What happens when a Docker container is removed?

When a Docker container is removed, the container and its filesystem are permanently deleted, which affirms the choice that states this outcome. In Docker, containers are essentially processes that run on top of an image, and their file systems are created from the image's layers. When a container is removed using commands like docker rm, Docker cleans up all the writable layers associated with that container.

This includes any changes made during the container's lifecycle, such as modifications to files or newly created files. This action is irreversible; once the container is removed, those changes cannot be recovered.

It's important to understand that this deletion does not affect the underlying image the container was created from, nor does it mean that any data in volumes attached to the container is lost, as volumes exist independently of the containers using them. Therefore, while the container's data and metadata are wiped, any data stored in volumes would persist. This context helps clarify why the notion of permanent deletion of the container and its filesystem encapsulates the essence of this action in Docker.