Jailbreak and install usb networking hack prior to 3.1 upgrade to retain a backdoor, even if you don't intend to use it right now. My understanding is the basic issue is that 3.1 verifies digital signatures against a public key with a specific filename, while 3.0.x took anything in the directory, which is what the jailbreak installed. With the network in place, it is possible to swap the keys to install another hack as usual, then swap it back re-enable amazon's updates (or better yet, leave hack key in place to prevent future down-your-throat forced updates from Big AZ that may further cannibalize usb network).
If you don't understand PKI or have decent Linux CLI background, better wait until another hack is published and tested that takes advantage of the hole to create alternate install mechanism for any new hacks. It is quite dangerous to telnet in and poke around the root fs if you don't know what you are doing.
That said, I can confirm the following sequence worked
for me (ymmv):
- jailbreak 0.4.N applied to vanilla 3.0.2
- 3.0.3 update applied from AZ "preview" download
- usb networking 0.30N, screensaver 0.18N, and SSTimeOut 0.2 installed per
NiLuJe's excellent thread/packages
- 3.1 update applied from AZ preview download (
not the smaller incremental pushed to me, probably ok but untested)
After this, all three hacks still work and, most importantly, I can still telnet in as root. If this is sounding kind of foreign,
don't do anything through usb network, just install it prior to 3.1 and you'll be ok.
The ironic thing is that in my case, I am not even interested in subverting DRM schemes, tethering their lame AT&T 3G or installing screensavers. I deal with embedded Linux at work all the time and could care less about hacking a Kindle on my day off - if it wasn't for Amazon's utter disregard for basic usability. All I wanted is for the DAMN SCREEN TO STAY ON FOR > 10MIN! Unbelievable what hoops we have to jump through for basic usability of the product, really.