Google Nexus S i9023 hard reset Nexus S Recovery Hboot

With the i9020 Nexus S turned off. Press VOLUME UP + POWER buttons.

In recovery menu select 3rd line Recovery with Volume down button then press power to confirm Nexus S factory data reset.

Nexus S hard reset

or in menu

Tap Settings > Privacy > Tap Factory Data reset > Reset phone > Erase everything