Docker Guide and Cheatsheet

1. Introduction to Docker

Docker is a platform that allows you to develop, ship, and run applications inside containers. Containers are lightweight, portable, and ensure consistency across multiple development, testing, and production environments.

2. Installation

• Windows and Mac: Install Docker Desktop from Docker's official website.
• Linux:

  sudo apt-get update
  sudo apt-get install docker-ce docker-ce-cli containerd.io

3. Basic Commands

• Check Docker Version:

  docker --version

• Pull an Image:

  docker pull <image_name>

• Run a Container:

  docker run -it <image_name> /bin/bash

• List Running Containers:

  docker ps

• List All Containers:

  docker ps -a

• Stop a Container:

  docker stop <container_id>

• Remove a Container:

  docker rm <container_id>

• Remove an Image:

  docker rmi <image_name>

4. Dockerfile

A Dockerfile is a script containing a series of instructions on how to build a Docker image.

Example Dockerfile:

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

# Set the working directory in the container
WORKDIR /usr/src/app

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

# 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"]

5. Building and Running a Docker Image

• Build an Image:

  docker build -t <image_name> .

• Run a Container from an Image:

  docker run -p 4000:80 <image_name>

6. Docker Compose

Docker Compose is a tool for defining and running multi-container Docker applications.

Example docker-compose.yml:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "8080:80"
  redis:
    image: "redis:alpine"

• Run Docker Compose:

  docker-compose up

7. Networking

• List Networks:

  docker network ls

• Create a Network:

  docker network create <network_name>

• Connect a Container to a Network:

  docker network connect <network_name> <container_id>

8. Volumes

Volumes are used to persist data generated by and used by Docker containers.

• Create a Volume:

  docker volume create <volume_name>

• List Volumes:

  docker volume ls

• Run a Container with a Volume:

  docker run -v <volume_name>:/path/in/container <image_name>

9. Common Commands Cheatsheet

Command	Description
docker --version	Check Docker version
docker pull <image>	Pull an image from Docker Hub
docker build -t <image_name> .	Build an image from a Dockerfile
docker run -it <image_name> /bin/bash	Run a container interactively
docker ps	List running containers
docker ps -a	List all containers
docker stop <container_id>	Stop a container
docker rm <container_id>	Remove a container
docker rmi <image_name>	Remove an image
docker-compose up	Run Docker Compose
docker volume create <volume_name>	Create a volume
docker network create <network_name>	Create a network

10. Best Practices

• Keep Dockerfile instructions ordered logically and layer them from less to more frequently changing.
• Use .dockerignore to avoid adding unnecessary files to the Docker image.
• Keep images small by using slim or alpine base images.
• Use multi-stage builds to reduce image size and improve build times.
• Always specify explicit versions of base images to ensure consistency.