Graylog Datanode SSL certificates

I cannot find the proper documentation on the building of the certificates for securing the datanode itself.

Basically, I have a standalone instance (server+datanode+mongo on same machine), and I want to skip the pre-flight by pre-populating the certs.

I’ve followed+adapted this How-To Guide: Securing Graylog with TLS but I don’t have any success.

Any help is welcome.