Redsn0w Can Jailbreak iOS 5.1

Yesterday, Apple has released iOS 5.1 and we’re all dying to try it out. But unfortunately for jailbreakers and unlocks, it’s not as easy as updating the device. Turns out that redsn0w can jailbreak iOS 5.1 on non-A5 devices. Some rules apply. Jump over the break for more details

• Soon after 5.1 appears on Apple’s public servers (i.e. iTunes starts to offer it), Apple will stop signing 5.0.1 SHSH blobs.
• If you have an iPhone4S, the basic rule above is really the only rule:  you cannot restore back to 5.0.1 once the 5.0.1 signing window is closed, no matter what (even if you saved your SHSH blobs).
• If you have an iPad2 with saved 4.x hashes, you can in fact downgrade to that 4.x but you won’t be able to get to 5.0.1 once the 5.0.1 signing window is closed (even if you saved your 5.0.1 SHSH blobs).
• If you have a device earlier than the iPad2, you can downgrade to whatever version you want, as long as you have saved SHSH blobs for that version.  You’ll need the assistance of geohot’s limera1n exploit with tools like redsn0w to get into “pwned DFU mode” and bypass the downgrade restriction.

Because of geohot’s limera1n exploit, those with devices earlier than the iPad2 can test the 5.1 jailbreak waters if they really want to, using redsn0w 0.9.10b6.  Here’s what you need to know:

• This is a *tethered* 5.1 jailbreak for non-A5 devices.  You’ll need to use redsn0w to “Just Boot” your device every time it power cycles, otherwise jailbreak apps won’t work (neither will Safari).
• If you use ultrasn0w for your carrier unlock, be sure to use a custom IPSW to get to 5.1 first!  Don’t ever restore to a stock Apple IPSW!  Use redsn0w’s “Custom IPSW” button to create a NO_BB_* version of the 5.1 IPSW and restore to that instead of the stock one.  (That option is available only to 3GS and iPhone4-GSM owners.)  ultrasn0w itself will be updated for 5.1 in the next few days (same baseband support, not 5.1’s baseband).
• If you’re lucky enough to have an old-bootrom 3GS, this jailbreak is actually untethered (redsn0w will figure that part out automatically).
• While we were at it, we added @pod2g’s steaks4uce exploit to support MC models of the iPod touch 2G (whose last firmware was 4.2.1).  So now redsn0w will auto-detect and jailbreak both MB and MC versions of that older device.
• iBooks won’t work until a future update of redsn0w

Here are the redns0w download links:

• redsn0w 0.9.10b6 for OS X
• redsn0w 0.9.10b6 for Windows (be sure to run in Administrator mode)