Rafael 
The DNW application can be used to upload and download images of the Mini2440's entire NAND flash. You can backup the NAND flash of Board-A to your computer and put that image on another Mini2440 Board-B that will act as a clone of the first one. I assume Board-A will cater for bad sectors on its own flash. Board-B will not have bad sectors at the same places as Board-A. Will simply cloning the NAND flash with an image create the possibility that important files might overlap with bad sectors on Board-B?