I downloaded the stock zip from the link in this post: http://forum.xda-developers.com/show...3&postcount=91 and then I changed the following from the stock zip file:
- Removed the bootloader and recovery.img updates
- Removed the backup_data.zip because it doesn't make sense, really (it looks like it just extracts to /backup/, but if you flash it it will wipe your /data partition?)
- Added busybox, Superuser and the su binary. Should be properly symlinked and permissions set correctly.
- Modified the updater-script for the above things.
Additionally, if you have the Market installed you may need to re-install it after updating since Amazon didn't do this as a patch - it just formats /system and replaces it. If you updated the Market manually then the newer version should survive in /data/app. Also, if you installed any custom frameworks or libraries (e.g. the maps framework to use Google Currents and whatnot) then you'll need to reinstall those. Basically, anything you added or modified on /system will be gone.
Edit: Thanks sadlius for pointing me to dsixda's kitchen! I've added a version with an unsecure boot image (so you get root by default on a shell). I'll leave the old one in case anyone would prefer the secure boot image. I've also uploaded the boot image itself for anyone who might have already flashed the secure 6.2.1 zip. I tried it with fastboot and it booted up fine, so you can test it first with:
fastboot boot 6_2_1rootboot.img
fastboot flash boot 6_2_1rootboot.img
MOD EDIT: Links no longer valid so removed.
Multiupload, courtesy sadlius:
Stock rooted update 6.2.1, secure boot image
Stock rooted update 6.2.1, unsecure boot image
Multiupload, courtesy intel352 (md5's should be the same):
6_2_1rootboot.img Unsecure 6.2.1 boot image
Removed these so Dropbox won't yell at me anymore