I'm using Mac OS High Sierra 10.13, and I'm facing some issues sharing a folder through NFS.

The configuration:

Built-in firewall is disabled and there is no third party firewall installed.

1. I made sure the nfs service is enabled:

   $ sudo nfsd enable
   

   The nfsd service is already enabled.

2. I made sure the nfs service is running:

   $ sudo nfsd start
   

   The nfsd service is already running.

3. I checked with nmap to see ports being listened to:

   $ nmap localhost
   

           
   Starting Nmap 7.60 ( https://nmap.org ) at 2017-10-17 21:53 CEST
   Nmap scan report for localhost (127.0.0.1)
   Host is up (0.00034s latency).
   Other addresses for localhost (not scanned): ::1 10.101.97.98
   Not shown: 995 filtered ports
   PORT     STATE SERVICE
   80/tcp   open  http
   111/tcp  open  rpcbind
   1021/tcp open  exp1
   1023/tcp open  netvenuechat
   2049/tcp open  nfs
   
   
   Nmap done: 1 IP address (1 host up) scanned in 4.34 seconds
   

4. rpcinfo

   $ rpcinfo -p
   

   program vers proto   port
   100000    2   udp    111  rpcbind 
   100000    3   udp    111  rpcbind 
   100000    4   udp    111  rpcbind 
   100000    2   tcp    111  rpcbind 
   100000    3   tcp    111  rpcbind 
   100000    4   tcp    111  rpcbind 
   100024    1   udp    612  status 
   100024    1   tcp   1021  status 
   100021    0   udp    843  nlockmgr 
   100021    1   udp    843  nlockmgr 
   100021    3   udp    843  nlockmgr 
   100021    4   udp    843  nlockmgr 
   100021    0   tcp   1017  nlockmgr 
   100021    1   tcp   1017  nlockmgr 
   100021    3   tcp   1017  nlockmgr 
   100021    4   tcp   1017  nlockmgr 

5. Test connection to nfs

   $ telnet localhost 2049
   

   Trying ::1…
   Connected to localhost.
   Escape character is '^]'.

6. Create folder to be shared

   $ mkdir -p ~/tmp/shared-test
   $ touch ~/tmp/shared-test/works.txt
   

7. Add it to /etc/exports

   $ sudo echo "/Users/user/tmp/shared-test -mapall=-2:-2 -ro" >> /etc/exports
   $ sudo chmod 640 /etc/exports
   

8. Make sure /etc/exports is correct

   $ sudo nfsd checkexports
   

The issue:

$ showmount -e

showmount: Cannot retrieve info from host: localhost: RPC failed:: RPC: Unable to send; errno = Bad file descriptor

$ syslog

Oct 17 21:56:28 Estebans-MacBook-Pro-2 rpc.lockd[215] : can't contact statd, 100024 RPC: Timed out
--- last message repeated 2 times ---
Oct 17 21:58:29 Estebans-MacBook-Pro-2 syslogd[43] : ASL Sender Statistics
Oct 17 21:59:31 Estebans-MacBook-Pro-2 rpc.lockd[215] : can't contact statd, 100024 RPC: Timed out
Oct 17 22:00:19 Estebans-MacBook-Pro-2 login[1328] : USER_PROCESS: 1328 ttys002
Oct 17 22:00:33 Estebans-MacBook-Pro-2 rpc.lockd[215] : can't contact statd, 100024 RPC: Timed out

I can see rpc.lockd[215] : can't contact statd, 100024 RPC: Timed out all over, as a recurrent log.

$ showmount 127.0.0.1

showmount: Cannot retrieve info from host: 127.0.0.1: RPC: Program not registered