Here are the steps that has to be followed in-order to untether your jailbreak of iOS 4.2.1
while taking the help of the the iPhone Dev-Team’s ‘backup plan’ method on Mac OS X.
Please remember that you must have a jailbroken device on iOS 4.2.1.
Note: Folks please make to backup your data before attemting this tutorial as it is Beta.
Click the Next button to continue. RedSn0w will now prepare the jailbreak data.
You will now be presented with a list of checkboxes
Select Jailbreak Monte (untether) from the list of checkboxes. You
will be asked to select the iOS 4.2b3 ipsw from the Pwnage folder on
your desktop then click Open. Click Next to continue.
Please plug your iPhone into the computer and make sure its OFF then
click the Next button
RedSn0w will now guide you through the steps to get into DFU mode.
Hold down both the Home button and the Power button for 10 seconds.
Release the Power button and continue holding the Home button until
RedSn0w detects the device
RedSn0w will prepare Jailbreak Monte files, exploit with Limera1n,
Upload RAM Disk and Kernel, and Send Jailbreak Monte files.
RedSn0w will inform you when it has completed successfully.