Mastering Docker: Building, Managing, and Maintaining Your Own Systems

🚀 1. Understanding Docker Basics

Before diving into management, let’s recap what Docker is built around:

🧩 2. Creating Your Own System (Container)

To start an Ubuntu-based system:

docker run -it --name myubuntu ubuntu:22.04 bash

What this does:

• -it: Interactive terminal mode
• --name myubuntu: Gives your container a friendly name
• ubuntu:22.04: Uses the official Ubuntu image
• bash: Starts a shell inside it

Inside, you can use apt install, create files, and modify configurations — just like a real Linux system.

Example:

apt update && apt install nano curl
echo "Hello Docker!" > /root/test.txt

💾 3. Keeping Your Container Persistent

By default, when you exit, the container stops — but doesn’t vanish.

To reopen the same environment:

docker start -ai myubuntu

That command:

• Starts the container (start)
• Attaches you to it (-ai)

You’ll find all your files and configurations just as you left them.

To view all containers (even stopped ones):

docker ps -a

🧱 4. Saving Your Custom System as a New Image

Once you’ve customized your container, you can snapshot it into a new image:

docker commit myubuntu myubuntu:stable

Now you can spin up new containers based on your saved configuration:

docker run -it myubuntu:stable bash

It’s your personal system image — preinstalled with everything you need.

📁 5. Using Volumes for Data Persistence

If you want your data to live outside the container (so it survives even if the container is deleted):

docker run -it -v ~/dockerdata:/root --name myubuntu ubuntu:22.04 bash

This command mounts your host folder ~/dockerdata into the container’s /root directory.

Now anything you save in /root is also available on your host system.

🔄 6. Managing Containers Efficiently

Here are your key Docker management commands:

🧠 7. Pro Tip: Create a Reusable Alias

You can create a shortcut for your personal Docker VM. Add this line to your .bashrc or .zshrc:

alias ubuntuvm='docker start -ai myubuntu || docker run -it --name myubuntu ubuntu:22.04 bash'

Then just type:

ubuntuvm

and Docker will:

• Reopen your saved container if it exists, or
• Create it if it doesn’t.

Instant Linux sandbox — every time.

🧹 8. Cleaning and Maintenance

Over time, unused images and stopped containers can fill up space. Clean them up safely:

# Remove stopped containers
docker container prune

# Remove unused images
docker image prune

# Remove unused volumes
docker volume prune

Or do it all in one go:

docker system prune -a

(Warning: this removes everything not currently running!)

⚙️ 9. Advanced: Docker Compose for Multi-Service Systems

If you want to run multiple services (like a web app + database + cache), use Docker Compose.

Example docker-compose.yml:

version: "3"
services:
  web:
    image: nginx:latest
    ports:
      - "8080:80"
  db:
    image: postgres:16
    environment:
      POSTGRES_PASSWORD: secret

Then run:

docker compose up -d

You now have a complete multi-container system — manageable with a single command.

🧰 10. Backups and Version Control

You can export and import containers or images:

# Export container to a tar file
docker export myubuntu > myubuntu.tar

# Import it later
cat myubuntu.tar | docker import - myubuntu:backup

This makes your system fully portable — share it, back it up, or migrate to another machine.