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Docker

Creates a virtual environment of your OS to allow deployment of software seamlessly.

It tends to be faster than running a entire virtual machine because it automizes using a single linux instance; however, would be slower if you can build to your OS natively.

Made to package and run an application in a loosely isolated environment called a container.

Breakdown

Consists of 3 components:

  1. Docker daemon, dockerd, manages Docker containers.
  2. Objects: Docker objects are used to assemble an application in Docker.
  3. Registries: A Docker registry is a repository for Docker images

Installation

Tools

  • Docker Compose: running multi-container Docker applications, but not necessary if application only uses a single container.
  • Docker Swarm
  • Docker Volume

Local Development

Docker Compose

With a single command, you create and start all the services from your configuration YAML file

To build and run image:

$ docker-compose up

To rebuild:

$ docker-compose up --build

or for a clean slate:

$ docker-compose down --volumes --remove-orphans
$ docker-compose up --build

Deployment

First, you need to create a Dockerfile which defines build instructions. It defines how to build a Docker image, being similar to requirements.txt in python or cmake in C/C++. 

$ touch Dockerfile
  • This file is unique to each container framework/library (cannot generalize file content).
  • After generating, add content through researching

Build the project by running the following command, swapping out DOCKER_USERNAME with your username:

$ docker build -t DOCKER_USERNAME/getting-started-todo-app .

To verify the image exists locally, you can use the docker image ls command:

$ docker image ls

The following command runs an container, attaches interactively to your local command-line session:

$ docker run -d -p 127.0.0.1:3000:3000 docker/getting-started-todo-app
  • The -d flag (short for --detach) runs the container in the background.
    • Don't add, I like messages in terminal
  • 3000:3000 is the <host_port>:<container_port>
    • “Hey Docker, if someone hits localhost:3000 on my machine, forward that to port 3000 inside the container.”
    • So they can be different

After a few seconds, open your web browser to http://localhost:3000. You should see your app.

Run the docker ps command in a terminal to list your containers.

$ docker ps

To push the image, use the docker push command. Be sure to replace DOCKER_USERNAME with your username:

$ docker push DOCKER_USERNAME/getting-started-todo-app

Depending on your upload speeds, this may take a moment to push.

Citations

  • https://en.wikipedia.org/wiki/Docker_(software)