On Nov 25, 2020, at 17:41, Richard Kimberly Heck rikiheck@lyx.org wrote:
But /home/rikiheck/files was an ordinary directory that I want to export, not the root for NFSv4. It was being mounted as NFSv3 (trying to mount with nfs4 would fail). But I'm guessing that it was being treated inconsistently between the client and the server. Removing the 'fsid=0' tag solved the problem. It's still a bit of a mystery what exactly the firewall was blocking, but it wasn't a firewall problem, in the end.
With NFSv4, the locking (NLM) is handed directly through the same rpc protocol as the mount, while in v3 and earlier, it’s a separate rpc protocol which was likely being blocked by the firewall. This is why v4 is so much easier to configure with firewalls.
-- Jonathan Billings