What command does a Docker ENTRYPOINT provide when the container is first run?

• A. A command to internet access
• B. A command to execute when the container is first run
• C. A command to open Docker documentation
• D. A command to modify container settings

Answer: (B)

The Docker ENTRYPOINT directive is specifically designed to define the command that will be executed when a container starts. By configuring an ENTRYPOINT, you ensure that the specified command runs as the primary process. This setup is essential for containers that are intended to execute specific applications or services upon launch.

For instance, when a container is created from an image with a defined ENTRYPOINT, that command becomes the main command line for that container instance. This is particularly useful for maintaining consistent behavior across container instances, as it allows you to encapsulate the initialization or startup behavior in a single, reusable manner.

The other options relate to functions that do not align with the primary purpose of the ENTRYPOINT. For example, no ENTRYPOINT command allows for internet access or modifies container settings directly. Additionally, opening documentation is not within the scope of a container's command upon startup.