Ao tentar executar o ./bin/elasticsearch, estou recebendo o seguinte erro:
org.elasticsearch.bootstrap.StartupException: java.lang.IllegalStateException: No match found
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:125) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:112) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.cli.SettingCommand.execute(SettingCommand.java:54) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:122) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.cli.Command.main(Command.java:88) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:89) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:82) ~[elasticsearch-5.2.0.jar:5.2.0]
Caused by: java.lang.IllegalStateException: No match found
at java.util.regex.Matcher.group(Matcher.java:536) ~[?:1.8.0_171]
at org.elasticsearch.monitor.os.OsProbe.getControlGroups(OsProbe.java:216) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.monitor.os.OsProbe.getCgroup(OsProbe.java:414) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.monitor.os.OsProbe.osStats(OsProbe.java:466) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.monitor.os.OsService.<init>(OsService.java:45) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.monitor.MonitorService.<init>(MonitorService.java:45) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.node.Node.<init>(Node.java:345) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.node.Node.<init>(Node.java:232) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.bootstrap.Bootstrap$6.<init>(Bootstrap.java:241) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:241) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:333) ~[elasticsearch-5.2.0.jar:5.2.0]
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:121) ~[elasticsearch-5.2.0.jar:5.2.0]
... 6 moreVersão do elasticsearch: 5.2.0
Versão do SO: Ubuntu 18.04
Encontrei esse link que fala do problema, pelo que entendi, na versão 5.3.1 o problema foi corrigido.
Irei fazer o curso com essa versão, caso eu não consiga realizar algo devido a versão, eu coloco aqui.