If you are a Nexus S i9020 owner, then there is way to get all those fun features of Android 4.2.1 Jelly Bean. If you wish to install the custom ROMs in Nexus, update your device to Android 4.2.1 with the help of CyanogenMod 10.1 Nightly ROM.

Before proceeding to update Nexus S i9020 to Android 4.2.1 CM10.1 Nightly ROM, remember that this is a nightly build, hence your device could get FC errors, boot loops apart from other bugs. But that is always reversible by installing the stock firmware or any other stable custom ROM.

General requirements before updating:

Create a backup of your existing ROMBefore flashing ensure that your device has 80% of more battery powerMake sure that ClockworkMod recovery is installedEnable the USB debugging option in Nexus S

How to install Android 4.2.1 CM10.1 Nightly ROM on Nexus S:

Download Android 4.2.1 CyanogenMod 10.1 NightlyROMandGoogle Appson your computerCheck if the USB drivers are properly installedConnect Nexus S with computer via USB cable and copy downloaded files to the SD cardTurn off your device and disconnect from USB cableNow Nexus S i9020 should enter Bootloader mode. Power on your device while pressing the Volume Up, Down and Power buttonsStep by step follow the instructions onscreen, choose Bootloader and then go to RecoveryPerform data wipe in CMW recovery and scroll down to elect Flash Zip from SD CardAnd then choose Zip from SD CardSelect ROM file after navigating to it. Confirm installation and the installation process should begin here

Repeat the above steps to install Google Apps and go to +++++Go Back. Reboot the device by choosing Reboot System Now to finish and update Nexus S i9020 to Android 4.2.1 CM10.1 Nightly ROM. The Jelly Bean update should now be installed on your Nexus S.