How to collect and visualize your logs with the Elastic stack (Elasticsearch, Logstash, Kibana - ELK Stack)

• compute
• ELK
• log
• Elastic
• Stack
• log
• files

Elastic Stack Overview

Historically ELK is a bundle of three open source software projects: Elasticsearch, Logstash, and Kibana. All these products are maintained by the company Elastic. This bundle consists of:

• Elasticsearch, a NoSQL database based on the Lucene search engine.
• Logstash, a server-side data processing pipeline that accepts data from various simultaneously, transforms it, and exports the data to various targets.
• Kibana, a visualization layer that works on top of Elasticsearch.

Elastic has recently included a family of log shippers called Beats and renamed the stack as Elastic Stack. The solution is flexible and is mostly used to centralize logging requirements.

Installing Elastic Stack

1. Start by installing Java, we use the OpenJDK package for this tutorial:

   apt install -y openjdk-8-jdk
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2. Now install the Elastic GPG Key to validate the packages to install:

   wget -qO - https://artifacts.elastic.co/GPG-KEY-elasticsearch | apt-key add -
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3. Install HTTPS transport to download the packages over a secure connection:

   apt install -y apt-transport-https
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4. Add the Elastic repository to the APT configuration:

   echo "deb https://artifacts.elastic.co/packages/7.x/apt stable main" | tee -a /etc/apt/sources.list.d/elastic-7.x.list
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5. Update APT and install Elasticsearch:

   apt update && apt install -y elasticsearch
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6. Edit the file /etc/elasticsearch/elasticsearch.yml and limit the connection to Elasticsearch to localhost by adding the following lines:

   network.host: 127.0.0.1
   http.port:9200
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7. Install Logstash and rsyslog

   apt install -y logstash rsyslog
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8. Install Filebeat

   apt install -y filebeat
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9. Install Kibana

   apt install -y kibana
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10. Start Elasticsearch:

    systemctl start elasticsearch
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    To verify if Elasticsearch is running, run a curl -X GET "localhost:9200". The output should be looking similar to this example:

    {
      "name" : "elastic-stack",
      "cluster_name" : "elasticsearch",
      "cluster_uuid" : "LiIyk5P1TMuR6MqOWcs_DQ",
      "version" : {
        "number" : "7.8.0",
        "build_flavor" : "default",
        "build_type" : "deb",
        "build_hash" : "757314695644ea9a1dc2fecd26d1a43856725e65",
        "build_date" : "2020-06-14T19:35:50.234439Z",
        "build_snapshot" : false,
        "lucene_version" : "8.5.1",
        "minimum_wire_compatibility_version" : "6.8.0",
        "minimum_index_compatibility_version" : "6.0.0-beta1"
      },
      "tagline" : "You Know, for Search"
    }
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11. Open the file /etc/kibana/kibana.yml and uncomment the following lines:

    server.port: 5601
    server.host: "localhost"
    elasticsearch.hosts: ["http://localhost:9200"]
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    Enable and start the Kibana service in systemd:

    systemctl enable kibana
    systemctl start kibana
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12. Install nginx as a proxy to Kibana:

    apt install -y nginx
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13. Use OpenSSL to create a user and password for the Elastic Stack webinterface. The command generates a htpasswd file, containing the user kibana and your password:

    echo "kibana:`openssl passwd -apr1`" | tee -a /etc/nginx/htpasswd.users
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14. Edit the file /etc/nginx/sites-available/elastic.local and paste the following content to create a proxy to Kibana. Make sure to replace elastic.local with the DNS name of your instance:

        server {
          listen 80;
          server_name elastic.local;
    
          auth_basic "Restricted Access";
          auth_basic_user_file /etc/nginx/htpasswd.users;
    
          location / {
            proxy_pass         http://localhost:5601;
            proxy_redirect     off;
    
            proxy_set_header   Host              $host;
            proxy_set_header   X-Forwarded-For   $proxy_add_x_forwarded_for;
            proxy_set_header   X-Forwarded-Proto $scheme;
          }
    
        }
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15. Create a symbolic link to enable the site in nginx:

    ln -s /etc/nginx/sites-available/elastic.local /etc/nginx/sites-enabled/elastic.local
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16. Reload the nginx configuration to activate the proxy:

    systemctl restart nginx
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17. You can now access your Elastic Dashboard at the DNS name of your instance, for example http://elastic.local:

You can either start with an empty stack and start collecting your metrics or load some samle data to play around:

Configuring rsyslog

Edit the file /etc/rsyslog.conf and uncomment the following lines, then save the file:

# provides UDP syslog reception
module(load="imudp")
input(type="imudp" port="514")
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Configuring Logstash

Logstash allows you to collect data from different sources, transform it into a common format, and to export it to a defined destination.

