I’ve been trying to jailbreak my iPhone (iOS 4.2.1) for few days. I thought it would be cool if I install Android on my phone, after jailbreaking it. I used redsn0w several times to jailbreak, however I couldn’t manage to jailbreak even if it says “it’s done”.

I didn’t want to downgrade the firmware. If I downgrade to iOS 4.0.1, I can easily jailbreak my phone over JailbreakMe.com, but this method does not provide me full access that I need for installing custom bootloader. So I had to try something else.

I found a tool (sn0wbreeze), that is not only able to jailbreak iOS 4.2.1, but also allow me to install custom boot loader. It sounds perfect! I created a custom (jailbroken) iOS 4.2.1 firmware using sn0wbreeze 2.2.1, restored it using iTunes and boom! My iPhone is now jailbroken!

After jailbreaking, I installed Android. There is a package in Cydia that handles this process. Install Bootlace to your phone using Cydia. Open it and follow the instructions. Once, your kernel is patched and your phone is rebooted, run Bootlace again. Go to OpeniBoot tab and install it. It’s a custom boot loader for iPhone which can boot both iOS and Android.

Installing Android requires download of lots of data. I recommend you to switch to Wi-Fi connection if you’re connected to the internet using cellular data network. There is a project which creates custom Android for iPhone. In Bootlace, go to iDroid tab and install it. This process can take a while. After installation is finished, click to “info” button on the top right corner. Install multitouch and wireless device firmwares too. Installation is now finished. You can switch to Android using QuickBoot tab in Bootlace. Voila!

Now, I have a iPhone which can dual boot iOS 4.2.1 and Android 2.3.2. Some features and not supported yet, and power consumption is high. But I loved it!

For list of supported devices and more information please refer to the official Installing iDroid using Bootlace document.