Introduction: Day 20 of #90DaysOfDevOps 🗓️ has arrived! After several hands-on sessions with Docker, I’m excited to share a comprehensive cheat-sheet covering the essential Docker and Docker Compose commands. Whether you’re diving into containerization for the first time or need a quick reference, this guide will help you manage containers like a pro. 🐳✨

Bonus: For easy access and sharing, I’ve created a GitHub repository with the cheat-sheet!
GitHub Repository: Cheat-Sheet for DevOps Engineers

Why Docker is Useful (In Simple Terms)

Docker is like a portable app environment that keeps everything an application needs in one place, making it run consistently across different computers. Here’s a simple and complete list of commands to help you master Docker!

Docker Commands Cheat-Sheet

🚀 1. Basic Commands for Everyday Use

These commands help you get started with Docker, like pulling images (the base file of a container) and starting/stopping containers.

🔍 docker --version
Check which version of Docker is installed.
🌐 docker pull <image>
Download an image (app package) from Docker Hub.
Example:
```
  docker pull nginx
```
Imagine this as downloading an app installer. Here, "nginx" is a web server image that will be used to create containers.
▶️ docker run <image>
Start a container from an image.
Example:
```
  docker run nginx
```
This is like launching an app you downloaded—now the web server runs inside a container!
🛑 docker stop <container>
Stop a running container.
Example:
```
  docker stop my-nginx
```
Useful if you need to pause a running app without deleting it.

🖼️ 2. Image Management (Your App Library)

Think of images as pre-configured app templates. These commands help you organize, create, and remove these images.

📜 docker images
See all images you have downloaded.
🛠️ docker build -t <image-name> <path>
Create an image from a Dockerfile (a recipe for your container).
Example:
```
  docker build -t my-app .
```
This creates an image from a Dockerfile, a script with instructions on how to set up your app.
🗑️ docker rmi <image>
Delete an image you no longer need.
Example:
```
  docker rmi nginx
```
If you’re done with an app version, delete it to save space!

🌐 3. Networking Commands

When containers need to “talk” to each other, these commands help you set up networks so containers can connect.

🌐 docker network ls
List all available networks.
➕ docker network create <network-name>
Create a custom network for containers.
Example:
```
  docker network create my-network
```
Think of this as setting up a virtual network that your containers can join.
🔗 docker network connect <network> <container>
Connect a container to a network.
Example:
```
  docker network connect my-network my-nginx
```
This lets the "my-nginx" container communicate with others on "my-network."

Docker Compose Commands Cheat-Sheet

Docker Compose lets you define and run multiple containers at once. Imagine needing a web server and a database—Docker Compose starts both with one command.

▶️ docker-compose up
Start all services defined in your docker-compose.yml file.
Example:
```
  docker-compose up
```
Like turning on a workspace with all the apps needed for your project.
🛑 docker-compose down
Stop and remove containers, networks, and volumes set up by Compose.
📜 docker-compose ps
List services defined in the docker-compose file.

Real-Life Example of Docker & Docker Compose:

Let’s say you’re creating an online shop with a web server and a database (e.g., PostgreSQL). You could use Docker Compose to start both the web server and the database with one simple command, making setup fast and consistent!

Example docker-compose.yml:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "8080:80"
  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD: example

To start both services, simply run:

docker-compose up

Now both the web server (for your shop) and the database (to store data) start at once. No need for individual commands!

Why Keep a Docker Cheat-Sheet?

This cheat-sheet is a go-to for keeping Docker commands at your fingertips. Whether you’re launching containers, managing images, or connecting services, this will save you time and make Docker simpler.

Conclusion:

Wrapping up Day 20 of #90DaysOfDevOps with this Docker command cheat-sheet! 🎉 Bookmark it for easy access, and if you have any tips or favorite commands, let me know in the comments below. 🚀 Happy Docker-ing!

Day 20: Docker Command Cheat-Sheet for DevOps Engineers