Installs Docker on Elementary OS 0.4 (Loki)

install-docker-elementary-loki.sh

#!/bin/bash
sudo apt-get install apt-transport-https ca-certificates -y
sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
sudo rm -f /etc/apt/sources.list.d/docker.list
sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -u -cs) \
   stable"
sudo apt-get update
sudo apt-get purge lxc-docker

sudo apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual
sudo apt-get install docker-engine
sudo service docker start

sudo groupadd docker
sudo usermod -aG docker $USER

# NOTE: you'll need to exit and reenter the shell before your user is actually recognised as part of the 'docker' group.

You can stick to the docker tutorial completely. https://docs.docker.com/engine/installation/linux/docker-ce/ubuntu/#set-up-the-repository
The only change you need to do is a the -u flag in the lsb_release subshell command. This gives you the codename of the underlying system. You can do this pretty much with every installation that fails if the apt repository 404's.

It's very similar to @NathanTheGr8 answer, though. It's just future proof for all elementary versions.

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

Thanks for all of the suggestions! :-) I've incorporated most of them. I had absolutely no idea that anyone had noticed this script; I'm glad that it's been at least a little helpful to you.

Is it possible to get notifications for gists?

I think docker-engine has been removed?

sudo apt-get install docker-engine
is not working now.

I changed to docker-ce and it worked perfectly.

The script failed on my system ... Loki Linux 4.13.0-32-generic

I followed the installation guide on Docker and replace the "loki" lsb_release by "xenial" and everything works :

sudo apt-get update
sudo apt-get install apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo apt-key fingerprint 0EBFCD88
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable"
sudo apt-get update
sudo apt-get install docker-ce