Using Docker Volumes for Persistent Storage

By default, data inside a container is lost when the container is removed. Volumes solve this by storing data outside the container lifecycle.

Types of Storage Mounts

• Named volumes: Managed by Docker, stored in /var/lib/docker/volumes/. Recommended for most use cases.
• Bind mounts: Map a specific host directory into the container. Useful for development or config files.

Named Volumes

# Create a volume:
docker volume create mydata

# List volumes:
docker volume ls

# Use a volume in a container:
docker run -d -v mydata:/var/lib/mysql mysql:8

# Inspect a volume (see where it is on disk):
docker volume inspect mydata

Bind Mounts

# Mount a host directory into a container:
docker run -d -v /home/user/html:/usr/share/nginx/html nginx

# Mount a config file:
docker run -d -v /etc/nginx/nginx.conf:/etc/nginx/nginx.conf:ro nginx

In Docker Compose

services:
  db:
    image: mysql:8
    volumes:
      - db_data:/var/lib/mysql       # Named volume
      - ./my.cnf:/etc/mysql/my.cnf  # Bind mount

volumes:
  db_data:

Backup a Volume

docker run --rm -v mydata:/data -v $(pwd):/backup ubuntu tar czf /backup/mydata-backup.tar.gz /data

Remove Volumes

docker volume rm mydata
docker volume prune    # Remove all unused volumes