I admit not fully understanding the concept of FQDN (fully Qualified Domain Name), does the name there need to be different of the server’s (I guess Y).
A short example for WebServers neophytes like me may help.
FQDN is something.something.tld. It does not matter what you choose, as long as it is a name that will eventually resolve and is not a domain you will be hosting mail for on the server. If I wanted to host a domain named virtualmin.com on my server, I might choose a FQDN of ns1.virtualmin.com or srv1.virtualmin.com or bob.virtualmin.com or whocares.virtualmin.com or srv1.someotherdomain.tld. The name does not have to have any relation to any other names on the server, but it can, as long as it is not a domain name you will be hosting mail for in Virtualmin.
Then, I would make an A record pointing to the server for that name wherever I host DNS.
That’s it. There is nothing complicated about it.
It has nothing to do with the web server, though. It only matters for email. If you have a webserver or web app problem, it has nothing to do with the FQDN.
it works with the default CentOS/Rocky Linux 9.1 (XFS) : I may not have worked because I has a custom partitions, BTRFS etc…
But realize that now I may have to create a virtual server, (fail to work out a visible external IP address), in order to install Wordpress (script)?
I fine, it seems the documentation to simply install is inadequate (at least for me).
I was able to manually install WordPress in the past, a long procedure but it worked.
It would be great if I could complete this using Virtualmin !
Does it exist a bit more detailed step by step documentation ?
Of course. You need a website if you want to run a web app. Virtualmin is for managing virtual hosts in a web server and all of the related configuration one would expect from a “hosting” account (mail, database, etc.).