🚀 Docker for DevOps – Part 3: Networking, Volumes & Docker Compose (Beginner to Advanced)

In our previous blogs, we covered:

• Part 1: Docker Basics, Architecture & Commands

• Part 2: Dockerfile & Docker Image Best Practices

Today, we’ll dive deeper into Docker Networking, Volumes, and Docker Compose – essential concepts for running real-world applications in containers.

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📌 Why is Networking Important in Docker?

When you run multiple containers (for example, an app container and a database container), they need to communicate with each other. Docker provides virtual networking that isolates containers but also allows controlled communication.

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🔹 Types of Docker Networks

Docker provides several network drivers:

1. Bridge Network (Default)

• Default network for standalone containers.

• Containers can communicate using container names.

• IPs are private (not accessible from outside).

✅ Command to list networks:

docker network ls

✅ Create a custom bridge network:

docker network create my_bridge_network

✅ Run containers on this network:

docker run -d --name container1 --network my_bridge_network nginx
docker run -d --name container2 --network my_bridge_network alpine sleep 5000

✅ Test connectivity:

docker exec -it container2 ping container1

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2. Host Network

• Shares the host machine’s network stack.

• No isolation from the host.

✅ Run container with host network:

docker run -d --network host nginx

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3. None Network

• No networking for the container.

• Useful for security-sensitive workloads.

✅ Run container with no network:

docker run -d --network none nginx

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4. Overlay Network

• Used in Docker Swarm or multi-host setups.

• Allows containers on different hosts to communicate.

✅ Create overlay network:

docker network create --driver overlay my_overlay

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📌 Inspecting a Network

docker network inspect bridge

This will show connected containers, IP addresses, and subnet details.

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🔍 Example: Web App + Database with Networking

# Create network
docker network create app_network

# Run MySQL container
docker run -d --name mydb --network app_network -e MYSQL_ROOT_PASSWORD=root mysql:8

# Run App container
docker run -d --name myapp --network app_network myapp-image

Now myapp can connect to mydb using hostname mydb.

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📌 Docker Volumes – Persisting Data

By default, when you remove a container, data is lost. Volumes solve this problem by storing data outside the container’s filesystem.

Types of Volumes

1. Anonymous Volumes – Created automatically by Docker.

2. Named Volumes – You name it and reuse it.

3. Bind Mounts – Mount a specific host directory into the container.

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Create & Use a Named Volume

docker volume create my_volume

docker run -d --name mysql_container \
  --mount source=my_volume,target=/var/lib/mysql \
  -e MYSQL_ROOT_PASSWORD=root mysql:8

✅ List volumes:

docker volume ls

✅ Inspect a volume:

docker volume inspect my_volume

✅ Remove a volume:

docker volume rm my_volume

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📌 Docker Compose – Multi-Container Setup Made Easy

Instead of running multiple docker run commands, Docker Compose lets you define all services in one file.

Example docker-compose.yml

version: '3'
services:
  db:
    image: mysql:8
    environment:
      MYSQL_ROOT_PASSWORD: root
    volumes:
      - db_data:/var/lib/mysql
    networks:
      - app_network

  app:
    image: myapp-image
    depends_on:
      - db
    networks:
      - app_network

networks:
  app_network:

volumes:
  db_data:

✅ Start containers:

docker-compose up -d

✅ Stop containers:

docker-compose down

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🔥 Important Docker Commands for Networking & Volumes

# List networks
docker network ls

# Create network
docker network create my_network

# Connect container to network
docker network connect my_network my_container

# List volumes
docker volume ls

# Create volume
docker volume create my_volume

# Remove volume
docker volume rm my_volume

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🧠 Common Docker Interview Questions (Part 3)

1. What is the difference between bridge and host network in Docker?

• Bridge: Isolated network; containers communicate using IP/hostname.

• Host: Container shares host’s network; no isolation.

2. How can two containers communicate with each other?

• By connecting both to the same Docker network and using container names.

3. What is the difference between a Docker Volume and a Bind Mount?

• Volume: Managed by Docker, stored in /var/lib/docker/volumes/.

• Bind Mount: Maps a host directory into a container.

4. What is Docker Compose and why is it used?

• Tool to define and manage multi-container applications using a YAML file.

5. How do you persist MySQL data in Docker?

• Use Docker Volumes or Bind Mounts.

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✅ What’s Next?

In the next part, we will cover Docker Compose in depth with real-world examples.

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👉 Previous Parts:

• Part 1: Docker Basics, Architecture & Commands

• Part 2: Dockerfile & Image Best Practices