How to Install and Configure Graylog2 on Debian 9

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What is Graylog?

Graylog is a powerful, free, open-source log management and analysis tool that can be used for monitoring SSH logins and unusual activity to debugging applications. It is based on Java, Elasticsearch, and MongoDB and provides a beautiful web interface for centralized log management and log analysis.

Graylog uses Elasticsearch for searching and storing the log messages, and MongoDB to store the meta information and configuration. Graylog collects, indexes and analyzes the logs from various inputs and displays them through a web interface. Compared to other log monitoring tools, Graylog is a more finished and enterprise-ready tool out of the box.

This guide shows you how to install and configure Graylog2 with Elasticsearch and MongoDB on a Debian 9 server.

The steps in this guide require root privileges. Be sure to run the steps below as root or with the sudo prefix. For more information on privileges, see our Users and Groups guide.

Before You Begin

  1. Familiarize yourself with our Getting Started guide and complete the steps for setting your Linode’s hostname and timezone.

  2. Not all required dependencies are available in the standard repository, so you will need to add Debian Backports to the list of package sources:

    echo "deb jessie-backports main" > /etc/apt/sour0es.list.d/backports.list
  3. Update your system:

    apt update && apt upgrade


  • Linode running Debian 9.
  • Minimum 4 GB RAM installed on your Linode.

Install Java

Both Graylog and Elasticsearch are Java-based, so you will need to install the latest version of Java on your system.

  1. Install the latest version of Java:

    apt-get install openjdk-8-jre-headless -y
  2. Once Java is installed, check the Java version:

    java -version

    You should see the following output on your screen:

    java version "1.8.0_131"
    Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
    Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)
  3. Install additional packages to your system:

    apt-get install apt-transport-https uuid-runtime pwgen -y

Install and Configure Elasticsearch

Graylog uses Elasticsearch for storing the log messages and also offers a searching facility. By default, Elasticsearch is not available in Debian 9 repository. So, you will need to add Elasticsearch repository to your system.

  1. Download and install the GPG key:

    wget -qO - | apt-key add -
  2. Add the Elasticsearch repository to apt:

    echo "deb stable main" | tee -a /etc/apt/sources.list.d/elasticsearch-2.x.list
  3. Update the repository:

    apt-get update -y
  4. After the system finishes updating, install Elasticsearch:

    apt-get install elasticsearch -y
  5. Start The Elasticsearch service, and enable the service to start on boot:

    systemctl start elasticsearch
    systemctl enable elasticsearch
  6. Next, you will need to edit elasticsearch.yml. It’s located in the /etc/elasticsearch/ directory:

    File: /etc/elasticsearch/elasticsearch.yml
    8 graylog 10s false [""]
    script.inline: false
    script.indexed: false
    script.file: false
    This guide uses Elasticsearch on a single server. If you are using Elasticsearch on a different server, replace the IP address with your server IP address. Refer to the Elasticsearch documentation for security best practices.

    Save and close the file, then restart the Elasticsearch service:

    systemctl restart elasticsearch

    Make sure the restart doesn’t return errors. Elasticsearch should be running properly at this point.

  7. Once Elasticsearch restarts, it should be listening on HTTP port 9200, The cluster nodes communicate on 9300. You can check the response by running the following command:

    curl -X GET http://localhost:9200
  8. You can also test the health of the Elasticsearch:

    curl -XGET 'http://localhost:9200/_cluster/health?pretty=true'
    For a complete list of the REST API endpoints, refer to the Elasticsearch documentation

Install MongoDB

Graylog uses MongoDB as a database to store meta-information and configurations. MongoDB is available in the Debian 9 repository, by default. Install MongoDB:

apt-get install mongodb-server -y

After completing the install, proceed to installing the Graylog server.

Install and Configure Graylog Server

In order to install the Graylog server, you need to download and install the Graylog repository to your system.

