解決：

org.elasticsearch.bootstrap.StartupException

啟動異常，報錯資訊：

[o.e.b.ElasticsearchUncaughtExceptionHandler] [node-1] uncaught exception in thread [main]
org.elasticsearch.bootstrap.StartupException: java.lang.IllegalStateException: failed to obtain node locks, tried [[/path/to/data/my-application]] with lock id [0]; maybe these locations are not writable or multiple nodes were started without increasing [node.max_local_storage_nodes] (was [1])?
	at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:140) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:127) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:124) ~[elasticsearch-cli-6.4.2.jar:6.4.2]
	at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-6.4.2.jar:6.4.2]
	at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:93) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:86) ~[elasticsearch-6.4.2.jar:6.4.2]
Caused by: java.lang.IllegalStateException: failed to obtain node locks, tried [[/path/to/data/my-application]] with lock id [0]; maybe these locations are not writable or multiple nodes were started without increasing [node.max_local_storage_nodes] (was [1])?
	at org.elasticsearch.env.NodeEnvironment.<init>(NodeEnvironment.java:243) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.node.Node.<init>(Node.java:274) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.node.Node.<init>(Node.java:256) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:213) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:213) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:326) ~[elasticsearch-6.4.2.jar:6.4.2]
	at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:136) ~[elasticsearch-6.4.2.jar:6.4.2]
	... 6 more
 

原因：後臺已經有一個elasticsearch程序了

解決辦法：

當然是殺掉程序重啟啦：

#檢視自己埠的使用情況 
netstat -alnp | grep 9200

#強殺
kill -9 1252

然後重新啟動就好了