NFS 是Network File System的縮寫，即網絡文件系統，一種使用於分散式文件系統的協定
NFS通過網絡讓不同的機器、不同的操作系統能夠彼此分享個別的數據，例如將/home設置爲共享目錄，然後共享給網絡中的其它服務器，這樣每臺機器就不必單獨建立自己的/home路徑了，NFS獨立於操作系統，容許不同硬件及操作系統的系統共同進行文件的分享，是在類Unix系統間實現磁盤文件共享的一種方法
NFS本身沒有提供信息傳輸的協議和功能，而是使用RPC服務完成這部分功能。可以說NFS本身就是使用RPC服務的一個程序，或者說NFS也是一個RPC SERVER。所以只要用到NFS的地方都要啓動RPC服務，不論是NFS server還是NFS client，可以這麼理解RPC和NFS之間的關係：NFS是一個文件系統，而RPC負責信息的傳輸
一，系統環境
Linux Distribution：Ubuntu 14
二，安裝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.)
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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) ...
通過安裝日誌可以發現總共會安裝keyutils，libgssglue1，libnfsidmap2，libtirpc1，nfs-common，nfs-kernel-server，rpcbind這7個包
很多文檔中安裝的包爲portmap，但是這個包已經被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包安裝完成後會自動啓動rpcbind服務
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
但是由於目前NFS的配置文件爲空，NFS服務並沒有啓動
三，配置NFS服務
從安裝日誌中我們可以發現NFS服務的配置文件爲/etc/exports，並且這個文件在安裝過程中已經生成好了，我們所要做的就是將NFS配置信息添加到這個文件中
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)
其中中的最後一行爲新添加的NFS配置，NFS配置信息格式如下：
<共享目錄> [客戶端1 選項（訪問權限,用戶映射,其他）] [客戶端2 選項（訪問權限,用戶映射,其他）]
1，共享目錄：
共享目錄是指NFS系統中需要共享給客戶機使用的目錄
2，客戶端：
客戶端是指網絡中可以訪問NFS共享目錄的計算機
客戶端常用的指定方式：
(1)指定ip地址的主機：192.168.0.1
(2)指定子網中的所有主機：192.168.0.0/255.255.255.0
(3)指定域名的主機：www.sean.com
(4)指定域中的所有主機：*.sean.com
(5)所有主機：*
3，選項：
選項用來設置輸出目錄的訪問權限、用戶映射等，NFS主要有3類選項：
訪問權限選項：
(1)設置輸出目錄只讀：ro
(2)設置輸出目錄讀寫：rw
用戶映射選項：
(1)all_squash：將遠程訪問的所有普通用戶及所屬組都映射爲匿名用戶或用戶組（nfsnobody）
(2)no_all_squash：與all_squash取反（默認設置）
(3)root_squash：將root用戶及所屬組都映射爲匿名用戶或用戶組（默認設置）
(4)no_root_squash：與rootsquash取反
(5)anonuid=xxx：將遠程訪問的所有用戶都映射爲匿名用戶，並指定該用戶爲本地用戶（UID=xxx）
(6)anongid=xxx：將遠程訪問的所有用戶組都映射爲匿名用戶組賬戶，並指定該匿名用戶組賬戶爲本地用戶組賬戶（GID=xxx）
其它選項：
(1)secure：限制客戶端只能從小於1024的tcp/ip端口連接nfs服務器（默認設置）
(2)insecure：允許客戶端從大於1024的tcp/ip端口連接服務器
(3)sync：將數據同步寫入內存緩衝區與磁盤中，效率低，但可以保證數據的一致性
(4)async：將數據先保存在內存緩衝區中，必要時才寫入磁盤
(5)wdelay：檢查是否有相關的寫操作，如果有則將這些寫操作一起執行，這樣可以提高效率（默認設置）
(6)no_wdelay：若有寫操作則立即執行，應與sync配合使用
(7)subtree：若輸出目錄是一個子目錄，則nfs服務器將檢查其父目錄的權限(默認設置)
(8)no_subtree：即使輸出目錄是一個子目錄，nfs服務器也不檢查其父目錄的權限，這樣可以提高效率
四，啓動NFS服務
sean@sean:~$ sudo service nfs-kernel-server start
* Exporting directories for NFS kernel daemon... exportfs: /etc/exports [1]: Neither 'subtree_check' or 'no_subtree_check' specified for export "192.168.137.129:/home/sean/shareDir".
Assuming default behaviour ('no_subtree_check').
