NFS的安装配置：
centos 5 :
yum install nfs-utils portmap
centos 6 :
yum install nfs-utils rpcbind


本节是使用centos 6的配置过程：
设备：两台 centos6 OS 安装的时候选择的是"Basic Server"软件配置包。
首先，让两台机器都安装NFS的 软件包，如下显示的是服务器端：
[root@roothomes /home]$ yum install nfs-utils rpcbind
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: centos.ustc.edu.cn
 * extras: centos.ustc.edu.cn
 * updates: centos.ustc.edu.cn
Setting up Install Process
Package rpcbind-0.2.0-8.el6.x86_64 already installed and latest version
Resolving Dependencies
--> Running transaction check
---> Package nfs-utils.x86_64 1:1.2.3-15.el6 set to be updated
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package            Arch            Version                 Repository     Size
================================================================================
Updating:
 nfs-utils          x86_64          1:1.2.3-15.el6          base          308 k

Transaction Summary
================================================================================
Install       0 Package(s)
Upgrade       1 Package(s)

Total download size: 308 k
Is this ok [y/N]: y
Downloading Packages:
nfs-utils-1.2.3-15.el6.x86_64.rpm                        | 308 kB     00:10
warning: rpmts_HdrFromFdno: Header V3 RSA/SHA1 Signature, key ID c105b9de: NOKEY
base/gpgkey                                              | 3.3 kB     00:00 ...
Importing GPG key 0xC105B9DE "CentOS-6 Key (CentOS 6 Official Signing Key) " from /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

Is this ok [y/N]: yRunning rpm_check_debugRunning Transaction TestTransaction Test SucceededRunning Transaction  Updating       : 1:nfs-utils-1.2.3-15.el6.x86_64                          1/2  Cleanup        : 1:nfs-utils-1.2.2-7.el6.x86_64                           2/2Updated:  nfs-utils.x86_64 1:1.2.3-15.el6Complete![root@roothomes /home]$服务器端： ###(建立挂载的目录，并且挂载目录。)[root@roothomes /etc]$ mkdir /opt/centos6[root@roothomes /etc]$ cd /opt/centos6/[root@roothomes /opt/centos6]$ mkdir thisISnfsFile[root@roothomes /opt/centos6]$ lsthisISnfsFile[root@roothomes /etc]$ vi /etc/exports[root@roothomes /opt/centos6]$ cat /etc/exports/opt/centos6 192.168.1.0/24(ro,no_root_squash)### 备注:/opt/centos6表示nfs共享的目录 192.168.1.0-192.168.1.254区间的IP可以访问，访问权限是自读，root 用户###(启动对应的服务)[root@roothomes /opt/centos6]$ chkconfig nfs on[root@roothomes /opt/centos6]$ /etc/init.d/rpcbind start[root@roothomes /opt/centos6]$ /etc/init.d/nfs startStarting NFS services:                                     [  OK  ]Starting NFS quotas:                                       [  OK  ]Starting NFS daemon:                                       [  OK  ]Starting NFS mountd:                                       [  OK  ][root@roothomes /opt/centos6]$ service iptables stopiptables: Flushing firewall rules:                         [  OK  ]iptables: Setting chains to policy ACCEPT: filter          [  OK  ]iptables: Unloading modules:                               [  OK  ]客户端：[root@roothomes /home]$ yum install nfs-utils rpcbind安装完毕！[root@vmBS00 ~]# service iptables stopiptables: Flushing firewall rules:                         [  OK  ]iptables: Setting chains to policy ACCEPT: filter          [  OK  ]iptables: Unloading modules:                               [  OK  ]###查看是否能访问nfs服务[root@vmBS00 ~]# showmount -e 192.168.1.75Export list for 192.168.1.75:/opt/centos6 192.168.1.0/24[root@vmBS00 ~]# mkdir /opt/centos6[root@vmBS00 ~]# mount -t nfs 192.168.1.75:/opt/centos6/  /opt/centos6/[root@vmBS00 ~]# ls /opt/centos6/thisISnfsFile###配置开机自动挂载[root@vmBS00 ~]# vi /etc/fstab### 添加 #192.168.1.75:/opt/centos6/ /opt/centos6/ nfs nodev,ro,rsize=32768,wsize=32768 0 0[root@vmBS00 ~]# init 6[root@vmBS00 ~]#login as: rootroot@192.168.1.116's password:Last login: Mon Mar  5 17:29:04 2012 from 192.168.1.23[root@vmBS00 ~]# ls /opt/centos6/thisISnfsFile[root@vmBS00 ~]#                                                                                                                                                             >

/data 本机mount的目录  

1.服务端和客户端都需要开启portmap服务。RCP是nfs mount和umount时通信的方式。

2.假如客户端portmap没有启动，mount时，会非常慢，最终会失败。umount时，即使本地的portmap是关闭的，也能umount成功。  

3.挂载完成后，服务端的portmap停止后，nfs仍然工作正常，但是umout财会提示： not found / mounted or server not reachable。重启服务器的portmap也无济于事。

4.假如服务端的portmap重启了，那么nfs也要跟着重启，否则nfs工作仍然是不正常的。

5.假如服务端nfs关闭(IP是通的)，这时客户端会无法umount，这时使用umount -f /nfs一般能成功，当服务端死机时，umount -f /nfs 有可能会失败，这时可以使用 umount -l /nfs .

最终建议：

1.使用NFS，就要使用portmap或者rpcbind，NFS严重依赖于portmap或者rpcbind，所以不要试图去停止它(portmap或者rpcbind)。

2.当不能umount /nfs 分区时，试着使用umount -f /nfs,一般都能成功。

3.当umount -f /nfs不能umount时，可以试试umount -l /nfs. umount -l是最终级的umount。