1. Obtaining letsencrypt
  2. Requesting free SSL certificates
  3. Configuring SSL in ISPConfig

Install cerbot CentOS 7

sudo yum install epel-release
sudo yum install python-certbot-apache
./certbot-auto --apache -d example.com -d www.example.com -d other.example.net

mkdir /usr/local/ispconfig/interface/ssl/self-signed_originals
mv /usr/local/ispconfig/interface/ssl/isp* /usr/local/ispconfig/interface/ssl/self-signed_originals

ln -s /etc/letsencrypt/live/server.domain.com/fullchain.pem /usr/local/ispconfig/interface/ssl/ispserver.crt
ln -s /etc/letsencrypt/live/server.domain.com/privkey.pem /usr/local/ispconfig/interface/ssl/ispserver.key
cd ~root
git clone https://github.com/alexalouit/ISPConfig-letsencrypt.git
cd ISPConfig-letsencrypt
php -q install.php
# Let's Encrypt SSL
#
location ^~ /.well-known/acme-challenge/ {
  root /usr/local/ispconfig/interface/acme/;
  default_type text/plain;
  allow all;
}