Hmmm... I agree with you that if "nfs4_disable_idmapping" is still at the default of 0 or N, that I'd expect to see names instead of numbers in the setattr parameters.

However, if you've been changing the value of the setting, keep in mind that a new value only comes into effect for a new mount. An existing mount (mounted while the setting was 1/Y) will continue to send UID# even if you change the setting to 0/N.

Another "gotcha" is that if idmapd (on the nfs client machine) has died, been killed, or was never started, that will cause UID# to be send instead of username@domain. Does "rcnfs status" report that idmapd is running? Or can you find it with "ps aux | grep idmapd"? In the days before NFSv4, even if you didn't run "rcnfs start" and just did a mount manually, all was well, because the nfs client didn't really rely on much else to be started first. But (at least on SLES 11 SP2, I didn't try others) if you don't run "rcnfs start" and just do a manual nfsv4 mount, the mount will succeed, but idmapd will not be running. And then you'll get UID#s instead of names.

Today I tried chown on a SLES 11 SP2 nfsv4 clients -- with nfs4_disable_idmapping set to 0/N, and idmapd running -- and then checked with tcpdump/wireshark, and it did indeed send username@domain within the setattr, not the UID# of the user.