In ELK, although Logstash and Kibana act as an interface to talk to Elasticsearch indices, it's still necessary to understand how Logstash and Kibana makes use of Elasticsearch RESTful APIs to perform various operations, such as creating and managing indices, storing and retrieving the documents, and forming various types of search queries around the indices. It is also often useful to know how to delete indices.
As we already know, Elasticsearch provides an extensive API to perform various operations. The generic syntax of querying the cluster from the command line is as follows:
$curl -X<VERB> '<PROTOCOL>://<HOST>:<PORT>/<PATH>/<OPERATION_NAME>?<QUERY_STRING>' -d '<BODY>'
Let's understand various parts of this ...