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To:     linux-nfs@vger.kernel.org
From:   Patrick Goetz <pgoetz@math.utexas.edu>
Subject: rpcbind redux
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My University information security office does not like rpcbind and will 
automatically quarantine any system for which they detect a portmapper 
running on an exposed port.

Since I exclusively use NFSv4 I was happy to "learn" that NFSv4 doesn't 
require rpcbind any more.  For example, here's what it says in the 
current RHEL documentation:

"NFS version 4 (NFSv4) works through firewalls and on the Internet, no 
longer requires an rpcbind service, supports Access Control Lists 
(ACLs), and utilizes stateful operations."

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_file_systems/exporting-nfs-shares_managing-file-systems#introduction-to-nfs_exporting-nfs-shares

I'm using Ubuntu 20.04 rather than RHEL, but the nfs-server service 
absolutely will not start if it can't launch rpcbind as a precursor:

-----------------------------
root@helios:~# systemctl stop rpcbind
Warning: Stopping rpcbind.service, but it can still be activated by:
   rpcbind.socket
root@helios:~# systemctl mask rpcbind
Created symlink /etc/systemd/system/rpcbind.service → /dev/null.

root@helios:~# systemctl restart nfs-server
Job for nfs-server.service canceled.
root@helios:~# systemctl status nfs-server
● nfs-server.service - NFS server and services
      Loaded: loaded (/lib/systemd/system/nfs-server.service; enabled; 
vendor preset: enabled)
     Drop-In: /run/systemd/generator/nfs-server.service.d
              └─order-with-mounts.conf
      Active: failed (Result: exit-code) since Fri 2020-09-25 14:21:46 
UTC; 10s ago
     Process: 3923 ExecStartPre=/usr/sbin/exportfs -r (code=exited, 
status=0/SUCCESS)
     Process: 3925 ExecStart=/usr/sbin/rpc.nfsd $RPCNFSDARGS 
(code=exited, status=1/FAILURE)
     Process: 3931 ExecStopPost=/usr/sbin/exportfs -au (code=exited, 
status=0/SUCCESS)
     Process: 3932 ExecStopPost=/usr/sbin/exportfs -f (code=exited, 
status=0/SUCCESS)
    Main PID: 3925 (code=exited, status=1/FAILURE)

Sep 25 14:21:46 helios systemd[1]: Starting NFS server and services...
Sep 25 14:21:46 helios rpc.nfsd[3925]: rpc.nfsd: writing fd to kernel 
failed: errno 111 (Connection refused)
Sep 25 14:21:46 helios rpc.nfsd[3925]: rpc.nfsd: unable to set any 
sockets for nfsd
Sep 25 14:21:46 helios systemd[1]: nfs-server.service: Main process 
exited, code=exited, status=1/FAILURE
Sep 25 14:21:46 helios systemd[1]: nfs-server.service: Failed with 
result 'exit-code'.
Sep 25 14:21:46 helios systemd[1]: Stopped NFS server and services.
-----------------------------

So, now I'm confused.  Does NFSv4 need rpcbind to be running, does it 
just need it when it launches, or something else?  I made a local copy 
of the systemd service file and edited out the rpcbind dependency, so 
it's not that.