First step on the way to your very own Kindleberry Pi is downgrading your Kindle:
Turn on the airplane mode
While jailbreak itself should survive firmware updates, custom hacks it enables might not. Proceed at your own risk.
At the time of writing, the most recent jailbreak works with firmware version 220.127.116.11. With a bit of URL trickery, we can download it from Amazon.
Copy the firmware to the Kindle root directory.
Do not disconnect or eject your Kindle just yet. Instead, restart it by long pressing the power button on the bottom edge. Update progress dialogue should appear.
Confirm that downgrade went well
From Home screen, tap Menu, then Settings.
From Settings screen, tap Menu again, then Device Info.
Firmware Version:Kindle 18.104.22.168 means we are golden and ready to jailbreak.
Make sure your Kindle is still yours
It seems like downgrading can unregister your device. If that’s the case, simply register it again.