Recommended Steps for Subdomain

My domain is I’m running on an EC2 instance and have a second instance for a subdomain (

Both are running nginx and both are currently separately encrypted.

I am wondering if there is a better/recommended procedure for securing both. More importantly, should I have some kind of link between the two, or can I keep the configuration as-is: each instance controlling its own certificate?

I was attempting to add the subdomain to my main server by running:
sudo certbot certonly --nginx -d,, --dry-run

I then received an invalid response from the .well-known/acme-challenge.

I’m not entirely sure I need to add the subdomain to the main domain, but others attempting to access the site had some suspicious warnings on both domains post-separate issuance.

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You don’t - use only names that the server is actually going to be serving traffic for.

Do you have a screenshot of the warnings?


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That’s the error when you tried to create a certificate containing the app subdomain on your www server, right? That’s normal and expected.

Sorry, I was trying to ask about a screenshot of the “suspicious warnings” that the visitors to your site were encountering, when you had used separate certificates.

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Correct, and figured as much!

Thanks for the response.

As far as the other screenshots - looks like it cannot be reproduced. I did not experience the issues myself.

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