Hi,

I have strange problems unmounting my nfs4 directories since SL6.x (6.0, 6.1 
and 6.2; actually 64Bit SL6.2 on client and server). 

If I try to umount such a nfs4 directory, then I get errors of the type:

#umount /9
/9 was not found in /proc/mounts
/9 was not found in /proc/mounts

and the directory is still fully functional and mounted. I tried to ignore 
this error but I have 19 nfs file-servers in the cluster running with SL6.2, 
which I can not reboot properly due to this problem. And the file-systems 
really don't like the hard power cycles.

I have no clue why this error occurs. Everything looks fine for a nice 
umount:

#cat /etc/fstab
[...]
10.10.70.9://raid_0 /9 nfs
[...]

#mount
10.10.70.9://raid_0 on /9 type nfs 
(rw,vers=4,addr=10.10.70.9,clientaddr=10.10.70.43)

#cat /proc/mounts
[...]
10.10.70.9:/raid_0/ /9 nfs4 
rw,relatime,vers=4,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,por
t=0,timeo=600,retrans=2,sec=sys,clientaddr=10.10.70.43,minorversion=0,local_
lock=none,addr=10.10.70.9 0 0
[...]

#cat /etc/exports (nfs server)
/raid_0 10.10.60.0/255.255.255.0(rw) 
10.10.70.0/255.255.255.0(rw,no_root_squash) 
10.10.10.0/255.255.255.0(rw,no_root_squash) 
10.10.0.0/255.255.255.0(rw,no_root_squash) 
192.168.1.0/255.255.255.0(rw,no_root_squash)

If I mount a nfs3 directory on the SL6.2 client, which is listed in 
/proc/mounts like this: 
10.10.0.2://glocal /glocal nfs 
rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,tim
eo=600,retrans=2,sec=sys,mountaddr=10.10.0.2,mountvers=3,mountport=39938,mou
ntproto=udp,local_lock=none,addr=10.10.0.2 0 0
then I can mount/unmount it as often as I want or until the keyboard breaks. 
 
It would be brilliant if someone has an idea why this happens with NFS4.

Thanks! 

best wishes
David