Introduction

Docker is a powerful tool that simplifies application deployment by using containerization. It allows developers to package applications and their dependencies into lightweight, portable containers that run seamlessly across different environments. This tutorial will introduce Docker, explain key concepts like images and containers, and provide simple examples to help beginners get started.

What is Docker?

Docker is an open-source platform that automates application deployment in lightweight, self-sufficient containers. These containers encapsulate everything an application needs to run, including the code, runtime, libraries, and dependencies. Docker ensures consistency across different computing environments, making it easier to develop, test, and deploy applications.

Why Use Docker?

• Portability: Run applications anywhere, from a developer’s laptop to a production server.
• Efficiency: Uses fewer resources compared to traditional virtual machines.
• Scalability: Easily scale applications up or down with minimal effort.
• Consistency: Works the same across different environments, reducing deployment issues.

Understanding Docker Images and Containers

Docker Images

A Docker image is a lightweight, standalone, and executable package that includes everything needed to run a piece of software. Images are read-only and serve as a blueprint for containers.

Docker Containers

A container is a running instance of a Docker image. Containers are isolated environments that run applications with all their dependencies. Unlike virtual machines, containers share the host system’s kernel, making them more efficient.

Key Differences Between Images and Containers:

Installing Docker

To start using Docker, install it on your system by following the official documentation for your operating system:

• Windows & Mac
• Linux

After installation, verify that Docker is installed correctly by running:

docker --version

Getting Started with Docker

1. Pulling a Docker Image

Docker images are stored in repositories like Docker Hub. To download an image, use the docker pull command:

docker pull ubuntu

This downloads the latest Ubuntu image from Docker Hub.

2. Running a Container

Once you have an image, you can create and start a container using the docker run command:

docker run -it ubuntu

This command starts an interactive terminal (-it) inside an Ubuntu container.

3. Listing Running Containers

To see active containers, run:

docker ps

To view all containers, including stopped ones, use:

docker ps -a

4. Stopping and Removing Containers

To stop a running container, use:

docker stop <container_id>

To remove a container:

docker rm <container_id>

5. Building a Custom Docker Image

You can create your own Docker images using a Dockerfile. Create a simple Dockerfile:

# Use an official image as a base
FROM ubuntu

# Install dependencies
RUN apt-get update && apt-get install -y curl

# Set a default command
CMD ["bash"]

Then build the image:

docker build -t my-ubuntu .

Now, you can run a container using your custom image:

docker run -it my-ubuntu

Conclusion

Docker simplifies application deployment by using containers. In this tutorial, we explored Docker basics, images, and containers with practical examples. You can now start experimenting with Docker and build your own containerized applications.

Stay tuned for more advanced Docker tutorials!