Docker Series: Episode 19 — Docker Volumes & Persistent Storage Deep Dive

In previous episodes, we explored Docker Compose, Networking, and Swarm. Now it’s time to tackle one of the most important aspects of containerized applications: data persistence.

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🔹 Why Persistent Storage Matters

By default, Docker containers are ephemeral:

• Any data stored inside a container is lost when the container is removed.
• To preserve data across container restarts or upgrades, we need volumes or bind mounts.

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🔹 Types of Docker Storage

1. Volumes

• Managed by Docker
• Stored in /var/lib/docker/volumes/ on the host
• Can be shared between containers
• Ideal for databases and persistent app data

1. Bind Mounts

• Use a directory from the host machine
• Provides full control over files
• Useful for development environments

1. Tmpfs Mounts

• Stored in memory only
• Great for caching or temporary data

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🔹 Creating and Using Volumes

# Create a volume
 docker volume create my_data

# Run a container using the volume
 docker run -d -v my_data:/app/data my_app

• my_data persists even if my_app is removed.

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🔹 Bind Mount Example

docker run -d -v /host/path:/container/path my_app

• Changes on the host path are immediately reflected inside the container.

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🔹 Using Volumes in Docker Compose

version: '3'
services:
  db:
    image: postgres:latest
    volumes:
      - db_data:/var/lib/postgresql/data

volumes:
  db_data:

• Data survives container restarts and docker-compose down.

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🔹 Best Practices

• Use named volumes for production data.
• Backup volumes regularly.
• Avoid storing sensitive credentials in volumes directly; use secrets instead.
• Use read-only mounts where appropriate for security.

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🔹 Hands-On Challenge

1. Create a PostgreSQL container with a named volume.
2. Insert some data.
3. Stop and remove the container.
4. Run a new container attached to the same volume and verify the data persists.

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✅ Next Episode: Episode 20 — Docker Security Best Practices & Secrets Management