Docker Volumes & Storage

Introduction to Docker Volumes

By default, Docker containers are ephemeral — meaning any data stored inside the container is lost once it stops. To persist data, Docker offers:

• Volumes: Managed by Docker, stored in /var/lib/docker/volumes.
• Bind Mounts: Direct mapping between host paths and container paths.

Creating and Managing Volumes

docker volume create my_volume

To list volumes:

docker volume ls

Inspect volume details:

docker volume inspect my_volume

Remove a volume:

docker volume rm my_volume

Using Volumes in Containers

Mount a volume into a container using the -v flag:

docker run -d -v my_volume:/app/data myapp

This mounts my_volume to /app/data inside the container.

Bind Mounts

Bind mounts map a specific path on the host to a container path:

docker run -d -v /home/user/app:/app myapp

• Great for development environments where you want live updates in the container.
• Risky in production due to tight host coupling.

Volumes in Docker Compose

services:
  web:
    image: myapp
    volumes:
      - app_data:/app/data

volumes:
  app_data:

This ensures volume persistence across service restarts and rebuilds.

Best Practices for Storage

• Use named volumes for persistence over anonymous volumes.
• Never hardcode host paths unless required.
• Use docker volume prune periodically to clean up unused volumes.
• Ensure secure permissions on host folders if using bind mounts.

Managing data properly with Docker volumes and mounts is essential for stateful applications. Volumes provide a safe, flexible, and scalable way to ensure data persistence in containerized systems.