Elasticsearch not working (expected one argument specifying path to ES_PATH_CONF)

Infos:

  • Used Zammad version: 3.6.x
  • Used Zammad installation source: (source, package, …) as package
  • Operating system: CentOS 7
  • Browser + version: -

I have Zammad running for 9 months without interruption. Suddenly (no updating from my side involved), the customer dropdown of new tickets was not anymore working. I realised that elastic search is down and throws the following error:

[root@ticket ~]# systemctl status elasticsearch.service
● elasticsearch.service - Elasticsearch
   Loaded: loaded (/usr/lib/systemd/system/elasticsearch.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Fri 2021-02-26 12:33:26 CET; 4s ago
     Docs: https://www.elastic.co
  Process: 31770 ExecStart=/usr/share/elasticsearch/bin/systemd-entrypoint -p      ${PID_DIR}/elasticsearch.pid --quiet (code=exited, status=1/FAILURE)
 Main PID: 31770 (code=exited, status=1/FAILURE)
Feb 26 12:33:23 ticket systemd[1]: Starting Elasticsearch...
Feb 26 12:33:26 ticket systemd-entrypoint[31770]: Exception in thread "main"     java.lang.IllegalArgumentException: expected one argument specifying path to ES_PATH_CONF but     was [/etc/elasticsearch, /usr/share/elasticsearch/plugins]
Feb 26 12:33:26 ticket systemd-entrypoint[31770]: at org.elasticsearch.tools.launchers.JvmOptionsParser.main(JvmOptionsParser.java:82)
Feb 26 12:33:26 ticket systemd[1]: elasticsearch.service: main process exited, code=exited, status=1/FAILURE
Feb 26 12:33:26 ticket systemd[1]: Failed to start Elasticsearch.
Feb 26 12:33:26 ticket systemd[1]: Unit elasticsearch.service entered failed state.
Feb 26 12:33:26 ticket systemd[1]: elasticsearch.service failed.

Does anyone know this error message and a potention fix / work-around?

Thank you very much!