iPhone iOS 4.2.1 Jailbreak Instructions (Redsn0w)

Submitted by Bob Bhatnagar on November 27, 2010 - 4:45pm

Now that redsn0w has been updated to jailbreak iOS 4.2.1 you may be wondering what's involved in actually jailbreaking your iPhone. Here are some tips and instructions to help. First of all, if you have an unlocked iPhone don't update your device to the official iOS 4.2.1 or use the redsn0w 0.9.6b4 jailbreak. You will lose your unlock.

UPDATE: Comex has released an easier method for newer 4.x firmwares. Click here for instructions on how to use JailbreakMe 3.0 to jailbreak your device.

Always back up your SHSH files before jailbreaking. This will preserve your ability to downgrade in the future. You must also find out if a tethered jailbreak is necessary on your device.

1. To see if you can jailbreak untethered find out if your iPhone is an MC model. All iPhone 4 models currently require a tethered jailbreak. If you don't want to have to boot your iPhone tethered every time you turn it off, then wait for Dev-Team to develop an untethered solution.

2. Ready to jailbreak? Download the redsn0w 0.9.6b4 software from iPhone Dev-Team. Install and run redsn0w.

3. Use redsn0w to select the IPSW file matching the current iOS version installed on your iPhone. You may want to make a backup of this file before jailbreaking, otherwise an official version can be downloaded later if necessary. These firmware files are stored in a directory on your computer. If you can't see the files in Windows make sure Windows is set to show hidden files. Here are example files:

Newest iPhone FAQs

iPhone 4 running iOS 4.2.1: iPhone3,1_4.2.1_8C148_Restore.ipsw
iPhone 3GS running iOS 4.2.1: iPhone2,1_4.2.1_8C148a_Restore.ipsw
iPhone 3G running iOS 4.2.1: iPhone1,2_4.2.1_8C148_Restore.ipsw

4. Redsn0w will verify the firmware file and prepare jailbreak data.

5. Select the check box next to Install Cydia and click Next.

6. Make sure your iPhone is plugged into the computer and TURNED OFF then click Next.

7. Follow the on-screen instructions carefully to put your device into DFU mode. When the iPhone enters DFU mode redsn0w will proceed to install jailbroken firmware.

8. Redsn0w will notify you when your jailbreak is complete. If you need the tethered jailbreak on your model iPhone, make sure to immediately boot tethered before using your device, otherwise Cydia and jailbreak apps will not work.

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Comments

Anonymous replied on August 12, 2011 - 10:41pmPermalink

Hi,
I am facing the same issue, can you please let me know what u did to fix this Apple logo issue?

Thanks

Anonymous replied on April 20, 2011 - 3:11amPermalink

I bought my iPhone 3G running 2.x already jailbroken with Redsn0w. I later “updated that” to 3.0, following detailed instructions from the vendor who now seem to be out of business. I realize this info is probably out there, but have not found info on “upgrading/updating”. Also do not understand what ‘tethered’ is and if it applies to me. I can currently use internet via SIM card when no wifi is available and that is important.
Can I now update to 4.2.1? How do I do this? Do I update on iTunes which will then lock the iPhone and then I jailbreak it using the correct Redsn0w version. Would be great to have detailed walk-thru. Am happy to do it if I have a guide for dummies. Thanks E

Anonymous replied on November 1, 2011 - 4:56amPermalink

I was in the process of jailbreaking my iphone 3G using redsn0w and it looked like it was successful until it got stuck on the apple logo on the reboot. In my attempt to get it going, I openend up itunes and a restore was performed to iOS 4.2.1 and now I guess I've lost the UNLOCK. I've since then tried many times to run thru the jailbreak process, but to no avail. Can anyone help me please.
many thanks

cam

Anonymous replied on November 30, 2011 - 1:18pmPermalink

does jailbreaking it allows me to put my tmobile simcard?

A Guy who Needs Help replied on December 2, 2011 - 10:18pmPermalink

how long does the reboot usually take!? im getting nervous

Eric H. replied on January 2, 2012 - 2:26pmPermalink

Anybody get this to successfully jailbreak their 3G recently? Seems everyone is getting stuck on the Apple boot logo.

Anonymous replied on January 3, 2012 - 12:44amPermalink

i got mine to go all as well planned and now i have no network at all, no 3d no edge, and wifi doesnt work.... Halp?

MS replied on January 24, 2012 - 12:25pmPermalink

im done with successful boot, but redsnow is not installing cydia on my phone... i dont know what the problem is... but im know really fedup... if anyone knows the solution plzz lemme know

fml replied on January 8, 2012 - 5:00pmPermalink

hey, every things ok until i get to the part where redsnow trys to get the ipad band data

the loading bar does nothing then then redsnow shuts off..................anyone any ideas?

