FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This "revision-image-auto-backup" setting was first introduced in V5.0.
This option is used to control whether the image will be automatically backed up on upgrading. It can be checked in the GUI by selecting the "Details" link next to "Firmware Image" in "System Information" widget.
config system global set revision-image-auto-backup enable end
The "exec revision list image" CLI command can be used to check the image revision info.