Logshash configuration files are written in JSON and can be found in the /etc/logstash/conf.d directory.

1. Configure a Filebeat input in the configuration file 02-beats-input.conf:

   nano /etc/logstash/conf.d/02-beats-input.conf
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   Copy the following information into the file, save and close it. This configuration lets the beats input listen on port 5044:

   input {
     beats {
       port => 5044
     }
   }
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2. Create a file /etc/logstash/conf.d/10-syslog-filter.conf and paste the following contents. This filter parses incoming system logs to make them structured and usable by the Kibana Dashboards. For more information you may refer to the official documentation. Save and close the file once edited.

   filter {
     if [type] == "syslog" {
       grok {
         match => { "message" => "%{SYSLOGTIMESTAMP:syslog_timestamp} %{SYSLOGHOST:syslog_hostname} %{DATA:syslog_program}(?:\[%{POSINT:syslog_pid}\])?: %{GREEDYDATA:syslog_message}" }
         add_field => [ "received_at", "%{@timestamp}" ]
         add_field => [ "received_from", "%{host}" ]
       }
       syslog_pri { }
       date {
         match => [ "syslog_timestamp", "MMM  d HH:mm:ss", "MMM dd HH:mm:ss" ]
       }
     }
   }
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3. Create a file /etc/logstash/conf.d/30-elasticsearch-output.conf and put the following content into it. Save and exit the file once edited. The output rules defined in this file sends the data to Elasticsearch, running at port 9200 on localhost. It also stores the data in an index named after the Beat used.

   output {
     elasticsearch {
       hosts => ["localhost:9200"]
       manage_template => false
       index => "%{[@metadata][beat]}-%{[@metadata][version]}-%{+YYYY.MM.dd}"
       document_type => "%{[@metadata][type]}"
     }
   }
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   In case you want to add filters that use the Filebeat input, make sure these filters are named between the input and output configuration (between 02 and 30).

4. Start and enable the Filebeat service:

   systemctl start logstash
   systemctl enable logstash
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Configuring Filebeat

The Elastic Stack uses lightweight data shippers (called Beats) to collect data from various sources and transport them to Logstash or Elasticsearch. This tutorial uses Filebeat to process log files.

Other Beats are available, for example: Metricbeat to collect metrics of systems and services, Packetbeat to analize network traffic or Heartbeat to monitor the availability of services.

1. Open the Filebeat configuration:

   nano /etc/filebeat/filebeat.yml
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   Note:

   The file is written in YAML format and it is important that you respect the formatting rules when you edit the file.

2. Add the following configuration for syslog in the filebeat.inputs section of the file:

     - type: syslog
       protocol.udp:
         host: "localhost:514"
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3. Search for output.elasticsearch and comment-out the lines as follows:

   [...]
   #output.elasticsearch:
     # Array of hosts to connect to.
     #hosts: ["localhost:9200"]
   [...]
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4. Search for output.logstash and uncomment the lines as follows:

   [...]
   output.logstash:
     # The Logstash hosts
     hosts: ["localhost:5044"]
   [...]
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5. Filebeat uses different modules to parse different log files. Enable the system plugin to handle generic system log files with Filebeat. Enable the plugin:

   filebeat modules enable system
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   Note:

   You can keep the default configuration of the module for this tutorial. If you want to learn more about the parsing rules applied, you may check the configuration of the module located at /etc/filebeat/modules.d/system.yml.

