What command in a Dockerfile is responsible for executing a command in the container?

The command that executes a command in a container when using a Dockerfile is indeed CMD. This command specifies the default command that should be run when the container is launched. It can be overridden by providing a command in the docker run command but serves as a convenient way to define what should happen in the container.

CMD can accept different forms of syntax, such as an array format or a string format, and is useful for defining the primary process of the container or any commands that should execute when the container starts.

For context, the other commands listed serve different purposes in a Dockerfile. COPY is used to copy files from the host file system into the container's file system. RUN executes commands at build time to install software or make changes to the image. WORKDIR sets the working directory for any subsequent instructions (including CMD) that follow in the Dockerfile. Each of these commands plays a vital role in configuring a Docker image, but CMD is specifically designated for the execution of commands within the container itself.