How to Jailbreak iPhone 4 iOS 6.0.1

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A tethered jailbreak is now available for devices running iOS 6.0.1. with any chip pre-A5.
For anyone with a post-A5 device unfortunately there is no jailbreak
yet, and no news of when it can be expected. Keep checking back, though,
because as soon as there is we will post it pronto for you along with a
complete how-to guide on the jailbreak.
Update : Snowbreeze for 6.0.1 Jailbreak Tutorial
Redsn0w has been tried and tested and the jailbreak has been confirmed to be working with devices susceptible to the Limera1n
exploit hence the A4 or lower condition, however, this is a tethered
jailbreak, which means that every time the phone needs to be shut down
or rebooted it must be connected to the computer via USB to get it back
up and running again.
How to jailbreak your pre-A5 chip device : iPhone 4 – iPod Touch 4 – iPhone 3GS

1. Download Redsn0w 0.9.15b1 for your computer running Windows or Mac OSX (Redsn0w version 0.9.15b2 and b3 also works) [You must be registered and logged in to see this image.]
   
2. Download and install the iOS 6.0.1 ipsw
   
3. Run Redsn0w (in Administrator Mode on Windows)
   
4. Navigate to Extras > Select ipsw and manually choose the iOS 6 ipsw (not iOS 6.0.1) file for the device you are going to jailbreak [You must be registered and logged in to see this image.]
   
5. Once Redsn0w has identified the file click back to the main screen
   
6. Choose Jailbreak and then Cydia and follow the onscreen instructions to put your iPhone into DFU mode
   
7. Once Redsn0w has finished choose ‘Autoboot this device when it connects in DFU mode’
   
8. You device will now have a tethered jailbreak
   

Steps for Tethered Boot :
When you need to reboot your device all you have to do is run Redsn0w and choose Extras > “Just boot” . All done . You have now jailbroken your iPhone on iOS 6.0.1 .Install the awesome jailbreak apps .
It
is strongly suggested that because of this if your A4 device is used
as your main go-to device then you don’t want to run the risk of getting
stranded or being in need or help with a phone that cannot aid you due
to the jailbreak – that isn’t the point of either! So if your iPhone
or iPod is more of a leisure device then continue, if not please
consider the implications of the tethered jailbreak before proceeding.
It is also advised that if you rely on a carrier unlock to avoid using
this jailbreak.