[box]The elk stack is a collection of three open-source products — Elasticsearch, Logstash, and Kibana — all developed, managed and maintained by Elastic. Logstash collects and parses logs, and then Elasticsearch indexes and stores the information. Kibana then presents the data in visualizations that provide actionable insights into one’s environment.[/box]

[box] Elk Concepts [/box]

Elasticsearch

Elasticsearch is a search engine based on the Lucene library. It provides a distributed, multitenant-capable full-text search engine with an HTTP web interface and schema-free JSON documents . Elasticsearch is developed in Java.

Logstash

Logstash, one of the core products of the Elastic Stack, is used to aggregate and process data and send it to Elasticsearch. Logstash is an open source, server-side data processing pipeline that enables you to ingest data from multiple sources simultaneously and enrich and transform it before it is indexed into Elasticsearch.

Kibana

Kibana is a data visualization and management tool for Elasticsearch that provides real-time histograms, line graphs, pie charts, and maps. Kibana also includes advanced applications such as Canvas, which allows users to create custom dynamic infographics based on their data, and Elastic Maps for visualizing geospatial data.

[box] Installation[/box]

When installing the Elastic Stack, you must use the same version across the entire stack. For example, if you are using Elasticsearch 7.9.0, you install Beats 7.9.0, APM Server 7.9.0, Elasticsearch Hadoop 7.9.0, Kibana 7.9.0, and Logstash 7.9.0.

Installing elasticsearch

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

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

   [elasticsearch-6.x]
    name=Elasticsearch repository for 6.x packages
    baseurl=https://artifacts.elastic.co/packages/6.x/yum
    gpgcheck=1
    gpgkey=https://artifacts.elastic.co/GPG-KEY-elasticsearch
    enabled=1
    autorefresh=1
    type=rpm-md

$ sudo yum install elasticsearch

$ sudo vi /etc/elasticsearch/elasticsearch.yml

    . . .
    cluster.name: behnam
    node.name: node1
    . . .
    network.host: localhost
    . . .

A node can only join a cluster when it shares its cluster.name with all the other nodes in the cluster. The default name is elasticsearch, but you should change it to an appropriate name which describes the purpose of the cluster.
Make sure that you don’t reuse the same cluster names in different environments, otherwise you might end up with nodes joining the wrong cluster.

Elasticsearch uses node.name as a human readable identifier for a particular instance of Elasticsearch so it is included in the response of many APIs. It defaults to the hostname that the machine has when Elasticsearch starts but can be configured explicitly in elasticsearch.yaml.
By default, Elasticsearch binds to loopback addresses only — e.g. 127.0.0.1 and [::1]. This is sufficient to run a single development node on a server.
In order to form a cluster with nodes on other servers, your node will need to bind to a non-loopback address. While there are many network settings, usually all you need to configure is network.host .

[button link=”https://www.elastic.co/guide/en/elasticsearch/reference/current/important-settings.html” color=”orange” newwindow=”yes”] Read more about Elasticsearch configuration[/button]

$ sudo systemctl enable elasticsearch

$ sudo systemctl start elasticsearch

$ curl -X GET “localhost:9200“

Installing kibana

$ sudo yum install kibana

$ sudo systemctl enable kibana

$ sudo systemctl start kibana

Configuring Reverse Proxy

Because Kibana is configured to only listen on localhost, we must set up a reverse proxy to allow external access to it.

$ echo “kibanaadmin:`openssl passwd -apr1`” | sudo tee -a /etc/nginx/htpasswd.users

$ sudo vi /etc/nginx/conf.d/example.com.conf

  server {
    listen 80;

         server_name example.com www.example.com;

        auth_basic “Restricted Access”;
        auth_basic_user_file /etc/nginx/htpasswd.users;

       location / {
             proxy_pass http://localhost:5601;
             proxy_http_version 1.1;
             proxy_set_header Upgrade $http_upgrade;
             proxy_set_header Connection ‘upgrade’;
             proxy_set_header Host $host;
             proxy_cache_bypass $http_upgrade;
    }
  }
$ sudo systemctl restart nginx

Installing logstash

$ sudo yum install logstash
$ sudo vi /etc/logstash/conf.d/02-beats-input.conf

    input {
      beats {
        port => 5044
      }
    }

$ sudo vi /etc/logstash/conf.d/10-syslog-filter.conf

    filter {
      if [fileset][module] == "system" {
        if [fileset][name] == "auth" {
          grok {
            match => { ..... }
            pattern_definitions => {
              "GREEDYMULTILINE"=> "(.|\n)*"
            }
            remove_field => "message"
          }
          date {
            match => [ "[system][auth][timestamp]", "MMM  d HH:mm:ss", "MMM dd HH:mm:ss" ]
          }
          geoip {
            source => "[system][auth][ssh][ip]"
            target => "[system][auth][ssh][geoip]"
          }
        }
        else if [fileset][name] == "syslog" {
          grok {
            match => { .... }
            remove_field => "message"
          }
          date {
            match => [ "[system][syslog][timestamp]", "MMM  d HH:mm:ss", "MMM dd HH:mm:ss" ]
          }
        }
      }
    }

$ sudo vi /etc/logstash/conf.d/30-elasticsearch-output.conf

    output {
      elasticsearch {
        hosts => ["localhost:9200"]
        manage_template => false
        index => "%{[@metadata][beat]}-%{[@metadata][version]}-%{+YYYY.MM.dd}"
      }
    }

If you want to add filters for other applications that use the Filebeat input, be sure to name the files so they’re sorted between the input and the output configuration, meaning that the file names should begin with a two-digit number between 02 and 30.

$ sudo -u logstash /usr/share/logstash/bin/logstash –path.settings /etc/logstash -t

$ sudo systemctl start logstash

$ sudo systemctl enable logstash

Installing Filebeat

The Elastic Stack uses several lightweight data shippers called Beats to collect data from various sources and transport them to Logstash or Elasticsearch. Here are the Beats that are currently available from Elastic:

• Filebeat: collects and ships log files.
• Metricbeat: collects metrics from your systems and services.
• Packetbeat: collects and analyzes network data.
• Winlogbeat: collects Windows event logs.
• Auditbeat: collects Linux audit framework data and monitors file integrity.
• Heartbeat: monitors services for their availability with active probing.

$ sudo yum install filebeat

$ sudo vi /etc/filebeat/filebeat.yml

     output.logstash:
       # The Logstash hosts
       hosts: ["localhost:5044"]
$ sudo filebeat modules list
$ sudo filebeat modules enable system
$ sudo systemctl start filebeat
$ sudo systemctl enable filebeat
To verify that Elasticsearch is indeed receiving this data, query the Filebeat index with this command:
$ curl -X GET ‘http://localhost:9200/filebeat-*/_search?pretty’

Installing on Docker

$ docker pull sebp/elk
$ vi docker-compose.yml
    elk:
      image: sebp/elk
      ports:
          – “5601:5601”
          – “9200:9200”
          – “5044:5044”

$ sudo docker-compose up elk