About to monkey with a custom bootable SD card for an ARM device. Got ahold of such part of a gear purchase... The normal dance moves to get this going are more time and patience than I have to spare. Since I am prone to trying stuff and blowing things away, would like to preserve the original SD card image and copy it back or to other SD cards when doing reinstall. Any recommend best process / tool for this? Want to make complete replica of the SD card. It's a bootable SD card with the OS.