This is all the elasticsearch log folder
sudo ls -l /var/log/elasticsearch/
total 788
-rw-r--r-- 1 elasticsearch elasticsearch 0 Jun 6 06:39 elasticsearch_audit.json
-rw-r--r-- 1 elasticsearch elasticsearch 0 Jun 6 06:39 elasticsearch_deprecation.json
-rw-r--r-- 1 elasticsearch elasticsearch 0 Jun 6 06:39 elasticsearch_deprecation.log
-rw-r--r-- 1 elasticsearch elasticsearch 0 Jun 6 06:39 elasticsearch_index_indexing_slowlog.json
-rw-r--r-- 1 elasticsearch elasticsearch 0 Jun 6 06:39 elasticsearch_index_indexing_slowlog.log
-rw-r--r-- 1 elasticsearch elasticsearch 0 Jun 6 06:39 elasticsearch_index_search_slowlog.json
-rw-r--r-- 1 elasticsearch elasticsearch 0 Jun 6 06:39 elasticsearch_index_search_slowlog.log
-rw-r--r-- 1 elasticsearch elasticsearch 24207 Jun 6 06:43 elasticsearch.log
-rw-r--r-- 1 elasticsearch elasticsearch 46505 Jun 6 06:43 elasticsearch_server.json
-rw-r--r-- 1 elasticsearch elasticsearch 270304 Jun 6 07:05 gc.log
-rw-r--r-- 1 elasticsearch elasticsearch 287918 Jun 6 06:40 gc.log.00
-rw-r--r-- 1 elasticsearch elasticsearch 168936 Jun 6 06:41 gc.log.01
indent preformatted text by 4 spaces
I tail the first 10 line from gc.log
yclin1822@elastic:~$ sudo tail -10 /var/log/elasticsearch/gc.log
[2019-06-06T07:07:59.369+0000][1997][safepoint ] Leaving safepoint region
[2019-06-06T07:07:59.369+0000][1997][safepoint ] Total time for which application threads were stopped: 0.0001376 seconds, Stopping threads took: 0.0000380 seconds
[2019-06-06T07:08:16.371+0000][1997][safepoint ] Application time: 17.0026062 seconds
[2019-06-06T07:08:16.371+0000][1997][safepoint ] Entering safepoint region: Cleanup
[2019-06-06T07:08:16.372+0000][1997][safepoint ] Leaving safepoint region
[2019-06-06T07:08:16.372+0000][1997][safepoint ] Total time for which application threads were stopped: 0.0001488 seconds, Stopping threads took: 0.0000447 seconds
[2019-06-06T07:09:07.379+0000][1997][safepoint ] Application time: 51.0073445 seconds
[2019-06-06T07:09:07.379+0000][1997][safepoint ] Entering safepoint region: Cleanup
[2019-06-06T07:09:07.379+0000][1997][safepoint ] Leaving safepoint region
[2019-06-06T07:09:07.379+0000][1997][safepoint ] Total time for which application threads were stopped: 0.0001421 seconds, Stopping threads took: 0.0000459 seconds