Compose Volumes

Volumes provide persistent storage for containers. Data in volumes persists even when containers are removed, making them essential for databases and stateful applications.

Volume Types

Type	Persistence	Performance	Use Case
Named Volume	✅ Persists	Fast	Databases, production
Bind Mount	✅ Persists	Host dependent	Development, config
tmpfs	❌ Memory only	Very fast	Temporary/sensitive data

Named Volumes

Named volumes are managed by Docker and persist data across container lifecycles.

services:
  db:
    image: postgres:16-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data

  redis:
    image: redis:7-alpine
    volumes:
      - redis_data:/data

volumes:
  postgres_data:
  redis_data:

services:
  db:
    image: postgres:16-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data

volumes:
  postgres_data:
    # Custom name
    name: my-postgres-data
    
    # Volume driver
    driver: local
    
    # Driver options
    driver_opts:
      type: none
      device: /data/postgres
      o: bind
    
    # Labels
    labels:
      - "com.example.project=myapp"
      - "com.example.environment=production"

# Use pre-existing volume
services:
  db:
    volumes:
      - existing_volume:/var/lib/postgresql/data

volumes:
  existing_volume:
    external: true
    name: my-existing-volume

# Create external volume first
docker volume create my-existing-volume

Bind Mounts

Bind mounts map a host directory to a container path. Ideal for development workflows.

services:
  web:
    build: .
    volumes:
      # Short syntax: HOST:CONTAINER
      - ./src:/app/src
      
      # Read-only
      - ./config:/app/config:ro
      
      # Long syntax
      - type: bind
        source: ./logs
        target: /app/logs
        read_only: false

  nginx:
    image: nginx:alpine
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
      - ./html:/usr/share/nginx/html:ro

Development Hot Reload

services:
  app:
    build:
      context: .
      target: development
    volumes:
      # Mount source code
      - .:/app
      # Preserve node_modules from image
      - /app/node_modules
    command: npm run dev

Node Modules

Exclude node_modules from bind mount to use the container's dependencies instead of host's.

tmpfs Mounts

tmpfs mounts store data in memory. Data is lost when the container stops.

services:
  app:
    image: myapp:latest
    tmpfs:
      # Simple
      - /tmp
      
      # With options
      - /run:size=100M,uid=1000
    
    # Alternative long syntax
    volumes:
      - type: tmpfs
        target: /app/cache
        tmpfs:
          size: 100000000  # 100MB
          mode: 1777

Use cases for tmpfs:

Temporary files
Sensitive data (credentials, tokens)
High-performance caching

Volume Syntax Comparison

services:
  app:
    volumes:
      # Named volume
      - data:/app/data
      
      # Bind mount
      - ./src:/app/src
      
      # Read-only
      - ./config:/app/config:ro
      
      # Anonymous volume
      - /app/temp

services:
  app:
    volumes:
      # Named volume
      - type: volume
        source: data
        target: /app/data
        volume:
          nocopy: true
      
      # Bind mount
      - type: bind
        source: ./src
        target: /app/src
        bind:
          create_host_path: true
      
      # tmpfs
      - type: tmpfs
        target: /app/cache
        tmpfs:
          size: 104857600

volumes:
  data:

Volume Options

Option	Description	Example
`ro`	Read-only	`./config:/app/config:ro`
`rw`	Read-write (default)	`./data:/app/data:rw`
`cached`	Host authoritative (macOS)	`./src:/app/src:cached`
`delegated`	Container authoritative	`./data:/app/data:delegated`
`consistent`	Full consistency (slow)	`./src:/app/src:consistent`

Database Volume Patterns

services:
  postgres:
    image: postgres:16-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql:ro
    environment:
      - POSTGRES_PASSWORD=secret

volumes:
  postgres_data:

services:
  mysql:
    image: mysql:8
    volumes:
      - mysql_data:/var/lib/mysql
      - ./init:/docker-entrypoint-initdb.d:ro
      - ./my.cnf:/etc/mysql/conf.d/my.cnf:ro
    environment:
      - MYSQL_ROOT_PASSWORD=secret

volumes:
  mysql_data:

services:
  mongo:
    image: mongo:7
    volumes:
      - mongo_data:/data/db
      - mongo_config:/data/configdb
    environment:
      - MONGO_INITDB_ROOT_USERNAME=root
      - MONGO_INITDB_ROOT_PASSWORD=secret

volumes:
  mongo_data:
  mongo_config:

services:
  redis:
    image: redis:7-alpine
    command: redis-server --appendonly yes
    volumes:
      - redis_data:/data

volumes:
  redis_data:

services:
  # Generator writes to shared volume
  generator:
    image: myapp:latest
    command: generate-reports
    volumes:
      - reports:/app/output

  # Web server reads from shared volume
  nginx:
    image: nginx:alpine
    volumes:
      - reports:/usr/share/nginx/html:ro
    depends_on:
      - generator

volumes:
  reports:

Backup and Restore

# Backup volume to tar file
docker run --rm \
  -v postgres_data:/data \
  -v $(pwd):/backup \
  alpine tar cvf /backup/postgres_backup.tar /data

# Restore volume from tar file
docker run --rm \
  -v postgres_data:/data \
  -v $(pwd):/backup \
  alpine sh -c "cd /data && tar xvf /backup/postgres_backup.tar --strip 1"

Database-specific Backup

services:
  db:
    image: postgres:16-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data

  backup:
    image: postgres:16-alpine
    volumes:
      - ./backups:/backups
    command: >
      sh -c "pg_dump -h db -U postgres mydb > /backups/backup_$$(date +%Y%m%d).sql"
    depends_on:
      - db
    profiles:
      - backup

volumes:
  postgres_data:

# Run backup
docker compose --profile backup run --rm backup

Volume Commands

# List volumes
docker volume ls

# Inspect volume
docker volume inspect postgres_data

# Create volume
docker volume create my-volume

# Remove volume
docker volume rm my-volume

# Remove unused volumes
docker volume prune

# Remove all unused volumes (including named)
docker volume prune -a

Best Practices

Common Issues

Issue	Cause	Solution
Permission denied	UID mismatch	Set correct ownership or user
Data not persisting	Using anonymous volume	Use named volume
Slow on macOS	File sync overhead	Use `:cached` or `:delegated`
Volume not found	Typo in volume name	Check volume names

Use named volumes for databases

Use bind mounts for development

Make config files read-only

Use tmpfs for sensitive data

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