运行owncloud docker容器时无法正确设置卷值

Question

我跟随this guide在我的VPS上安装了owncloud服务器，它可以正常工作。但是，当我尝试将文件卷挂载到主机服务器时出现问题。以下是我使用的docker-compose.yml文件。如果我直接使用yml文件运行docker映像，即使我手动创建了/mnt/data，我的VPS目录/mnt/data下也找不到任何owncloud数据。

version: '2.1'

volumes:
  files:
    driver: local
  mysql:
    driver: local
  backup:
    driver: local
  redis:
    driver: local

services:
  owncloud:
    image: owncloud/server:${OWNCLOUD_VERSION}
    restart: always
    ports:
      - ${HTTPS_PORT}:443
      - ${HTTP_PORT}:80
    depends_on:
      - db
      - redis
    environment:
      - OWNCLOUD_DOMAIN=${OWNCLOUD_DOMAIN}
      - OWNCLOUD_DB_TYPE=mysql
      - OWNCLOUD_DB_NAME=owncloud
      - OWNCLOUD_DB_USERNAME=owncloud
      - OWNCLOUD_DB_PASSWORD=owncloud
      - OWNCLOUD_DB_HOST=db
      - OWNCLOUD_ADMIN_USERNAME=${ADMIN_USERNAME}
      - OWNCLOUD_ADMIN_PASSWORD=${ADMIN_PASSWORD}
      - OWNCLOUD_UTF8MB4_ENABLED=true
      - OWNCLOUD_REDIS_ENABLED=true
      - OWNCLOUD_REDIS_HOST=redis
    healthcheck:
      test: ["CMD", "/usr/bin/healthcheck"]
      interval: 30s
      timeout: 10s
      retries: 5
    volumes:
      - files:/mnt/data

  db:
    image: webhippie/mariadb:latest
    restart: always
    environment:
      - MARIADB_ROOT_PASSWORD=owncloud
      - MARIADB_USERNAME=owncloud
      - MARIADB_PASSWORD=owncloud
      - MARIADB_DATABASE=owncloud
      - MARIADB_MAX_ALLOWED_PACKET=128M
      - MARIADB_INNODB_LOG_FILE_SIZE=64M
      - MARIADB_INNODB_LARGE_PREFIX=ON
      - MARIADB_INNODB_FILE_FORMAT=Barracuda
    healthcheck:
      test: ["CMD", "/usr/bin/healthcheck"]
      interval: 30s
      timeout: 10s
      retries: 5
    volumes:
      - mysql:/var/lib/mysql
      - backup:/var/lib/backup

  redis:
    image: webhippie/redis:latest
    restart: always
    environment:
      - REDIS_DATABASES=1
    healthcheck:
      test: ["CMD", "/usr/bin/healthcheck"]
      interval: 30s
      timeout: 10s
      retries: 5
    volumes:
      - redis:/var/lib/redis

因此，我尝试将files:/mnt/data行修改为files:/mnt/data:/mnt/data，然后提示以下错误。

ERROR: for ownclouddockerserver_owncloud_1  Cannot create container for service owncloud: invalid bind mount spec "ownclouddockerserver_files:/mnt/data:/mnt/data": invalid mode: /mnt/data

ERROR: for owncloud  Cannot create container for service owncloud: invalid bind mount spec "ownclouddockerserver_files:/mnt/data:/mnt/data": invalid mode: /mnt/data

有人可以帮助我找出将外部目录挂载到容器的正确方法吗？非常感激。