How do I re-issue OpenSSL snakeoil cert?

You can use this one-liner to regenerate both files in one shot. You'll need to restart Apache after the cert has been re-created.

openssl req -x509 -nodes -days 3650 -newkey rsa:2048 -keyout /etc/ssl/private/ssl-cert-snakeoil.key -out /etc/ssl/certs/ssl-cert-snakeoil.pem

If you're at all concerned about security (and you should be), then you should regenerate certificates on all affected critical servers, followed by an exhaustive service restart or a system reboot.

If you're just running a play-around box on your LAN that's one thing, but anything you've got on the internet you should definitely reissue.

Here I found that there is this command:

sudo make-ssl-cert generate-default-snakeoil --force-overwrite