Upgrading a Fortinet via USB

Upgrade the FortiOS version

Step 1:
Connect the FortiGate to your PC via console-to-serial cable.
Connect to the console port using your favourite terminal emulator.
The default baud rate for the connection should be 9600.

Step 2:
Log-in to the ForiGate, on a fresh box the default credentials are:
Username: admin
Password:

Verify current firmware version

get sys stat

Step 3:
Login to FortiNet Support using credentials you have.
If credentials do not work, login to FortiNet Partner Support
Navigate to the download page related to the current firmware version on the FortiGate.
Download the appropriate FortiOS images.

Be advised that you should not jump builds, download all sequential releases between the current and the desired

Step 4:
Format a USB stick to FAT16 (must be 4GB or smaller)
In Windows CMD use the follow command to format, where E: is the volume letter for that disk:

format E: /fs:fat

Copy firmware to USB stick, renaming the file to "image.out"

Step 5:
If the box is configured for auto-install from USB already, skip to Step 6
Log into the CLI and enter the following commands:

config system auto-install
   set default-image-file <filename>
   set auto-install-image {enable | disable}
end

Step 6:
Insert USB stick into the FortiGate, reboot device using the execute reboot command.
The device should automatically retrieve the image off the USB stick and commence installation upon boot.
Keep an eye on the terminal to see when the firmware update is complete; you will need to remove the USB stick when it initializes an automatic reboot.
Once it recovers, verify the firmware version.

Step 7 (Optional):
Rinse and repeat until you've reached the desired version

Update the configuration file

Step 1:
Back up the existing configuration from the defective box.
To do this, navigate to the WebGUI. Navigate to System > Dashboard > Status
Under the System Information widget, select the Backup button associated with System Configuration

When prompted, save the configuration to your Local PC

Step 2:
Copy the downloaded configuration file to the USB stick
Rename the file to system.conf

Step 3:
If the box is configured for auto-install from USB already, skip to Step 4
Log into the CLI
Enter the following commands:

config system auto-install
   set default-config file <filename>
   set auto-install-config {enable | disable}
end

Step 4:
Insert the USB stick into the FortiGate.
Issue the execute reboot command on the FortiGate. Upon boot, it will automatically retrieve the configuration file stored on the USB stick.
Once complete, remove the USB stick and verify that it was loaded correctly either through CLI or the WebGUI