Image

A container image, Docker image, or image, is a static file containing executable code that cannot be changed.

An image is a collection of libraries, tools, and other platform settings used in order to run a containerization platform.

Images act as a starting point and a set of instructions for a Docker container. All the components needed to run a container is within an image, and can be reused and deployed by any host.

DigitalOcean Container Registry (DOCR) hosts private Docker images.

App Platform

App Platform can build and analyze code from a container image you have already uploaded to DigitalOcean Container Registry or Docker Hub. To see more on how to deploy using container images, see How to Deploy from Container Images.

Container Registry

Images have the following layers:

  • Base image: built from scratch with a build command, used as a foundation for all other layers
  • Parent image: base image alternative which is a reused image with the foundation needed for all other layers
  • Layers: layers added on top of the base or parent image; code that is runnable in a container
  • Container layer: writable layer which hosts changes made to the running container and stores the new and changed files
  • Docker manifest: additional file that describes the image using image tags and a digital signature

You can create Droplets, App Platform apps, and Kubernetes clusters from images. A container registry stores those images securely and privately. You can tag images with a destination path, using the docker tag command, and upload them with docker push.

You cannot see untagged images in the control panel.

Kubernetes

DigitalOcean Marketplace provides a variety of apps and stacks that you can install to run pre-configured container images on Kubernetes clusters. You can install these apps directly to a new or existing Kubernetes cluster.