Docker HOL

08/05/2026

Most Docker beginners skip resource limits — until a container eats all their RAM at 2 AM. 🐳

I just published a new article in my Docker Zero to Hero series:
👉 Docker Resource Limits — Memory, CPU & What Happens When They're Exceeded

Here's what you'll learn:
✅ How to monitor containers live with docker stats
✅ Setting memory limits with --memory and --memory-swap
✅ Controlling CPU with --cpus and --cpu-shares
✅ What the OOM Killer actually does (and how to detect it)
✅ How CPU throttling differs from an OOM kill
✅ Common mistakes beginners make + a hands-on challenge

If you're running multiple services on one machine without resource limits, you're one misbehaving container away from a bad day.

Read the full article here 👇
https://dockerhol.com/blog/docker-resource-limits-memory-cpu-what-happens-next

So you've been running containers for a while now. You know how to spin one up, map ports, maybe even write a Dockerfile. But here's a question — have you ...

03/05/2026

Most Docker beginners focus on getting containers to run.

Nobody talks about keeping them secure.

Here are 4 habits that will instantly make your Docker setup more production-ready:

1/ Scan your images — Tools like Trivy and Docker Scout check your images for known vulnerabilities (CVEs) before they reach your server. One command. Huge impact.

2/ Stop running as root — By default, your container process runs as root. If anything goes wrong, an attacker has full control. Add a non-root user to your Dockerfile. It takes 3 lines.

3/ Handle secrets properly — Never put passwords in ENV inside a Dockerfile. They get baked into image layers and anyone who pulls your image can find them. Pass secrets at runtime or use Docker Secrets.

4/ Keep images updated — Your container is frozen in time. Rebuilding regularly picks up base image patches. Set it on a schedule and forget about it.

I wrote a full beginner-friendly guide covering all four — with real commands, common mistakes, and a hands-on challenge at the end.

https://dockerhol.com/blog/docker-security-basics-every-developer-should-know

29/04/2026

Ever emailed a Docker image as a tar file to a teammate? 😅

Yeah, we've all been there. That's exactly what a private Docker registry fixes.

In my latest article, I walk you through setting up your own private Docker registry from scratch — no Docker Hub, no third-party services, just your own server:

🔐 Add basic auth with htpasswd so only your team gets in

📦 Push and pull images using simple docker push / docker pull

👥 Wire it up for a multi-developer team workflow

🛡️ Understand insecure-registry configs and when TLS matters

Plus — 5 common mistakes people make (and how to avoid them), a Docker Compose setup for production use, and a hands-on 7-step challenge at the end to test yourself.

This is part of my Docker Zero to Hero series on C # Corner. If you're learning Docker or teaching it, bookmark this one.

🔗 Read it here → https://dockerhol.com/blog/host-your-own-private-docker-registry-in-minutes

So you've been using Docker Hub to pull images. You type and boom — it just works. But here's a question: what happens when you build something of your ow...

25/04/2026

🐳 Is your Docker container "Up" but your app completely broken?

That's more common than you think — and it's exactly the problem HEALTHCHECK solves.

In my latest article for the Docker Zero to Hero series, I cover:

✅ How the HEALTHCHECK instruction works (with real Dockerfile examples)
🔄 All 4 restart policies — and when to use each one
🩺 How to monitor unhealthy containers and build self-healing setups
⚠️ The #1 gotcha: why unhealthy ≠ automatic restart
🐍 A hands-on challenge with a Flask app that deliberately fails

If you're moving from hobby Docker usage to production-grade deployments, this one's for you.

🔗 Read it here → https://dockerhol.com/blog/docker-healthcheck-restart-policies-container-monitoring

Practice it free on DockerHOL 👉 dockerhol.com

Health Checks — HEALTHCHECK Instruction, Restart Policies, and Monitoring Unhealthy Containers So you've got your Docker container running. The terminal sh...

12/04/2026

Just published a new article 🐳

"Django in Docker: Base Images, PostgreSQL & Migrations"

If you've ever broken a Django setup because your teammate had a different Python version or no PostgreSQL installed — this one's for you.

In this article, I cover:

→ Choosing the right Python base image (slim vs alpine vs full)

→ Pinning dependencies in requirements.txt the right way

→ Wiring Django + PostgreSQL using Docker Compose

→ Running migrations inside containers (3 approaches)

→ Fixing the "PostgreSQL not ready" race condition

Built for students and developers just getting started with Docker + Django. Practical commands, common mistakes, and a hands-on challenge at the end.

🔗 https://dockerhol.com/blog/django-in-docker-base-images-postgresql-migrations

So you've been hearing about Docker for a while now. Maybe you've already containerized a simple Python script or a "Hello World" Flask app. That's great —...

09/04/2026

🐳 Containerizing Node.js just got a whole lot clearer.

I just published a new article in my Docker Zero to Hero series — and this one covers everything students always get stuck on:

✅ Writing a production-aware Dockerfile for Express
✅ The layer caching trick that speeds up every build
✅ Nodemon hot reload inside Docker (no rebuilds!)
✅ Docker Compose with MongoDB — full working setup
✅ The double-volume pattern that everyone gets wrong

If you've ever typed `docker run` and immediately regretted it, this one's for you. 😄

Built for beginners. Packed with real explanations — not just copy-paste commands.

