How To Root Galaxy Nexus I9250 On Android 4.2.2 Jelly Bean (JDQ39) Official Firmware And Install CWM Recovery

Step 1 - Download Android SDK from the Android Developers website and install with USB drivers.
Step 2 - Enable USB Debugging mode in your phone.
Step 3 - Download SuperSU v1.04 (UPDATE-SuperSU-v1.04.zip) and copy it to your sdcard (on the root of it. not in any folders) on your device.
Step 4 - Download CWM 6.0.2.3 (recovery-clockwork-touch-6.0.2.3-maguro.img)
Step 5 - Go into Fastboot Mode on your device by pressing "Volume Down" + "Volume Up" + "Power" keys for a few seconds till you see some text on the screen. This is Bootloader Mode.
Step 6 - Type in the following command and press Enter.

sudo fastboot flash recovery ~/Downloads/Adnroid/recovery-clockwork-touch-6.0.2.3-maguro.img

Step 7: Select recovery from fastboot menu and you’ll be taken to the newly-flashed ClockworkMod recovery.
Step 8: In ClockworkMod recovery, scroll down to “flash zip from SD card” and press the power button to select it.
Step 9: Press the Power button again and select “choose zip from sdcard”.
Step 10: Use Volume keys to navigate to UPDATE-SuperSU-v1.04.zip. Select it by using the Power button and flash it.
Step 11: Once flashing is complete, reboot the device by selecting “reboot system now” from the Recovery menu. The first boot may take some time.