Intro

• Ops Jargon

• Important distinction: Containers are NOT Docker. Docker includes multiple products (i.e. Docker Desktop) and Open Source containerization technologies (i.e. container engine), see Docker's github repo

• Docker Desktop is recommended because it includes the Docker daemon (dockerd), the Docker client (docker), Docker Compose, Docker Content Trust, Kubernetes, and Credential Helper.

• Install Docker engine (aka Docker CE) for various Linux Distros here vs. install Docker Desktop for linux here. The Docker Engine is licensed under the Apache License, Version 2.0.

• How Kubernetes works under the hood with Docker Desktop

• architecture of docker on mac and how how-docker-for-mac-works-under-the-hood or the-magic-behind-the-scenes-of-docker-desktop and docker-on-macos-is-slow-and-how-to-fix-it

• Check userland hypervisor qemu here

• Authenticate to registries docker login registry.example.com concretly docker login -u dejanualex docker.io

Docker

• What is a container here, just a fancy way to run a process

• After Docker installation, we have the hello world for containers. Using docker CLI we can do:

# list all containers from your machine (by all we mean running and also stopped). 
# The output should be empty (since there are no containers which have been ran)
docker ps -a

# list all images from your machine. 
# The output should be empty (since there are no images pulled on your machine)
docker images

# run your first container. 
# The container engine tried to find an image named hello-world, and it did not find it, 
# therefore it goes to its default Docker registry, which is Docker Hub, to look for an image named “hello-world
# It finds the image there, pulls it down, and then runs it in a container
docker run hello-world

# rerun commands. What are the changes?
docker ps -a
docker images

• Docker flags (Display system-wide information and Go templates to manipulate the output format)

  • Search official images for desired : docker search --format "table {{.Name}}\t{{.StarCount}}\t{{.IsOfficial}}" <IMAGE>
  • Output image name and tag: docker images --format '{{.Repository}} and {{.Tag}}'
  • Output image name, tag and elapsed time + timestamp since the image has been created: docker images --format "{{.Repository}}:{{.Tag}} {{.CreatedSince}} --> {{.CreatedAt}}"
  • Inspect Cmd for desired : docker inspect -f '{{.Config.Cmd}}' <IMAGE>
  • Inspect Entrypoint for desired : docker inspect -f '{{.Config.Entrypoint}} <IMAGE>'
  • Inspect attached containers to bridge network: docker inspect network bridge --format "{{json .Containers }}"
  • Check root directory for Docker storage, defaults to /var/lib/docker: docker info -f 'Storage drive: {{.Driver}} and storage path {{.DockerRootDir}}'
  • Show docker disk usage docker system df
  • Inspect container runtimes: docker system info --format "{{.Runtimes}} {{.DefaultRuntime}}" or docker system info --format "Runtimes: {{.Runtimes}} with default {{ .DefaultRuntime }}"
  • Check container resource usage docker stats [OPTIONS] [CONTAINER], or docker stats --no-stream
  • Check events docker events --filter event=restart --since=60m or docker events --filter event=restart --since=60m > events.log 2>&1

• Flow: Using a Dockerfile we build a Docker image, and using a Docker image we start/run a container.

flowchart LR;
		Dockerfile-->Image;
		Image-->Container;

Loading

• Debug Docker with systemctl/service and journalctl

systemctl status docker
systemctl daemon-reload
systemctl start docker
service docker restart
journalctl -xeu docker.service
journalctl -u docker

Kubernetes

• Cluster Architecture A high-level overview
• From Docker to Kubernetes
• Create Cluster
• Deploy App

---

⚠️ Avoid being stuck in tutorial hell and always use the official documentation.