👇 Read it here: https://dockerhol.com/blog/containerize-node-js-dockerfile-nodemon-mongodb-compose

So you've been writing Node.js apps for a while now. Maybe you've even gotten comfortable with Express. And then someone says, "just Dockerize it" — and su...

04/04/2026

I spent an entire Saturday trying to get Apache, PHP, and MySQL running on my laptop.

MysQL wasn't talking to Apache. Apache couldn't find PHP. Three versions of PHP installed — none of them right.

That whole disaster? Could've been avoided with Docker Compose.

So I wrote the guide I wish I had back then. 👇

𝗕𝘂𝗶𝗹𝗱 𝗮 𝗳𝘂𝗹𝗹 𝗟𝗔𝗠𝗣 𝗦𝘁𝗮𝗰𝗸 𝘄𝗶𝘁𝗵 𝗗𝗼𝗰𝗸𝗲𝗿 𝗖𝗼𝗺𝗽𝗼𝘀𝗲 — working code included.

Here's what the article covers:

🐳 Custom PHP 8.2 + Apache Dockerfile
🗄️ MySQL 8.0 with health checks (the RIGHT way to handle startup)
🔗 Container networking — why $host = 'db' just works
🖥️ phpMyAdmin wired in for free
⚠️ 5 common mistakes beginners make + how to fix them
🎯 3 hands-on challenges at the end

The part most tutorials skip?

I explain every single line of the docker-compose.yml — not just paste it and move on.

If you're learning Docker or teaching it, this one's worth bookmarking.

🔗 https://dockerhol.com/blog/lamp-stack-with-docker-compose-complete-beginner-s-guide

Let me tell you something that happened to me early in my developer journey. I spent an entire Saturday afternoon trying to get a PHP project running on my...

31/03/2026

🐋 New Article Drop: Docker Compose — Managing Multi-Container Apps Like a Pro

Running containers one by one with docker run is fine… until it isn't.

When you have a web app + database + cache all needing to work together, things get complicated fast.

That's where Docker Compose comes in. 🎯

One file. One command. Your entire stack is up and running.

In my latest article, I cover:

📦 The structure of docker-compose.yml — broken down simply

🔗 How containers talk to each other using service names (no IPs!)

🐍 A real Flask + PostgreSQL multi-container project

⚠️ The depends_on trap that trips up every beginner

🔐 How to handle secrets with .env files

🚀 A hands-on challenge with 3 difficulty levels

Whether you're just starting out or moving beyond single-container setups — this one's for you.

🔗 Read it here: https://dockerhol.com/blog/docker-compose-manage-multi-container-apps-like-a-pro

So you've been running Docker containers one by one. You pull an image, fire up a command with a bunch of flags, and it works. Great! But here's where thi...

30/03/2026

Most Dockerfiles work. Very few are actually good. 🐳

After reviewing dozens of beginner Dockerfiles, I keep seeing the same four mistakes over and over.

Here's what separates a Dockerfile that "just works" from one that's fast, secure, and production-ready:

🚀 Layer Caching — The order of your instructions matters more than you think. One wrong COPY and you're reinstalling 300 packages every single build.

🚫 .dockerignore — Most beginners skip this file. It's silently bloating your build context and could be shipping your .env secrets into the image without you knowing.

📦 Base Image Choice — ubuntu? slim? alpine? distroless? Each has a real tradeoff. Picking wrong means either a 900MB image or mysterious runtime errors at 2am.

🔒 Don't Run as Root — Docker does this by default. It's a security risk and a surprisingly easy fix that most tutorials never mention.

I wrote a full beginner-friendly breakdown covering all four — with real Dockerfile examples, common mistakes, and a hands-on challenge at the end.

If you're learning Docker or want to level up your container game, this one's worth a read. 👇

🔗 https://dockerhol.com/blog/dockerfile-best-practices-every-developer-should-know

So you've written your first Dockerfile. Maybe it builds. Maybe it even runs. You're feeling pretty good. But here's the thing — there's a big difference b...

30/03/2026

Most beginners copy Dockerfiles from Stack Overflow without understanding a single line.

I was guilty of that too.

So I wrote the article I wish existed when I started — breaking down every Dockerfile instruction with zero jargon.

Here's what FROM, RUN, COPY, and CMD actually do:

🔵 FROM → Picks your base image (think: choosing the bread for your sandwich)
🟢 RUN → Installs packages at build time, not at runtime
🟡 COPY → Brings your local files into the image
🔴 CMD → The command that runs when your container starts

We also build a real Python Flask app image from scratch — step by step.

Bonus: The layer caching trick that stops Docker from reinstalling packages on every single build. Saves minutes. Adds up fast.

📖 Full article https://dockerhol.com/blog/your-first-dockerfile-from-run-copy-cmd-explained

So, you've been playing around with Docker for a bit. You pulled some images, ran a few containers, maybe even did a and felt like a genius. And then some...

10/04/2025

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