SOLVED No working solution found for "kernel: NLM: failed to contact remote rpcbind"

[callmr]

Since yesterday I am seeing an awful lot of these messages in syslog-ng (this wasn't seen in syslog at all before):

kernel: NLM: failed to contact remote rpcbind, stat = 5, port = 28416

Having looked for a solution there is actually not really much to find, also threads where people have the same problem but no solutions.
I tried what I found and it did not solve the issue:

shut down NFS clients
rm /var/db/statd.status
service statd restart
service lockd restart
start NFS clients

This happens on 12.0 U8. So I upgraded to 12.0 U8.1, but that also did not solve it.
The clients all are Debian 11 (and one Debian 10).

I hope someone knows a working solution, fingers crossed.

 

[callmr]

Looking at the actual meaning of the error I figured out that the TN cannot contact the NFS client's rpcbind. :)
An NFS server wants to call the NFS client's rpcbind to determine the port numbers for lockd or statd in the case of file locking or shutdown, respectively. The reason for failure was the host firewall of the NFS client.

Solution:
Either you open all ports for the TN filer on the NFS client machine, or you need to first configure the NFS client so that the ports used for statd and lockd are not random but fixed. Then you may open these fixed ports in the firewall for the TN filer. How this is done depends on what OS your NFS client is running.