• Docker image
  • Universal app packaging
  • docker build
• Docker registry
  • Universal app distribution
  • docker push
  • docker pull
• Docker container
  • Identical runtime environment

Build -> ship -> run

docker version verifies CLI can talk to Docker engine

docker info shows config values of Docker engine

Docker command line structure

• Old is docker <command> e.g. docker run
• New is docker <command> <subcommand> e.g. docker container run

In CLI, no need to type a full container ID. If the first few characters can identify a unique container ID, that's enough

docker container run --publish 80:80 nginx means

1. Download nginx image from Docker Hub
2. Start a new container from the image
3. Open the port 80 (left number of :) on the host IP (localhost)
   1. We can use any port number (left number) if 80 is used.
4. Routes the traffic to the container IP (right number of :) port 80

run always starts a new container, while start starts an existing stopped container.

What happens in the background of docker container run

1. Looks for the image locally in image cache
2. If not found, looks for in remote image repository default to Docker Hub
3. Downloads the latest version
4. Create new container based on the image
5. Give virtual IP on a private network inside docker engine
6. Open port 80 on host and forwards to port 80 in container
7. Start container by CMD in the image Dockerfile

docker container run -d -p 3306:3306 --name db -e MYSQL_RANDOM_ROOT_PASSWORD=yes mysql

docker container run -d --name webserver -p 8080:80 httpd can be seen in localhost:8080

docker container run -d --name proxy -p 80:80 nginx can be seen in localhost

docker ps is old command. New command is docker container ls

docker container stop CONTAINER_IDs stops the process

docker container rm CONTAINER_IDs deletes the containers

docker image ls shows that even if we deleted the containers, the local images still exist.

No SSH needed to interact with a running container. Use docker CLI instead

Dockerize is to say that we are making a Dockerfile for an existing app or service and we are getting it work properly in a container.

Image is the application we run such as source code

Container is a running instance of the image. So we can have multiple containers running the same image.

• Locally by Docker Desktop, RD
• Servers by Docker Engine, K8s
• PaaS by Cloud Run, Fargate