Force unmount of NFS-mounted directory
LinuxMountNfsUmountNfsclientLinux Problem Overview
I have an NFS-mounted directory on a Linux machine that has hung. I've tried to force an unmount, but it doesn't seem to work:
$ umount -f /mnt/data
$ umount2: Device or resource busy
$ umount: /mnt/data: device is busy
If I type "mount", it appears that the directory is no longer mounted, but it hangs if I do "ls /mnt/data", and if I try to remove the mountpoint, I get:
$ rmdir /mnt/data
rmdir: /mnt/data: Device or resource busy
Is there anything I can do other than reboot the machine?
Linux Solutions
Solution 1 - Linux
You might try a lazy unmount:
umount -l
Solution 2 - Linux
If the NFS server disappeared and you can't get it back online, one trick that I use is to add an alias to the interface with the IP of the NFS server (in this example, 192.0.2.55).
Linux
The command for that is something roughly like:
ifconfig eth0:fakenfs 192.0.2.55 netmask 255.255.255.255
Where 192.0.2.55 is the IP of the NFS server that went away. You should then be able to ping the address, and you should also be able to unmount the filesystem (use unmount -f). You should then destroy the aliased interface so you no longer route traffic to the old NFS server to yourself with:
ifconfig eth0:fakenfs down
FreeBSD and similar operating systems
The command would be something like:
ifconfig em0 alias 192.0.2.55 netmask 255.255.255.255
And then to remove it:
ifconfig em0 delete 192.0.2.55
man ifconfig(8) for more!
Solution 3 - Linux
Try running
lsof | grep /mnt/data
That should list any process that is accessing /mnt/data that would prevent it from being unmounted.
Solution 4 - Linux
I had the same problem, and
neither umount /path -f,
neither umount.nfs /path -f,
neither fuser -km /path,
works
finally I found a simple solution >.<
sudo /etc/init.d/nfs-common restart, then lets do the simple umount ;-)
Solution 5 - Linux
Your NFS server disappeared.
Ideally your best bet is if the NFS server comes back.
If not, the "umount -f" should have done the trick. It doesn't ALWAYS work, but it often will.
If you happen to know what processes are USING the NFS filesystem, you could try killing those processes and then maybe an unmount would work.
Finally, I'd guess you need to reboot.
Also, DON'T soft-mount your NFS drives. You use hard-mounts to guarantee that they worked. That's necessary if you're doing writes.
Solution 6 - Linux
Couldn't find a working answer here; but on linux you can run "umount.nfs4 /volume -f" and it definitely unmounts it.