Debugging NFS Hangs

[J. Bruce Fields]

On Fri, Dec 07, 2007 at 10:02:46AM -0500, Norman Elton wrote:
> I've got NFSv4 setup and working (thanks to this list!) between two  
> RHEL5 boxes. After adding a few extra NFS exports, I've noticed that  
> the connection "hangs" mysteriously. I can mount the share, but when I  
> try to write a file, it just sits there waiting. Yesterday, it did the  
> same when I tried to get a directory listing ("ls"). I have to "kill  
> -9" the process.
> 
> We've occasionally experienced these issues with NFSv3,

and without krb5?

> but remounting  
> the share typically took care of it. It's as if there is a firewall/ 
> acl problem, but I've already disabled iptables. Both client and  
> server are on the same network. I am working to see if SELinux is  
> getting in the way of things.
> 
> I've included my exports and fstab files below.
> 
> tcpdump doesn't show anything out of the ordinary. Running "svcgssd - 
> vvv" looks okay too.
> 
> What is the best way to troubleshoot these types of issues? Any ideas  
> would be appreciated, thanks!

You could run ethereal/wireshark while the problem happens and try to
see what's happening on the wire.  If the client is retransmitting the
same requests over and over, then the problem is probably on the server
side.  If the server seems to responding normally, more likely it's on
the client side.  If the server is returning errors, it'd be interesting
to know what the errors were.

Is only one client hung?  Can other clients mounting the same export
still access it normally?

--b.

> 
> Norman Elton
> 
> 
> ====== /etc/exports
> /exports                gss/ 
> krb5(rw,fsid=0,crossmnt,insecure,no_subtree_check,sync)
> /exports/backup         gss/krb5(rw,nohide,insecure,no_subtree_check)
> 
> /exports                10.1.0.0/16(fsid=0,insecure,no_subtree_check,rw)
> 
> ====== /etc/fstab
> dev0:/exports           /nfs3                   nfs      
> auto,rw                 0 0
> dev0:/                  /nfs4                   nfs4     
> auto,rw,sec=krb5        0 0
> 
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