umount: /mnt: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1))

Yupp i was faced this issue many times.

when you see this issue

step1:-
 check and see you might be in same directory. in my case i was in /mnt and i am trying to unmounting. using umount /mnt command. (#umount /mnt)
then i got the below error

[root@test mnt]# umount -f /mnt
umount: Device or resource busy
umount: /mnt: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount: Device or resource busy.

step2:-

if you are not in same directory and still you are getting this error means some prcoess are still holding this .

then try with -f   ( umount -f /mnt)

In some cases even -f option also wont help. Then check which process are running with fuser command.

#fuser -u /mnt  or
#fuser -m /mnt

you will get some process ID's which are running. So if you can kill those you can umount.

even it didnt help ? then you can try with "l" option.

# umount -l /mnt  ( l is lazy mount. you can check with man umount   for more options)

umount -l will work for sure.


if you still see stale error or  mount point even after lazy unmount. Then their could be chancess of issue is from NAS side. it means this server may not have permissions for this export.