Default [GUIDE] Root and Recovery for the Nexus S

First, reboot into your bootloader/fastboot mode. (Volume + Power Up, or adb reboot bootloader)

fastboot oem unlock
Then, install this recovery:

fastboot flash recovery recovery-clockwork-crespo.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, THIS IS OPTIONAL, THE ABOVE STEPS ALREADY GOT YOU ROOT):

fastboot flash boot rootboot.img
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