yifanlu
First: congrats on having 3.1 running an a K2, that is great!
Regarding the restore/recovery.
Both my K3's are working (@ this moment) but because I like to mess with them I can imagine I mess one up one of these days..

That is why it would be handy to have some sort of recovery package handy.
I did create a backup of the rootfs and I did made serial connector to use with my buspirate, but a "just in case" or as a go back to square one when my efforts go to far, a way to restore to my factory rootfs would be great, but not important at this moment.
(although it would be good for me to learn how the recovery works)
But still, you letting others run 3.1 on a K2 is way cooler.
I will follow that thread, because I know I'll learn a lot from it.
Thanks for all your efforts!