# (log in) 
sudo su
apt-get update
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add -
add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
apt-get update
apt-get install -y docker-ce
exit
sudo usermod -aG docker $USER
exit

# (log back in)
docker run hello-world ; if [ $? -eq  0 ] ; then echo '### docker ok' ; else echo '### docker not ok' ; fi