问题：
查看elasticsearch日志

$ cat es-cluster.log

出现

Caused by: java.lang.IllegalStateException: failed to obtain node locks, tried [[/home/cyj/cluster/elasticsearch-5.6.2/data/es-cluster]] with lock id [0]; maybe these locations are not writable or multiple nodes were started without increasing [node.max_local_storage_nodes] (was [1])?

解决方法：
在配置文件elasticsearch.yml

vim ./config/elasticsearch.yml

最后加入node.max_local_storage_nodes: 2