Installing Docker on Ubuntu 20.04 (probably similar process with a different repository for newer versions).

install-docker.sh

#!/usr/bin/env bash

# update list of packages
apt update

# https prerequisites for apt
apt install apt-transport-https ca-certificates curl software-properties-common

# add GPG key for official docker repository
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

# add docker repository to apt sources
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"

# check for docker repository download URLs
apt-cache policy docker-ce

# install docker
apt install docker-ce