UMOUNT FORCEFULLY COMMAND

• umount file system when device is busy

          # umount /data

              Umount /dev/sdb1 : device is busy

               Umount /dev/sdb1 : device is busy

         So

                   # fuser –m /data

                      /data     : 4582c

               Then give command

                  # ps –ef |grep 4582

              And kill the process

                Then unmount the file system

 Or 

give command for umount 

# umount -l /data