The external alternative of this MagicMemoryUpgradeMod would do so for you. You can download it in the first post.
On a shell you might do something like:
Code:
# insert ext. card
killall nickel sickel pickel fickel
umount /mnt/onboard /mnt/sd
mount -o remount,ro /
dd bs=1M if=/dev/mmcblk0 of=/dev/mmcblk1
sync
# eject ext. sd card
reboot
On devices without external SD card you could also grab an image of /dev/mmcblk0 over the wire.
Using my WebPortal / FileManager mod you could also download an image of /dev/mmcblk0 through your PC's webbrowser.