Mastering Containerization with Docker and Kubernetes

Getting Started with Docker

Welcome to your first practical step into the world of containerization! Docker is an open platform for developing, shipping, and running applications. It enables you to separate your applications from your infrastructure so you can deliver software quickly. If you haven't already, you might want to review What is Containerization? to understand the "why" behind Docker.

1. Installing Docker

Docker is available for Windows, macOS, and various Linux distributions. The installation process is straightforward:

• Docker Desktop for Windows and macOS: This is the easiest way to get started. It includes Docker Engine, Docker CLI client, Docker Compose, Docker Content Trust, Kubernetes, and Credential Helper.
  • Download from the official Docker website.
• Docker Engine for Linux: For Linux users, Docker Engine can be installed on most major distributions.
  • Follow the official installation guides for your specific distribution (e.g., Ubuntu, CentOS, Debian) available on the Docker Engine installation page.

2. Verifying Your Installation

Once Docker is installed, you can verify it by running a few simple commands in your terminal or command prompt:

Check Docker Version:

docker --version

This command should output the installed Docker version, confirming the CLI is working.

Run the `hello-world` Container:

This is the traditional first step to ensure Docker is running correctly. The `hello-world` image is a tiny image designed to test your Docker installation.

docker run hello-world

If successful, you'll see a message explaining that your installation appears to be working correctly. This command performs several actions:

1. The Docker client contacts the Docker daemon.
2. The Docker daemon pulls the "hello-world" image from Docker Hub (if not already present locally).
3. The Docker daemon creates a new container from that image.
4. The Docker daemon streams the output from the container to the Docker client, which sends it to your terminal.

3. Core Docker Concepts (A Quick Overview)

We'll dive deeper into these in the Docker Deep Dive section, but here’s a quick introduction:

• Images: A Docker image is a lightweight, standalone, executable package that includes everything needed to run a piece of software, including the code, a runtime, libraries, environment variables, and config files.
• Containers: A container is a runnable instance of an image. You can create, start, stop, move, or delete a container using the Docker API or CLI.
• Dockerfile: A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. `docker build` uses this file to automate the creation of images.
• Docker Hub / Registries: Docker Hub is a public registry where you can find and share container images. There are also private registries.

4. Basic Docker Commands

Here are a few essential commands to get you started:

• docker pull <image_name>: Downloads an image from a registry (Docker Hub by default).
  Example:

  docker pull nginx

• docker images: Lists all images stored locally.
• docker run [OPTIONS] <image_name> [COMMAND] [ARG...]: Creates and starts a new container from an image.
  Example (run an Nginx web server):

  docker run -d -p 8080:80 --name my-nginx nginx

  This command runs an Nginx container:
  • -d: Runs the container in detached mode (in the background).
  • -p 8080:80: Maps port 8080 on the host to port 80 in the container.
  • --name my-nginx: Assigns a custom name to your container.
  • nginx: Specifies the image to use.
  You should then be able to access the Nginx welcome page at http://localhost:8080 in your browser.
• docker ps: Lists running containers. Add -a (docker ps -a) to see all containers (including stopped ones).
• docker stop <container_id_or_name>: Stops a running container.
• docker rm <container_id_or_name>: Removes a stopped container.
• docker rmi <image_id_or_name>: Removes an image.

Next Steps

Congratulations! You've taken your first steps with Docker. You can now pull images, run containers, and manage them. This foundation is crucial for understanding more advanced topics.

To continue your journey and explore Docker in more detail, including how to build your own images with Dockerfiles and manage container data, head over to our Docker Deep Dive section.

Understanding Docker is a key part of Modern DevOps Practices and can be complemented by exploring technologies like WebAssembly for different types of application portability.