The authors of the project CoolBooter offered iPhone users the ability to simultaneously load two different operating systems – iOS 6 and iOS 9. To take advantage of the decision by the owners of a 32-bit jailbroken devices.
Dual boot is often used on a desktop OS. That is, the user installs on the same computer for two different OSes and when the PC starts, chooses one of them. In order to organize such a thing on iOS, you must have a 32-bit device with jailbreak, which is free of at least 4.5 GB.
Utility CoolBooter is in the testing phase. Today the developer released beta version, which fixed most of the errors. However, users are advised to wait for the final version to be sure a reliable work.
How to dual-boot iOS 6 and iOS 9:
Step 1: Open Cydia and navigate to sources.
Step 2: Click “Add” and enter the repository address http://coolbooter.com.
Step 3: Wait for the update repositories, go to the Search tab, locate the utility CoolBooter. The app is free, install it.
Step 4: go Back to the desktop and find the iPhone a new icon CoolBooter.
Step 5: Run CoolBooter and click the Install button. Select the version to install from 6.0 to 6.1.4. Currently installing the latest version has problems, so it is better to choose one of the earlier releases.
Step 6: CoolBooter will offer to jailbreak iOS 6.0. Click Yes or No to continue, then select whether to display the list of commands during the installation. Wait until it is finished.
Step 7: Disconnect the cable from the iPhone (this is important) and reboot the device. Click Boot to start screen. Wait for iOS 6 and perform the initial device setup. That’s all!
Installation instructions CoolBooter from EverythingApplePro: