NFS 是Network File System的缩写，即网络文件系统，一种使用于分散式文件系统的协定
NFS通过网络让不同的机器、不同的操作系统能够彼此分享个别的数据，例如将/home设置为共享目录，然后共享给网络中的其它服务器，这样每台机器就不必单独建立自己的/home路径了，NFS独立于操作系统，容许不同硬件及操作系统的系统共同进行文件的分享，是在类Unix系统间实现磁盘文件共享的一种方法
NFS本身没有提供信息传输的协议和功能，而是使用RPC服务完成这部分功能。可以说NFS本身就是使用RPC服务的一个程序，或者说NFS也是一个RPC SERVER。所以只要用到NFS的地方都要启动RPC服务，不论是NFS server还是NFS client，可以这么理解RPC和NFS之间的关系：NFS是一个文件系统，而RPC负责信息的传输
一，系统环境
Linux Distribution：Ubuntu 14
二，安装Linux NFS
sean@sean:~$ sudo apt-get install nfs-kernel-server [sudo] password for sean: Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: keyutils libgssglue1 libnfsidmap2 libtirpc1 nfs-common rpcbind Suggested packages: open-iscsi watchdog The following NEW packages will be installed: keyutils libgssglue1 libnfsidmap2 libtirpc1 nfs-common nfs-kernel-server rpcbind 0 upgraded, 7 newly installed, 0 to remove and 159 not upgraded. Need to get 460 kB of archives. After this operation, 2,049 kB of additional disk space will be used. Do you want to continue? [Y/n] Y Get:1 http://cn.archive.ubuntu.com/ubuntu/ trusty/main libgssglue1 amd64 0.4-2ubuntu1 [19.7 kB] Get:2 http://cn.archive.ubuntu.com/ubuntu/ trusty/main libnfsidmap2 amd64 0.25-5 [32.2 kB] Get:3 http://cn.archive.ubuntu.com/ubuntu/ trusty/main libtirpc1 amd64 0.2.2-5ubuntu2 [71.3 kB] Get:4 http://cn.archive.ubuntu.com/ubuntu/ trusty/main keyutils amd64 1.5.6-1 [33.6 kB] Get:5 http://cn.archive.ubuntu.com/ubuntu/ trusty-updates/main rpcbind amd64 0.2.1-2ubuntu2.2 [37.1 kB] Get:6 http://cn.archive.ubuntu.com/ubuntu/ trusty-updates/main nfs-common amd64 1:1.2.8-6ubuntu1.2 [181 kB] Get:7 http://cn.archive.ubuntu.com/ubuntu/ trusty-updates/main nfs-kernel-server amd64 1:1.2.8-6ubuntu1.2 [85.8 kB] Fetched 460 kB in 16s (27.2 kB/s) Selecting previously unselected package libgssglue1:amd64. (Reading database ... 168701 files and directories currently installed.) Preparing to unpack .../libgssglue1_0.4-2ubuntu1_amd64.deb ... Unpacking libgssglue1:amd64 (0.4-2ubuntu1) ... Selecting previously unselected package libnfsidmap2:amd64. Preparing to unpack .../libnfsidmap2_0.25-5_amd64.deb ... Unpacking libnfsidmap2:amd64 (0.25-5) ... Selecting previously unselected package libtirpc1:amd64. Preparing to unpack .../libtirpc1_0.2.2-5ubuntu2_amd64.deb ... Unpacking libtirpc1:amd64 (0.2.2-5ubuntu2) ... Selecting previously unselected package keyutils. Preparing to unpack .../keyutils_1.5.6-1_amd64.deb ... Unpacking keyutils (1.5.6-1) ... Selecting previously unselected package rpcbind. Preparing to unpack .../rpcbind_0.2.1-2ubuntu2.2_amd64.deb ... Unpacking rpcbind (0.2.1-2ubuntu2.2) ... Selecting previously unselected package nfs-common. Preparing to unpack .../nfs-common_1%3a1.2.8-6ubuntu1.2_amd64.deb ... Unpacking nfs-common (1:1.2.8-6ubuntu1.2) ... Selecting previously unselected package nfs-kernel-server. Preparing to unpack .../nfs-kernel-server_1%3a1.2.8-6ubuntu1.2_amd64.deb ... Unpacking nfs-kernel-server (1:1.2.8-6ubuntu1.2) ... Processing triggers for man-db (2.6.7.1-1ubuntu1) ... Processing