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Thread: unknown error (21) while restoring iPhone

  1. #1
    Join Date
    Apr 2010

    unknown error (21) while restoring iPhone

    Ok.. so I pursued the steps on an assortment of web pages and on the forum in order to upgrade to 2.2 and jailbreak. The whole thing in pwnagetool 2.2 was disappearing well put it in expert mode, booted it up to 1000, fabricated the ipsw. Restored phone, set it into recovery mode, option clicked "restore" preferred ipsw built from pwnage and it starts up then, "iphone could not be restored an unknown error (21) occured" rebuilt the ipsw two times at the moment and still the identical thing. I don't know what else to do I am wedged and frantic for an explanation. Hoping that someone over there will provide some helpful reply.

  2. #2
    Join Date
    Oct 2008

    Re: unknown error (21) while restoring iPhone

    The iPhone / iPod Touch has two modes 'special'; Recovery mode and DFU mode. They may look the same, but there are some differences: The first way you activate itself when iTunes restore. DFU mode is a bit more 'deep', as it somehow, and can be triggered in the iPhone itself, simultaneously pressing the home button (below) and power (also known as sleep) at the top right . After having pressed for at least 10 seconds, release only the power button and leave the home for another 10 seconds down. We must listen to the sound system have disconnected a USB device if you use Windows. After putting the iPhone in DFU mode, we can try to restore it again from iTunes.

  3. #3
    Join Date
    Oct 2008

    Re: unknown error (21) while restoring iPhone

    Try using another computer. Once the iPhone is restored, you can go to yours to sync music and applications without problems. It is important to have the latest version of iTunes. In the application menu, I ask you to look for new updates. Because many times it happens that updating an applications fixes an errors. So you should try to update all possible applications.

  4. #4
    Join Date
    Oct 2008

    Re: unknown error (21) while restoring iPhone

    Try to Reinstall iTunes. Sometimes iTunes may have some temporary files in your folders (for example, firmwares that have been downloaded with each iPhone firmware update) that can cause errors. If these folders do not know well, the best way to get rid of them is to delete iTunes and reinstall it. Remember that you purchase music from the iTunes Store will have to download it again. The local you have on your system, you will have to import it again. Also, Mac users, the user can activate Guest (Guest account) and enter it to use a completely clean iTunes. Closing the meeting, all files are automatically deleted, so it can be useful for testing without changing anything about your current system. iTunes, of course, is a free download from the Apple website.

  5. #5
    Join Date
    Oct 2008

    Re: unknown error (21) while restoring iPhone

    Some Macs with Leopard OS 10.5.6 have problems with DFU mode detected by a bug in the kernel of this particular update the system. It can be easily solved by connecting the iPhone to a USB hub instead of directly to your computer. Hopefully Apple fixes this bug in the 0.7 upgrade the system.

    It may seem obvious, but sometimes we have avoided such problems by changing the iPhone USB port on the same computer, or especially on Windows, simply rebooting the computer and trying again.

  6. #6
    Join Date
    Dec 2007

    Re: unknown error (21) while restoring iPhone

    Try DFU mode (iPhone plugged into the computer, iTunes launched, press the power button and home button for 10 seconds. After 10 seconds passed, the iPhone turns off, release the power button but keep pressing the Home button. iTunes will suggest the recovery mode and your iPhone will remain off).
    • Restart your computer
    • Be sure to have administrator rights
    • Change session on your computer
    • Change the USB port
    • Update your computer (drivers, Windows)
    • Change the USB cable if you can
    • If you go through a router, connect your computer directly to the Internet
    • Change your computer (Yes, it is not given to everyone)

    I hope these tips will help you solve the error "The iPhone could not be restored an unknown error occurred (21)".

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