Volumes

Bind mounts vs Named volumes

In Docker Compose, a small change in syntax completely changes where your data is stored.

Bind Mounts (Local Folders)

Managed in the repo.

volumes:
  - ./foo:/root/bar/foo

As ./foo (not dotslash is needed) or ~/foo or /foo.

Named volumes

Managed by Docker. Persists if you delete the repo.

If you omit the ./, Docker assumes you are referencing a Named Volume.

services:
  foo:
    volumes:
      - foo:/root/bar/foo

volumes:
  foo:

Summary

Feature	Named Volume	Bind Mount
Location	Managed by Docker	Your project folder (./data)
Performance	Native speed	Slower (especially on Mac/Win)
Ease of Use	Set it and forget it	Can have permission issues
Best For	Production, Databases	Config files, Source code

Examples

Samples from compose file docs.

Short syntax

• docker-compose.yml

    volumes:
      # Just specify a path and let the Engine create a volume
      - /var/lib/mysql
  
      # Specify an absolute path mapping
      - /opt/data:/var/lib/mysql
  
      # Path on the host, relative to the Compose file
      - ./cache:/tmp/cache
  
      # User-relative path
      - ~/configs:/etc/configs/:ro
  
      # Named volume
      - datavolume:/var/lib/mysql
  

Named volumes

• docker-compose.yml

    services:
      web:
        image: nginx:alpine
          
        volumes:
          - type: volume
            source: mydata
            target: /data
            volume:
              nocopy: true
                
          - type: bind
            source: ./static
            target: /opt/app/static
  
      db:
        image: postgres:latest
          
        volumes:
          - "/var/run/postgres/postgres.sock:/var/run/postgres/postgres.sock"
          - "dbdata:/var/lib/postgresql/data"
  
    volumes:
      mydata:
      dbdata:
  

Another example, from the Docker Compose file specification.

• docker-compose.yml

    services:
      backend:
        image: awesome/backend
          
        volumes:
          - type: volume
            source: db-data
            target: /data
            volume:
              nocopy: true
                
          - type: bind
            source: /var/run/postgres/postgres.sock
            target: /var/run/postgres/postgres.sock
  
    volumes:
      db-data: