What is the role of the 'ENTRYPOINT' command in a Dockerfile?

The 'ENTRYPOINT' command in a Dockerfile is used to specify the command that should always be executed when the container starts. It sets the main process of the container, allowing it to run as intended regardless of any arguments passed during container execution.

When you define an ENTRYPOINT, you are essentially locking in the command that the container will run, providing a clear and defined behavior upon startup. This is particularly useful for containers that are designed to run specific applications or services, ensuring that these applications always execute with the correct parameters.

For example, if you have an application script or a server that needs to run for the container to fulfill its purpose, configuring ENTRYPOINT ensures that this command is the focal point of the container's behavior. Additionally, you can override or append additional commands through the use of the CMD instruction, allowing for flexible command line options while preserving the primary behavior.

In contrast, other commands such as defining the base image, setting environment variables, or specifying the working directory serve different roles and do not influence the main execution behavior of the container in the same way as ENTRYPOINT does.