【背景】
折腾：
【已解决】在远程Ubuntu服务器中开通NFS服务供别人访问服务器上的文件
期间，需要去搞懂：
作为NFS服务器端Ubuntu中的已安装的nfs的server的版本
和
作为NFS客户端的CentOS的已安装的nfs的client的版本
以便于去设置对应的fstab中的nfsvers的值。
【解决过程】
1.好像没有什么nfs -v之类，去查看版本信息。
2.参考：
14.04 – Can’t auto-mount NFS share using fstab – Ask Ubuntu
去试试：
man nfs
结果没有显示当前版本：
root@chantyou:~# man nfs
NFS(5) File Formats Manual NFS(5)
NAME
nfs - fstab format and options for the nfs file systems
SYNOPSIS
/etc/fstab
DESCRIPTION
NFS is an Internet Standard protocol created by Sun Microsystems in 1984. NFS was developed to allow file sharing between
systems residing on a local area network. The Linux NFS client supports three versions of the NFS protocol: NFS version
2 [RFC1094], NFS version 3 [RFC1813], and NFS version 4 [RFC3530].
The mount(8) command attaches a file system to the system's name space hierarchy at a given mount point. The /etc/fstab
file describes how mount(8) should assemble a system's file name hierarchy from various independent file systems (includ‐
ing file systems exported by NFS servers). Each line in the /etc/fstab file describes a single file system, its mount
point, and a set of default mount options for that mount point.
For NFS file system mounts, a line in the /etc/fstab file specifies the server name, the path name of the exported server
directory to mount, the local directory that is the mount point, the type of file system that is being mounted, and a
list of mount options that control the way the filesystem is mounted and how the NFS client behaves when accessing files
on this mount point. The fifth and sixth fields on each line are not used by NFS, thus conventionally each contain the
digit zero. For example:
server:path /mountpoint fstype option,option,... 0 02.搜：
check nfs version
参考：
linux – How to determine if NFS mount is mounted as v3 or v4? – Unix & Linux Stack Exchange
去试试：
root@chantyou:~# nfsstat --help
Usage: nfsstat [OPTION]...
-m, --mounts Show statistics on mounted NFS filesystems
-c, --client Show NFS client statistics
-s, --server Show NFS server statistics
-2 Show NFS version 2 statistics
-3 Show NFS version 3 statistics
-4 Show NFS version 4 statistics
-o [facility] Show statistics on particular facilities.
nfs NFS protocol information
rpc General RPC information
net Network layer statistics
fh Usage information on the server's file handle cache
rc Usage information on the server's request reply cache
all Select all of the above
-v, --verbose, --all Same as '-o all'
-r, --rpc Show RPC statistics
-n, --nfs Show NFS statistics
-Z[#], --sleep[=#] Collects stats until interrupted.
Cumulative stats are then printed
If # is provided, stats will be output every
# seconds.
-S, --since file Shows difference between current stats and those in 'file'
-l, --list Prints stats in list format
--version Show program version
--help What you just did
root@chantyou:~# nfsstat -m
root@chantyou:~# mount -t nfs 121.41.120.185:/home/share/image /root/nfs_client_root/
root@chantyou:~# nfsstat -m
/root/nfs_client_root from 121.41.120.185:/home/share/image
Flags: rw,relatime,vers=4.0,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=120.26.121.239,local_lock=none,addr=121.41.120.1853.再去试试另外一种：
结果无输出：
root@chantyou:~# mount -v | grep /root/nfs_client_root/
4.所以现在确定了：
NFS的vers=4.0
5.NFS服务器中，去试试：
root@iZ23lqgttauZ:image# nfsstat -m
很明显，没输出，是因为NFS服务器中没有mount。所以没有结果输出。
所以再去搜：
NFS server check nfs version
参考：
Example: Linux Command To Find NFS Version
root@iZ23lqgttauZ:image# nfsstat -s Server rpc stats: calls badcalls badclnt badauth xdrcall 324 0 0 0 0 Server nfs v4: null compound 3 0% 321 99% Server nfs v4 operations: op0-unused op1-unused op2-future access close commit 0 0% 0 0% 0 0% 23 4% 3 0% 0 0% create delegpurge delegreturn getattr getfh link 0 0% 0 0% 0 0% 104 20% 18 3% 0 0% lock lockt locku lookup lookup_root nverify 0 0% 0 0% 0 0% 14 2% 0 0% 0 0% open openattr open_conf open_dgrd putfh putpubfh 19 3% 0 0% 3 0% 0 0% 127 24% 0 0% putrootfh read readdir readlink remove rename 3 0% 0 0% 3 0% 0 0% 0 0% 0 0% renew restorefh savefh secinfo setattr setcltid 181 35% 0 0% 0 0% 2 0% 3 0% 5 0% setcltidconf verify write rellockowner bc_ctl bind_conn 5 0% 0 0% 0 0% 0 0% 0 0% 0 0% exchange_id create_ses destroy_ses free_stateid getdirdeleg getdevinfo 0 0% 0 0% 0 0% 0 0% 0 0% 0 0% getdevlist layoutcommit layoutget layoutreturn secinfononam sequence 0 0% 0 0% 0 0% 0 0% 0 0% 0 0% set_ssv test_stateid want_deleg destroy_clid reclaim_comp 0 0% 0 0% 0 0% 0 0% 0 0%
可以看出：
Server nfs v4
的确，NFS服务器版本是4
【总结】
1.NFS的客户端中：
nfsstat -m
中的vers=4.0确定NFS版本是4。
2.NFS服务器中：
nfsstat -s
中的Server nfs v4确定NFS版本的确是4。
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