系统版本：CentOS Linux release 7.4.1708 (Core)

 $ vi /etc/nfsmount.conf
 #
# /etc/nfsmount.conf - see nfsmount.conf(5) for details
#
# This is an NFS mount configuration file. This file can be broken
# up into three different sections: Mount, Server and Global
#
# [ MountPoint "Mount_point" ]
# This section defines all the mount options that
# should be used on a particular mount point. The '<Mount_Point>'
# string need to be an exact match of the path in the mount
# command. Example:
#     [ MountPoint "/export/home" ]
#       background=True
# Would cause all mount to /export/home would be done in
# the background
#
# [ Server "Server_Name" ]
# This section defines all the mount options that
# should be used on mounts to a particular NFS server.
# Example:
#     [ Server "nfsserver.foo.com" ]
#       rsize=32k
#       wsize=32k
# All reads and writes to the 'nfsserver.foo.com' server
# will be done with 32k (32768 bytes) block sizes.
#
[ NFSMount_Global_Options ]
# This statically named section defines global mount
# options that can be applied on all NFS mount.
#
# Protocol Version [2,3,4]
# This defines the default protocol version which will
# be used to start the negotiation with the server.
 Defaultvers=4
### 修改此处，版本2，3，4 ############
####################################
#
# Setting this option makes it mandatory the server supports the
# given version. The mount will fail if the given version is
# not support by the server.
# Nfsvers=4
#
# Network Protocol [udp,tcp,rdma] (Note: values are case sensitive)
# This defines the default network protocol which will
# be used to start the negotiation with the server.
# Defaultproto=tcp
#
# Setting this option makes it mandatory the server supports the
# given network protocol. The mount will fail if the given network
# protocol is not supported by the server.
# Proto=tcp
#
# The number of times a request will be retired before
# generating a timeout
# Retrans=2
#
# The number of minutes that will retry mount
# Retry=2
#
# The minimum time (in seconds) file attributes are cached
# acregmin=30
#
# The Maximum time (in seconds) file attributes are cached
# acregmin=60
#
# The minimum time (in seconds) directory attributes are cached
# acregmin=30
#
# The Maximum time (in seconds) directory attributes are cached
# acregmin=60
#
# Enable Access  Control  Lists
# Acl=False
#
# Enable Attribute Caching
# Ac=True
#
# Do mounts in background (i.e. asynchronously)
# Background=False
#
# Close-To-Open cache coherence
# Cto=True
#
# Do mounts in foreground (i.e. synchronously)
# Foreground=True
#
# How to handle times out from servers (Hard is STRONGLY suggested)
# Hard=True
# Soft=False
#
# Enable File Locking
# Lock=True
#
# Enable READDIRPLUS on NFS version 3 mounts
# Rdirplus=True
#
# Maximum Read Size (in Bytes)
# Rsize=8k
#
# Maximum Write Size (in Bytes)
# Wsize=8k
#
# Maximum Server Block Size (in Bytes)
# Bsize=8k
#
# Ignore unknown mount options
# Sloppy=False
#
# Share Data and Attribute Caches
# Sharecache=True
#
# The amount of time, in tenths of a seconds, the client
# will wait for a response from the server before retransmitting
# the request.
# Timeo=600
#
# Sets all attributes times to the same time (in seconds)
# actimeo=30
#
# Server Mountd port mountport
# mountport=4001
#
# Server Mountd Protocol
# mountproto=tcp
#
# Server Mountd Version
# mountvers=3
#
# Server Mountd Host
# mounthost=hostname
#
# Server Port
# Port=2049
#
# RPCGSS security flavors
# [none, sys, krb5, krb5i, krb5p ]
# Sec=sys

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