Export server side:

1. sudo apt-get install nfs-server nfs-common
2. vim /etc/exports
   <path>/<to>/<export> hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check)
3. sudo service ufw stop && sudo ufw disable
4. sudo service nfs-server restart && sudo service nfs-kernel-server restart
5. sudo service portmap start

Client side(hostname1 and hostname2):

1. sudo usermod -u <id-same-with-a-server-user> <user>
2. mkdir <mountpoint>
3. mount -F -t nfs <server-user-same-with-step-1>:<path>/<to>/<export> <mountpoint>
   NB: client user wants to remotely access the remote share folder, must make sure same user id. I.e. <client user id> == <server user id>