Documentation and debugging for NFSv4

[Thomas Mueller]

from Doug McIntyre:

> 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
> OSes. 

> > 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. 

One question has bugged me, how to set up /etc/exports to be able to export by either NFSv3 or NFSv4, without having to have two files and copy to /etc/exports every time you want to use the other (NFSv3 or 4) protocol.

I believe an OS that does not support NFSv4 (such as NetBSD) can not mount_nfs when the server is using NFSv4?

Tom