umount - it is used to unmounts a mounted filesystem, informing the system
to complete
any pending read or write operations, and safely detaching it
To unmount all the filesystems mentioned in /etc/mtab
$ sudo umount -a
To forcefully unmount a filesystem
$ sudo umount -f /backup
To lazy unmount of a filesystem
$ sudo umount -l /backup
To unmount a Partition or Filesystem
$ sudo umount /mnt
To recursively unmount a target with all its children
$ sudo umount -R /mnt
To umount without writing in /etc/mtab
$ sudo umount -n /mnt
To unmount more than mount point in a single execution
$ sudo umount /mnt /backup
regards,
T.Dhanasekar