Tag: nfs
How to unmount NFS share mounted with hard option
29 Aug2007

Few days ago I worked on some customer’s server and there was a problem – their nfs server went down and we were forced to change some settings on their FC4 clients to prevent shares from dieing because of kernel bug. But when we’ve changed settings in /etc/fstab there was one more step before task was completed – we need to remount this share (I mean unmount/mount). But how to perform this operation if there are some processes in D (non-interruptible sleep) waiting for dead share and prevent it from unmounting? They wait because of hard option on the share and lack of intr option and any unmount request would produce a following results:

streaming01:~# umount /storages/2
umount: /storages/2: device is busy
umount: /storages/2: device is busy

So, here is a list of steps you need to do to be able to remount your share.

First of all, you need to send KILL(9) signal to all you processes waiting for share. I’ve used ps axu and filtered all processes in D state. When all processes ‘killed’ (they can’t be killed actually), you’ll need to send the same signal to rpciod processes in your system. After this all your sleeping processes will die and you’ll be able to unmount your share.

That’s it – simple and really useful tip for people using NFS in their systems.