Docker Bind Mounts

What Are Bind Mounts?

Bind mounts create a direct connection between a directory on your host machine and a directory inside a container. Changes in either location are immediately reflected in the other - perfect for development where you want to edit code on your host and see changes in the container.

Bind Mount vs Named Volume vs Anonymous Volume

Type	Syntax	Use Case	Persistence
Bind Mount	./local/path:/container/path	Development, config files	On host filesystem
Named Volume	volume_name:/container/path	Production data, databases	Docker-managed
Anonymous Volume	/container/path	Temporary/cache data	Docker-managed, auto-deleted

Bind Mount Examples

services:
  backend:
    volumes:
      # Development: Edit code on host, run in container
      - ./my_custom_app:/home/frappe/frappe-bench/apps/my_custom_app

      # Configuration: Override container config with host file
      - ./custom-config.json:/home/frappe/frappe-bench/sites/common_site_config.json:ro # :ro = read-only

      # Logs: Access container logs on host for debugging
      - ./logs:/home/frappe/frappe-bench/logs

      # Database (not recommended for production)
      - ./data/mysql:/var/lib/mysql

  # Named volume for production database
  db:
    volumes:
      - db_data:/var/lib/mysql # Managed by Docker, survives container deletion

volumes:
  db_data: # Define named volume

Performance Optimization (macOS/Windows)

Docker on macOS/Windows uses a VM, making bind mounts slower. Use these flags:

volumes:
  # :cached - Host writes are buffered (good for general development)
  - ./development:/home/frappe/frappe-bench:cached

  # :delegated - Container writes are buffered (best when container writes heavily)
  - ./development:/home/frappe/frappe-bench:delegated

  # :consistent - Full synchronization (slowest but safest)
  - ./development:/home/frappe/frappe-bench:consistent

Recommendation: Use :cached for most development work on macOS/Windows.