Docker for Absolute Beginners: Daily Commands Explained!
🚀 Whether you’re developing applications, deploying services, or just getting started with containers — this guide gives you a complete, beginner-friendly reference for Docker. With real-world examples and all the daily-used commands explained clearly, you’re about to Docker like a pro 🚀
🧠 What is Docker?
Docker is a tool that lets you package applications with their environment (libraries, OS, dependencies) into portable containers. It helps you:
- Avoid “It works on my machine” problems
- Standardize environments across dev/staging/prod
- Easily scale and ship apps
🛠️ Basic Commands
🧱 Image Commands
List available images:
docker images
Shows all images (base OS, app, etc.) stored locally on your machine.
Pull an image from Docker Hub:
docker pull nginx
Downloads the nginx image from Docker Hub if not already present.
Build an image from a Dockerfile:
docker build -t myapp:latest .
Builds an image in the current directory using Dockerfile, and tags it as myapp:latest.
Remove an image:
docker rmi myapp
Deletes the specified image from your local system.
📦 Container Commands
Run a container:
docker run -d --name mynginx -p 8080:80 nginx
Runs the nginx container in detached mode (-d), names it mynginx, and maps port 8080 (host) to 80 (container).
List running containers:
docker ps
Lists all currently running containers.
List all containers (including stopped):
docker ps -a
Lists all containers regardless of their status.
Stop a running container:
docker stop mynginx
Gracefully stops the specified container.
Start a stopped container:
docker start mynginx
Starts a container that was previously stopped.
Restart a container:
docker restart mynginx
Stops and then restarts the container.
Remove a container:
docker rm mynginx
Deletes a stopped container permanently.
Execute a command inside a running container:
docker exec -it mynginx bash
Runs bash inside the container interactively (-it), allowing you to explore the container like a mini VM.
🔍 Inspecting
View logs from a container:
docker logs mynginx
Displays standard output (like console.log or print) from the container.
Inspect container details:
docker inspect mynginx
Gives JSON with low-level details like IP address, mounts, environment variables, etc.
📂 Volumes (Persistent Data)
Create a volume:
docker volume create mydata
Creates a named volume that can be shared between containers.
List volumes:
docker volume ls
Shows all volumes on your Docker host.
Mount a volume in a container:
docker run -v mydata:/data alpine
Mounts the mydata volume at /data inside the alpine container.
🌐 Networks
List Docker networks:
docker network ls
Shows all available networks (bridge, host, none, custom).
Create a new network:
docker network create mynetwork
Creates a custom bridge network named mynetwork.
Connect a container to a network:
docker network connect mynetwork mycontainer
Attaches a running container to the specified network.
🐝 Docker Compose
docker-compose.yml example:
version: '3.8'
services:
web:
image: nginx
ports:
- "8080:80"
Defines a service named web using nginx image, and maps port 8080 to 80.
Start services in background:
docker-compose up -d
Starts all services defined in docker-compose.yml in detached mode.
Stop services:
docker-compose down
Stops and removes all services, networks, and volumes created by docker-compose up.
Rebuild services:
docker-compose up --build
Rebuilds the images before starting the services.
🐳 Docker Swarm (for Production Clustering)
Initialize Swarm:
docker swarm init
Starts Docker Swarm mode and makes the current node the manager.
Join Swarm from another machine:
docker swarm join --token <TOKEN> <MANAGER-IP>:2377
Allows another node to join the Swarm cluster as a worker or manager.
List all nodes in Swarm:
docker node ls
Only from a manager — shows all machines in the Swarm and their roles.
Deploy a stack using Docker Compose:
docker stack deploy -c docker-compose.yml mystack
Deploys services defined in docker-compose.yml as a stack called mystack.
List deployed stacks:
docker stack ls
Displays all active stacks in the Swarm.
List services in a stack:
docker stack services mystack
Shows all services that belong to the stack mystack.
Remove a stack:
docker stack rm mystack
Deletes the stack and all its services.
📌 Always deploy stacks from the Swarm manager node.
🔐 Docker Secrets (Store Sensitive Info)
Create secret from a file:
echo "my_db_password" > db_pass.txt
docker secret create db_password db_pass.txt
Creates a secret named db_password using the contents of db_pass.txt.
Create secret using stdin:
echo "my_secret" | docker secret create my_secret -
Creates a secret from piped input, avoiding file creation.
List all secrets:
docker secret ls
Shows all defined secrets in the Swarm.
Use secrets in docker-compose.yml:
services:
app:
image: myapp
secrets:
- db_password
secrets:
db_password:
external: true
Mounts the secret inside the container at /run/secrets/db_password.
🧹 Clean Up Unused Resources
Remove stopped containers:
docker container prune
Remove dangling images (untagged):
docker image prune
Remove unused volumes:
docker volume prune
Remove everything unused (⚠️ dangerous):
docker system prune -a
👨🔧 Dockerfile Quick Reference
A sample Dockerfile for Node.js:
FROM node:18-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "start"]
Build the image:
docker build -t my-node-app .
Run the container:
docker run -p 3000:3000 my-node-app
🧪 Debugging Tips
Access container’s shell:
docker exec -it <container_id> /bin/sh
Check container environment variables:
docker exec <container_id> env
Monitor real-time resource usage:
docker stats
📚 Summary
✅ Learn daily-used Docker commands
✅ Build, run, debug, and deploy containers
✅ Use volumes, networks, secrets, and stacks
✅ Practice cleanups and write Dockerfiles
🧠 Further Reading:
Happy Dockering! 🐋✨