This guide and tutorial will show you how to jailbreak your iPhone 3G running firmware 3.1, using PwnageTool for Mac OS X. So far, only PwnageTool is available for jailbreaking the 3.1 iPhone 3G and it is only for Mac. I believe a RedSn0w method for both Mac and PC will be available soon.
1. Make sure you have installed the latest version of iTunes (iTunes 9).
2. On your desktop, create a folder called "jailbreak" or whatever name you want to give it. It doesn't really matter. Download PwnageTool 3.1 and the 3.1 IPSW (iPhone1,2_3.1_7C144_Restore.ipsw) from here and save them into the "jailbreak" folder. Note that you should download the firmware using FireFox as Safari often brings up issues. Also note that the PwnageTool download link is a torrent and you will need a torrent downloader (ie. uTorrent) to download it.
3. Launch PwnageTool. It will give you some sort of warning. Just click OK. On the next screen, choose the "Expert Mode".
4. Select your iPhone model and click the blue arrow to continue.
5. Browse for the IPSW you downloaded in step 2. You should then get a green check mark.
6. You will now be offered several options. Choose "General". Make sure the "Activate the phone" box is left UNCHECKED if you use an official carrier (such as AT&T in the US, Roger in Canada, etc...). This is very important. If you are not using an official carrier, then CHECK "Activate the iPhone".
7. Increase the root partition size to 700 MB. This is not necessary but it is safer. Then click the blue arrow to continue. Click the blue arrow one more time to skip the bootneuter settings, which aren't available for the iPhone 3G.
8. You will now have the possibility to pre-install a few packages from Cydia so you don't have to do it manually later. I will skip this part. Click the blue arrow to go to the next step.
9. You will now be in the "Custom packages settings". Make sure Cydia is selected and you may want to select Icy as well. For what it's worth, I do not use Icy. I only use Cydia but you're free to select both if you want. Whatever you do, make sure at least Cydia is selected. Click the blue arrow to continue.
10. You can now set your own "Custom logos settings". I don't use any but again, you can choose the one pre-selected or you can even upload your own. If you choose to upload your own, remember the logo mustn't be bigger than 320 x 480. Click the blue arrow when done to continue.
11. It is now time to start the pwnage process. You should be on the main options screen offering you 6 different options. Choose "Build" and click the blue arrow to continue.
12. You will now have to save your custom IPSW file. Save it in the "jailbreak" folder we created in step 2.
13. Your custom IPSW firmware will now be built, which may take up to 15 minutes, so be patient.
14. You will most likely be asked for your administrator password. Fill in the blanks and click OK.
15. You will then be asked if your iPhone has been pwned before. Just answer "No".
16. Now is the most important step. You will first be asked to turn off your iPhone. Follow the instructions on your computer screen to put your iPhone into DFU mode. Basically, you have to hold the home and power buttons together for 10 seconds, then release the power button but still hold the home button. If done correctly, PwnageTool will tell you you successfully entered the DFU mode.
17. If iTunes hasn't launched automatically, open it. iTunes should tell you it has detected an iPhone in recovery mode. Click OK.
18. In iTunes, hold the "Alt/Option" key and click Restore at the same time. DO NOT click "restore" without holding the "Alt/Option" key! A window will pop up and you'll be able to choose the custom IPSW file you created in step12 that you saved in your "jailbreak" folder.
19. iTunes will now work on restoring your iPhone using the custom firmware.
20. Done! You will now be offered the option to set up your iPhone as a new phone or restore from a previous backup. I personally like to start fresh and I always choose to set it up as a new phone, but it's your choice.
21. You should now see the Cydia icon on the second page of applications on your iPhone. Congratulations, you just jailbreaked your iPhone 3G 3.1 with PwnageTool.
If you have any question or concern, please leave a comment.