Free Alternative To Splunk

is a great tool for searching logs, but its high cost makes it prohibitive for many teams. In this article, we present a free and open-source alternative to Splunk by combining three open source projects: Elasticsearch, Kibana, and Fluentd.

is an open-source search engine well-known for its ease of use. is an open-source Web UI that makes Elasticsearch user friendly for marketers, engineers and data scientists alike.

By combining these three tools (Fluentd + Elasticsearch + Kibana) we get a scalable, flexible, easy to use log search engine with a great Web UI that provides an open-source Splunk alternative, all for free.

In this guide, we will go over the installation, setup, and basic use of this combined log search solution. This article was tested on Ubuntu 24.04. If you're not familiar with Fluentd, please learn more about Fluentd first.

Prerequisites

Java runtime (OpenJDK - JRE 21)

You can install Fluentd via major packaging systems.

Java for Elasticsearch

Please confirm that Java version 21 or higher is installed:

$ java --version
openjdk 21.0.5 2024-10-15
OpenJDK Runtime Environment (build 21.0.5+11-Ubuntu-1ubuntu124.04)
OpenJDK 64-Bit Server VM (build 21.0.5+11-Ubuntu-1ubuntu124.04, mixed mode, sharing)

Set Up Elasticsearch

To install Elasticsearch, please download and extract the Elasticsearch package as shown below:

$ curl -O https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-8.17.1-linux-x86_64.tar.gz
$ tar -xf elasticsearch-8.17.1-linux-x86_64.tar.gz
$ cd elasticsearch-8.17.1

Once the installation is complete, start Elasticsearch:

$ ./bin/elasticsearch

You can create enrollment token for kibana. Use ./bin/elasticsearch-create-enrollment-token -s kibana.
You can reset default password for elastic, Use ./bin/elasticsearch-reset-password -u elastic.

Set Up Kibana

$ curl -O https://artifacts.elastic.co/downloads/kibana/kibana-8.17.1-linux-x86_64.tar.gz
$ tar -xf kibana-8.17.1-linux-x86_64.tar.gz
$ cd kibana-8.17.1-linux-x86_64

Once the installation is complete, start Kibana i.e. ./bin/kibana. You can modify its configuration file (config/kibana.yml).

$ ./bin/kibana

Access http://localhost:5601 in your browser.

Set Up Fluentd (`fluent-package`)

You can install Fluentd via major packaging systems.

Next, we'll install the Elasticsearch plugin for Fluentd: fluent-plugin-elasticsearch. Then, install fluent-plugin-elasticsearch.

We'll configure fluent-package (Fluentd) to interface properly with Elasticsearch. Please modify /etc/fluent/fluentd.conf as shown below:

# get logs from syslog
<source>
  @type syslog
  port 42185
  tag syslog
</source>

# get logs from fluent-logger, fluent-cat or other fluentd instances
<source>
  @type forward
</source>

<match syslog.**>
  @type elasticsearch
  host localhost
  user elastic
  password (ELASTIC_USER_PASSWORD_HERE)
  logstash_format true
  scheme https
  ssl_verify false
  include_timestamp true
  <buffer>
    flush_interval 10s # for testing
  </buffer>
</match>

In this article, it disables verification of TLS explicitly for elasticsearch because of demonstration. Do not disable on production.

fluent-plugin-elasticsearch comes with a logstash_format option that allows Kibana to search through the stored event logs in Elasticsearch.

Once everything has been set up and configured, start fluentd:

$ sudo systemctl start fluentd

Set Up `rsyslogd`

The final step is to forward the logs from your rsyslogd to fluentd. Please create the file with following line to /etc/rsyslog.d/90-fluentd.conf, and restart rsyslog. This will forward the local syslogs to Fluentd, and Fluentd in turn will forward the logs to Elasticsearch.

*.* @127.0.0.1:42185

Please restart the rsyslog service once the modification is complete:

$ sudo systemctl restart rsyslog

Store and Search Event Logs

Once Fluentd receives some event logs from rsyslog and has flushed them to Elasticsearch, you can view, search and visualize the log data using Kibana.

For starters, let's access http://localhost:5601 and click the Set up index patterns button in the upper-right corner of the screen.

Kibana will start a wizard that guides you through configuring the data sets to visualize. If you want a quick start, use logstash-* as the index pattern, and select @timestamp as the time-filter field.

After setting up an index pattern, you can view the system logs as they flow in:

To manually send logs to Elasticsearch, please use the logger command:

$ logger -t test foobar

<filter syslog.**>
  @type stdout
</filter>

<match syslog.**>
  @type elasticsearch
  host localhost
  user elastic
  password (ELASTIC_USER_PASSWORD_HERE)
  logstash_format true
  scheme https
  ssl_verify false
  include_timestamp true
  <buffer>
    flush_interval 10s # for testing
  </buffer>
</match>

Conclusion

This article introduced the combination of Fluentd and Kibana (with Elasticsearch) which achieves a free alternative to Splunk: storing and searching machine logs. The examples provided in this article have not been tuned.

If you will be using these components in production, you may want to modify some of the configurations (e.g. JVM, Elasticsearch, Fluentd buffer, etc.) according to your needs.

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Prerequisites

Java for Elasticsearch

Set Up Elasticsearch

Set Up Kibana

Set Up Fluentd (fluent-package)

Set Up rsyslogd

Store and Search Event Logs

Conclusion

Learn More

Prerequisites

Java for Elasticsearch

Set Up Elasticsearch

Set Up Kibana

Set Up Fluentd (fluent-package)

Set Up rsyslogd

Store and Search Event Logs

Conclusion

Learn More

Set Up Fluentd (`fluent-package`)

Set Up `rsyslogd`

Set Up Fluentd (`fluent-package`)

Set Up `rsyslogd`