Build a file system from existing BBB

Hi guys:

I bought a BBB and I have done some action on it, now i want to copy this file system to the other BBB, how should I do?? And the other questions, yesterday I transfered a file named “uEnv.txt” in /boot/uboot/ to the other BBB(called “OtherBBB”), and later “OtherBBB” couldn’t enter its file system, i found the difference between uEnv.txt between each BBB only on one line about declaring “UUID”, does anyone what happened???

'uuid' = Universally unique identifier

So microSD(1)'s uuid doesn't equal microSD(2)'s uuid..