Technical Tip: Boot the backup firmware and config via console

[rvillaroman]

Description	This article describes how to recover the previous firmware and config using the console after the FortiOS upgrade.
Scope	FortiGate.
Solution	Scenario: In some cases after an upgrade, the device is unable to boot or unable to login. This may be due to following the incorrect path or a corrupted firmware image file. As the admin user is unable to log in to the device, the possible option are: Hard Reset the device. See Technical Tip: How To Reset To Factory Default Configuration using external button. Initializing the firewall using the backup firmware. A console cable is necessary for this. See Technical Tip: How to connect to the FortiGate and FortiAP console port. Once the console cable is connected follow this process: Reboot the device and press any key to display the configuration menu. On the configuration menu, press B. Note: In some scenarios, PuTTY becomes unresponsive after a reboot. Downloading the Tera Term terminal emulator tool is recommended, as it does not encounter the same issue and allows for key presses to display the configuration menu easily. Tera Term can be downloaded from this GitHub link https://github.com/TeraTermProject/teraterm/releases/tag/v4.108. [B]: Boot with backup firmware and set as default. The FortiGate will boot on the previous working firmware version. With the 'diagnose sys flash list' command, it is possible to verify the backup and the current working firmware.  If the previous steps did not work, upload the firmware version of the firewall using the config menu. See this guide. Related article:   Technical Tip: Selecting an alternate firmware for the next reboot