🐳 Docker Beginner to Advanced – Single Markdown

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Feature	VMs	Containers
Virtualizes	Hardware	OS / Runtime
OS Requirement	Own OS per VM	Shared host OS
Size	Heavy (GBs)	Light (MBs)
Boot Time	Minutes	Seconds
Performance	Moderate	Near-native
Isolation	Strong	Moderate–Strong
Portability	Good	Excellent
Use Case	Monolithic / Legacy	Microservices / Cloud

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Real-World Examples

VMs Used In:

• AWS EC2, Azure VM
• Running Windows + Linux on same server
• Banking and enterprise systems

Containers Used In:

• Docker
• Kubernetes
• Microservices like Netflix, Uber, Spotify
• CI/CD pipelines

What Is Docker?

Docker is a platform that lets you build, run, and manage applications in lightweight containers.

Containers include everything needed to run apps — code, libraries, runtime, and configs.

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1. Install Docker

Check Docker version

docker --version

If not installed → download from Link

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Run a container in background

docker run -d -p 80:80 docker/getting-started

Meaning:

• -d → detached mode
• -p 80:80 → hostPort:containerPort
• docker/getting-started → image name

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Run container in foreground interactive

docker run -it -p 8001:8080 --name my-nginx nginx

Meaning:

• -it → interactive shell
• --name my-nginx → give name, if not random name is given
• nginx → image name

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2. Basic Docker Commands

Command	Use
docker images	List images
docker rm <name/id>	Remove container
docker logs <name/id>	View logs
docker exec -it <name/id> bash	Enter container shell

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3. Containers

• Start a container

docker start <name/id>

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• Stop a container

docker stop <name/id>

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• Restart a container

docker restart <name/id>

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• Stop a container

docker stop <name/id>

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• Kill a container

docker kill <name/id>

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• Clean All

Cleans up dangling images, containers, volumes, and networks (ie, not associated with a container)

docker system prune

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Additionally, remove any stopped containers and all unused images (not just dangling images)

docker system prune -a

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3. Information

Example	Description
docker ps	List running containers
docker ps -a	List all containers
`docker logs <name/id>	Container Logs
docker inspect <name/id>	Inspecting Containers
docker events <name/id>	Containers Events
docker port <name/id>	Public Ports
docker top <name/id>	Running Processes
docker stats <name/id>	Container Resource Usage
docker diff <name/id>	Lists the changes made to a container.

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4. Update

1. Create Container (without running)

docker create --name my_redis --expose 6379 redis

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2. Rename a existing container

docker rename oldName newName

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3. Update Resources

docker update --cpu-shares 512 -m 300M <name/id>

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5. Manipulating

Example	Description
docker images	Listing images
docker rmi nginx	Removing an image
docker load < ubuntu.tar.gz	Loading a tarred repository
docker load --input ubuntu.tar	Loading a tarred repository
docker save busybox > ubuntu.tar	Save an image to a tar archive
docker history	Showing the history of an image
docker commit nginx	Save a container as an image.
docker tag nginx eon01/nginx	Tagging an image
docker push eon01/nginx	Pushing an image

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6. Docker HUB

docker login
docker push myrepo/nginx

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• Commit Container → Image

docker commit containerName newImageName

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• docker search

docker search nginx

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• logout

docker logout

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7. Build Your Own Image (Dockerfile)

docker build -t myapp .

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8. Docker Networking

List Networks

docker network ls

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Inspect Network

docker network inspect MyNetwork

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Create Network

docker network create MyNetwork

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Run Container With Network

docker run -d --network MyNetwork nginx

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Connect Running Container

docker network connect MyNetwork my-nginx

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Disconnect

docker network disconnect MyNetwork my-nginx

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Remove Network

docker network rm MyNetwork

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9.Volumes (Persistent Storage)

1. Create Volume

docker volume create myVolume

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2. Attach Volume

docker run -d -v myVolume:/data nginx

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3. List Volumes

docker volume ls

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4. Remove Unused

docker volume prune

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9.Adding DNS to Docker Containers

You can control how containers resolve domain names using Docker DNS options.

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Add DNS While Running a Container

Use the --dns flag with docker run

docker run -it --name myapp --dns 8.8.8.8 --dns 1.1.1.1 ubuntu bash

Meaning:

• 8.8.8.8 → Google DNS
• 1.1.1.1 → Cloudflare DNS
• Multiple DNS servers allowed (Docker tries in order)

🔎 Check DNS Inside Container

cat /etc/resolv.conf

You will see entries like:
nameserver 8.8.8.8
nameserver 1.1.1.1

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