Can you explain what the ENTRYPOINT directive in Docker means and why it is used?

The ENTRYPOINT directive in Docker specifies the command that will be executed when the container starts. Unlike CMD, which sets default arguments, ENTRYPOINT defines the main process of the container.

It is used to ensure that the container always runs this specific command, and additional parameters can be passed as arguments at runtime.

Example:

ENTRYPOINT ["/usr/bin/python3", "app.py"]

When starting the container, you can add arguments that will be passed to app.py. This is convenient for creating containers with a fixed startup logic.