I got a call today from a colleague who was on site and needed to factory reset a Fortigate 60E but didn't have a serial to USB cable. I immediately thought of how often I take having a console cable and serial to USB cable for granted.
If you have the proper tools, performing a factory reset is pretty straightforward:
Commands
Login in via SSH
Enter the following command and confirm
#exec factoryreset
*This operation will reset the system to factory default!
Do you want to continue? (y/n)*
After that, the system will reboot and you're set. In this case, we didn't have the luxury of the console. I naturally told him to press the reset button. He told me he had tried that and it did not work.
I performed research and I landed on a forum post where someone mentioned that the firewall has to be reset within the first 20-30 seconds of the device booting up. I was initially confused about the term powering on. I had my colleague power the device on and then after 20-30 seconds hit reset. This did nothing.
Upon further research, I found the reset button needs to be pressed within the first 20-30 seconds after* the device has fully booted up*. With this being the case, the sequence of events is as follows:
Unplug the power.
Watch and wait for the LEDs to start to blink (LAN, WAN and STA LEDs).
5 seconds after the STA LED blinks, press the small reset button at the back using a paper clip, keeping it pressed until you see the LEDs blink orange, then red.
At this stage, you can release the button.
Final Note
Once this is performed you have manually factory-reset your Fortigate firewall!