🧩 Problem

I wanted to bring my 3 separate ESXi hosts (running on local storage, no shared storage/NAS) under centralized management by deploying vCenter Server Appliance (VCSA) 8.0.3, then clustering all 3 hosts together.

Along the way, I hit a persistent firstboot failure that took significant troubleshooting to root-cause:

Error

The supplied System Name <hostname> is not valid.

  

Resolution

If the supplied system name is a FQDN, then make sure the DNS forward lookup

results in at least one valid IP address in the system. If the supplied

system name is an IP address, then it should be one of the valid IP

address(es) in the system.

This happened with both vcenter.local and vcenter.lab as the FQDN, despite DNS appearing to be configured correctly.