Installing a Flask webapp on a Digital Ocean VPS (or Linode, etc.)

Here I sum up how to install a Flask webapp on a Digital Ocean VPS that has Ubuntu Linux on it. The following topics will be covered:

• server configuration
• the big picture
• Nginx
• a simple Flask app in a virtual environment served by gunicorn
• gunicorn is started automatically upon boot

Originally I wrote these notes for Ubuntu 14.04, but later it was updated for Ubuntu 16.04. Both versions are available:

• Ubuntu 14.04 -- gunicorn is started with upstart
• Ubuntu 16.04 -- gunicorn is started with systemd