Zookeeper之Error contacting service. It is probably not running.

安装ZooKeeper时，无论是修改zoo.cfg；还是myid，都检查了几遍都没有错误。但是开启Zookeeper服务时出现：

Error contacting service. It is probably not running.

后来查看日志发现，是我的hosts文件，之前手误出错了，变成了27.0.0.1 

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4