One user forgot USG9100 console interface code，in order to clear the code，after access to bootrom，choose ctrl+z，then delete configuration files，the cosole interface code did not recover to default code after reboot.
1.After bootrom，choose control+z, delete the configuration file
2.Press control+t，select erase nand flash.
3.After reboot the firewall, it start by empty configuration, code recovered to default value.
1.Reboot the firewall, access to bootrom for viewing，configuration in flash file remained.
2.After format flash，reload the version，and reboot, configuration in flash file remained.
3.USG9100 backup the configuration file in nand flash for avoiding the flash invalidation，if the configuration in flash lost，it will re-write back to flash from nand flash.