The dedicated Android community has a way of tracking down OTA update files almost before the rollout begins. This is again the case for the newest Android 4.1.2 update for some variants of the unlocked Nexus S. Waiting for updates is for chumps, so get your Nexus S in hand, and proceed with caution.
To use this update file, your Nexus S has to meet the following conditions:
- The device must be the Soju variant with model number i9020T or i9023. In case you don't recall, the i9020T has T-Mobile 3G, and the i9023 is one of the overseas versions.
- The device must be running JRO03E (Android 4.1.1). There are some very similar versions of the Nexus S that have different software revisions right now, but the current OTA file is only going to successfully install over top JRO03E.
If your device qualifies, grab the update file from the link below, rename it update.zip, and drop it on your SD card. Turn off your phone, then boot into the bootloader by holding the volume up and power buttons as the device starts up. From the stock recovery, just choose to install the update file, and you're done. Other versions of the Nexus S might get their updates soon, including the i9020A which is usually a few weeks behind. Sprint's WiMAX Nexus will probably be waiting longer.