Google Nexus S has been rooted and unlocked within 24 hours of its availability through Best Buy. Here unlocking doesn’t mean that the device is freed from any carrier.
Unlocking the bootloader allows you to go into Custom Recovery Mode so you can install custom ROMs on it. On the side rooting the Nexus S gives you full access to file system. After the phone is rooted, you can modify the OS files or inject the news commands and files into pre-installed firmware.
How to Unlock Nexus S Bootloader:
Step 1: Download android 2.3 SDK with Fastboot from here.
Step 2: Hold down Volume Up and Power key simultaneously.
Step 3: Now you are in Standard Recovery Mode.
Step 4: Install Android 2.3 SDK with Fastboot.
Step 5: Open the Command Prompt if you are a Windows user or open Terminal app if you are a Mac user.
Step 6: Type “fastboot devices” (without quotes) to check if your phone is connected vis USB.
Step 7: Type “adb reboot bootloader”.
Step 8: Type “fastboot oem unlock”.
Step 9: Use volume keys to choose “Yes, unlock bootloader”. User power button to select options.
Step 10: Your Google Nexus S bootloader is unlocked now.
Note: Unlocking Bootloader will also reset the device to factory settings.
Your Google Nexus is unlocked now but right now there are no custom recovery images or custom ROMs available to install on it. The custom ROMs will be available soon as some well-known developers have already started cooking up something nice.
How to Root Nexus S:
Here is the how-to guide to get full Root Access on Nexus S as posted on XDA-Developers forums:
First, reboot into your bootloader/fastboot mode as metioned above. (Volume + Power Up, or adb reboot bootloader)
fastboot oem unlock
Then, install this recovery:
fastboot flash recovery recovery-clockwork-herring.img
Then boot into Clockwork recovery and install the Superuser zip file (adb reboot recovery, or from fastboot choose recovery):
To install a rooted/insecure boot image (adb has root):
fastboot flash boot rootboot.img
ROM Manager support is coming soon. Stay tuned to this blog for updates as they happen.