Update Nexus S I9020 to Android 4.1.2 JZO54K Slim Bean Custom Firmware
Galaxy Nexus, Nexus 7 and Samsung Galaxy series phones have already got a number of custom ROMs that are based on the new Android 4.1.2 JZO54K AOSP release. Slim Bean is one of them and will give you a stripped down version of Android 4.1.2 Jelly Bean. You can now install Android 4.1.2 JZO54K Slim Bean on Nexus S I9020. Remember, this is a custom firmware with additional features on top of stock AOSP Android 4.1.2 Jelly Bean. This is not an official firmware.
In this tutorial, we will tell you how to install Android 4.1.2 JZO54K Slim Bean custom ROM on Nexus S I9020 with complete steps and instructions on how to backup your phone. Your Nexus S should be rooted and ClockworkMod recovery should be installed. Let’s get on with the tutorial now and flash a new custom ROM on the phone.
Disclaimer: All the tools, mods or ROMs mentioned below belong to their respective owners/developers. We (TeamAndroid.com) or the developers are not to be held responsible if you damage or brick your device. We don’t have you on gun point to try out this tutorial 
Make sure you have installed all your USB drivers for the Samsung Nexus S to connect it with the computer. Download Samsung Nexus S USB drivers! Apart from just the USB drivers, there are a few more things that you need to take care of.
1. You need to enable USB debugging mode. This helps to connect your Android phone with the PC. See here: How to Enable USB Debugging.
2. Your phone battery should be 80-85% charged. If your phone goes off suddenly because of battery, during flashing ROMs or installing mods and updates — your phone might go dead permanently. See here: How to Check Battery Percentage.
3. Backup all your important data that you might need as soon as your flash a new ROM, or make a backup for just in case, you never know when anything might go wrong. See below on how to backup data:
- Backup your SMS messages. How? –> How to Backup/Restore SMS Messages.
- Backup Contacts, Gmail and Google Data. How? –> Sync with Google Sync.
- Backup Call History. How? –> How to Backup Call History.
- Backup WhatsApp Messages. How? –> How to Backup/Restore WhatsApp Messages.
- Backup APN Settings: GPRS, 3G, MMS Settings.
4. Your phone should be factory unlocked. Additional instructions for locked Android devices will be added in the tutorial for unlocking devices.
5. Remember, this is not an official firmware update. This is a custom ROM, based on AOSP release of the Android 4.1 Jelly Bean.
Now, let’s proceed with the tutorial on the next page and update Nexus S I9020 to Android 4.1.2 JZO54K Slim Bean custom ROM.
