[tvjon]

For anyone looking to upgrade a Pi1 installation for use with Pi2, while using the Pi1, upgrade with the RPi2 tar. Once the upgrade is complete, the system will reboot to a rainbow boot screen (as you're now booting the ARMv7 kernel). Shutdown (pull the power) and transfer the SD card into your Pi2, which will boot normally.

To go back to the Pi1: While using the Pi2, upgrade with the RPi tar. Once the upgrade is complete, the system will reboot to a rainbow boot screen (as you're now using the ARMv6 kernel). Shutdown (pull the power) and transfer the SD card into your Pi1, which will boot normally.

Thank you for posting that, as I've no joy with the (correct, 501) Pi2 image so far, not getting beyond the 4 colour screen.

However, I suggest if anyone finds this update method doesn't progress beyond the initial rainbow, check the existing overclock settings in config.txt, & edit or remove them, otherwise the result may be ARM register dumps for one or more cores, & frame pointer errors, etc. (I edited cmdline.txt to remove "quiet" so I could see boot progress)

It's working fine now thanks.