Final answer:
The command 'diagnose sys ha checksum cluster' calculates the checksum for the HA configuration in a cluster, helping identify if all units are synchronized in their configurations.
Step-by-step explanation:
The command diagnose sys ha checksum cluster is used on FortiGate appliances to calculate the checksum for the High Availability (HA) configuration of a cluster. This ensures that all units in the cluster have the same HA configuration by comparing the checksums. If there is a mismatch, it indicates that the HA configurations are out of sync, which could lead to issues with HA functionality.