Five days ago, Sprint announced that the Ice Cream Sandwich OTA was finally ready for the Nexus S 4G, but many of you still haven't received the update prompt. Yesterday, Google released the full OS image for the NS4G, but installing it does a full wipe, which may not be ideal for those just itching to upgrade.
Fortunately, the OTA link on Google's servers was finally found today by a number of AC forum members, which means you no longer have to wait for Sprint/Google and instead update your Nexus on your own. Since the OTA file contains the full OS image, including recovery and radio, rather than an incremental update from a specific version, you should be able to update no matter what you're currently running on your phone (feel free to point out otherwise in the comments).
- Download the update file and rename it to update.zip (make sure it's named update.zip and not update.zip.zip if you're using Windows and have it set to hide file extensions).
- Move the file to your phone's /sdcard directory using your favorite method - the easiest way is probably mounting the phone as disk using a USB cable.
- Reboot your phone and when it starts booting back up, hold Volume Up + Power.
- Select Recovery.
- The phone will reboot into recovery but first it'll show an exclamation point and a triangle. At this point, mash the Power and Volume Up buttons a few times until the recovery screen shows up.
- Select Apply sdcard update.zip, which should start the update process.
- Reboot and enjoy Android 4.0.4.
Image via Muffinabus