In Docker, what is a Docker image?

In Docker, what is a Docker image?

• A. A running container instance.
• B. A Docker daemon process.
• C. A network bridge.
• D. A read-only template used to create containers.

Answer: (D)

A Docker image is a read-only template used to create containers. It serves as the blueprint for a container, capturing the filesystem, installed software, dependencies, and configuration defined in its Dockerfile. Images are built in layers and remain immutable, so you can reuse them to spawn multiple containers. When you run a container, Docker adds a writable layer on top of the image to hold any changes during that container’s lifetime, while the base image stays unchanged. The other options describe runtime or infrastructure elements (a live container, the Docker daemon, or a network component), not the template from which containers are created.

A Docker image is a read-only template used to create containers. It serves as the blueprint for a container, capturing the filesystem, installed software, dependencies, and configuration defined in its Dockerfile. Images are built in layers and remain immutable, so you can reuse them to spawn multiple containers. When you run a container, Docker adds a writable layer on top of the image to hold any changes during that container’s lifetime, while the base image stays unchanged. The other options describe runtime or infrastructure elements (a live container, the Docker daemon, or a network component), not the template from which containers are created.