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🐳 Docker Guide

🚀 Introduction​

Docker is a powerful platform for developing, shipping, and running applications using containers. Containers ensure that your applications run consistently across different environments.

🛠 Prerequisites​

  • A computer running Linux, macOS, or Windows
  • Basic command-line knowledge

When using Docker, several components are typically installed to effectively manage and utilize containers:

  • Docker Engine
  • Docker Compose
  • Docker CLI (Command Line Interface)
  • Docker Registry
  • Docker Toolbox (for older systems or Windows/Mac OS)
  • Docker Swarm (optional)

🔧 Installing Docker​

On Linux​

  1. Update your package list and install dependencies:
sudo apt-get update
sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release
  1. Add Docker's official GPG key and set up the stable repository:
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
  1. Install Docker Engine:
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin
  1. Verify the installation:

docker --version

On macOS & Windows​

  1. Download and install Docker Desktop from the Docker website.
  2. Follow the instructions to complete the installation.

🐳 Docker Basics manipulation​

Running Your Container​

Run a simple Docker container to verify the installation:

docker run hello-world

Pulling an Image​

Pull an image from Docker Hub:

docker pull ubuntu

Listing Images​

List all Docker images on your system:

docker images

Running a Container​

Run a container from an image:

docker run -it ubuntu

This command starts a new Ubuntu container and provides an interactive terminal.

Listing Containers​

List running containers:

docker ps

List all containers, including stopped ones:

docker ps -a

Stopping a Container​

Stop a running container:

docker stop <container_id>

Removing a Container​

Remove a stopped container:

docker rm <container_id>

Removing an Image​

Remove an image from your system:

docker rmi <image_id>

📄 Dockerfiles​

Creating a Dockerfile​

A Dockerfile is a script that contains instructions for building a Docker image. Here's an example:

# Use an official Python runtime as a parent image
FROM python:3.8-slim-buster

# Set the working directory in the container
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Define environment variable
ENV NAME World

# Run app.py when the container launches
CMD ["python", "app.py"]

Building an Image​

Build a Docker image from a Dockerfile:

docker build -t my-python-app .

Running an Image​

Run the newly built image:

docker run -p 4000:80 my-python-app

This command maps port 4000 on the host to port 80 in the container.

📦 Docker Compose​

Creating a docker-compose.yml File​

Docker Compose is a tool for defining and running multi-container Docker applications. Here's an example docker-compose.yml file:

version: '3'
services:
  web:
    image: my-python-app
    build: .
    ports:
      - "4000:80"
  redis:
    image: "redis:alpine"

Running Docker Compose​

Use Docker Compose to start your application:

docker-compose up

Stopping Docker Compose​

Stop the application:

docker-compose down

🐳 Docker Must-Know Commands for Debugging & Container Management​

# List running containers
docker ps

# Follow logs from a running container
docker logs -f container_name

# Follow the last 200 lines of logs from a running container
docker logs -f -n 200 container_name

# Execute a command inside a running container
docker exec -it container_name /bin/bash

# Stop a running container
docker stop container_name

# Remove a stopped container
docker rm container_name

# List all containers (including stopped ones)
docker ps -a

# Remove all stopped containers
docker container prune

# List all Docker images
docker images

# Remove a Docker image
docker rmi image_name_or_id

🎉 Conclusion

There is no reason not to use Docker