1、Exception java.lang.RuntimeException: can not run elasticsearch as root
因为用root启动而报错，改用其他用户重新启动就可以了。
[2022-02-17T17:23:19,808][ERROR][o.e.b.Bootstrap ] [localhost..local] Exception
java.lang.RuntimeException: can not run elasticsearch as root
at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:103) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:183) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:358) [elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:166) [elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:157) [elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:77) [elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:112) [elasticsearch-cli-8.0.0.jar:8.0.0]
at org.elasticsearch.cli.Command.main(Command.java:77) [elasticsearch-cli-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:122) [elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:80) [elasticsearch-8.0.0.jar:8.0.0]
[2022-02-17T17:23:19,817][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [localhost..local] 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:170) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:157) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:77) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:112) ~[elasticsearch-cli-8.0.0.jar:8.0.0]
at org.elasticsearch.cli.Command.main(Command.java:77) ~[elasticsearch-cli-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:122) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:80) ~[elasticsearch-8.0.0.jar:8.0.0]
Caused by: java.lang.RuntimeException: can not run elasticsearch as root
at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:103) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:183) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:358) ~[elasticsearch-8.0.0.jar:8.0.0]
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:166) ~[elasticsearch-8.0.0.jar:8.0.0]
2、[WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64440}
拒绝连接，就要看看什么原因导致的不连接，查看日志。
[2022-02-19T14:37:19,865][INFO ][o.e.n.Node ] [node-1] started
[2022-02-19T14:37:19,980][INFO ][o.e.l.LicenseService ] [node-1] license [2921425f-8cbb-4a49-bc24-1e9f67ea0b2a] mode [basic] - valid
[2022-02-19T14:37:19,981][INFO ][o.e.x.s.a.Realms ] [node-1] license mode is [basic], currently licensed security realms are [reserved/reserved,file/default_file,native/default_native]
[2022-02-19T14:37:19,987][INFO ][o.e.g.GatewayService ] [node-1] recovered [2] indices into cluster_state
[2022-02-19T14:37:20,327][INFO ][o.e.c.r.a.AllocationService] [node-1] current.health="GREEN" message="Cluster health status changed from [RED] to [GREEN] (reason: [shards started [[.security-7][0], [.geoip_databases][0]]])." previous.health="RED" reason="shards started [[.security-7][0], [.geoip_databases][0]]"
[2022-02-19T14:37:20,727][INFO ][o.e.i.g.DatabaseNodeService] [node-1] successfully loaded geoip database file [GeoLite2-Country.mmdb]
[2022-02-19T14:37:20,824][INFO ][o.e.i.g.DatabaseNodeService] [node-1] successfully loaded geoip database file [GeoLite2-ASN.mmdb]
[2022-02-19T14:37:21,615][INFO ][o.e.i.g.DatabaseNodeService] [node-1] successfully loaded geoip database file [GeoLite2-City.mmdb]
[2022-02-19T14:39:02,514][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64440}
[2022-02-19T14:39:03,583][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64441}
[2022-02-19T14:39:03,610][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64444}
[2022-02-19T14:39:03,687][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64446}
[2022-02-19T14:39:04,024][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64447}
[2022-02-19T14:39:09,101][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64448}
[2022-02-19T14:39:09,130][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64452}
[2022-02-19T14:39:09,193][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64454}
[2022-02-19T14:39:39,266][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64469}
[2022-02-19T14:40:39,338][WARN ][o.e.x.s.t.n.SecurityNetty4HttpServerTransport] [node-1] received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:64506}
{"@timestamp":"2022-02-19T06:50:14.180Z", "log.level": "WARN", "message":"received plaintext http traffic on an https channel, closing connection Netty4HttpChannel{localAddress=/1.2.3.4:9200, remoteAddress=/1.2.3.4:50404}", "ecs.version": "1.2.0","service.name":"ES_ECS","event.dataset":"elasticsearch.server","process.thread.name":"elasticsearch[node-1][transport_worker][T#8]","log.logger":"org.elasticsearch.xpack.security.transport.netty4.SecurityNetty4HttpServerTransport","elasticsearch.cluster.uuid":"prPqgk72QAalYvuHmOiaog","elasticsearch.node.id":"6KgKzmiVTHaGcr0Y3DzdGQ","elasticsearch.node.name":"node-1","elasticsearch.cluster.name":"my-application"}
ES（elasticsearch）已启动成功但服务器IP却打不开_m0_64295612的博客-CSDN博客https://blog.csdn.net/m0_64295612/article/details/123019551
