How to manually create a certificate request (CSR)
If you want to bypass all automated means for more control, you can create a
bit key and certificate request using the following commands:
/usr/bin/openssl genrsa 4096 > private.key
/usr/bin/openssl req -new -key private.key
where you can replace 4096
if you want different size key.
The genrsa will ask you all information for the certificate.
Once created, you give the certificate request to a certificate authority.
They'll give you a new certificate, which you'd use with your private.key.
For a multi-domain certificate request, you'd create a config for the SubjectAltName entries, san.cfg.