Documentation and debugging for NFSv4

[Norman Gray]

Greetings.

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've never had major problems with NFS and the associated RPC services, 
but I currently find myself in a situation where some combination of v4 
exports from FreeBSD servers (11.3 and 12.1) and heterogeneous Linux 
clients is behaving in a rather inconsistent way (in a context where I 
can't just reboot everything in sight, which often sorts out NFS 
problems...), and I'm having great difficulty diagnosing the current 
service status: is server A offering what I think it is? is client B 
asking for what I think it is?  Normally some combination of netstat and 
tcpdump would make some headway, but SunRPC is blacker magic than that.

Oddnesses include the handbook [1] not mentioning NFSv4 at all, neither 
starting up NFSv4 support (with nfsv4_server_enable=YES) nor mentioning 
V4 in exports.  It's therefore hard to be sure what counts as good 
practice here.

nfsv4(4) is comprehensive, which is good, but exports(5), though 
comprehensive, is sometimes far from clear.  Also, nfsdumpstate(8) 
refers to 'the NFSv4 experimental server', which isn't reassuring, and 
the state which it dumps is clearly low-level and not illuminating.  I 
anticipate visiting bugs.freebsd.org with some docbugs, once I'm more 
confident I know what 'correct' is.

I see with rpcinfo that program 100003, for NFS, advertises versions 2 
and 3, but not 4, and I can't work out, from any manpages I can find, 
whether this is correct or not.  Pages I can find on the web seem to 
suggest that I ought to expect to see a version 4 here (though these are 
mostly referring to Linux NFS servers), and RFC 3530 ([4] page 266) does 
seem to mention a version 4 identifier associated with program 100003.  
But relevant posts on the FreeBSD forum (eg [2, 3] from 2012 and 2018) 
illustrated apparently working configurations which advertise only 
versions 2 and 3.

Would the forum be a better place to ask, than here?

Any advice warmly received,

Norman


[1] https://www.freebsd.org/doc/handbook/network-nfs.html
[2] 
https://forums.freebsd.org/threads/nfsv4-problem-rpc-remote-system-error-operation-timed-out.34550/
[3] https://forums.freebsd.org/threads/nfs-server-access-denied.57514/
[4] https://www.ietf.org/rfc/rfc3530.txt

-- 
Norman Gray  :  http://www.astro.gla.ac.uk/users/norman/it/
Research IT Coordinator
SUPA School of Physics and Astronomy, University of Glasgow, UK
Charity number SC004401