ELI5: Add more domains to existing Let's Encrypt cert on single IPv4

I have one Virtualmin-powered server with a single IPv4 address. On this server reside six different domains with different virtual hosts.

Let’s call them alpha.tld, beta.tld, gamma.tld, delta.tld and epsilon.tld.

The virtualmin server lives at hostfoo.beta.tld:123

The virtual host for gamma.tld is configured with a Let’s Encrypt cert.

I would like to expand this existing cert to cover virtualmin itself, along with five domains and with their accompanying mailservers. There are currently no subdomains nor plans for any.

How do I do this?

Let’s Encrypt doesn’t care. It just need to be able to validate that you own the domain. So, create the domains in Virtualmin, make sure they’re working (i.e. you can browse to the site), enable SSL, and then request a Let’s Encrypt certificate.

Then, for whatever domain you want to be the Virtualmin domain, use the Copy to Webmin feature.

Hello Joe,

I’m trying to add an alias domain .de to my current main domain .com. But it is not possible to request Let’s Encrypt for that new alias domain.
It says hostname doesnt match. I checked DNS, they all use the same NS addresses, they all have same A record. When open in browser, they all resolve correctly to the common public_html folder (main website). What else I should check, any idea please?

Parsing account key…
Parsing CSR…
Registering account…
Already registered!
Verifying only-approved.com
only-approved.com verified!
Verifying only-approved.de
Traceback (most recent call last):

File “/usr/lib/python2.7/ssl.py”, line 269, in match_hostname
% (hostname, ', '.join(map(repr, dnsnames))))
ssl.CertificateError: hostname ‘www.only-approved.de’ doesn’t match either of ‘only-approved.com’, ‘only-approved.dk’, ‘www.only-approved.com’, ‘www.only-approved.dk’