Registry, CI & Deploy — Module Overview

What is a container registry?

Once you have built a Docker image it lives only on your machine. A registry is a server that stores and distributes images so that other machines — a CI runner, a cloud server, a colleague’s laptop — can pull and run exactly the same image.

The workflow is always the same three steps:

Build → Tag → Push          (your machine / CI runner)
                  ↓
              Registry
                  ↓
         Pull → Run          (deployment server)

Every step maps to a Docker command you already know (or will learn in this module):

docker build -t myapp:1.0 .
docker tag  myapp:1.0 docker.io/acme/myapp:1.0
docker push docker.io/acme/myapp:1.0
# --- on the server ---
docker pull docker.io/acme/myapp:1.0
docker run -d docker.io/acme/myapp:1.0

Docker Hub vs other registries

Registry	Address	Notes
Docker Hub	`docker.io` (default)	Largest public registry; free public repos
GHCR	`ghcr.io`	GitHub Container Registry; integrated with GitHub Actions
ECR	`.dkr.ecr..amazonaws.com`	AWS-native; IAM auth
GAR	`*.pkg.dev`	Google Artifact Registry
Self-hosted	Any host	Run `registry:2` yourself

When no registry address is specified, Docker defaults to docker.io. The snippet FROM node:22-alpine is shorthand for FROM docker.io/library/node:22-alpine.

What this module covers

Lesson	What you will learn
This page	Registries, image distribution workflow, Docker Hub vs alternatives
Docker Hub	Accounts, repos, public vs private, `docker login`, rate limits
Tag, Push & Pull	Naming convention, `docker tag`, `docker push`, `docker pull`, version tags
GitHub Actions CI	Automated build & push with `docker/build-push-action`
Deploy basics	`docker run -d`, `--restart`, rolling updates, secrets on the host

Hands-on: pull and run a public image

No credentials needed — any public image on Docker Hub can be pulled straight from Play with Docker. Try it now.

# Pull a public image from Docker Hub
docker pull docker.io/library/hello-world:latest

# Run it
docker run --rm hello-world

# Pull an nginx image and check the tag
docker pull nginx:1.27-alpine
docker images nginx