Unmounting filesystems

You can also unmount (the reverse of mounting) a filesystem. As you may have guessed, unmounting refers to the process of detaching a filesystem or a storage device. To unmount a filesystem, you can use umount as follows:

umount filesystem

Change to the /games directory and try to unmount the /dev/sdb1 filesystem:

root@ubuntu-linux:/games# umount /dev/sdb1 
umount: /games: target is busy.

Oops! It is saying that the target is busy! That's because I am inside the mount point /games; I will back up one directory and then try again:

root@ubuntu-linux:/games# cd .. 
root@ubuntu-linux:/# umount /dev/sdb1

This time it worked! You have to be careful and never unmount a filesystem or any storage device while it is actively being used; otherwise, you may lose data!

Now let's verify the filesystem /dev/sdb1 is indeed unmounted:

root@ubuntu-linux:/# lsblk
NAME   MAJ:MIN RM SIZE  RO TYPE MOUNTPOINT
sda      8:0   0  20G   0  disk
| sda1   8:1   0  20G   0  part /
sdb  ...