Docker

Docker is an open-source platform for developing, shipping, and running applications in lightweight, portable containers. Containers allow applications to run consistently across different environments by packaging the code, dependencies, and system libraries together.

Key Features

Containers: Lightweight, portable units of software that run isolated processes.
Images: Immutable templates used to create containers. Built using Dockerfile.
Portability: Ensures applications run consistently across development, testing, and production environments.
Efficiency: Shares the host OS kernel, making containers more efficient than virtual machines.
Docker Hub: A public repository for finding and sharing container images.

Common Commands

docker run - Run a new container from an image.
docker ps - List running containers.
docker build - Build an image from a Dockerfile.
docker pull - Download an image from Docker Hub.
docker exec - Run commands inside a running container.
docker stop - Stop a running container.
docker rm - Remove stopped containers.
docker rmi - Remove unused images.

Example Workflow

Write a Dockerfile:

 # Use a base image
 FROM python:3.9-slim
    
 # Set the working directory
 WORKDIR /app
    
 # Copy application files
 COPY . /app
    
 # Install dependencies
 RUN pip install -r requirements.txt
    
 # Define the default command
 CMD ["python", "app.py"]

Build the image:
```
 docker build -t my-python-app .
```

Run the container:

 docker run -d -p 5000:5000 my-python-app

Key Concepts

Dockerfile: A text file with instructions to build a Docker image.
Volumes: Persistent storage for containers.
Networks: Virtual networks connecting containers and services.
Orchestration: Tools like Kubernetes work with Docker to manage clusters of containers.

Useful Resources

Docker Documentation: docker.com/docs
Docker Hub: hub.docker.com
Play with Docker: A free online environment to practice Docker (play-with-docker.com).