Anonymous replied on January 8, 2012 - 9:31pmPermalink

OK, I've JB a 3G before and everything went well. Today I tried JB another 3G running 4.2.1 and BB 05.15.04. I used the latest Redsn0w and ipsw FW. Everything goes smoothly until I put it in DFU mode. Just as it's about to start the process of JB right after putting it in DFU mode, Redsn0w just stops running and closes down......!!! Very frustrating.... Anybody know what I'm doing wrong??? Any help would be appreciated. Thanks!

Chris replied on January 9, 2012 - 3:20pmPermalink

Trying to jailbreak my iphone 3g. firmware 4.2.1 using redsn0w_mac_0.9.10b3 once the phone is put into DFU mode redsn0w just quits.

I tried restoring it with iTunes and retrying the jailbreak, it enters DFU mode starts the processing but quits without finishing. when i say quits, i mean JUST QUITS. without a warning, prompt, message, nothing. just quits...

Macbook pro 13" OSX Lion
iphone 3G 8 gigs(first-gen) 4.2.1(8c148)

I need to jailbreak/unlock this thing plz help.

Slick replied on January 10, 2012 - 7:01pmPermalink

I just JB my phone using redsn0w 0.9b4. Everything works good there is something thats bothering me. When ever I change screens or slide over it flickers. Nothing major but it just bugs me

The noobnes replied on January 17, 2012 - 11:54amPermalink

1) running redsn0w_win_0.9.10b4 as admin and regular does not let me set affinity for CPU. 2) It starts up and runs, i set it to search for appropriate iPhone1,2_4.2.1_8C148_Restore.ipsw and it sees it, builds the files, flies through that part, then just quits. Any ideas?

Win 7 Pro x64
iPhone 3g 16GB w/ 4.2.1 FW
Dont care if 3g or edge work as i use it as an iTouch but Wifi is a must

Thank you in advance for reply,
JB Noob

MS replied on January 24, 2012 - 11:50amPermalink

same problem is accuring with me, if u hv find the solution or in future... plzz let me know

Slick replied on January 10, 2012 - 7:04pmPermalink

I just JB my iphone 3g 4.2.1 using redsn0w 0.9b4. Everything works fine but there is something that is bugging me. Every time I change screens or slide over there is a flicker. Nothing major, it just bugs me.

Kund replied on January 23, 2012 - 8:13pmPermalink

i am trying to JB my Iphone 4 4.3.5 version and everytime i run redsnow iTunes quits automaticly and when i brows with redsnow it says ''Unable to recognize specified IPSW'' any ideas why is like that :) iTunes quits when i start redsnow even i havent connected my phone to iTunes .... thanks in advanced

Kunda replied on January 23, 2012 - 8:15pmPermalink

MS replied on January 24, 2012 - 11:44amPermalink

im not getting cydia on my iphone sg after successful process of jailbreak through this procedure. Plz help ASAP plzzzzzz

MS replied on January 24, 2012 - 11:47amPermalink

i am not getting cydia on my iphone 3Gm after successful procedure(the one mentioned here) of jailbreak.. PLZZZZ help me plzzzzz ASAP

Anonymous replied on January 28, 2012 - 7:40pmPermalink

Hi. I need help please. i jailbroke my iphone 3gs new bootrom 4.2.1. Cydia is working but i cant install any apps (i mean from app trackr website) please help me itunes starts installing the app but at the end says unknown error :(

Anonymous replied on February 6, 2012 - 4:44pmPermalink

I have jail break on my iphone how do i get the games free

Anonymous replied on February 15, 2012 - 3:42pmPermalink

do you have to have firmware to jailbreak ?????/

Anonymous replied on February 23, 2012 - 8:35pmPermalink

Whats an IPSW? I dont understand what to do or how to find it

Anonymous replied on April 5, 2012 - 9:25amPermalink

Can i use redsn0w0.9.10b6 to jailbreak my iphone 3g 4.2.1 MB model

Anonymous replied on April 13, 2012 - 1:41pmPermalink

Will i lose any data if i do this?

alyssa replied on May 30, 2012 - 1:25amPermalink

when i go to press redsnow then press browse for the files its shows dfu and it shows all_flash but there both empty ... help please!!??

alyssa replied on May 30, 2012 - 1:29amPermalink

when i go to press redsnow then press browse for the files its shows dfu and it shows all_flash but there both empty ... help please!!??

Ed replied on June 1, 2012 - 10:35amPermalink

Followed all the instructions and jailbroke my 3g but it wont recognize the sim card or connect to itunes, any ideas?

Anonymous replied on June 10, 2012 - 12:45pmPermalink

Can I JB and unlock iphone 3G 4.2.1 with baseband 05.15.04.
Tried to jailbreak with redsnow 0.9.6b4, Cydia is installed after this but there is no ultrasnow which can unlock the above baseband.
Tried to open redsnow 0.9.6b5 but that link does not work.
Can anyone please help

Anonymous replied on June 10, 2012 - 12:50pmPermalink

iPhone iOS 4.2.1 Jailbreak Instructions (Redsn0w)

Newest iPhone FAQs

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