NOTE: this default has changed since nfs-utils version 1.0.x
[ OK ]
* Starting NFS kernel daemon
sean@sean:~$ sudo service nfs-kernel-server status
nfsd running
sean@sean:~$ ps -ef|grep nfsd
root 10536 2 0 23:40 ? 00:00:00 [nfsd4]
root 10537 2 0 23:40 ? 00:00:00 [nfsd4_callbacks]
root 10539 2 0 23:40 ? 00:00:00 [nfsd]
root 10540 2 0 23:40 ? 00:00:00 [nfsd]
root 10541 2 0 23:40 ? 00:00:00 [nfsd]
root 10542 2 0 23:40 ? 00:00:00 [nfsd]
root 10543 2 0 23:40 ? 00:00:00 [nfsd]
root 10544 2 0 23:40 ? 00:00:00 [nfsd]
root 10545 2 0 23:40 ? 00:00:00 [nfsd]
root 10546 2 0 23:40 ? 00:00:00 [nfsd]
sean 10566 9528 0 23:41 pts/6 00:00:00 grep --color=auto nfsd
通過命令可以看到文件夾已經被共享
sean@sean:~$ showmount -e
Export list for sean:
/home/sean/shareDir 192.168.137.129
五，客戶端掛載NFS共享目錄
sean@ubuntu:~$ sudo mount 192.168.137.128:/home/sean/shareDir /home/sean/shared
mount: wrong fs type, bad option, bad superblock on 192.168.137.128:/home/sean/shareDir,
missing codepage or helper program, or other error
(for several filesystems (e.g. nfs, cifs) you might
need a /sbin/mount.<type> helper program)
In some cases useful info is found in syslog - try
dmesg | tail or so
上網查看了一下錯誤原因，是因爲客戶端沒有安裝nfs-common包
sean@ubuntu:~$ sudo apt-get install nfs-common
之後再次使用掛載命令即可，此時如果我們再次查看客戶端掛載的磁盤，就可以看到NFS共享目錄已經被掛載上了
sean@ubuntu:~$ df
Filesystem 1K-blocks Used Available Use% Mounted on
udev 488800 4 488796 1% /dev
tmpfs 99904 1456 98448 2% /run
/dev/sda1 19478204 3745568 14720156 21% /
none 4 0 4 0% /sys/fs/cgroup
none 5120 0 5120 0% /run/lock
none 499512 152 499360 1% /run/shm
none 102400 40 102360 1% /run/user
/dev/sr0 1044480 1044480 0 100% /media/sean/Ubuntu 14.04.4 LTS amd64
192.168.137.128:/home/sean/shareDir 19478272 4288896 14176896 24% /home/sean/shared
此時如果我們在128的/home/sean/shareDir目錄下創建一個文件，在129的/home/sean/shared目錄下可以看到一個名稱相同的文件，並且文件的內容也相同
六，開機啓動NFS服務
安裝完成之後查看系統服務
sean@sean:~$ runlevel
N 2
sean@sean:~$ ll /etc/rc2.d
total 20
drwxr-xr-x 2 root root 4096 6月 20 23:25 ./
drwxr-xr-x 132 root root 12288 6月 26 20:16 ../
-rw-r--r-- 1 root root 677 2月 17 12:59 README
lrwxrwxrwx 1 root root 20 2月 22 06:33 S20kerneloops -> ../init.d/kerneloops*
lrwxrwxrwx 1 root root 27 6月 20 23:25 S20nfs-kernel-server -> ../init.d/nfs-kernel-server*
lrwxrwxrwx 1 root root 15 2月 22 06:33 S20rsync -> ../init.d/rsync*
lrwxrwxrwx 1 root root 27 2月 22 06:33 S20speech-dispatcher -> ../init.d/speech-dispatcher*
lrwxrwxrwx 1 root root 15 2月 22 06:33 S50saned -> ../init.d/saned*
lrwxrwxrwx 1 root root 19 2月 22 06:33 S70dns-clean -> ../init.d/dns-clean*
lrwxrwxrwx 1 root root 18 2月 22 06:33 S70pppd-dns -> ../init.d/pppd-dns*
lrwxrwxrwx 1 root root 21 2月 22 06:33 S99grub-common -> ../init.d/grub-common*
lrwxrwxrwx 1 root root 18 2月 22 06:33 S99ondemand -> ../init.d/ondemand*
lrwxrwxrwx 1 root root 18 2月 22 06:33 S99rc.local -> ../init.d/rc.local*
nfs-kernel-server是自動啓動，就不需要再進行修改了，而rpcbind就比較麻煩了，找了半天才找到vi /etc/init/rpcbind-boot.conf
# portmap-boot
description "Upstart job to start rpcbind on boot only"
author "Clint Byrum"
emits start-rpcbind
start on virtual-filesystems and net-device-up IFACE=lo
task
exec initctl emit --no-wait start-rpcbind ON_BOOT=y
可以見到這個服務設爲開機啓動了
七，開機自動掛載共享盤
這時候我們需要修改的文件是/etc/fstab，命令格式如下：
<NFS服務端>:<共享目錄> <本地目錄> <文件系統類型> <選項> <dump> <pass>每個字段的具體含義這裏就不詳細解釋了，vi /etc/fstab，在文件中添加下面這行配置
192.168.137.128:/home/sean/shareDir /home/sean/shared nfs defaults 0 0系統每次啓動時即會自動掛載共享盤