This will configure an Asustor NAS to use letsencrypt certificate without exposing it to the internet.
To achieve this we use certbot with DNS-01 challenge to Cloudflare.
- Setup cloudflare secret.
mkdir /volume1/system/letsencrypt
touch /volume1/system/letsencrypt/cloudflare.ini
chown root:root /volume1/system/letsencrypt
chmod 700 /volume1/system/letsencrypt
chmod 600 /volume1/system/letsencrypt/cloudflare.ini