Install Elastic search 5.x in ubuntu 20, 18, 16

Look for OpenJDK in APT

sudo apt search openjdk

Install OpenJDK 8

sudo apt-get install openjdk-8-jdk

Add the proper GPG key for ElasticSearch

wget -qO - https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add -

Make sure to install/update transport

sudo apt-get install apt-transport-https

Save the repo definition

echo "deb https://artifacts.elastic.co/packages/5.x/apt stable main" | sudo tee -a /etc/apt/sources.list.d/elastic-5.x.list

Update APT and install ElasticSearch from APT

sudo apt-get update && sudo apt-get install elasticsearch

Reload the daemon

sudo /bin/systemctl daemon-reload

Allow ElasticSearch to start on boot

sudo /bin/systemctl enable elasticsearch.service

Lets fire up ElasticSearch...

sudo systemctl start elasticsearch.service

Lets see if we have some logs

sudo ls -la /var/log/elasticsearch/

Have a look at the logs and make sure that ElasticSearch has properly initiated

sudo cat /var/log/elasticsearch/elasticsearch.log

If logs are looking good, You can CURL the ElasticSearch server

curl -XGET 'localhost:9200/?pretty' 

        Output:

               {

                  "name" : "y-489FI",

                  "cluster_name" : "elasticsearch",

                  "cluster_uuid" : "nltcKRHLTL6-aLX3o6auug",

                  "version" : {

                        "number" : "5.6.16",

                        "build_hash" : "3a740d1",

                        "build_date" : "2019-03-13T15:33:36.565Z",

                        "build_snapshot" : false,

                        "lucene_version" : "6.6.1"

                  },

                  "tagline" : "You Know, for Search"

            }

Completely uninstall Elasticsearch from linux