What is the main difference between CMD and ENTRYPOINT in a Dockerfile?

The main difference between CMD and ENTRYPOINT in a Dockerfile lies in their intended use and functionality. ENTRYPOINT is designed to define the main command that will always be executed when the container starts. It allows you to set up a container to run a specific application or script, effectively making the container behave like that application.

On the other hand, CMD provides default arguments to the ENTRYPOINT or specifies a command to be run when the container is launched without overriding the ENTRYPOINT. If you combine both in a Dockerfile, ENTRYPOINT sets the main application to run, while CMD can add any additional arguments that the application requires.

This distinction is crucial when designing your containerization strategy, as it allows for clearer definitions of how the container should behave and interact, particularly when modifications are needed when running the container with different parameters or environments. Understanding this enables better management of Docker containers, particularly when it comes to adjusting how applications are executed within them.