Elasticsearch is an open source full text search and analytics engine tool used in storing, searching and analysing big volumes of data real time. It supports RESTful operations i.e you can use HTTP methods in combisnation with a HTTP URI to manipulate data. This guide demonstrates how to install and configure Elasticsearch on Rocky and AlmaLinux.

Elastic search is popular due to its amazing features such as:

1. Scalability and resiliency.
2. Easy to use.
3. REST APIs.
4. Has improved security.
5. Automatic node recovery.
6. Automatic data balancing.

For Cluster setup setup checkout: Setup Three Node Elasticsearch Cluster on Rocky Linux 8 Using Ansible

Step 1: Install Java runtime

One of the dependencies that Elasticsearch uses is Java. In this guide, we will install Java OpenJDK 17.

sudo dnf install java-17-openjdk-devel

Dependency tree:

...
Transaction Summary
================================================================================
Install  3 Packages

Total download size: 43 M
Installed size: 177 M
Is this ok [y/N]: y

Verify the installed version.

$ java -version
openjdk version "17.0.11" 2024-04-16 LTS
OpenJDK Runtime Environment (Red_Hat-17.0.11.0.9-3) (build 17.0.11+9-LTS)
OpenJDK 64-Bit Server VM (Red_Hat-17.0.11.0.9-3) (build 17.0.11+9-LTS, mixed mode, sharing)

Step 2: Install Elasticsearch

First install GPG key fro Elasticsearch rpm packages.

sudo rpm --import https://artifacts.elastic.co/GPG-KEY-elasticsearch

Second, create a yum repository for Elasticsearch as below:

sudo vi /etc/yum.repos.d/elasticsearch.repo

In the file, paste the below lines:

• Elasticsearch 7.x

[elasticsearch-7.x]
name=Elasticsearch repository for 7.x packages
baseurl=https://artifacts.elastic.co/packages/7.x/yum
gpgcheck=1
gpgkey=https://artifacts.elastic.co/GPG-KEY-elasticsearch
enabled=1
autorefresh=1
type=rpm-md

• Elasticsearch 8.x

[elastic-8.x]
name=Elastic repository for 8.x packages
baseurl=https://artifacts.elastic.co/packages/8.x/yum
gpgcheck=1
gpgkey=https://artifacts.elastic.co/GPG-KEY-elasticsearch
enabled=1
autorefresh=1
type=rpm-md

With the created repository file, we an now install Elasticsearch using the below command:

sudo dnf install elasticsearch

Dependency tree:

...
Transaction Summary
================================================================================
Install  1 Package

Total download size: 312 M
Installed size: 520 M
Is this ok [y/N]: y

Step 3: Configure Elasticsearch

With a complete installation, we edit the configurations in /etc/elasticsearch/elasticsearch.yml

sudo vi /etc/elasticsearch/elasticsearch.yml

Set the node.name and cluster.name, they are set by finding these lines and uncomment them then edit them as below.

Edit the file as below:

cluster.name: my new cluster
     node.name: node-1
     path.data: /var/lib/elasticsearch
     network.host: 127.0.0.1

You can also specifiy a different path.data by uncommenting the path.data and changing the directory as

path.data: /path/to/media

Start and enable Elasticsearch service

sudo systemctl enable --now elasticsearch

Check the status of the service;

systemctl status elasticsearch

Step 4: Test Elasticsearch installation

Now we test and see if the installed Elasticsearch is working. Elasticsearch should be running on port 9200. Test this using the curl command as below.

• Elasticsearch 7

curl -X GET 'http://localhost:9200'

• Elasticsearch 8

sudo curl --cacert /etc/elasticsearch/certs/http_ca.crt -u elastic https://localhost:9200

With the above response, Elasticserach is working properly on port 9200

Step 5: Using Elasticsearch

Here we will add we add some data and use manual queries.

Using CURL, we will add this entry:

curl -H 'Content-Type: application/json' -X POST 'http://localhost:9200/tutorial/helloworld/1' -d '{ "message": "Hello World!" }'

Output:

{"_index":"tutorial","_type":"helloworld","_id":"1","_version":1,"result":"created","_shards":{"total":2,"successful":1,"failed":0},"_seq_no":0,"_primary_term":1

We sent a HTTP POST request to the Elasticsearch server with the URI tuitorial/helloworld/1. There are parameters in the URI, tuitorial is the index of the data, helloworld is the type and 1 is the ID of the entry

Now lets retrieve the entry using HTTP GET request

curl -X GET 'http://localhost:9200/tutorial/helloworld/1'

Output:

{"_index":"tutorial","_type":"helloworld","_id":"1","_version":3,"_seq_no":2,"_primary_term":1,"found":true,"_source":{ "message": "Hello World!" }

We can modify the existing entry using HTTP PUT as below

curl -H 'Content-Type: application/json' -X PUT 'localhost:9200/tutorial/helloworld/1?pretty' -d '
{
  "message": "Welcome Back!"
}'

Output:

{
  "_index" : "tutorial",
  "_type" : "helloworld",
  "_id" : "1",
  "_version" : 4,
  "result" : "updated",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 3,
  "_primary_term" : 1
}

From the output, we have modified the message to “Welcome Back!” and the version number now increases to 2

The output of GET can be changed to a more readable/human-language by using the pretty argument

curl -X GET 'http://localhost:9200/tutorial/helloworld/1?pretty'

Output:

{
  "_index" : "tutorial",
  "_type" : "helloworld",
  "_id" : "1",
  "_version" : 4,
  "_seq_no" : 3,
  "_primary_term" : 1,
  "found" : true,
  "_source" : {
    "message" : "Welcome Back!"
  }
}

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