When experimenting with Docker containers using CLI commands, developers often create anonymous volumes (auto-generated hashed names like a1b2c3d4...) for temporary storage. However, when transitioning to Docker Compose for production deployment, these unnamed volumes pose data persistence challenges.

The most reliable approach involves creating named volumes and transferring data from anonymous volumes. Here's a step-by-step method:

# 1. Identify anonymous volumes
docker volume ls -f dangling=true

# 2. Create new named volume
docker volume create my_app_data

# 3. Run temporary container for data transfer
docker run --rm -it \
    -v source_anonymous_volume:/from \
    -v my_app_data:/to \
    alpine ash -c "cp -av /from/* /to"

After migration, reference the named volume in your docker-compose.yml:

version: '3.8'
services:
  app:
    image: your_image
    volumes:
      - my_app_data:/app/data

volumes:
  my_app_data:
    external: true

For advanced users, Docker's low-level volume commands can rename volumes directly:

# 1. Stop all containers using the volume
# 2. Find volume path
VOL_PATH=$(docker volume inspect anonymous_vol --format '{{.Mountpoint}}')

# 3. Create new named volume pointing to same data
docker volume create --driver local \
    --opt type=none \
    --opt device=$VOL_PATH \
    --opt o=bind \
    named_volume

• Always specify volumes section in Docker Compose files
• Use external: true for volumes created outside Compose
• Document volume purposes in project README
• Consider volume backup strategies

For a WordPress container with anonymous volumes:

# Transfer wp-content data
docker run --rm -v old_wp_content:/from -v wp_data:/to \
    wordpress:cli \
    cp -a /from/. /to/

When experimenting with Docker containers through CLI commands, it's common to create anonymous volumes (those with hash-like names) that later become difficult to manage. The real challenge emerges when transitioning to Docker Compose while preserving existing data.

Docker offers three volume types:

1. Anonymous volumes: Created with -v /container/path or Dockerfile VOLUME instruction
2. Named volumes: Created with -v name:/container/path
3. Host volumes: Bind mounts with -v /host/path:/container/path

Here are practical approaches to handle anonymous volume migration:

Method 1: Direct Volume Conversion

# Step 1: Identify anonymous volumes
docker volume ls -f dangling=true

# Step 2: Create new named volume
docker volume create my_app_data

# Step 3: Copy data using temporary container
docker run --rm -it \
    -v anonymous_volume_hash:/source \
    -v my_app_data:/target \
    alpine sh -c "cp -a /source/. /target/"

Method 2: Docker Compose Migration

Create a docker-compose.yml with named volumes first:

version: '3.8'
services:
  app:
    image: your_image
    volumes:
      - app_data:/data

volumes:
  app_data:

Then use this command sequence:

# Start new container with named volume
docker-compose up -d

# Find container ID with anonymous volume
docker ps -a

# Copy data between containers
docker cp old_container:/path/to/data .
docker cp data new_container:/path/to/data

• Always use named volumes in production
• Document volume usage in docker-compose files
• Regularly prune unused volumes (docker volume prune)
• Consider volume drivers for specific use cases

For a PostgreSQL container originally run with:

docker run -d \
    -e POSTGRES_PASSWORD=secret \
    -v /var/lib/postgresql/data \
    postgres:13

Migration compose file:

version: '3.8'
services:
  db:
    image: postgres:13
    environment:
      POSTGRES_PASSWORD: secret
    volumes:
      - pg_data:/var/lib/postgresql/data

volumes:
  pg_data:

Migration command:

# Find anonymous volume
OLD_VOL=$(docker volume ls -q -f dangling=true)

# Create and migrate
docker run --rm -it \
    -v $OLD_VOL:/source \
    -v pg_data:/target \
    busybox sh -c "cp -a /source/. /target/"