In order to check the filesystem of the partition and where that partition maps to that address use:

mount -l

It will show for example that you have a partition that mounted by NFS or that a partition is ext4 and so on:

/dev/mapper/vg-var on /var type ext4 (rw,relatime,stripe=384,data=ordered)

#linux #mount #ext4 #nfs #filesystem #partition

https://www.linode.com/docs/networking/nfs/how-to-mount-nfs-shares-on-debian-9/

#nfs #debian #mount #export #fstab

Cannot umount a busy driver.

If you haven't tried to force umount by -f try it:

umount -f /mnt/your-mounted-drive

Now in case using -f it still gives error. Try this:

apt-get install psmisc

Now user fuser command like below:

fuser -c /mnt/your-mounted-drive
 /mnt/your-mounted-drive/: 2510c 11086

It outputs the pid of the processes using this volume. The extra character at the end of pid will give some extra info. ( c in 2510c)

c - the process is using the file as its current working directory

m - the file is mapped with mmap

o - the process is using it as an open file

r - the file is the root directory of the process

t - the process is accessing the file as a text file

y - this file is the controlling terminal for the process

Kill these processes:

kill -9 2510 11086

Now umount it:

umount /mnt/your-mounted-drive

#umount #NFS #fuser #psmisc