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Docker architecture

Learn the architecture of daemon, CLI and registry.

Docker architecture

Docker has a client-server structure:

  • Docker CLI (the docker command): takes the commands you type.
  • Docker daemon (dockerd): runs in the background; manages images, containers, networks and volumes.
  • Registry: the store where images are kept (Docker Hub, GitHub Container Registry...).
docker pull redis   # CLI -> daemon -> download from the registry
docker run redis    # CLI -> daemon -> create a container

A remote daemon

The CLI and the daemon don't have to be on the same machine. The CLI talks to a REST API over a socket or the network; with the DOCKER_HOST variable or docker context you can manage a daemon on another machine:

docker context create sunucu --docker host=ssh://ali@10.0.0.5
docker context use sunucu
docker ps        # now lists the containers on the remote server

Practice Pull and run

Write two commands that first pull the redis image, then start a container named cache from it in the background.

Starter code

terminal
# buraya yaz

Sample solution

terminal
docker pull redis
docker run -d --name cache redis

Expected output

Using default tag: latest
Status: Downloaded newer image for redis:latest
9b1c2d3e4f50

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which component actually creates and manages containers?

  • Docker Hub
  • The Dockerfile
  • The Docker daemon (dockerd) Correct answer
  • The Docker CLI

Explanation: The CLI only sends requests to the daemon over a REST API.

2 Download an image from the registry.

Question 
docker ____ redis
Answer 
docker pull redis

Explanation: docker pull downloads the image from the registry into the local store.

3 Match the components with their jobs.

Term Meaning
Docker CLI Sends commands
dockerd Manages containers
registry Stores images
docker context Which daemon to connect to

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project