6. Load the index template into Elasticsearch:

   filebeat setup --template -E output.logstash.enabled=false -E 'output.elasticsearch.hosts=["localhost:9200"]'
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7. Disable the Logstash output and enable Elasticsearch output to load the dashboards when Logstash is enabled:

   filebeat setup -e -E output.logstash.enabled=false -E output.elasticsearch.hosts=['localhost:9200'] -E setup.kibana.host=localhost:5601
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   An output similar to the following displays:

   [...]
   Loaded machine learning job configurations
   2020-07-22T11:48:00.660Z    INFO    eslegclient/connection.go:97    elasticsearch url: http://localhost:9200
   2020-07-22T11:48:00.667Z    INFO    [esclientleg]   eslegclient/connection.go:306   Attempting to connect to Elasticsearch version 7.8.0
   2020-07-22T11:48:00.670Z    INFO    eslegclient/connection.go:97    elasticsearch url: http://localhost:9200
   2020-07-22T11:48:00.674Z    INFO    [esclientleg]   eslegclient/connection.go:306   Attempting to connect to Elasticsearch version 7.8.0
   2020-07-22T11:48:01.405Z    INFO    fileset/pipelines.go:134    Elasticsearch pipeline with ID 'filebeat-7.8.0-system-auth-pipeline' loaded
   2020-07-22T11:48:01.637Z    INFO    fileset/pipelines.go:134    Elasticsearch pipeline with ID 'filebeat-7.8.0-system-syslog-pipeline' loaded
   2020-07-22T11:48:01.637Z    INFO    cfgfile/reload.go:262   Loading of config files completed.
   2020-07-22T11:48:01.637Z    INFO    [load]  cfgfile/list.go:118 Stopping 1 runners ...
   Loaded Ingest pipelines
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8. You can now start and enable the Filebeat service:

   systemctl start filebeat
   systemctl enable filebeat
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9. To verify that your Filebeat service is running, you may run the following command:

   curl -XGET 'http://localhost:9200/filebeat-*/_search?pretty'
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   The output should look like the following example:

   {
     "took" : 11,
     "timed_out" : false,
     "_shards" : {
       "total" : 2,
       "successful" : 2,
       "skipped" : 0,
       "failed" : 0
     },
     "hits" : {
       "total" : {
         "value" : 2058,
         "relation" : "eq"
       },
       "max_score" : 1.0,
       "hits" : [
         {
           "_index" : "filebeat-7.8.0-2020.07.22",
           "_type" : "_doc",
           "_id" : "ZIpbdnMBenM2E5SX9FAi",
           "_score" : 1.0,
           "_source" : {
             "message" : "Jul 22 11:17:44 eleastic-stack kernel: Command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-1018-kvm root=PARTUUID=fc220e13-bb33-43c7-a49a-90d85d9edc7f ro console=tty1 console=ttyS0 panic=-1",
             "@version" : "1",
             "fileset" : {
               "name" : "syslog"
             },
             "host" : {
               "containerized" : false,
               "mac" : [
                 "de:1c:4c:3e:90:3a"
               ],
               "hostname" : "eleastic-stack",
               "name" : "eleastic-stack",
               "os" : {
                 "codename" : "focal",
                 "version" : "20.04 LTS (Focal Fossa)",
                 "kernel" : "5.4.0-1018-kvm",
                 "family" : "debian",
                 "name" : "Ubuntu",
                 "platform" : "ubuntu"
               },
               "architecture" : "x86_64",
               "id" : "a4d9477d47d14c4fb551f52adb5eb810",
               "ip" : [
                 "10.65.100.115",
                 "2001:bc8:47b0:1239::1",
                 "fe80::dc1c:4cff:fe3e:903a"
               ]
             },
             "ecs" : {
               "version" : "1.5.0"
             },
             "service" : {
               "type" : "system"
             },
             "log" : {
               "offset" : 344,
               "file" : {
                 "path" : "/var/log/syslog"
               }
             },
             "input" : {
               "type" : "log"
             },
             "@timestamp" : "2020-07-22T11:49:57.578Z",
             "agent" : {
               "ephemeral_id" : "348ca814-7f48-408e-9956-d8650d74420b",
               "version" : "7.8.0",
               "type" : "filebeat",
               "hostname" : "eleastic-stack",
               "name" : "eleastic-stack",
               "id" : "76a478aa-6c78-47c8-a045-a962e89a1046"
             },
             "tags" : [
               "beats_input_codec_plain_applied"
             ],
             "event" : {
               "dataset" : "system.syslog",
               "module" : "system",
               "timezone" : "+00:00"
             }
           }
         },
   [...]
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Exploring Kibana

Data collected by your setup is now available in Kibana, to visualize it:

Use the menu on the left to navigate to the Dashboard page and search for Filebeat System dashboards. You can browse the sample dashboards included with Kibana or create your own dashboards based on the metrics you want to monitor.

For more information how to use the Elastic stack, refer to the official documentation.