- Docker Images:
- Templates for containers - used to create an instance of a container
- Comprised of multiple layers
- They are build time constructs while containers are run time constructs
- An image cannot be deleted until all containers using that image have been deleted
- Built from instructions (Dockerfile)
- Layers:
- Images are made of multiple layers
- Each layer represents an instruction in the image’s Dockerfile
- Each layer, except the very last one, is read-only
- Each layer is only a set of differences from the layer before it
- Containers add a new writable layer on top of the underlying layers
- All changes made to a running container are made to the container layer
- Container and Layers:
- Containers are the top level writable layer
- All changes made are stored in the writable layer
- The writable layer is deleted when the container is deleted
- The image remains unchanged even after the container is deleted