As part of an ongoing experiment with kubernetes and lots of WordPress instances I wanted to set up a site that talked to an Amazon RDS MySQL database. The unknown part was how to do this over SSL using the WordPress docker image...
Docker allows software and dependencies to be bundled together in ‘containers’. This is a whole level up from a script that installs the libraries for a piece of software to run. A container holds the full environment in its own file system. This means anything you can install/setup on a server can be bundled in the container. The big advantage here is that we then have a portable unit which can be run consistently from machine to machine. Think of Docker as lighter-weight than a VM (e.g. Docker containers don’t have their own kernels, where as a VM would), but giving a similar level of separation, structure and consistency.