Docker Explained from Real Project Pain (Not Theory)

The Problem We Were Fighting ## 1. OS and Version Compatibility ## 2. Onboarding New Developers Was Slow ## 3. Small Changes Had Big Side Effects ## Enter Docker ## What Are Containers Really? ## Why OS Knowledge Matters ## Containers vs Virtual Machines ## Images vs Containers ## Why Docker Changed DevOps ## Getting Started with Docker ## Supported Platforms ## Install on Ubuntu (Quick Path) ## Your First Container ## Core Docker Commands ## Final Thoughts Docker didn’t click for me because of tutorials or diagrams. It clicked when a real project started breaking in very real ways. I was working on an end-to-end application stack that included: On paper, it looked manageable. In reality, it was chaos. Here’s the thing. Each component worked fine on its own, but getting them to live together was painful. Some services worked only on specific OS versions. Others needed different library versions. One service wanted library v1. Another needed v2. The OS supported only one. That’s when you hit what many engineers call the dependency matrix from hell. Every new team member had to: Days were wasted before anyone wrote real code. Updating one component could break others. Even OS patching became risky. That’s when I started looking for a better way. Docker solved the problem by changing where dependencies live. Instead of installing everything on the host machine: Once Docker was set up, onboarding became simple: Same app. Same behavior. Any machine. Containers are isolated environments that include: But unlike virtual machines, they share the host OS kernel. This makes containers: Docker didn’t invent containers, but it made them usable for everyday developers. Most Linux systems consist of: Because Docker containers share the kernel: On Windows and macOS, Docker runs Linux containers inside a lightweight VM. Docker isn’t replacing VMs. It complements them. In real environments, containers often run inside VMs. One image can spawn multiple containers. If a container fails, you delete it and start another. No drama. This guide uses Docker Community Edition (CE). If you see a whale talking back, you’re good. Execute inside a container: Docker removes environment friction. It lets you focus on building, not fixing setups. If you’re learning Docker, follow structured labs first. Hands-on beats theory every time. Happy containerizing 🐳 Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well For further actions, you may consider blocking this person and/or reporting abuse COMMAND_BLOCK: docker run <service> Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: docker run <service> COMMAND_BLOCK: docker run <service> COMMAND_BLOCK: sudo apt-get remove docker docker.io docker-engine sudo apt-get update curl -fsSL https://get.docker.com -o get-docker.sh sudo sh get-docker.sh Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: sudo apt-get remove docker docker.io docker-engine sudo apt-get update curl -fsSL https://get.docker.com -o get-docker.sh sudo sh get-docker.sh COMMAND_BLOCK: sudo apt-get remove docker docker.io docker-engine sudo apt-get update curl -fsSL https://get.docker.com -o get-docker.sh sudo sh get-docker.sh COMMAND_BLOCK: docker version Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: docker version COMMAND_BLOCK: docker version COMMAND_BLOCK: docker run docker/whalesay cowsay Hello Docker Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: docker run docker/whalesay cowsay Hello Docker COMMAND_BLOCK: docker run docker/whalesay cowsay Hello Docker COMMAND_BLOCK: docker run nginx docker ps docker ps -a docker stop <container> docker rm <container> docker images docker rmi <image> docker pull redis Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: docker run nginx docker ps docker ps -a docker stop <container> docker rm <container> docker images docker rmi <image> docker pull redis COMMAND_BLOCK: docker run nginx docker ps docker ps -a docker stop <container> docker rm <container> docker images docker rmi <image> docker pull redis COMMAND_BLOCK: docker run -d redis Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: docker run -d redis COMMAND_BLOCK: docker run -d redis COMMAND_BLOCK: docker exec <container> cat /etc/*release* Enter fullscreen mode Exit fullscreen mode COMMAND_BLOCK: docker exec <container> cat /etc/*release* COMMAND_BLOCK: docker exec <container> cat /etc/*release* - Node.js web server - MongoDB database - Redis messaging system - Ansible for orchestration - Install the correct OS - Install multiple services - Match exact versions - Run long setup commands - Debug environment-specific issues - Each service runs inside its own container - Each container carries its own libraries and dependencies - All containers share the same OS kernel, but remain isolated - Their own processes - Their own network stack - Their own filesystem - Lightweight - Fast to start - Easy to reproduce - The kernel (common across distros) - The user-space software (differs per distro) - You can run Ubuntu, Debian, CentOS containers on the same host - As long as the host kernel is Linux - Image → blueprint or template - Container → running instance of that image - Devs wrote apps - Ops struggled to reproduce environments - Configuration lives in a Dockerfile - Devs and Ops collaborate on the same artifact - The app behaves the same in dev, test, and prod - Cloud VMs (AWS, Azure)