If you want certs only, do this:

sudo yum install epel-release
sudo yum install certbot
sudo letsencrypt certonly -a standalone -d srv08.karloluiten.nl
crontab -e
add: 30 */12 * * * /usr/bin/letsencrypt renew >> /var/log/le-renew.log
(add the previous logfile in /etc/logrotate.d/syslog for example, or make your own)
certs are now in /etc/letsencrypt/live/srv08.karloluiten.nl/cert.pem