cli/components/engine/docs/sources/terms/image.rst

title

Images

description

Definition of an image

keywords

containers, lxc, concepts, explanation, image, container

Image

In Docker terminology, a read-only layer_def is called an image. An image never changes.

Since Docker uses a ufs_def, the processes think the whole file system is mounted read-write. But all the changes go to the top-most writeable layer, and underneath, the original file in the read-only image is unchanged. Since images don't change, images do not have state.

Parent Image

Each image may depend on one more image which forms the layer beneath it. We sometimes say that the lower image is the parent of the upper image.

Base Image

An image that has no parent is a base image.