The last part of this chapter is about containers and storage. Every build tool that can create images provides the option to add data to your container.
You should use this feature only to provide configuration files. Data for applications should be hosted, as much as possible, outside the container: if you want to quickly update/remove/replace/scale, and so on, your container, it's almost impossible if the data is within the container.
There are often multiple ways to do this: you can use your local storage, or mounts on the host, and so on. Here is just one example in Rkt:
rkt run --volume data,kind=host,source=/directory>,readOnly=false \
<container>
This will make /srv/data on the localhost available on /var/data.
For Docker, there are solutions such as https://github.com/ContainX/docker-volume-netshare.
If you are using Docker and...