Since our data volume container will just hold our data, we should keep it as small as possible to start with so that it doesn't take lots of unnecessary space on the server. The data inside the container can, of course, grow to be as big as the space on the server's disk. We don't need anything fancy at all; we just need a working file storage system.
For this book, we'll keep all our data (MySQL database files and WordPress files) in the same container. You can, of course, separate them into two data volume containers named something like dbdata and webdata.
Our data volume image does not need anything other than a working filesystem that we can read and write to. That's why our base image of choice will be BusyBox. This is how BusyBox describes itself:
"BusyBox combines tiny versions of many common UNIX utilities into a single small executable. It provides replacements for most of the utilities you usually find in GNU fileutils, shellutils,...