Moving to a smaller card, HOW?

[Otaku Wally]

Hi,

I want to move my XBian system from my 32G card into a 4G card. Since a 1:1 copy is not possible obviously, I created partitions on the small card and simply copied (cp -dpRx ...) all the stuff from the running 32G system onto the new (small) card onto the apprioprate partitions. The system however will NOT boot, though ALL files have been copied correctly. I there some bootcode I need to copy too, or WHY will the system NOT boot from the new small card? I mean even the XBian-Startup-splash will not be shown, so it obviously doesn't start AT ALL. Any help or ideas?