The iPod touch that I have came with 3.1.3 and when iOS 4 was announced I upgraded it to 4.1; that’s as far as I went . With the recent announcement of greenpoisOn’s untethered jailbreak for 4.2.1, I decided to upgrade the iPod.
Before upgrade
Backup via iTunes
1. As a rule of thumb always do a backup before messing around with the OS. Just connect the device to iTunes, right click on it and select “Back Up” and let iTunes do it’s magic.
If you have previously jailbreak your device and already have loads of apps installed via Cydia, make sure you backup that as well. There are several methods of doing so but the two easiest ones are via aptbackup or pkgbackup. Both can be downloaded via Cydia though please take note that pkgbackup is a paid app. Based on some of the forums I’ve been reading seems like pkgbackup is a more reliable solution though it’s still not a 100% guarantee.
New device or restore
2. After the backup, click on “Update” to download and install the new firmware.
3. Once the device is upgraded, iTunes will prompt to setup the device as new or restore from a backup, choose “Set Up A New ..” and continue, cancel the sync and eject the device.
4. Click here to download greenpois0n for MAC or WINDOWS. Save the file to your computer desktop.
5. Locate the file and open the application. You may need to extract/unzip the file.
6. With Greenpois0n open, and your powered off device connected, click the “Jailbreak” button.
greenpoisOn jailbreak
7. You will now follow the instructions to place your device into DFU mode:
- Press & Hold the Power button for 3 seconds
- Continue holding the Power button and press and hold the Home Button for 10 seconds
- Release the Power Button and continue to hold the Home Button
Booting into DFU
8. Be patient with the process as it will take some time as the device runs greenpoisOn jailbreak.
Loader icon
9. Once the device reboots, you’ll see the “Loader” icon. Running this enables the installation of Cydia but I constantly had problems getting Cydia to install. I keep getting not enough disk space error. No matter how many times I restored and did the jailbreak, I kept getting the same message. Manage to find the solution after much digging
.10. Just download the latest RedSn0w, Click on Browse, Navigate to iOS 4.2.1 IPSW file (remember to download the IPSW file first), Click next, Click on Install Cydia, follow the instruction to put it in DFU. You can restore your device after connecting to iTunes. That’s it! Enjoy your jailbroken 4.2.1 device 🙂
Install Cydia
Downloads
Redsn0w 0.9.6b4 for Mac
- http://www.iphone-storage.de/redsn0w_mac_0.9.6b4.zip
- http://cdn.nspwn.com/redsn0w_mac_0.9.6b4.zip
- http://tgq.nl/redsn0w_mac_0.9.6b4.zip
Redsn0w 0.9.6b4 for Windows
- http://cdn.nspwn.com/redsn0w_win_0.9.6b4.zip
- http://tgq.nl/redsn0w_win_0.9.6b4.zip
- http://bubele.eu/redsn0w_win_0.9.6b4.zip
- http://kwek.no-ip.org/redsn0w_win_0.9.6b4.zip
iOS 4.2.1 for iPad:
iOS 4.2.1 for iPhone:
iOS 4.2.1 for iPod touch:
just.yoga 
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