lubuntu@lubuntu:~$ sudo fuser -km /dev/sda6
lubuntu@lubuntu:~$ sudo umount /dev/sda6 && sudo mount /dev/sda6 /mnt
umount: /mnt/boot-sav/sda6: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(

or fuser(1))
lubuntu@lubuntu:~$