Install Docker on Debian 9

docker-debian-install.sh

# update install packages
$ apt update

# install a few prerequisite packages
$ apt install apt-transport-https ca-certificates curl gnupg2 software-properties-common

# add the GPG key for the official Docker repository
$ curl -fsSL https://download.docker.com/linux/debian/gpg | apt-key add -

# Docker repository to APT sources
$ add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian $(lsb_release -cs) stable"

# update install packages
$ apt update

# install from the Docker repo
$ apt-cache policy docker-ce

# finally, install Docker
$ apt install docker-ce

# start daemon
$ service docker start

# check docker daemon status
$ service docker status

# check docker running with 
$ docker info