如何更改docker-compose中的默认弹性search密码？

Elasticsearch的官方 docker-compose.yml 镜像文档提供了这个docker-compose.yml示例：

 version: '2' services: elasticsearch1: image: docker.elastic.co/elasticsearch/elasticsearch:5.6.3 container_name: elasticsearch1 environment: - cluster.name=docker-cluster - bootstrap.memory_lock=true - "ES_JAVA_OPTS=-Xms512m -Xmx512m" ulimits: memlock: soft: -1 hard: -1 mem_limit: 1g volumes: - esdata1:/usr/share/elasticsearch/data ports: - 9200:9200 networks: - esnet elasticsearch2: image: docker.elastic.co/elasticsearch/elasticsearch:5.6.3 environment: - cluster.name=docker-cluster - bootstrap.memory_lock=true - "ES_JAVA_OPTS=-Xms512m -Xmx512m" - "discovery.zen.ping.unicast.hosts=elasticsearch1" ulimits: memlock: soft: -1 hard: -1 mem_limit: 1g volumes: - esdata2:/usr/share/elasticsearch/data networks: - esnet volumes: esdata1: driver: local esdata2: driver: local networks: esnet: 

但是，它不解释如何自定义密码。 它确实将我们引导到一个X-Pack文档页面 ，但是我拒绝相信我只是为了更改密码而烦恼。 是否有更简单，规范的方式在Docker Compose文件上configuration弹性search的自定义密码？