Reset device in Recovery mode Galaxy Nexus

See options for backing up and restoring your data before performing a factory data reset. To perform a factory data reset, select your device from the list below and follow the instructions. 

1. Open the Settings  menu on your device.
2. Touch Backup & reset.
3. Touch Factory data reset.
4. Read the information on the screen and touch Reset phone.
5. If your phone is password protected, you'll be prompted to enter your pattern, PIN, or password.
6. When prompted, touch Erase everything to erase all data from your phone.

Note: If your phone becomes unresponsive at any point during these steps, you can restart it by holding down the Power button for several seconds.