thx arci - i thought there would be a way to analyze the kernel.img...
OK - then I mark the kernel version of the fullbackup using the kernel description (ULK for new, anything else for old kernels)...
only thing left: testing my fullbackup with azup

my new procedere:
  • box in rescue mode? if no reboot to rm
  • box overclocked? if yes switch it to normal mode and reboot
  • enough ram available?
  • started tool from /tmp? otherwise big warning for flashing
  • check kernel CRC on PC
  • check for same kernel CRC after uploading
  • check for same kernel CRC after flashing (if it fails - install old kernel again)
  • setting up environment for either old or new kernel
  • flash image
  • done