Let's encrypt
$ git clone https://github.com/certbot/certbot $ cd certbot $ ./certbot-auto certonly --standalone --rsa-key-size 4096 -d meinedomain.de
$ git clone https://github.com/certbot/certbot $ cd certbot $ ./certbot-auto certonly --standalone --rsa-key-size 4096 -d meinedomain.de