How to create self signed certificates

• Create a key and a self-signed certificate in one step without being prompted for any questions using OpenSSL, e.g. for a host called host.domain.tld:

  openssl req -new -x509 -batch -days 3650 -newkey rsa:2048 -nodes -subj /CN=host.domain.tld -keyout host.domain.tld.key.pem -out host.domain.tld.cer.pem

• For a multidomain certificate, download self_signed_mdcert.sh. Then:

  $ ./self_signed_mdcert.sh www.domain1.tld www.domain2.tld ...
  

  For a certificate based on an elliptic curve key, pass -ec as first parameter:

  $ ./self_signed_mdcert.sh -ec www.domain1.tld www.domain2.tld ...