When i installed virtualmin a default domain virtual server was created using my hostname, that was server.example.tld, the problem is that i host example.tld as a virtual server and later i found out in the docs that it isnt right to do that, so my question is if i delete the server.example.tld virtual server and change the default domain to example.tld, maintaining the hostname server.exemple.tld will it brake stuff?
no thats fine.
from docs
If your system does not have a fully qualified domain name (FQDN), the installer will stop and ask you to choose one. This is mandatory because many services rely on having a fully qualified domain name in order to function. Mail, in particular, but some Apache configurations and many of the Virtualmin-created configuration files, also require a valid fully qualified domain name to function correctly. A fully qualified domain name is one of the form “srv1.virtualmin.com”, or simply “virtualmin.com” (but do not use a name you’ll be hosting in Virtualmin). We recommend you choose a name that is not one for which you will be receiving mail, in order to simplify later configuration. A good choice is to use a name server designator, such as “ns1.virtualmin.com”. Some customers also choose something like “host1.virtualmin.com” or “primary.virtualmin.com”. Any of these would be valid and would satisfy the install script and the services that rely on this option. The install script will add this name to /etc/hosts, which will satisfy all local services. It is even better if this name resolves correctly when looked up from outside of the system–this requires the name be added to your DNS zone for the second level domain. If the Virtualmin server you are installing will be the authoritative name server for this zone, you can later use Webmin to add a record for this name to the zone.
I’m sorry for the confusion. The default automatic domain (with the same name as your system hostname) is special (and I continue to contend it is a bad idea, but I haven’t yet convinced @Ilia and Jamie of that), and is not hosting mail and won’t cause any conflict with other stuff.
I’ll try to update the docs to make this less confusing.