How to upgrade the Firmware in Fortigate firewall

Upgrade path is 6.4.3-b1778 => 6.4.5-b5651 => 6.4.7-b1911 => 6.4.8-b1914
 
Fortigate Model: FG_100E / FG_100F
 
Ensure you have downloaded the required incremental firmware for the fortigate model FG_100F as per the below upgrade path:
6.4.3-b1778 => 6.4.5-b5651 => 6.4.7-b1911 => 6.4.8-b1914
 
1. Login to VPN if available.
 
2. Login to the FortiGate Firewall: https://<IP-ADDR>
 
3. Take configuration backup
Login to FortiGate >> Dashboard >> System Information widget >> Backup >> Local PC >> OK >> fg100f-<hostname>_xxxx.conf
 
4. Navigate to System >> Firmware >> Check Current version say for instance: FortiOS v6.4.2 build1723 (GA) >> Upload Firmware >> Select File: Browse >> 6.4.5-b5651 >> Enable the HA sync option if available (But currently its standalone) >> Click upload the firmware >> Ok
 
5. After the new firmware has been installed, the system reboots.
 
6. Repeat the above steps for Ver: 6.4.7-b1911 => 6.4.8-b1914
 
7. Upon completion check the Fortigate Firmware version on both Primary and Standby nodes.