This tutorial is only for Mac owners or for those who have installed Mac OSX on a virtual machine. For Windows there is no program that can do this yet, but keep your fingers crossed for sn0wbreeze. What does custom ipsw mean? Learn here.
Step 1
Create a folder anywhere in the system called pwnage. Download PwnagteTool 3.1.4 by here and iPhone firmware version 3.1.2 of here.
It is best to download the firmware with Firefox because other download managers will unzip it, but if you extracted using anything other than Firefox and the firmware has the zip extension instead of ipsw, then you just need to change the extension from zip to ipsw.
Step 2
Mount the image with PwnageTool and open the application.
You will receive a warning message, press OK to continue.
Step 3
Select expert mode from the menu bar.
Step 4
Select the iPhone version for which you are doing the ipsw.
Step 5
Press continue and you will be asked to search the computer for the location where you downloaded the Apple firmware. Press the broswe button and go to the relevant directory. There is a possibility that the firmware will be found automatically if you copy the application to the folder where you downloaded the firmware.
Choose the firmware, then press continue.
Step 6
You will arrive in front of a menu with 6 options that give you the opportunity to customize the firmware in order to launch it. The General option will give you the opportunity to specify the size you want to allocate to the system partition (the one where applications will be installed, from Cydia, themes, etc.). Tick activate the phone if you have a phone taken from another operator and you do not have the sim card for activation. PwnageTool is created not to update baseband, so the option to enable baseband update should be disabled.
Bootneuter options exist only for 2G owners, so press the blue button to continue.
The Cydia settings option will give you the opportunity to download applications from Cydia and insert them into the firmware to be installed automatically in the restore process. Click on the Download packages tab, double-click on the desired applications to download them, then select what you downloaded and press the blue button to continue.
You will be brought to a window where only the selected applications will appear, press the blue button to continue.
The menu will appear where Cydia and Icy will be displayed, if you want to install only one of them, it is enough to leave the desired application checked.
The Custom Logos Settings option will give you the opportunity to change the boot logos. Press browse to choose the images from your computer, but they must not be larger than 320×480.
Press the blue button to continue.
Step 7
You will reach the initial page of optuni. To start the process press the build button then the blue button to continue.
You will be asked to choose the location where the custom ipsw will be saved, choose it, click and click save to start the process. The process can take up to 10 minutes or more, depending on your computer.
You will be asked to enter your username and system password, which you must specify to continue the process.
You will receive a warning message in which you will be asked if the iPhone has ever been jailbroken. It is best to press No for an efficient restore.
Congratulations! After finishing the custom ipsw creation process, you can begin the installation.
