A common debate in the networking community is whether FortiOS is just a "hardened Linux distribution." The short answer is no.
A fascinating aspect of FortiOS is how it handles updates. It doesn't restart the box to load new signatures. It hot-patches the running engine. This "in-memory" patching capability is a testament to the architecture's stability. However, if your firmware is too old to understand the format of the new signatures, the update pipeline breaks—another reason why staying on supported firmware is non-negotiable. fortinet firmware
When a FortiGate boots, it loads the firmware image into RAM. The configuration is stored in a reserved partition (often called flash or config ). This separation of firmware binary and configuration data is what makes FortiOS upgrades relatively robust. Even if an upgrade fails halfway, the bootloader can often recover the previous image because the config remains untouched in its dedicated partition. A common debate in the networking community is