Install Let's Encrypt on Ubuntu Sever
First of all, let’s install certbot client.
Define the certbot repository:
add-apt-repository ppa:certbot/certbot
Update the package list:
apt-get install python-certbot-apache
Install the SSL certificate:
certbot --apache -d domain.com
Install domain with subdomains:
certbot --apache -d domain.com -d sub1.domain.com