triggers for ureadahead (0.100.0-16) ... ureadahead will be reprofiled on next reboot Setting up libgssglue1:amd64 (0.4-2ubuntu1) ... Setting up libnfsidmap2:amd64 (0.25-5) ... Setting up libtirpc1:amd64 (0.2.2-5ubuntu2) ... Setting up keyutils (1.5.6-1) ... Setting up rpcbind (0.2.1-2ubuntu2.2) ... Removing any system startup links for /etc/init.d/rpcbind ... rpcbind start/running, process 12074 Processing triggers for ureadahead (0.100.0-16) ... Setting up nfs-common (1:1.2.8-6ubuntu1.2) ... Creating config file /etc/idmapd.conf with new version Creating config file /etc/default/nfs-common with new version Adding system user `statd' (UID 118) ... Adding new user `statd' (UID 118) with group `nogroup' ... Not creating home directory `/var/lib/nfs'. statd start/running, process 12307 gssd stop/pre-start, process 12341 idmapd start/running, process 12399 Processing triggers for ureadahead (0.100.0-16) ... Setting up nfs-kernel-server (1:1.2.8-6ubuntu1.2) ... Creating config file /etc/exports with new version Creating config file /etc/default/nfs-kernel-server with new version * Not starting NFS kernel daemon: no exports. Processing triggers for libc-bin (2.19-0ubuntu6.7) ... Processing triggers for ureadahead (0.100.0-16) ...</div>
通过安装日志可以发现总共会安装keyutils，libgssglue1，libnfsidmap2，libtirpc1，nfs-common，nfs-kernel-server，rpcbind这7个包
很多文档中安装的包为portmap，但是这个包已经被rpcbind替代
sean@sean:~$ sudo apt-get install portmap
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'rpcbind' instead of 'portmap'
rpcbind is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 164 not upgraded.
rpcbind包安装完成后会自动启动rpcbind服务
sean@sean:~$ ps -ef|grep rpcbind
root 807 1 0 22:27 ? 00:00:00 rpcbind
sean 10215 9528 0 22:48 pts/6 00:00:00 grep --color=auto rpcbind
但是由于目前NFS的配置文件为空，NFS服务并没有启动
三，配置NFS服务
从安装日志中我们可以发现NFS服务的配置文件为/etc/exports，并且这个文件在安装过程中已经生成好了，我们所要做的就是将NFS配置信息添加到这个文件中
sean@sean:~$ sudo vi /etc/exports # /etc/exports: the access control list for filesystems which may be exported # to NFS clients. See exports(5). # # Example for NFSv2 and NFSv3: # /srv/homes hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check) # # Example for NFSv4: # /srv/nfs4 gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check) # /srv/nfs4/homes gss/krb5i(rw,sync,no_subtree_check) /home/sean/shareDir 192.168.137.129(rw,no_root_squash,async)</div>
其中中的最后一行为新添加的NFS配置，NFS配置信息格式如下：
<共享目录> [客户端1 选项（访问权限,用户映射,其他）] [客户端2 选项（访问权限,用户映射,其他）]
1，共享目录：
共享目录是指NFS系统中需要共享给客户机使用的目录
2，客户端：
客户端是指网络中可以访问NFS共享目录的计算机
客户端常用的指定方式：
(1)指定ip地址的主机：192.168.0.1
(2)指定子网中的所有主机：192.168.0.0/255.255.255.0
(3)指定域名的主机：www.sean.com
(4)指定域中的所有主机：*.sean.com
(5)所有主机：*
3，选项：
选项用来设置输出目录的访问权限、用户映射等，NFS主要有3类选项：
访问权限选项：
(1)设置输出目录只读：ro
(2)设置输出目录读写：rw
用户映射选项：
(1)all_squash：将远程访问的所有普通用户及所属组都映射为匿名用户或用户组（nfsnobody）
(2)no_all_squash：与all_squash取反（默认设置）
(3)root_squash：将root用户及所属组都映射为匿名用户或用户组（默认设置）
(4)no_root_squash：与rootsquash取反
(5)anonuid=xxx：将远程访问的所有用户都映射为匿名用户，并指定该用户为本地用户（UID=xxx）
(6)anongid=xxx：将远程访问的所有用户组都映