Root Nexus S

1. Switch off the phone.

2. Holding the POWER & VOL UP button until you see the bootloader screen.

3. Install USB driver, follow the instruction on 'Installing SDK'.

4. Download files

$ wget http://www.androidmi.com/uploadfile/2010/1217/20101217063436958.zip
$ wget http://www.androidmi.com/uploadfile/2010/1217/20101217063339991.rar
$ wget http://www.androidmi.com/uploadfile/2010/1217/20101217063614166.rar

5. Unzip all downloaded files.


drwxrwxr-x  5 user user    4096 Sep 22 17:13 ./
drwxrwxrwt 22 root root    4096 Sep 22 16:59 ../
drwxrwxr-x  2 user user    4096 Sep 22 17:05 app/
drwxrwxr-x  2 user user    4096 Sep 22 17:05 bin/
drwxrwxr-x  3 user user    4096 Sep 22 17:05 META-INF/
-rw-rw-r--  1 user user 4087808 Sep 22 16:39 recovery-clockwork-herring.img
-rw-rw-r--  1 user user 2949120 Dec 17  2010 rootboot.img


6. $ fastboot flash recovery recovery-clockwork-herring.img
sending 'recovery' (3992 KB)...
OKAY [  0.590s]
writing 'recovery'...
OKAY [  0.507s]
finished. total time: 1.098s

7. Flash the rooted boot image.

$ fastboot flash boot rootboot.img 

sending 'boot' (2880 KB)...

OKAY [  0.426s]

writing 'boot'...

OKAY [  0.377s]

finished. total time: 0.802s

8. Install su & SuperUser.apk

$ adb remount

remount succeeded

$ adb push bin/su /system/bin/

638 KB/s (26248 bytes in 0.040s)

$ adb push app/Superuser.apk /system/app/

678 KB/s (27688 bytes in 0.039s)

$ adb shell chmod 6755 /system/bin/su

$ adb reboot

9. Enter recovery mode again,install the superroot.apk

Update for TWRP recovery 

Follow step 1~3 above.

4. $fastboot flash recovery twrp-crespo-2.0.0RC0.img

5. Reboot to recovery boot

6. Mount sdcard, copy SuperUser.zip and unmount.

7. Back to main menu, INSTALL > select SuperUser.zip and install, after install reboot the phone.