dockerfile ubuntu 18.04 code example
Example 1: install docker on ubuntu 18.04
sudo apt install docker-ce
https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-ubuntu-18-04
Example 2: installer docker ubuntu 18.04
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -