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Images

  • Read only template that contains instructions on how to create the container.

  • The template is called a Dockerfile.

  • Usually based upon other images.

  • You can create your own images or use an image created by someone else / published in a registry

    • Registry being something like Docker hub, GCP, AWS, Azure etc

Dockerfile Example:

FROM node:12.18.4-alpine # Install Alpine (version of Linux) with Node V12.18.4

WORKDIR /usr/src/app # Create directory

COPY package*.json ./ # Copy files over
COPY ./src ./src # Copy files over
RUN npm install && npm run build # Install dependencies and build
CMD npm run start # Run the app

Containers:

  • The running instance of an image which is the result of running the image via Docker.

  • Immutable

    • Once created from an image with any configuration options, it can’t be updated
  • Stateless

    • When we delete a container, it is gone forever
  • We can create, start, stop or delete a container using the Docker CLI.


Images are recipes, containers are cakes

Images Containers


What's inside a container?

whoami
docker run -it busybox

whoami

ls

exit
docker ps -a

See that it looks like a Linux O/S