I broke ES while upgrading from 2.3 to 5.6 :(

I'm on CentOS7, using Elastic Search for Graylog. I'm a rookie, learning as I go. I upgraded ES from 2.3 to 5.6 using yum. When I start ES now it fails and doesn't give me any useful feedback.

[root@locker2 ~]# systemctl status elasticsearch
● elasticsearch.service - Elasticsearch
Loaded: loaded (/usr/lib/systemd/system/elasticsearch.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Sat 2019-07-27 19:22:44 EDT; 5min ago
Docs: http://www.elastic.co
Process: 1902 ExecStart=/usr/share/elasticsearch/bin/elasticsearch -p {PID_DIR}/elasticsearch.pid --quiet -Edefault.path.logs={LOG_DIR} -Edefault.path.data={DATA_DIR} -Edefault.path.conf={CONF_DIR} (code=exited, status=1/FAILURE)
Process: 1898 ExecStartPre=/usr/share/elasticsearch/bin/elasticsearch-systemd-pre-exec (code=exited, status=0/SUCCESS)
Main PID: 1902 (code=exited, status=1/FAILURE)

Jul 27 19:22:38 locker2 systemd[1]: Starting Elasticsearch...
Jul 27 19:22:38 locker2 systemd[1]: Started Elasticsearch.
Jul 27 19:22:44 locker2 systemd[1]: elasticsearch.service: main process exited, code=exited, status=1/FAILURE
Jul 27 19:22:44 locker2 systemd[1]: Unit elasticsearch.service entered failed state.
Jul 27 19:22:44 locker2 systemd[1]: elasticsearch.service failed.

How can I troubleshoot this? How do I get ES to produce some useful logs? Where are they located? Is there a debug mode?

Thanks in advance


please see our documentation when installing Elasticsearch from the rpm package. Among other things you'll find the directory layout documented there which says that the default path for the log files is in /var/log/elasticsearch.