1、elasticsearch启动失败如下：

[root@bogon home]# /home/elasticsearch-6.3.0/bin/elasticsearch
[2019-02-11T07:15:14,874][WARN ][o.e.b.ElasticsearchUncaughtExceptionHandler] [] uncaught exception in thread [main]
org.elasticsearch.bootstrap.StartupException: java.lang.RuntimeException: can not run elasticsearch as root
    at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:140) ~[elasticsearch-6.3.0.jar:6.3.0]
    at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:127) ~[elasticsearch-6.3.0.jar:6.3.0]
    at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-6.3.0.jar:6.3.0]
    at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:124) ~[elasticsearch-cli-6.3.0.jar:6.3.0]
    at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-6.3.0.jar:6.3.0]
    at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:93) ~[elasticsearch-6.3.0.jar:6.3.0]
    at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:86) ~[elasticsearch-6.3.0.jar:6.3.0]
Caused by: java.lang.RuntimeException: can not run elasticsearch as root
    at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:104) ~[elasticsearch-6.3.0.jar:6.3.0]
    at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:171) ~[elasticsearch-6.3.0.jar:6.3.0]
    at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:326) ~[elasticsearch-6.3.0.jar:6.3.0]
    at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:136) ~[elasticsearch-6.3.0.jar:6.3.0]
    ... 6 more

原因：出于对root用户的安全保护，需要使用其他用户组进行授权启动

解决：

groupadd elsearch           
useradd elsearch -g elsearch -p elasticsearch
chown -R elsearch:elsearch  elasticsearch-6.3.0

说明： 添加用户组 elsearch  

       添加用户 elsearch 密码为 elasticsearch 到用户组 elsearch

       将elsearch安装目录授权给 用户组：用户  即 elsearch：elsearch


重新启动

su elsearch

/home/elasticsearch-6.3.0/bin/elasticsearch