Disclaimer: This guide is taken from multiple sources and for my own use
I do not write this guide.
Step by step for Kitkat ROM installation: article from AndroidGeeks
Reproduce here :
1. Download the custom ROM build. I use AOSP 4.4.3 this, taken from xda-developers
2. Download Gapps for this ROM from here.
3. Connect your Nexus S with your PC, then move both zip files on your device’s internal storage.
– disconnect the device from computer when all files are copied successfully.
4. Power off the device now.
5. Boot it in CWM Recovery Mode now. Here is another guide showing how to do so. I ended up using the 3rd method (via adb) .
6. First you need to create a full NANDROID Backup of your current ROM by selecting ‘backup and restore’ option.
– save the file on the Nexus S internal storage, then continue to the next step.
7. Now, apply the factory reset:
– select ‘wipe data/factory reset’. Confirm the process.
8. Install the custom ROM zip by selecting ‘install zip from sdcard’, then ‘choose zip from sdcard’.
– find the AOSP Android 4.4 custom ROM and confirm its installation.
=> issue encountered in the 1st run :
According to this StackOverflow thread:
In short, if you want to flash KitKat Android 4.4, you’ll have to upgrade to a version of CWM greater than v126.96.36.199. Or, use an alternate bootloader.
Mine was CWM v188.8.131.52 => need to upgrade to the latest v184.108.40.206
Download from ROM-manager, latest version at the time of writing : v220.127.116.11
Once downloaded this CWM image, copy it over to my sdk/platform-tools/ folder, and then execute this :
fastboot flash recovery clockworkmod.img
where clockworkmod.img is the filename of your image
My first attempt failed with some error in [Invalid parameters], I just re-download the image and it worked fine
Once flashing completes, from CWM, select **Recovery**, your phone should enter CWM v18.104.22.168 now.
Btw, make sure your device is connected by firing : fastboot devices
If your device is not visible to fastboot it is probably due to a few common reasons:
a. phone is not in fastboot mode -> need to reboot into fastboot mode -> for Nexus S: To enter into Bootloader/Fastboot : (while turned off) Press and hold Volume Up + Power
b. missing driver -> for Nexus S, install driver following these steps:
i. Download Google USB Driver, latest one here, or direct link
ii. Update the driver by : Device Manager -> right click and select “Update Drives Software”
Browse my computer for driver software -> Let me pick from a list of device drivers on my computer -> Android Phone -> Have Disk, then browse for file android_winusb.inf (in SKD folder) -> Android ADB
Windows will prompt some warning, just proceed.
9. After the ROM is flashed, repeat step 8 actions and flash the Gapps zip too.
Note: 1st attempt fails due to insufficient space (image)
Download the micro GApps version here, or direct link
10. Return to the main custom Recovery screen when both files are flashed successfully.
11. Reboot the phone.
– note that the first boot process takes several minutes to complete, which is why you shouldn’t press any buttons until all files are loaded.
12. Enter your Google Account details when the home screen appears.
That’s it, now you need to take control over your device and start testing all the new features.