Debugging NFS Hangs

[Norman Elton]

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, 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!

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