It’s actually not that difficult. ISPConfig3 already sets the option there. We just need to provide all the necessary tools.

Getting certbot

Refer to Let’s Encrypt in Debian for Wheezy or manual setup.

For Debian 8 Jessie, enable Backports repo to install certbot.

echo "deb jessie-backports main" | sudo tee /etc/apt/sources.list.d/debian-backports.list
sudo apt update
sudo apt install certbot -t jessie-backports

For Debian 9 Stretch, you just have to install it.

sudo apt install certbot

According Perfect Guide tutorial, we have to make a directory. I don’t know if this is a necessary thing to do. I’m doing it just for the sake of completeness.

sudo mkdir /opt/certbot
sudo ln -s /usr/bin/certbot /opt/certbot/certbot-auto