If you have your OS cloned in a card. This linux utility is very useful.
http://www.partimage.org/Main_Page
You can use as backup.
Or you can have several OS in your card!.
If you have used initfs boot menu from fanous when cloned, you can boot from several card partitions (e.g.:by default part2 and part3 ext2 type in your internal card) You can make several partitions in your card (e.g.: make a third partition similar to second). And then use partimage to backup your cloned OS partition ( by default the second) and restore in other (e.g.:the third partition).
So you can have a "experimental" OS in one partition and a "clean" OS in other. And both with backup!.

i find that winimage works well for mine...coures i only have my os cloned to sd...someone else can verify...ill give partimage a try may be faster