CentOS - Jan 2011 - how to unmount an NFS share when the NFS server is unavailable?

Hi All,

How do I unmount an NFS share when the NFS server is unaivalable?

I tried "umount /bck" but it "hangs" indefinitely
"umount -f /bck" tells me the mount if busy and I can't unmount
it:

root at saturn:[~]$ umount -f /bck
umount2: Device or resource busy
umount: /bck: device is busy
umount2: Device or resource busy
umount: /bck: device is busy




This non-working NFS share is causing problems on the server and I
need to unmount it until such a time when the NFS server (faulty NAS)
is repaired.


-- 
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532

Hi,

On 1/26/11 5:23 PM, Rudi Ahlers wrote:
> Hi All,
> 
> How do I unmount an NFS share when the NFS server is unaivalable?
> 
> I tried "umount /bck" but it "hangs" indefinitely
> "umount -f /bck" tells me the mount if busy and I can't
unmount it:
Try:

  umount -f -l /bck

HTH,

-- 
- Edwin - mailto:ml2edwin at gmail.com
?Happy is the man that has found wisdom ...??Proverbs 3:13

on 10:23 Wed 26 Jan, Rudi Ahlers (Rudi at SoftDux.com)
wrote:
> Hi All,
> 
> How do I unmount an NFS share when the NFS server is unaivalable?
> 
> I tried "umount /bck" but it "hangs" indefinitely
> "umount -f /bck" tells me the mount if busy and I can't
unmount it:
> 
> root at saturn:[~]$ umount -f /bck
> umount2: Device or resource busy
> umount: /bck: device is busy
> umount2: Device or resource busy
> umount: /bck: device is busy
> 
> This non-working NFS share is causing problems on the server and I
> need to unmount it until such a time when the NFS server (faulty NAS)
> is repaired.
The specific solution is 'umount -fl <dir|device>'.

The general solution's a little stickier.

I'd suggest the automount route as well (you're only open to NFS issues
while the filesystem is mounted), but you then have to maintain
automount maps and run the risk of issues with the automounter (I've
seen large production environments in which the OOM killer would
arbitrarily select processes to kill ....).

Monitoring of client and server NFS processes helps.  If it's the filer
heads which are failing, and need warrants it, look into HA failover
options.

Soft mounts as mentioned won't hange processes, but may result in data
loss.  This is most critical in database operations (where atomicity is
assumed and generally assured by the DBMS).  If the issue is one of
re-running a backup job, and you can get a clear failure, risk would be
generally mitigated.

-- 
Dr. Ed Morbius
Chief Scientist
Krell Power Systems Unlimited