Apple released iOS 4.2 (or iOS 4.2.1) for iPhone, iPad and iPod Touch earlier today.

iPhone Dev team has provided a quick update for users who want to jailbreak and/or unlock their iPhone.

Before they go on to explain the current situation, they have advised users to avoid updating to iOS 4.2.1 until they release tools for iOS 4.2.1.

iPhone Dev team has provided the following details for users who want to jailbreak their iPhone, iPad and iPod Touch:

The best news of all is for owners of iPhone3G, older iPhone3GS, and non-MC iPod touch 2G.  Due to a combination of our original pwnage2 exploit, the arm7_go exploit, 24kpwn, and limera1n, your device is “just as jailbreakable as ever.”  You reap the full benefit of an untethered 4.2.1 jailbreak.

Next are the owners of all the more recent devices.  The good news there is that due to geohot’s limera1n exploit, all recent devices can be jailbroken (this will be true until Apple released new hardware that fixes geohot’s limerain exploit in the bootrom).  The bad news is that right now, the 4.2.1 jailbreak is *tethered* on all of these recent devices.  A tethered jailbreak means that each time your device loses battery power or needs to be rebooted, you must attach it to a PC or Mac to boot into the jailbroken state.  @comex is working hard on a method that may untether the 4.2.1 jailbreak, but it will require you to have your 4.1 SHSH blobs in order to use it.  No word on how much more effort it will take though (please don’t bug @comex about it!).  (We also have an alternative method that may work, but @comex’s method is much more elegant.)

iPhone Dev team hope to release tools to jailbreak iOS 4.2.1 later today:

Well if you’re a JB developer or tinkerer, you’ve already probably used the redsn0w mentioned in our last post to jailbreak 4.2.1 and at least get SSH working.  But beyond that, there are still some last minute issues with MobileSubstrate and comex’s kernel patches that are being fixed.  We’ll tweet and post a blog update when it’s all available (we hate to give ETAs, but barring any unforeseen problems, probably later today).

iPhone Dev Team has provided the following details on their blog for users who want to unlock their iPhone:

As always, ultrasn0w unlockers please stay far far away from this official firmware (and all official firmware). Wait for the ability to create custom 4.2.1. IPSWs that don’t update your baseband!

Dev team has also provided an update for users who are eagerly waiting for Ultrasn0w for iOS 4.1 and now will be looking forward to one for iOS 4.2.1:

After redsn0w is officially released with the new Cydia and kernel patches, we’ll be able to assess the unlock situation.  It’s already looking very promising though, so expect the unlock for the 3G and 3GS to be coming this week.  The i4 unlock is taking more effort though, and no further concrete info is available about that yet.

Dev team has also adviced users to take a backup of SHSH Blobs (ECID) using Firmware Umbrella. Please note that if you have already jailbroken your iPhone, iPod Touch then Cydia would have taken the backup automatically.

As always, we’ll let you know as soon as we’ve any further updates. So stay tuned here at iPhone Hacks or follow us on Twitter or subscribe to our RSS feed.

Do you plan to jailbreak or unlock iOS 4.2.1? Please let us know in the comments section below.