To install Docker on Ubuntu 16.04, run following commands as user root.

apt -y remove docker docker-engine
apt -y install  apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
apt update
apt -y install docker-ce

Back to Docker.