[phkx]

What kind of files would you like to change? Anything that comprises the environment within the container (image) is indeed changed by rebuilding the container, but not the whole - just the layers which changed. Layering in a smart way increases reuse. Also, this way you reflect versions (tags) of the environment. Configuration can be passed in via parameters.

The data you work with should be stored externally (volume, database, accessed via API, …). You don‘t keep persistent state of your workload in the container.