About This Course

The Linux Filesystems and Container Images module explains how Docker builds container filesystems using read-only image layers, mount namespaces and a container-specific writable layer. Through OverlayFS and copy-on-write, changes made inside a container are stored in the writable layer without modifying the underlying image, while persistent data should generally be stored using volumes. It also explains how layer reuse, content-addressable storage, SHA-256 digests and build caching make container images efficient to store, distribute and rebuild. Overall, a Docker image is a reusable stack of immutable filesystem layers, while a running container adds a writable layer to create the final filesystem the application sees.