Elasticsearch启动报错：

org.elasticsearch.bootstrap.StartupException: java.lang.RuntimeException: can not run elasticsearch as root
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:163) ~[elasticsearch-6.8.9.jar:6.8.9]
        at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:150) ~[elasticsearch-6.8.9.jar:6.8.9]
        at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-6.8.9.jar:6.8.9]
        at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:124) ~[elasticsearch-cli-6.8.9.jar:6.8.9]
        at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-6.8.9.jar:6.8.9]
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:116) ~[elasticsearch-6.8.9.jar:6.8.9]
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:93) ~[elasticsearch-6.8.9.jar:6.8.9]
Caused by: java.lang.RuntimeException: can not run elasticsearch as root
        at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:103) ~[elasticsearch-6.8.9.jar:6.8.9]
        at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:170) ~[elasticsearch-6.8.9.jar:6.8.9]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:333) ~[elasticsearch-6.8.9.jar:6.8.9]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) ~[elasticsearch-6.8.9.jar:6.8.9]
        ... 6 more

        这个意思是ES不能使用root用户启动，只能通过建立其它用户来启动，可以建立一个es用户来启动：       

useradd es

su es

      切换回来后再启动es即可