How to do a clean install of Iphone?

Posted on 2010-11-25
Last Modified: 2012-06-27
How to do a clean install of Iphone? I recently upgraded to 4.2.1 and found out the baseband firmware cannot be unlocked. I tried to use pwnagetool to resotre to 4.1, but still the baseband doesn't change...... why?
Question by:okamon
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Expert Comment

ID: 34214569
Once you have upgraded, your baseband cannot be changed or downgraded (depending on you phone, 3GS or above I believe).  So, at this point, you will need to wait for a future unlock as you will currently not be able to.  Developer and hacker @musclenerd who is one of the unlockers will always tweet with this fact stating "Unlockers, do not update the firmware to preserve your baseband!".  If you are in need of an unlock, you will have to stay on the lesser firmwares in the future or until a new baseband unlock is released.  At this point, to answer your question fully, you cannot change your baseband and you will have to wait for a compatible unlock.  Whether you want to continue upgrading and forget about unlocking or stay on 4.2.1 and unlock in a few months, it is your choice.

Author Comment

ID: 34214937
thank you SpeedyApocalypse! I am just surprised even with a clean install i cannot downgrade baseband. Do you know if I have a ipsw firmware, how can I perform clean install + jailbreak?
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LVL 13

Expert Comment

ID: 34214949
Well, if you managed to downgrade to iOS 4.1, you can jailbreak using L1meRa1n or GreenPois0n.  For a guide, see here:

As for iOS 4.2, there is a tethered jailbreak released through RedSn0w (tethered means you will have to run a tool upon every restart and reboot).  However, I would not recommend jailbreaking iOS 4.2 as there is not much compatible.  

To do a fresh install, you can downgrade through PwnageTool (like you had said).  If you have SHSHs backed up, you can redirect your hosts file to whatever server the SHSH files are stored, and hold Shift and click on Restore in iTunes.  Then, browse to your selected firmware and simply restore.

Author Comment

ID: 34215100
Just want to be clear. so you are saying I can use PwnageTool to do downgrade (fresh install) and jail break correct?

And I don't know what is SHSHs backed up, what I have done so far is just to hold Shift, browse the firmware and Restore in iTunes..... is that ok?
LVL 13

Accepted Solution

SpeedyApocalypse earned 300 total points
ID: 34215109
Well, you said earlier how you used Pwnage Tool to downgrade... so use that?  If you indeed did not ever downgrade before, you will need SHSHs saved up (encrypted hashes) so you can downgrade your firmware.  You can only acquire these if you were on a previous firmware and manually saved them (so if you do not have them, then mark that way out).  

To clarify, every time you downgrade or upgrade, Apple sends you new encrypted hashes that work for your device (SHSHs).  You can back these up to be able to restore to previous firmwares (using Firmware Umbrella software).  However, you must be on the firmware you want to downgrade to in order to save the SHSHs (then if you upgrade, you can downgrade back to this).  It should return an error if you have not saved SHSHs and redirected your hosts file if you restore to iOS 4.1.  However, you can Shift-Click and try...

To jailbreak, once you are on 4.1, use LimeRa1n or Greenpois0n (see guide above).  To jailbreak on 4.2.1, use RedSn0w (it is tethered, also see above).

Author Comment

ID: 34215380
thanks SpeedyApocalypse.... but I still don't understand what you are trying to explain.... I am a novice so please forgive me.

Can you just tell me that if I downloaded a firmware and use pwnagetool then use the custom firmware, will I be able to either do clean upgrade or downgrade of my phone? This is the tutorial i followed...

so in this case, I don't need to use any of the tools and SHSHs backup you mentioned above right?

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Expert Comment

ID: 34215387
I am not familiar with pwnage tool directly but IF you can get to 4.1 with it, then jailbreak using either that, GreenPois0n, or LimeRa1n.  However, your basement will stay upgraded.  Additionally, if you can indeed diwngrade with pwnage tool, then you wouldn't need your SHSHs saved.

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