我也遇到这个问题了,先确认下在postman里发put请求建索引能否成功,我这边直接报
"reason": "unknown setting [index.content] please check that any required plugins are installed, or check the breaking changes documentation for removed settings"
感觉可能是我的elasticSearch启动时,有的插件没加载成功,重新启动了一下,就解决了