cd /opt/letsencrypt
./letsencrypt-auto certonly -a webroot --webroot-path=/usr/share/nginx/html -d example.com -d www.example.com
sudo ls -l /etc/letsencrypt/live/your_domain_name
sudo openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048
sudo ln -s /etc/nginx/sites-available/example.com.conf /etc/nginx/sites-enabled/example.com.conf
Set Up Auto Renewal
/opt/letsencrypt/letsencrypt-auto renew