PW2 Downgrading from 5.7.2.1 (jailbroken Kindle via diags)

So I was not completely satisfied with v5.7.2.1 and decided to downgrade and go back to version 5.4.5 (mine's a jailbroken 9017 4GB PW2 and, according to the wiki, needs this version to run KUAL). After reading a bunch of threads, posts and readmes I came up with a list of steps and decided to go ahead and do it (after verifying my list with @knc1). All went well and now I'm successfully back to v5.4.5. Here's what I did (like I said mine's a 9017 4GB PW2 device but I assume it would be applicable for other devices as well).

Important Notice: After completing this tutorial you will lose all your collections, bookmarks, book progress etc. Please consider this before continuing. Also, you do this at your own risk.

Prerequisites:

i) a jailbroken device with the latest jb version (this won't work on non-jailbroken devices as you should be able to boot into diags and ssh into the Kindle)

ii) rescue pack and coward's rescue pack installed - you can find them in NiLuJe's snapshots thread

iii) it would be a good idea to also install the USBNetwork hack (also available in NiLuJe's snapshots thread), setup ssh access (the process is described in the wiki) and try to connect to the Kindle; I used PuTTY on a Windows PC.

Steps:

1. Download the previos firmware update_... .bin you want to downgrade to. Make sure it is not older than the original firmware your device was shipped with! For my device I went with v5.4.5 linked in the wiki

2. Extract the contents of the .bin file using kindletool - you can download it from NiLuJe's snapshots thread. Run the follwing command:

kindletool.exe extract path/to/.bin path/to/output/folder

E.g. on my Windows PC i ran it like that:
After extracting the firmware .bin you should be able to locate two files inside the output directory: rootfs.img.gz (the root file system) and uImage (the kernel). On my PC the uImage file was under a imx60_wario directory in the output folder.

3. Connect your Kindle to your PC and put the uImage and rootfs.img.gz files on the root of the usb storage.

4. Eject the Kindle and select Restart from the Kindle settings menu. Do not unplug the USB cable - if you installed the coward's rescue pack the Kindle will automagically enter into diags during the reboot

5. Once into diags, enable USB networking - touch on the following nemu items: N -> U -> Z -> X (as described in ixtab's readme)

6. Once USB networking is enabled you should be able to ssh into the Kindle - in PuTTY connect to 192.168.15.244 ip address, leaving the port to default (22); enter root as the username and mario as the password - you should see the root prompt

7. Clear the database to avoid potential DB schema issues (this will erase all your collections, bookmarks, book progress etc.):

8. Install the kernel and rootfs (double check those dd commands):

This will copy the contents of uImage into mmcblk0 using 4 Kbyte chuncks with (4096*65=) 260 Kbytes offset

This will unzip and copy the contents of rootfs.img.gz into mmcblk0p1 using 4 Kbyte chuncks (rootfs.img.gz is a larger file so it will take some time)

9. Reboot you Kindle:

Unplug the USB cable from the Kindle once PuTTY reports it has lost the connection.

10. If you had the latest jb version installed the jailbreak should bridge itself during the reboot. Re-apply any .bin hacks after the device boots. You will also have to redo all your collections, bookmarks, book progress etc.

An interesting thing happened after I downgraded. I turned airplane mode off to sync my cloud collections as I had trouble recreating/viewing them on my device. The popup to register my Kindle appeared (?!) so I re-registered it. During the sync a notice file appeared on my Kindle (Test Kindle Installation Result.azw) saying After that I was unable to launch KUAL (?!). Starting to sweat a little, I re-apllied the latest jailbreak - all was fine after the reboot; I also re-applied my .bin hacks just to make sure. Haven't had issues after that although I usually keep my Kindle in airplane mode.

Special thanks to @knc1, @NiLuJe, @ixtab, @dsmid and all the other guys here for providing invaluable knowedge and tools.