Custom ROMs are certainly one of the reasons why owning an Android device is great. Personalization and customization are two of the things you can freely do to your Android device, and to tell you honestly, the options are almost endless. With the number of Android devices we have today, custom ROMs have also grown in number.

The Google Nexus S was given attention by developers and they have developed several ROMs for the phone. Just recently, an AOSP-based CyanogenMod 10 ROM was released to bring Jelly Bean to Nexus S owners. It really is great news but keep in mind that this ROM is an unofficial preview of the CM10 ROM. It will mostly give you a stock Jelly Bean experience with a few tweaks and mods.

Want this custom ROM on your Nexus S?  Read on to learn how to upgrade the Nexus S I9020 to Android 4.1.1 Jelly Bean via CyanogenMod 10 (preview build).

Warning

• The instructions in this guide are intended for use with the Google Nexus S, model number GT-I9020. Applying these instructions on another device or model may produce undesired outcomes.
• The information in this guide is provided for instructional and educational purposes only. There is no guarantee that these instructions will work under your specific and unique circumstances.
• Use these instructions at your own risk. We shall not hold any responsibility or liability for whatever happens to you or your device arising from your use of the info in this guide.
• Read and understand the whole guide first before actually performing the instructions.

Requirements

• A Google Nexus S GT-I9020 (international GSM variant) with unlocked bootloader and ClockworkMod Recovery installed.
  • To help you unlock your phone's bootloader, you can use a one-click tool. Check our guide to help you root, unlock the bootloader, and install CWM using a one-click tool.
• A Windows PC.
• Your phone's USB cable.
• Download the following files to your computer:
  • Jelly Bean CM10 Build 6 (20120720Legolas6CM10b.zip, 135.55 MB)
  • GApps (Google Apps) package (gapps-jb-20120717-signed.zip, md5sum: 10988c023495b7871514f2d69cbc2503)
  • Root package (Superuser-3.2-RC2-arm-signed.zip, 1.1 MB)
  • GPS Fix package (GPSFixforTestCM10.zip, 172.38 kB)
• Make sure your phone's battery is charged up to 75% or more to avoid interruptions during the process.
• Backup all personal data on your phone to make sure you have a copy of your personal data (e.g., contacts, SMS, MMS, Internet settings, Wi-Fi passwords, and the like) in case the procedure in this guide erases such data.
  • For backup tips, check our guides on how to sync your data to the cloud and how to create local backups of your mobile data.

Instructions

1. Copy all downloaded ZIP files to your phone's SD card.
2. Switch your phone off.
3. Boot into ClockworkMod Recovery. To do this, press and hold down the Volume Down and Power buttons together to enter Fastboot Mode. In this mode, highlight the Recovery option using the Volume keys and select the item using the Power button. This will boot your phone into recovery.
4. Make a NANDroid backup of your existing ROM in case of problems. To perform a backup, select Backup and Restore and choose Backup. After backup is made, go back to the main recovery menu.
5. Select Wipe Data/Factory Reset and confirm the action on the next screen.
6. Select Install ZIP from SD card and select Choose ZIP from SD card. Choose and confirm installing the following files in the order shown below:Flash the additional files in the same manner as step 5 in this order:
   • CyanogenMod 10 build 6 for Nexus S
   • Root package
   • GApps package
   • GPS Fix package
7. Once all necessary files have been installed, select Go back and choose Reboot system now. This will reboot your phone to the newly installed CM10 ROM.

Allowing Apps to Gain Root Access

1. Launch the Superuser app on your phone.
2. Tap on OK on the pop-up screen.
3. Click on the wrench icon found in the top right to access Settings or you can tap the Menu button and select Settings/Preferences.
4. Select Security then click on Automatic Response. Select the Allow option.
5. Close the Superuser app.

Congratulations! You have successfully the preview build of CyanogenMod 10 on your Google Nexus S GT-I9020. How do you find the ROM so far? We'd love to know what you think through commenting below.