Look here if flashing the root method via Clockwork doesn't work

[Jerry Hildenbrand]

Not sure exactly what the issue is, but it's affecting a lot of folks. Here's the temporary fix to get rooted:
Download Koush's unsecure boot image here: http://koush.tandtgaming.com//samsung/herring/rootboot.img

put it in your /sdk/tools/ folder

Boot into fastboot, and connect to your PC

at the command prompt:

fastboot flash boot rootboot.img

reboot.

Download CHainsDD's superuser zip here: https://dl.dropboxusercontent.com/u/6408470/su-releases/su-2.3.6.1-ef-signed.zip

open the zip file, and place the su binary and the Superuser.apk (look in the folders) in your sdk/tools/ folder

Connect to your computer and:

adb remount
adb push su /system/bin/
adb push Superuser.apk /system/app/
adb shell
chmod 6755 /system/bin/su
exit
adb reboot

This manually does what the zip flashing doesn't seem to be doing.

 

[civicdrivr]

Thanks! This worked perfectly.

 

[jeromesheerin]

im not sure if this will help me..
my problem is the phone will not boot after applying the rootboot.img

it stays stuck in google(white writing) black screen

The computer will not regconsie the sd card so i cant put on the su....zip file...

any ideas as im phoneless now :-(

Thanks in advance

 

[TDR]

I don't think there's a problem these days with flashing the superuser zip from Clockwork Recovery (go into mount options and mount /system first!). Much less hassle than flashing an unknown boot image

BTW, if you want to boot your Nexus S into fastboot mode directly, hold power + volume up. Handy when you've clobbered something important.