Data Persistence: Managing Docker Volumes and Bind Mounts

By default, the filesystem inside a running container is temporary. When a container is deleted, any data created or modified inside it is lost. To persist data (like databases or upload folders), Docker uses Volumes and Bind Mounts.

1. Comparing Storage Options

graph TD
    A[Docker Storage Models] --> B[Named Volumes: Managed by Docker /var/lib/docker/volumes]
    A --> C[Bind Mounts: Mapped directly to specific host folders]

• Named Volumes: Docker manages where the volume data is stored on your host machine. They are the recommended way to persist database data (like PostgreSQL or MySQL).
• Bind Mounts: Mapped directly to a specific folder on your host machine. They are useful for local development, allowing you to mount your source code directory so changes are reflected in the container immediately.

2. Using Volumes and Bind Mounts

Mounting Named Volumes

To run a database container and mount a named volume called db-data:

# Mount db-data to the Postgres data storage path
docker run -d -e POSTGRES_PASSWORD=secret -v db-data:/var/lib/postgresql/data postgres

Mounting Bind Mounts

To map your active project directory into a web server container:

# Map host folder /Users/app to container path /app
docker run -d -p 8080:80 -v /Users/app:/usr/share/nginx/html nginx

3. Managing Volumes via CLI

Use these commands to manage volumes on your system:

# Create a named volume
docker volume create uploads-data

# List all volumes
docker volume ls

# Delete a volume
docker volume rm uploads-data

# Delete all unused volumes
docker volume prune