On a 18.04-client NFS4 over Kerberos is fine against an old ubuntu 10.04 nfs4-server. It would not work however against a Netapp FAS3140 (which is accessible from 14.04 clients).
client_18.04_# mount -v netapp:/resource /mont/netapp-res -t nfs4 -o sec=krb5
mount.nfs4: timeout set for Thu Aug 2 10:13:25 2018
mount.nfs4: trying text-based options 'sec=krb5,vers=4.2,addr=xxxx,clientaddr=yyyy'
mount.nfs4: mount(2): Protocol not supported
mount.nfs4: trying text-based options 'sec=krb5,vers=4.1,addr=xxxx,clientaddr=yyyy'
mount.nfs4: mount(2): Protocol not supported
mount.nfs4: trying text-based options 'sec=krb5,vers=4.0,addr=xxxx,clientaddr=yyyy'
mount.nfs4: mount(2): Permission denied
client_18.04_# klist /tmp/krb5ccmachine_... # shows a krbtgt only, no nfs ticket
This applies to Ubuntu Kernel 4.15.0-20-generic and 4.15.0-29-generic (amd64). vanilla kernel 4.14.0 is fine.
How can I help to trace this kind of error?
rpcinfo 10.162.229.2
show? Are you sure "vers" needs a decimal point? The error points to "protocol" so the "vers" option. I almost only see "vers=2", "vers=3" or "vers=4" in all my setups even when the version has a point release.