On Thu, May 03, 2012 at 03:10:01PM -0700, Steve Rikli wrote:
> 
> By chance do your NFS server & NFS clients have different DNS domainnames
> configured?
> 


I am not sure there is such a thing as a "DNS domainname".

There is many confusions - i.e. some people think that the command 
"domainname" returns the domain name - when in fact it returns the NIS domain name.

So there is:
a) the NIS domain name (returned by "domainname", should have been named "ypdomainname").
b) the DNS search path in /etc/resolv.conf (usually is set to "triumf.ca", but may
contain multiple entries, in fact does contain multiple entries often enough)
c) there is the domain name part of the hostname ("hostname" returns "foo.triumf.ca",
".triumf.ca" is taken as the domain name). Where is the value of "hostname" come
from? Good luck finding out. At TRIUMF it comes from DHCP, set randomly either
to "foo" and "foo.triumf.ca". Also can be set in /etc/sysconfig/network.
d) there is the domain name part of the reverse-DNS entry for the network interface,
i.e. IP address 12.34.56.78 resolves to "foo.triumf.ca", ".triumf.ca" is taken
as domain name. In the case of multiple network interfaces, things become
confused. Also things become confused if /etc/hosts and reverse-DNS are
not consistent (i.e. /etc/hosts has foo.TRIUMF.CA while DNS returns foo.triumf.ca,
did the software write remember to use strcasecmp() to compare them?).

So it's a mystery which domain name is used by idmapd if nothing is specified
in the config file.


>
> Or, maybe the NFS server simply defines a different NFSv4 domainname than
> your clients' default DNS domainname?
> 

Right. Default DNS domainname, NFSv4 domainname. I guess these terms
are clearly defined in some RFC somewhere. I know not what they mean. (See above).

> 
> Whether the NFSv4 domain is defined separately, or the default value of
> DNS domainname is used, both client & server must have the same setting.
> IME when ownership comes up with nobody.nobody it's usually a mis-match
> between client & server NFSv4 domain names.  Or rpc.idmapd is dead or
> otherwise out in the weeds.  :-)
> 

I confirm this. NFSv4 server and client have to use the same domain name,
and by luck, idmapd has a debug mode where it complains about mismatched
usernames and does report what domain names it is trying to use.

As I said before, SL6.2 machines part of an NIS cluster seem to get
the NFSv4 domain name correctly every time automatically. Good.


-- 
Konstantin Olchanski
Data Acquisition Systems: The Bytes Must Flow!
Email: olchansk-at-triumf-dot-ca
Snail mail: 4004 Wesbrook Mall, TRIUMF, Vancouver, B.C., V6T 2A3, Canada