问题一：elasticsearch不能使用root启动问题解决
[root@VM-0-17-centos elasticsearch-7.13.2]# bin/elasticsearch warning: usage of JAVA_HOME is deprecated, use ES_JAVA_HOME warning: usage of JAVA_HOME is deprecated, use ES_JAVA_HOME Java HotSpot(TM) 64-Bit Server VM warning: Option UseConcMarkSweepGC was deprecated in version 9.0 and will likely be removed in a future release. [2021-07-01T13:41:40,065][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [VM-0-17-centos] 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:163) ~[elasticsearch-7.13.2.jar:7.13.2] at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:150) ~[elasticsearch-7.13.2.jar:7.13.2] at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:75) ~[elasticsearch-7.13.2.jar:7.13.2] at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:116) ~[elasticsearch-cli-7.13.2.jar:7.13.2] at org.elasticsearch.cli.Command.main(Command.java:79) ~[elasticsearch-cli-7.13.2.jar:7.13.2] at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:115) ~[elasticsearch-7.13.2.jar:7.13.2] at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:81) ~[elasticsearch-7.13.2.jar:7.13.2] Caused by: java.lang.RuntimeException: can not run elasticsearch as root at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:101) ~[elasticsearch-7.13.2.jar:7.13.2] at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:168) ~[elasticsearch-7.13.2.jar:7.13.2] at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:397) ~[elasticsearch-7.13.2.jar:7.13.2] at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) ~[elasticsearch-7.13.2.jar:7.13.2] ... 6 more uncaught exception in thread [main] java.lang.RuntimeException: can not run elasticsearch as root at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:101) at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:168) at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:397) at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:150) at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:75) at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:116) at org.elasticsearch.cli.Command.main(Command.java:79) at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:115) at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:81)
解决办法：参考此文章得以解决 https://www.cnblogs.com/gcgc/p/10297563.html
问题二：启动成功，但是外网访问失败，
[elasticsearch@VM-0-17-centos bin]$ sh elasticsearch -d warning: usage of JAVA_HOME is deprecated, use ES_JAVA_HOME warning: usage of JAVA_HOME is deprecated, use ES_JAVA_HOME Java HotSpot(TM) 64-Bit Server VM warning: Option UseConcMarkSweepGC was deprecated in version 9.0 and will likely be removed in a future release. ERROR: [1] bootstrap checks failed. You must address the points described in the following [1] lines before starting Elasticsearch. bootstrap check failure [1] of [1]: the default discovery settings are unsuitable for production use;
at least one of [discovery.seed_hosts, discovery.seed_providers, cluster.initial_master_nodes] must be configured ERROR: Elasticsearch did not exit normally - check the logs at /usr/local/elasticsearch/elasticsearch-7.13.2/logs/elasticsearch.log
解决办法：参考此文章解决 https://www.cnblogs.com/sirdong/p/11768928.html