuser
Segmentation fault
[root@smallfry root]#

Daemon Errors

The yppasswdd daemon must be running on both the client and server for password changes to work correctly. When they aren't running, you'll get errors.

[root@smallfry etc]# yppasswd -p nisuser
yppasswd: yppasswdd not running on NIS master host ("bigboy").
[root@smallfry etc]#

You'll also get a similar error if you attempt to change an NIS password on an NIS master server in a master and slave configuration.

Considerations For A Non NFS Environment

In many cases NFS, isn't used to create a centralized home directory for users and, therefore, you'll have to create it on each NIS client and not on the server.

This example creates the home directory for the NIS client, smallfry. After doing this, you have to copy a BASH login profile file into it and modify the ownership of the directory and all the files to user nisuser.

Logins should proceed normally once this has been done and all the other steps have been followed.

[root@smallfry tmp]# mkdir /home/nisuser
[root@smallfry tmp]# chmod 700 /home/nisuser/
[root@smallfry tmp]# ll /home
total 2
drwx------    2 nisuser users        1024 Aug  4 08:05 nisuser
[root@smallfry tmp]#
[root@smallfry tmp]# cp /etc/skel/.* /home/nisuser/
cp: omitting directory `/etc/skel/.'
cp: omitting directory `/etc/skel/..'
cp: omitting directory `/etc/skel/.kde'
[root@smallfry tmp]# chown -R nisuser:users /home/nisuser
[root@smallfry tmp]#

NIS Troubleshooting

Troubleshooting is always required as any part of your daily routine, NIS is no exception. Here are some simple steps to follow to get it working again.

1. The rpcinfo provides a list of TCP ports that your NIS client or server is using. Make sure you can TELNET to these ports from the client to the server and vice versa. If this fails, make sure all the correct NIS daemons are running and that there are no firewalls blocking traffic on the network or on the servers themselves. These ports change from time to time, so memorizing them won't help much.

The example tests from the client to the server.

[root@bigboy tmp]# rpcinfo -p
    program vers proto   port
     100000    2   tcp    111  portmapper
     100000    2   udp    111  portmapper
     100024    1   udp  32768  status
     100024    1   tcp  32768  status
     391002    2   tcp  32769  sgi_fam
     100009    1   udp   1018  yppasswdd
     100004    2   udp    611  ypserv
     100004    1   udp    611  ypserv
     100004    2   tcp    614  ypserv
     100004    1   tcp    614  ypserv
     100007    2   udp    855  ypbind
     100007    1   udp    855  ypbind
     100007    2   tcp    858  ypbind
     100007    1   tcp    858  ypbind
  600100069    1   udp    874  fypxfrd
  600100069    1   tcp    876  fypxfrd
[root@bigboy tmp]#
 
 
[root@smallfry tmp]# telnet 192.168.1.100 858
Trying 10.41.32.71...
Connected to 10.41.32.71.
Escape character is '^]'.
^]
telnet> quit
Connection closed.
[root@smallfry tmp]#

2. Always use the ypmatch, getent, and ypwhich commands to check your NIS connectivity. If there is any failure, check your steps over again and you should be able to find the source of your problem.

3. Do not fail to create a user's home directory, set its permissions, and copy the /etc/skel files correctly. If you forget, which is a common error, your users may have incorrect login prompts and no ability to create files in their home directories.

It can never be overemphasized that one of the best places to start troubleshooting is by looking in your error log files in the /var/log directory. You'll save a lot of time and effort if you always refer to them whenever the problem doesn't appear to be obvious.

Conclusion

NIS is a very useful tool for centralized login management, but it has two shortcomings: NIS clients are typically limited to Unix or Linux operating systems, and the password information passes over the network unencrypted.

Newer authentication schemes overcome these issues. For example, LDAP, which is discussed in Chapter 31, "Centralized Logins Using LDAP and RADIUS", provides both encryption and the ability to be used on varied types of equipment. Unfortunately older operating systems don't support it, making NIS the preferred option in some cases.

As always, explore your options when deciding on a centralized login scheme. A wrong decision could haunt you for a long time.