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 the upgrade, the device is unable to boot or unable to login.
As the admin user is unable to log in to the device, the possible option is to use the console instead of formatting the device. It is possible to boot from the previous firmware.
It also loads with the same configuration before the upgrade.
Step 1: Reboot the device and press any key to display the configuration menu.
Step 2: On the configuration menu press B.
[B]: Boot with backup firmware and set as default.
The FortiGate will boot on the previous working firmware.
Step 3: On the ‘diagnose flash list’ command, it is possible to verify the backup and the current working firmware.
