execute : set-next-reboot
 
set-next-reboot
Use this command to start the FortiGate unit with primary or secondary firmware after the next reboot. Available on models that can store two firmware images. By default, the FortiGate unit loads the firmware from the primary partition.
VDOM administrators do not have permission to run this command. It must be executed by a super administrator.
Syntax
execute set-next-reboot {primary | secondary}