In many ways, Docker abstracts the server away from the application. It no longer matters which Linux distribution a server is running. A Docker application can be based on any distribution available. Multiple applications can run on the same server and use different base images. Despite that, without the server, nothing runs.
In Chapter 9 , Using Continuous Integration to Build, Test, and Deploy Containers, we discussed the importance of having a consistent build process for Docker images because doing so provides consistency and reliability. The same is true for the servers those applications run on. If the servers are not consistent, it could cause problems for the containers running on them. This section will discuss different ways of ensuring that the server images are consistent.