The commands to innstall docker on Ubuntu 18.04

docker-install-ubuntu18.04.sh

#!bin/bash

#add repo gpg key
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

#add the repo
sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"

#update repos
sudo apt-get update

#install the docker software
sudo apt-get install -y docker-ce=18.06.1~ce~3-0~ubuntu

#prevent docker from updating
sudo apt-mark hold docker-ce

#You can verify that docker is working by running this command:
sudo docker version