As you know iPhone Dev team released Redsn0w 0.9.6b4. Latest release of Redsn0w supports all iDevices but this method provides untethered jailbreak for iPhone 3G, iPhone 3GS Old bootrom and iPod Touch non-MC model. For all other devices, unfortunately, the jailbreak is currently tethered type.
Tethered means that the jailbreak needs to be reapplied every time you power down your iDevice. If you let the battery run to zero or restart your iDevice then you will need to reapply the jailbreak by connecting to your computer (tethering) and running Redsn0w again. Un Tethered jailbreak naturally quite the opposite. You have an untethered jailbreak if you reboot your iPhone with no issues.
If you are having problems like white cydia icon, cydia crashing, safari crashing then you need to reboot your iDevice with Redsn0w “just boot tethered now” option. For complete step by step instructions head over to our previous guide to Fix your iPhone, iPod, iPad iOS 4.2.1 Stuck on Apple Logo Reboot Cycle
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