Log into FGT (locally or remotely) as admin
.
# config system global
set hostname NEW_HOSTNAME
end
# config system central-management
set type fortimanager
set fmg "123.123.123.123" # IP address of FMG
end
# exec central-management register-device FMG_SERIAL_NUMBER ""
Reboot FGT.
# exec reboot
Log into FMG. The FGT will be listed in the root
ADOM as a managed device.