Documentation and debugging for NFSv4

Doug McIntyre merlyn at
Fri May 22 18:26:44 UTC 2020

On Fri, May 22, 2020 at 03:15:01PM +0100, Norman Gray wrote:
> I'm having difficulty finding consistent documentation and debugging tools
> for NFSv4.  Is there some handbook-like source that I'm missing?  Or some
> layer of documentation for configuration or debugging that I've failed to
> find?

I think in general, that NFSv4 is not widely deployed outside of
hetrogenous linux environments. Given the state of things, I'd imagine
it is downgraded to NFSv3 more often than not in other use cases of mixed

> Normally some combination of netstat and tcpdump would make some headway,
> but SunRPC is blacker magic than that.

NFSv4 is a big change, most implementations I've seen operate over TCP instead of UDP
whereas TCP was optional in v2 and v3. NFSv4 doesn't need rpc portmapper, nor
other helper daemons. The IDmapper is a big change as well, no more UID passed
through, but all UIDs have to be mapped back and forth on both sides.

Make sure you use V4 definitions in /etc/exports.  From what I
remember even connecting as a client needed 'V4: /' in there to
connect right to a linux NFSv4 server, but I could be misremembering. 

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