Using Dockerfiles to Build and Run Locally

Earlier in this chapter, we leveraged the Docker plugin for Visual Studio to generate Dockerfiles for each of the three services. As noted, the generated files contain several FROM directives, which allow Docker to use a specific image when building that layer. In some cases, Dockerfiles can be very simple—sequential lines installing or configuring aspects of the image for optimal use. But when does it make more sense to use a sequential file instead of one that has multiple build stages?

Sequential vs. multistage files

Chances are, if we have Docker experience, we’ve constructed a few Dockerfiles already. Starting off, we might have taken a base image and added a few programs to it, installed specific frameworks on it, or even configured more complex options for the image itself. A good rule to follow when writing a Dockerfile is to look at what needs to happen during the build process itself. For example, when building images that will ultimately run a compiled program, .NET or otherwise, we’ll see multistage files in most cases. The reason for that is simple—it allows us to separate the building of the application from the packaging and configuration required to run the application.

Take the command API, for example. The ...