Letsencrypt is a revolutionary step forward on web security. Free, valid SSL certificates for everyone. I won’t write about how to install and config letsencrypt on Directadmin machine. I will show only how to generate and install letsencrypt certificate on your Directadmin hostname.
When you installed Letsencrypt on Directadmin and tried to install certificate for your server hostname, there is a possibility that you came to this problem: HTTP/1.1 400 Bad Request
Just do this:
cd /usr/local/directadmin/custombuild ./build update ./build letsencrypt
And than install certificate on your server hostname:
/usr/local/directadmin/scripts/letsencrypt.sh request my.serverhostname.com 4096
Open your Directadmin configuration file and change
SSL=0 to SSL=1
Also add this:
carootcert=/usr/local/directadmin/conf/carootcert.pem
Restart your Directadmin and you should be set.