Learn Docker Containers: Images, Configuration, and Volumes
Image versus container
An image is a packaged template; a container is a running instance created from that image. A registry stores and distributes images. Tags help identify versions, but production workflows should also consider immutable digests and provenance.
Build small, understandable images
A Dockerfile describes build steps. Keep only necessary runtime dependencies, use a suitable base image, and avoid copying local credentials or unrelated files into an image. Review what each layer contains before publishing.
Configure at runtime
Environment-specific values should be supplied through an approved runtime configuration mechanism. Do not bake secrets into a Dockerfile, image layer, or public repository. Use persistent volumes only when data must outlive a container and backup needs are understood.
Plan lifecycle and resource use
Know how to start, inspect, stop, and remove test containers and images. Containers still consume host resources and require updates, permissions, network boundaries, and monitoring.