I tried to update my wife’s iPhone to iOS 4 yesterday, and failed, will try again tonight. I figured I would document the procedure for others.

Just a note though – I didn’t have this much trouble updating my iPhone to iOS 4, and a lot of people seem to have been able to accomplish it in 15 minutes. I think it has a lot to do with what your sync settings are in iTunes and how often you sync (both of us rarely sync).

Also – my Sprint EVO had a firmware update when I first bought it. I just accepted a notification sent to my phone and it updated over the air in a few minutes.

1. Find out on a blog or tweet than an update is available.
2. Wait until you get home from work and start the process so it can run overnight when you don’t need your cellphone.
3. Bring your iPhone to your computer (the one with the iTunes library your iPhone is synced to)
4. Find proprietary USB cable (hint: its probably on your desk at work or in your car)
5. Make sure your laptop is plugged into an AC adapter so it doesn’t run out of power in the middle of the firmware update and brick your phone.
6. Run software update and update iTunes to new version
7. Wait for iTunes to ‘update your media library’
8. Connect your phone to your laptop with the proprietary USB cable
9. Wait for iTunes to discover your iPhone is connected
10. Wait for iTunes to do automatic syncing
11. Click on your iPhone icon, navigate to ‘summary’ page on iTunes
12. Select ‘Check for Update’
13. Select update
14. Update tells you you have to transfer all of your purchases to the computer first, as its going to wipe all your data from your phone.
15. Wait while a few gigs of apps, and music, and video get transferred back to your computer. (If you run out of disk space on your SSD stop here and ‘figure something out’)
16. Run update
17. Update will start downloading – eta 3 hours over 25 Mbps FIOS.
18. 60% through download, download will fail due to an ‘unexpected error’
19. For some reason you have been signed out of your iTunes account, dialog requests that you log back in.
20. Log back in
21. Attempt to update iPhone again
22. Download does not resume but starts over from the beginning, but for some reason now only takes 5 minutes instead of 3 hours.
23. iTunes now starts … to backup your entire iPhone. No ETA but progress bar seems to infer ‘forever’
24. Go to sleep
25. Wake up to find out your laptop ALSO went to sleep – during your backup – which did not complete.
26. Go to work
27. Come home
28. Configure your laptop not to go to sleep
29. Start backup over again
30. Go to sleep
31. Wake up. If something went wrong, go to work, repeat as necessary.

I will update this procedure when I start it over tonight.