Jailbreak 101 Primer, notes from a self-learned newbie

I have been playing around for many hours on my ATV2, upgrading, downgrading, etc. I don’t have any other Apple devices, and I had to piece information together from many sources. This is what I learned from my experience, hope my notes will help others.

 

  • Many JB operations involve plugging ATV2 into the computer via microUSB. But USB doesn’t always provide enough power, so commands will fail at times. So you should plugin USB first, then after hearing the chime that the PC has recognized ATV2, plugin the power cord as well.

 

  • An ipsw is a OS disk image file from 380mb to 550mb depending on release. Apple releases an iOS version (e.g. 6.1.4), then customizes for ATV2’s usage to become ATV2 software version 5.3. Click the center button on remote in the About page will toggle the 2 version numbers.

 

  • Seas0nPass jailbreaks by downloading a factory OS image, injecting JB code to create a JB image, then calling iTune to put the new image onto ATV2.

 

  • Seas0nPass will create a directory in Documents folder. The ipsw file with SP in the name is the jailbroken image, without is the factory image. These files are a by-product of the JB process, and can be used to restore to an ealier release once you have upgraded in the future.

 

  • Before restoring an ipsw OS image, iTune will contact Apple mothership with the serial number of your ATV2 to ask if it is ok to restore this OS version for this ATV2. If the mothership responds “yes”, this is called signing the digital signature or signing the firmware.

 

  • Apple puts out a new OS release every few months, in order to prevent people from going back to an old version of OS, Apple will stop signing an old release at some point. Example, if 5.3 is the current version, Apple will still sign 5.3 and 5.2, but not 5.1 anymore.

 

  • So in order to prepare of a future downgrade, JB tools can create the firmware signature specific to your ATV2 and specific to the current OS on the ATV2. The signature is commonly sent to a server called Cydia, or can be stored locally on your own PC. 

 

  • Cydia is a company that runs an app store for apps that require JB. The apps are relevant to iphones and ipads, not ATV. Storing firmware signature is a free service for all Apple devices.

 

  • For a future downgrade, JB tools modify the hosts file to trick iTune to contact Cydia or a local JB tool, then replay a signature Apple in fact is no longer signing.

 

  • ipsw files are generic files for any ATV2, and can be found on the web easily or be downloaded automatically within a JB tool. firmware signatures are unqiue to a specific ATV2 and a specific OS version, so make sure to create the firmware signature for every OS version you use, include the original one when you first bought the ATV2.

 

  • the firmware signatures are also called shsh blob. TinyUmbrella can save them locally, default in username/.shsh folder.

 

  • Seas0npass can upload firmware signature to Cydia and JB ATV2 with a few mouse clicks. Very easy to use, you don’t have to understand what is going on. Recommended for beginners.

 

  • TinyUmbrella can save firmware signature locally, so you don’t have to worry about Cydia being down when you need it. It can also use a built-in server to trick iTune to get signature from it or from Cydia instead of Apple.

 

  • Redsn0w can restore ATV2 without iTune if you provide ipsw file and local or Cydia firmware signature. It can check what shsh blobs Cydia has saved for your ATV2. Seems full featured and seems to includes all TinyUmbrella signature manimulation functions, but it can’t handle ATV2 JB as well as Seas0npass.

 

  • JB requires finding a loophole in the Apple OS and tricking it to do something new. An untethered JB means ATV2 is fully broken and can work as before and ready to install apps not from Apple’s app store. A tethered JB means ATV2 will need to connect to a PC via USB, run Seas0npass to help it boot, then connect to regular power and HDMI to fully function.

 

  • Depending on the OS version, some jailbreaks are tethered (e.g. 5.3), some untethered (e.g. 5.2).

 

  • v5.x use more memory and space. If you only use XBMC on ATV2, stay with v4.x for better performance.

 

  • Remember, always save your firmware signature if you ever plan to downgrade. 

 

  • JB is legal in US, not sure in other countries.