Error in method invocation Errno 1 Unknown host details

The error comes at the beginning of the Stage 2 process:

This is an error that ones see at the beginning of Stage 2 of the Upgrade process. When you click Continue on the screen shown above, it begins its first prerequisite check after the new VCSA appliance has been deployed, you will see the error pop up, that has the messaging: Error in method invocation Errno 1 Unknown host.

The cause of the issue

If you note closely below, instead of a hostname being used for the ESXi host or vCenter Server that manages the source vCenter Server, we see an IP address.

The upgrade process evidently has an issue with the use of an IP address here, even if the vCenter Server Installer and all appliances involved can connect to the ESXi or vCenter Server by IP address.

The resolution

Instead of using an IP address for the ESXi host or vCenter Server that manages the source vCenter Server, you need to use a hostname instead. If you are targeting an ESXi host that you typically don’t have in DNS, just create a temporary DNS record for the upgrade process and use that DNS name in the wizard instead of the IP address.

After entering in the FQDN/hostname of the ESXi host or vCenter Server that manages the appliance, you will be able to get past the error message. I am not sure what the requirement is here for FQDN vs IP address, especially if targeting the ESXi host directly.

However, VMware vCenter Server upgrades have historically been sensitive to DNS being correct and making sure you had the DNS records in place before running an install, etc. So, I am guessing this is more of the same underlying pickiness on DNS being setup correctly, even if connectivity is successful to an IP address.

**Note** Also, you do not have to start all the way back over. Instead, close out of the vCenter Server Installer wizard and then connect to the temporary IP address of the new appliance port 5480. When you do this, it will let you change the values of what you want to target to recontinue the wizard.

Hopefully this little quick tidbit will help any who may be struggling with the Error in method invocation Errno 1 Unknown host error message when upgrading their vCenter Server VCSA appliance to VCSA 8. The workaround is fairly simple in using the FQDN vs IP address. I just wish VMware would make this part of the preflight checks instead of just throwing a generic error message.