HELP Downgrading 4.2.1 to 4.1

[wongjmeng388]

Hello,
I am hoping to downgrade my iPod Touch 4G (iOS 4.2.1) from 4.2.1 to 4.1 for obvious reasons (themes not fully working... stupid crApple). Is there any way to do this without having to restore using iTunes? (This would include keeping all my themes, media (music, videos, apps) and app save progresses (like my level status on Plants vs Zombies )) I have official iOS 4.1 FW downloaded... so do I like re-jailbreak with that firmware instead of the 4.2.1 ipsw? I want to keep all my stuff...

If there isn't, is there a way to actually do a COMPLETE, 100% backup including app save progress, downloaded winterboard themes, cydia and itunes store apps... and music, video, books, all that stuff? (Yes, I have books. SHUT UP! ) I'm a jailbreak n00b but can I like SSH and copy my entire root path ( / ) to my computer and recopy it back on my iPod after I downgrade?

Thanks in advance!

[lanulos]

If you had SHSH blobs saved for 4.1 at the Cydia servers, you could even downgrade with iTunes (if you modify your hosts file, details elsewhere). That might be your best chance of saving at least the game progress. Also the Cydia apps AppBackup and PkgBackup might help. But I'm guessing you got the iPod with 4.2.1 installed, meaning you don't have the blobs saved, in which case you can't downgrade at all.

[wongjmeng388]

um... i got it with 4.1 installed but i upgraded to apple ofw 4.2.1 and then jailbroke...
I'm new here so could you explain what a SHSH blob is and how i could use that to backup?

[lanulos]

SHSH blobs are digital signatures Apple uses when installing firmware on your iDevice. They use your ECID (the number at the bottom of the Cydia front page) to personalize your firmware so that A) your device will accept it and B) no other device will. An Apple server generates this every time you restore or upgrade your firmware. When Apple brings out a new firmware they very soon stop signing the old one. They stopped signing 4.1 on Dec 2 2010. That means iTunes will not reinstall 4.1 unless it is tricked into doing so. That is what "Saurik", the author of Cydia, figured out how to do. Cydia and TinyUmbrella have the ability request the signature for current firmware from Apple and save the result on a server at Cydia. Then later when Apple is not signing that firmware anymore, your iTunes can be tricked into getting the old signature from the Cydia server rather than Apple. This is done by putting the following line in the "hosts" file on your computer:
74.208.10.249 gs.apple.com
The take-home message is, if you don't have the SHSH blob saved for it, you can't reinstall or downgrade to old firmware. No one has figured out how Apple generates the signatures yet. One new development is, the programmer "iH8sn0w" is working on a way to extract the signature for the present firmware on your device without asking Apple. But this still wouldn't help you, because you didn't get a 4.1 blob saved when Apple was still giving them out. Bummer.
More info:
Caching Apple's Signature Server - Jay Freeman (saurik)
SHSH - The iPhone Wiki
TinyUmbrella - The iPhone Wiki

About AppBackup and PkgBackup:
Best thing is to read their descriptions in Cydia.
AppBackup is for the data for AppStore apps and PkgBackup is for Cydia apps and their data. I've backed up with Appbackup but never restored; I've not use PkgBackup yet. There is something called AptBackup for Cydia apps but I had a disaster with it and won't ever use it again.

[wongjmeng388]

Thanks for quick reply,
I heard about AptBackup's failure... and AppBackup looks pretty good... but is there a free alternative to Pkgbackup
?

[lanulos]

Thanks for quick reply,
I heard about AptBackup's failure... and AppBackup looks pretty good... but is there a free alternative to Pkgbackup
?

Not that I've heard of.

[wongjmeng388]

Meh. I'll just wait till some themes are 4.2.1 approved...