How do I generate a self-signed certificate
This example will produce a file called mycert.pem which will contain both the private key and the public certificate based on it. The certificate will be valid for 365 days, and the key (thanks to the -nodes option) is unencrypted.
openssl req \
-x509 -nodes -days 365 -sha256 \
-newkey rsa:2048 -keyout mycert.pem -out mycert.pem
Using this command-line invocation, you’ll have to answer a lot of questions: Country Name, State, City, and so on. The tricky question is “Common Name.” You’ll want to answer with the hostname or CNAME by which people will address the server. This is very important. If your web server’s real hostname is mybox.mydomain.com but people will be using www.mydomain.com to address the box, then use the latter name to answer the “Common Name” question.
Once you’re comfortable with the answers you provide to those questions, you can script the whole thing by adding the -subj option. I’ve included some information about location into the example that follows, but the only thing you really need to include for the certificate to be useful is the hostname (CN).
openssl req \
-x509 -nodes -days 365 -sha256 \
-subj '/C=US/ST=Oregon/L=Portland/CN=www.madboa.com' \
-newkey rsa:2048 -keyout mycert.pem -out mycert.pem