With the popularity of the Nexus S, there has been a great demand for unlocking the bootloader for the Nexus S phone. The bootloader was unlocked shortly after the release of the Nexus S phone. Unlocking the Nexus phone will let you slip into the custom recovery mode where you can install any custom boot loader.
The procedure for unlocking the Nexus S on Android 2.3 Gingerbread is as follows.
Step 1. Make sure that you are equipped with Android 2.3 SDK with fastboost on your laptop.
Step 2. Switch off the Power from your Nexus S.
Step 3. Press the Volume Up key and Power Up Key and hold it while pressing. By doing this you will load Bootloader of Nexus S and will let it slip in recovery mode.
Step 4. If you are using Windows – Open command prompt. If you are a MAC user open the terminal.
Step 5. Give the command – ‘adb reboot bootloader’.
Step 6. Give the command – ‘fastboot oem unlock’.
Step 7. By using the volume keys and select ‘yes, unlock bootloader’.
Once you have followed these instructions, you have successfully unlocked bootloader of your device. Your Nexus S is ready for custom built ROMs including Cyanogenmod.