These are instructions on how to jailbreak your iPhone 4, 3GS on the iOS 5.0 firmware using RedSn0w for Mac.
This procedure will cause you to upgrade your baseband potentially ruining your chances for an unlock. Please wait until we have posted a tutorial on how to update to iOS 5 using a custom ipsw if you need an unlock. The jailbreak is also tethered for all devices except the old bootrom iPhone 3GS which means you will need to connect your device to the computer each time you reboot.
Step One
- Download RedSn0w 0.9.9b5 from here
- Download the 5.0 firmware: For iPhone here, For iPad here (Note: you do not need to download the 5.0 firmware if you are already on iOS 5.0)
Extract the RedSn0w zip file by double clicking it.
Step Two: (You can skip this step if iOS 5 is already installed on your device)
Connect your iPhone to the computer and launch iTunes. 
Select your iPhone from the list of devices on the left. Now hold down Option and click the Restore button. Restore is preferred as it won't create any wasted space on your iPhone. 
Find and select the 5.0 firmware ipsw of your iDevice model. Click the Choose button to continue. iTunes will now update your iDevice to the new firmware.
Step Three
Launch the redsn0w application we extracted earlier.
Step Four
Once RedSn0w opens click the Jailbreak button 
Step Five
Plug your iDevice into the computer and make sure its OFF then click the Next button 
Step Six
RedSn0w will now guide you through the steps to get into DFU mode.
Hold down both the Home button and the Power button for 10 seconds. 
Release the Power button and continue holding the Home button until RedSn0w detects the device. 
Step Seven
Your iDevice will now reboot 
Step Eight
RedSn0w will now prepare the jailbreak data. 
Step Nine
Select Cydia from the list of options and click Next. 
Step Ten
Your iDevice will now be rebooted again and RedSn0w will begin uploading the new RAM Disk and Kernel. 
Step Eleven
Once this is complete you will be notified that RedSn0w is done. When your iDevice finishes rebooting (5 minutes or so) it will be jailbroken with Cydia on the SpringBoard. 
BOOT TETHERED
Once you have jailbroken you will need to rerun redsn0w to boot tethered.
Step One
From the main RedSn0w menu click the Extras button. 
Step Two
Select Just boot from the Extras menu to just boot tethered. 
*As usual a big thanks to the iPhone Dev-Team and Geohot for their hard work and contribution to the iPhone community.
