centos 啓動 elasticsearch 失敗集

環境： elasticsearch 6.5.2, java

連接失敗

啓動後當你 使用 curl http://localhost:9200 測試時，得到如下結果

Curl: (7) Failed connect to localhost:9200; Connection refused

這個問題一般是其他問題導致的，請看你啓動日誌，如果用的管理服務工具來啓動的，則看它的日誌，我這裏是 systemctl ，然後命令以及輸出結果是

root@localhost ~]# systemctl status elasticsearch
● elasticsearch.service - Elasticsearch
   Loaded: loaded (/usr/lib/systemd/system/elasticsearch.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Mon 2018-12-10 15:26:08 EST; 11min ago
     Docs: http://www.elastic.co
  Process: 22651 ExecStart=/usr/share/elasticsearch/bin/elasticsearch -p ${PID_DIR}/elasticsearch.pid --quiet (code=exited, status=1/FAILURE)
 Main PID: 22651 (code=exited, status=1/FAILURE)

Dec 10 15:26:08 localhost.localdomain systemd[1]: Started Elasticsearch.
Dec 10 15:26:08 localhost.localdomain systemd[1]: Starting Elasticsearch...
Dec 10 15:26:08 localhost.localdomain elasticsearch[22651]: which: no java in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin)
Dec 10 15:26:08 localhost.localdomain elasticsearch[22651]: could not find java; set JAVA_HOME or ensure java is in PATH
Dec 10 15:26:08 localhost.localdomain systemd[1]: elasticsearch.service: main process exited, code=exited, status=1/FAILURE
Dec 10 15:26:08 localhost.localdomain systemd[1]: Unit elasticsearch.service entered failed state.
Dec 10 15:26:08 localhost.localdomain systemd[1]: elasticsearch.service failed.

沒有發現 java 環境

如上圖錯誤細節，告訴我們沒有java 相關環境，首先確認下 是否能 運行 java，不過不能，請配置Java環境然後source,具體請百度。

解決了java 環境問題，還需要將 java 可執行命令 放到 /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin 下的任意一箇中， 這裏放到 /usr/bin

命令： ln -s /usr/local/jdk1.8.0_XXX/bin/java /usr/bin/java