For those who want to ensure the filesystem is completely wiped and the firmware is re-installed fresh, you can format the boot partition via the BIOS menu. Connect via Console cable.

If you still have administrative access to the device (via SSH or the Console port), this is the cleanest and fastest method.

The system will ask for confirmation: Do you want to continue? (y/n) . Type .

The FortiGate 30D, while now a legacy model, remains a workhorse for small offices and lab environments. However, there comes a time in every admin's life when a "clean slate" is necessary—whether you’ve inherited a locked device, misconfigured a complex VLAN, or are prepping the unit for decommissioning.