Course 05 — Docker & containers

Containers,made visible.

Docker is hard to learn because you can't see it. Here you can: images stack their layers, containers light up as they start, ports wire the host to a container, and a rebuild shows which layers come from cache.

Start lesson one Open the sandbox

13 lessons · 5 chapters · free

Docker — pull, run, publish a port
  1. 01 · Read

    Each lesson is one idea, explained in a few short paragraphs — no walls of theory.

  2. 02 · Do

    Type into a live environment and watch it react. Tab completes, ↑ recalls, undo takes back any step.

  3. 03 · Match

    Reach the goal any way you like — you're judged on the result, not the keystrokes. Par is the shortest route.

01

Images & containers

The difference between them, and the life of a container.

  1. 01 Your first container docker run, and what it actually did.
  2. 02 One image, many containers Background containers with names.
  3. 03 Stop and remove A container's life: running, exited, gone.
02

Running services

Background containers, ports, environment variables, logs and exec.

  1. 04 Publish a port -p connects the host to the container.
  2. 05 Configure with environment variables -e, and reading the logs when a container dies.
  3. 06 Run commands inside a container docker exec — a way in.
03

Keeping data

Why containers forget, and how volumes remember.

  1. 07 Containers forget — volumes remember Put a database's data somewhere that outlives the container.
  2. 08 Replace a container, keep its data Containers are disposable. The volume is the database.
04

Building images

Dockerfiles, layers and the build cache.

  1. 09 Build your own image A Dockerfile, docker build, and running the result.
  2. 10 Make builds fast with the layer cache Order your Dockerfile so dependencies are cached.
  3. 11 Ship a change Rebuilding an image doesn't change running containers.
05

Networking

Containers talking to each other by name.

  1. 12 Containers that find each other User-defined networks give containers DNS by name.
  2. 13 Run a whole stack with Compose compose.yaml — every service, port and network in one file.

Docker is simulated — the CLI, image layers, the build cache, ports, volumes and networks follow real Docker's rules and wording, but nothing actually runs. Your commands transfer directly to a real engine.