Docker Architecture

Ref: https://learn.cantrill.io/courses/docker-fundamentals/lectures/44151958 =OR= https://www.youtube.com/watch?v=52SmfrVctB0

DEMO: https://learn.cantrill.io/courses/docker-fundamentals/lectures/44706186 =OR= https://www.youtube.com/watch?v=DkIUPdRF7Fg

Docker Architecture - Components

🔧 Docker Architecture follows a client-server paradigm (Docker Client-Docker Host)
Docker Host - includes:
1. Docker Daemon = dockerd
  - engine/brains of Docker Host
  - long-running service
  - exposes Docker API for clients to interact with it
2. Images
  - immutable, read-only templates
  - can be used to launch/run containers
3. Containers
  - running process inside Docker OS
  - running instance of an image = an image with an added writable layer
Docker Client
- E.g. Docker Desktop, CLI, other apps that interact with dockerd…
- Uses Docker API to send commands to dockerd
Registry (HUB)
- E.g. Docker Hub
- Public/private remote storage for images

Registry/HUB interaction
- docker pull <imgID> - dockerd pulls (downloads) image, stores it locally in Host
- docker push <imgID> - dockerd pushes an image to registry/HUB
Container running status interaction
- docker run <imgID> - dockerd runs an image (creates new container or starts old one)
  - pulls image from registry if needed, i.e. if image not pulled into Docker Host yet
- docker stop <contID> - dockerd stops a running container
- docker start <contID> - dockerd starts a stopped container
- docker restart <contID> - dockerd restarts a container (stops and starts it again)
Overview
- docker ps - show all running containers.
  - docker ps -a - show all containers (whether running or stopped).
  - 💡 ps = “process status”. -a = “all”
- docker images - show all images
Image creation
- docker build <file> - dockerd uses a Dockerfile to create a new image
💡Most of these commands map directly to API endpoints
- e.g. docker ps = GET /containers/json

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