set -exu

DOCKER_VERSION="${DOCKER_VERSION:-}"

DOCKER_HOST="${DOCKER_HOST:-}"

if [[ -n $DOCKER_VERSION ]]; then

sudo -E apt-get -q -y --purge remove docker-engine docker-ce

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

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

sudo apt-get update

sudo apt-cache madison docker-ce

sudo apt-get install "docker-ce=$DOCKER_VERSION"

if [[ -n $DOCKER_HOST ]]; then

sudo mkdir -p /etc/systemd/system/docker.service.d/

echo "

" | sudo tee -a /etc/systemd/system/docker.service.d/override.conf

sudo systemctl daemon-reload

sudo service docker restart || sudo journalctl -xe

sudo service docker status

while (! docker ps ); do

echo "Waiting for Docker to launch..."

sleep 1

docker version

docker info

docker run --rm hello-world