問題一：elasticsearch不能使用root啟動問題解決

[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)

解決辦法：參考此文章得以解決https://www.cnblogs.com/gcgc/p/10297563.html

問題二：啟動成功，但是外網訪問失敗，

[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

解決辦法：參考此文章解決 https://www.cnblogs.com/sirdong/p/11768928.html