The Docker ecosystem

Summary: Docker is not an isolated tool. Around it revolves a rich ecosystem: Docker Hub to share images, Docker Compose to orchestrate several containers, Kubernetes to handle production load, and alternatives like Podman or containerd that nibble at market share. This lesson lays out the complete map.

1. Overview of the ecosystem

Each of these branches is a craft in its own right. It is impossible to master everything at once. The recommended learning order:

Docker Engine (the basic commands)
Docker Hub (downloading and publishing images)
Dockerfile (building your own images)
Docker Compose (orchestrating locally)
Kubernetes (orchestrating in production)
Alternatives and specialized tools

This course gives you the conceptual understanding of points 1 to 6. Practical mastery is the subject of the Premium Docker Course and of Kubernetes Discovery.

2. Docker Hub — the central catalog

Docker Hub is the public registry managed by Docker Inc. It is the world library of container images, free for open source.

2026 figures:

More than 15 million images available.
More than 400 billion cumulative downloads since 2013.
The nginx image alone exceeds 10 billion downloads.

Security advice: always prefer the official images (blue "Docker Official Image" badge) or the verified publishers. A community image can contain vulnerabilities or malicious code — it has happened several times in history.

Alternatives to Docker Hub:

GitHub Container Registry (ghcr.io) — free, integrated with GitHub, very popular since 2021.
GitLab Container Registry — integrated into every GitLab project.
Amazon ECR, Google Artifact Registry, Azure ACR — for private enterprise images in the cloud.
Harbor, Nexus, Artifactory — for self-hosted registries in the enterprise.

3. Docker Compose — orchestrating several containers

A modern application is never a single container. It is composed of several services that must coexist: a web application, a database, a cache, a search engine, a worker, a reverse proxy.

Launching 6 containers by hand with command lines quickly becomes painful. That is the role of Docker Compose: describing the whole stack in a single YAML file and launching it with a single command.

What a docker-compose.yml file looks like (excerpt, for illustration):

services:
  web:
    image: myapp:v2.3.0
    ports:
      - "3000:3000"
    depends_on:
      - db
  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_PASSWORD: example
    volumes:
      - db_data:/var/lib/postgresql/data

volumes:
  db_data:

Three reasons why developers adore Compose:

A single file to version in Git — the stack is self-documented.
A single command to start, stop, restart everything.
Total reproducibility — the colleague who clones the repository runs docker compose up and gets back exactly your environment.

Compose is the number 1 tool for the local development environment in almost all modern companies. It is not enough for high-availability production — that is where Kubernetes comes on stage.

4. Docker Swarm — the first attempt at orchestration at scale

Docker Swarm is Docker's native orchestration system, launched in 2015 to answer a real need: how do you manage 500 containers spread across 20 servers?

State in 2026: Swarm still exists and works well for small infrastructures. But it lost the standardization battle against Kubernetes. Most teams starting today go straight to Kubernetes.

5. Kubernetes — the world standard for orchestration

Kubernetes (often abbreviated K8s) is the most used container orchestrator in the world. Created by Google in 2014 based on their internal tool Borg, then donated to the CNCF open source foundation.

Important point: Kubernetes uses Docker (or more precisely its successors — see below) to run the containers. Kubernetes sits above Docker, not in its place. In summary: Docker builds and launches the containers, Kubernetes orchestrates them.

Kubernetes is a world of its own, with a real learning curve. It is covered in depth in the Kubernetes Discovery course and in the Premium Kubernetes Course.

6. The alternatives to Docker in 2026

Since 2020, several credible alternatives to Docker Engine have emerged. Here are the main ones.

6.1 · containerd — the low-level engine

containerd is the low-level container engine used internally by Docker itself since 2017, extracted into a separate project under the CNCF's umbrella. Kubernetes has been using containerd directly since 2022, gradually abandoning Docker as a runtime.

6.2 · Podman — the daemonless alternative

Podman is developed by Red Hat as a practical replacement for Docker, with two major differences:

No central daemon — each podman command launches the container directly, without a permanent background process.
Rootless by default — containers run with the user's privileges, not as root. Safer.

Compatibility is close to 100%: the podman run command accepts the same syntax as docker run. Many organizations that reject Docker Desktop's commercial license use Podman as a free alternative.

6.3 · Other notable alternatives

Tool	Positioning
Buildah	Building images without a daemon (often used with Podman)
Skopeo	Manipulating images between registries without launching them
CRI-O	Lightweight container runtime designed for Kubernetes
Colima	Free alternative to Docker Desktop on macOS
Rancher Desktop	Graphical alternative to Docker Desktop, free, with built-in Kubernetes
OrbStack	Paid alternative to Docker Desktop on Mac, very fast

7. Docker Desktop and the developer experience

On Windows and macOS, one generally uses Docker Desktop: a graphical application combining Docker Engine, Docker Compose, a small background Linux VM, and a visual management interface.

Since 2022, Docker Desktop is paid for companies with more than 250 employees or exceeding 10 million dollars in revenue. It remains free for:

Personal use.
Open source projects.
Small businesses and startups.
Education.

This is the main reason Podman, Rancher Desktop and Colima have gained users — they offer the same experience while remaining completely free.

8. VS Code Dev Containers — the ready-to-use dev environment

Since 2020, Visual Studio Code has integrated an extraordinary feature for developers: Dev Containers. It relies entirely on Docker.

This feature changed the life of teams that regularly welcome new members: technical onboarding goes from several days to a few minutes. GitHub Codespaces pushes the concept even further, running these containers in the cloud — you no longer even need to install Docker on your workstation.

9. The orchestration landscape in 2026

To close this lesson, here is the hierarchy of tools you will encounter during your career.

You will not have to learn everything at the same time. Each level becomes useful as your project grows.

Remember in 30 seconds

Docker Hub = the GitHub of images, 15 million public images.
Docker Compose = a YAML to orchestrate a complete stack locally, THE foundation of modern dev.
Docker Swarm = native orchestration but now a minority option against Kubernetes.
Kubernetes = the world standard for production orchestration, above Docker (or containerd).
containerd = the true low-level engine, now used by Kubernetes without Docker.
Podman, Rancher Desktop, Colima = free alternatives to Docker Desktop gaining ground since 2022.
Docker Desktop + VS Code Dev Containers = the ultimate developer experience in 2026.

Next: Real use cases: dev, CI/CD, microservices, ML →

1. Overview of the ecosystem​

2. Docker Hub — the central catalog​

3. Docker Compose — orchestrating several containers​

4. Docker Swarm — the first attempt at orchestration at scale​

5. Kubernetes — the world standard for orchestration​

6. The alternatives to Docker in 2026​

6.1 · containerd — the low-level engine​

6.2 · Podman — the daemonless alternative​

6.3 · Other notable alternatives​

7. Docker Desktop and the developer experience​

8. VS Code Dev Containers — the ready-to-use dev environment​

9. The orchestration landscape in 2026​

Remember in 30 seconds​