Install Docker on El Capitan

install.sh

# Ensure you have brew cask installed http://caskroom.io
brew install caskroom/cask/brew-cask

# Install Docker Toolbox (this will install docker machine and virtualbox)
brew cask install dockertoolbox

# Create a linux machine for docker container to run on
docker-machine create --driver virtualbox default

# Add ENV variables for the machine to your profile (and restart your terminal)
echo 'eval "$(docker-machine env default)"' >> ~/.bashrc

# If you didn't restart your terminal, run this now:
eval "$(docker-machine env default)"

You'll also probably want docker machine to start each time your machine does. See https://gist.github.com/ericboehs/45e2f2e349249b8253a2.