  1. Download and install the Graylog repository:

     dpkg -i graylog-2.2-repository_latest.deb
  2. Update the Graylog repository, then install the Graylog server:

    apt-get update -y
    apt-get install graylog-server -y
  3. You will need to set a password-secret and hash password for the root user. First, set a password-secret using the pwgen command:

    pwgen -N 1 -s 96

    Running this will output a series random letters and numbers:


    Set a hash password for the root user. Use the following command, making sure to replace hashedpassword with your desired password.

    echo -n hashedpassword | sha256sum

    You should see the following output:

    You will need this password to log in to the Graylog web interface.
  4. Open the Graylog servers main configuration file: server.conf, located in the /etc/graylog/server/ directory. Replace root_password_sha2 and password_sercret with the console output from above:

    File: /etc/graylog/server/server.conf
    is_master = true
    node_id_file = /etc/graylog/server/node-id
    password_secret = nNPjRmvyyyPc0YKySXhkebfwUYvW2dQz7kD1GxBq7qhJre1eIAySsUbmlYNKiYZnHquHPu8pTswvc3MFSVDrwn5AmdwOSMri
    root_username = admin
    root_password_sha2 = 4c941dd2a116bf235e943771ad16c4e8877d75c597936accf168e08c5f93ce24
    root_timezone = UTC
    plugin_dir = /usr/share/graylog-server/plugin
    rest_listen_uri =
    rest_enable_cors = true
    web_listen_uri =
    rotation_strategy = count
    elasticsearch_max_docs_per_index = 20000000
    elasticsearch_max_number_of_indices = 7
    retention_strategy = delete
    elasticsearch_shards = 4
    elasticsearch_replicas = 1
    elasticsearch_index_prefix = graylog
    allow_leading_wildcard_searches = true
    allow_highlighting = false
    elasticsearch_cluster_name = graylog
    elasticsearch_discovery_zen_ping_unicast_hosts =
    elasticsearch_http_enabled = false
    elasticsearch_network_host =
    elasticsearch_discovery_initial_state_timeout = 3s
    elasticsearch_analyzer = standard
    output_batch_size = 500
    output_flush_interval = 1
    output_fault_count_threshold = 5
    output_fault_penalty_seconds = 30
    ring_size = 65536
    inputbuffer_ring_size = 65536
    inputbuffer_processors = 2
    inputbuffer_wait_strategy = blocking
    processbuffer_processors = 5
    outputbuffer_processors = 3
    processor_wait_strategy = blocking
    message_journal_enabled = true
    message_journal_dir = /var/lib/graylog-server/journal
    async_eventbus_processors = 2
    lb_recognition_period_seconds = 3
    alert_check_interval = 60
    mongodb_uri = mongodb://localhost/graylog
    mongodb_max_connections = 1000
    mongodb_threads_allowed_to_block_multiplier = 5
    transport_email_enabled = true
    content_packs_dir = /usr/share/graylog-server/contentpacks
    content_packs_auto_load = grok-patterns.json
    proxied_requests_thread_pool_size = 32

    Save the file when you are finished. Finally, start the Graylog server and enable it to start at boot:

    systemctl start graylog-server
    systemctl enable graylog-server
  5. Check the Graylog if the server log is working:

    tail -f /var/log/graylog-server/server.log

Access Graylog

Graylog is now up and running, It’s time to access the Graylog web interface.

  1. Open your web browser and navigate to the URL: where is the public IP address of your linode. You will be redirected to the Graylog login page as shown below:

    Consider limiting Graylog access to a private network, if you are deploying Graylog in a production environment. In the context of this guide, instances of can be replaced with the Linode’s public IP address to access on the browser.
  2. Provide the username admin and password as the hashedpassword generated earlier, then click on the Sign In button. You should see the Graylog default dashboard:

  3. Configure Graylog Input to receive the logs from external source. Click on System > Inputs. Then select Syslog UDP from the drop down, click on the Launch new input button. You should see the following image:

  4. Fill in all of the details shown below. When you finish click on the Save button, you should see the local input in the following image:

  5. Your Graylog input is configured and listening on port 8514. Now, you will need to configure rsyslog to send system logs to the newly created input. To do this, edit the rsyslog.conf file:

    File: /etc/rsyslog.conf
    $template GRAYLOGRFC5424,"%protocol-version% %timestamp:::date-rfc3339% %HOSTNAME% %app-name% %procid% %msg%\n"
    *.* @;GRAYLOGRFC5424

    Save and close the file when you are finished, then restart your server with the Linode Manager to apply these changes.

  6. After restarting, log in to your Graylog server web interface and click on System > Inputs. Then, click on the Show received messages button. You should see the syslog messages in the following image:

Next steps

You now have a fully configured a Graylog server. Graylog can be used to monitor logs of any size. So whether your use case is security, IT, development & devops, or anything else. Graylog will house your log data in one central location.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

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