This guide describes the fastest way to install Graylog on RHEL/CentOS 6. All links and packages are present at the time of writing.

Warning: This guide does not cover security settings! The server administrator must make sure the Graylog server is not publicly exposed and is following security best practices.

Prerequisites

Graylog 5.0 requires the following to maintain compatibility with its software dependencies: 

  • OpenJDK 17 (embedded in the 5.0 installation file)
  • Elasticsearch 7.10.2 OR OpenSearch 2.x
  • MongoDB (5.x or 6.x)

MongoDB

Installing MongoDB on Red Hat should follow the tutorial for Red Hat from the MongoDB documentation.

Graylog 5.0 is compatible with MongoDB v5.x-6.x.

First, add the repository file /etc/yum.repos.d/mongodb-org.repo with the following contents (replacing 5.x with your selected version):

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[mongodb-org-5.x]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/Red Hat/$releasever/mongodb-org/5.x/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-5.x.asc

After that, install the latest release of MongoDB with sudo yum install mongodb-org.

Additionally, run these last steps to start MongoDB during the operating system’s boot and start it right away:

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sudo systemctl daemon-reload
sudo systemctl enable mongod.service
sudo systemctl start mongod.service
sudo systemctl --type=service --state=active
grep mongod

Hint: For the following sections on OpenSearch and Elasticsearch, select which data node you will be using for your Graylog instance and complete only the requisite section.

OpenSearch

If you are using OpenSearch as your data node, then follow the steps below to install OpenSearch 2.0.1.

You may prefer to disable transparent hugepages to improve performance before installing.

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sudo su

cat > /etc/systemd/system/disable-transparent-huge-pages.service <<EOF
Description=Disable Transparent Huge Pages (THP)
DefaultDependencies=no
After=sysinit.target local-fs.target
[Service]
Type=oneshot
ExecStart=/bin/sh -c 'echo never | tee /sys/kernel/mm/transparent_hugepage/enabled > /dev/null'
[Install]
WantedBy=basic.target
EOF

sudo systemctl daemon-reload
sudo systemctl enable disable-transparent-huge-pages.service
sudo systemctl start disable-transparent-huge-pages.service

First, install the OpenSearch GPG key:

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sudo rpm --import https://artifacts.opensearch.org/publickeys/opensearch.pgp

Download the RPM package for the desired version directly from the OpenSearch downloads page. The RPM package can be downloaded for both x64 and arm64 architectures.

Import the public GNU Privacy Guard (GPG) key. This key verifies that your OpenSearch instance is signed.

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sudo rpm --import https://artifacts.opensearch.org/publickeys/opensearch.pgp

From the CLI, you can install the package with rpm or yum.

For yum x64:

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sudo yum install opensearch-2.0.1-linux-x64.rpm

For rpm x64.

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sudo rpm -ivh opensearch-2.0.1-linux-x64.rpm

Edit the opensearch.yml file:

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sudo nano /usr/share/opensearch/config/opensearch.yml

At a minimum the following changes are required (for a single instance install):

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cluster.name: 
path.data: /var/lib/opensearch
path.logs: /var/log/opensearch
action.auto_create_index: false
plugins.security.disabled: true
network.host: 0.0.0.0  
discovery.type: single-node

After the installation succeeds, enable the OpenSearch service.

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sudo systemctl enable opensearch

Then, start OpenSearch.

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sudo systemctl start opensearch

Finally, verify that OpenSearch launched correctly.

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sudo systemctl status opensearch

Elasticsearch

Graylog 5.0 can be used with Elasticsearch 7.10.2 only. Please follow the below instructions to install the open-source version of Elasticsearch.

First, install the Elastic GPG key with rpm --import https://artifacts.elastic.co/GPG-KEY-elasticsearch then add the repository file /etc/yum.repos.d/elasticsearch.repo with the following contents:

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[elasticsearch-7.10.2]
name=Elasticsearch repository for 7.10.2 packages
baseurl=https://artifacts.elastic.co/packages/oss-7.x/yum
gpgcheck=1
gpgkey=https://artifacts.elastic.co/GPG-KEY-elasticsearch
enabled=1
autorefresh=1
type=rpm-md

followed by the installation of the latest release with sudo yum install elasticsearch-oss.

Modify the Elasticsearch configuration file (/etc/elasticsearch/elasticsearch.yml) and set the cluster name to graylog and uncomment action.auto_create_index: false to enable the action:

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sudo tee -a /etc/elasticsearch/elasticsearch.yml > /dev/null <<EOT
cluster.name: graylog
action.auto_create_index: false
EOT

After you have modified the configuration, you can start Elasticsearch:

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sudo systemctl daemon-reload
sudo systemctl enable elasticsearch.service
sudo systemctl restart elasticsearch.service
sudo systemctl --type=service --state=active
grep elasticsearch

Graylog

Now install the Graylog repository configuration and Graylog itself with the following commands:

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sudo rpm -Uvh https://packages.graylog2.org/repo/packages/graylog-5.0-repository_latest.rpm
sudo yum install graylog-server

If you are installing Graylog Operations, then you will use the following commands:

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sudo rpm -Uvh https://packages.graylog2.org/repo/packages/graylog-5.0-repository_latest.rpm
sudo yum install graylog-enterprise

Edit the Configuration File

Read the instructions within the configurations file and edit as needed, located at /etc/graylog/server/server.conf. Additionally add password_secret and root_password_sha2 as these are mandatory and Graylog will not start without them.

To create your root_password_sha2 run the following command:

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echo -n "Enter Password: " && head -1 </dev/stdin | tr -d '\n' | sha256sum | cut -d" " -f1

To be able to connect to Graylog you should set http_bind_address to the public host name or a public IP address of the machine you can connect to. More information about these settings can be found in Configuring the web interface.

Hint: If you’re operating a single-node setup and would like to use HTTPS for the Graylog web interface and the Graylog REST API, it’s possible to use NGINX or Apache as a reverse proxy.

The last step is to enable Graylog during the operating system’s start up:

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sudo systemctl daemon-reload
sudo systemctl enable graylog-server.service
sudo systemctl start graylog-server.service
sudo systemctl --type=service --state=active
grep graylog

If you are running Graylog Operations, you can verify it is running: 

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sudo systemctl daemon-reload
sudo systemctl enable graylog-enterprise.service
sudo systemctl start graylog-enterprise.service
sudo systemctl --type=service --state=active
grep graylog

The next step is to ingest messages into your Graylog and extract the messages with extractors or use the Pipelines to work with the messages.

SELinux Information

Hint: We assume that you have policycoreutils-python installed to manage SELinux.

If you’re using SELinux on your system, you need to take care of the following settings:

  • Allow the web server to access the network: sudo setsebool -P httpd_can_network_connect 1
  • If the policy above does not comply with your security policy, you can also allow access to each port individually:
    • Graylog REST API and web interface: sudo semanage port -a -t http_port_t -p tcp 9000
    • Elasticsearch (only if the HTTP API is being used): sudo semanage port -a -t http_port_t -p tcp 9200
  • Allow using MongoDB’s default port (27017/tcp): sudo semanage port -a -t mongod_port_t -p tcp 27017

If you run a single server environment with NGINX or Apache proxy, enabling the Graylog REST API is enough. All other rules are only required in a multi-node setup. Having SELinux disabled during installation and enabling it later, requires you to manually check the policies for MongoDB, Elasticsearch and Graylog.

Hint: Depending on your actual setup and configuration, you might need to add more SELinux rules to get to a running setup.

Further Reading

Multiple Server Setup

If you plan to have multiple server taking care of different roles in your cluster like we have in this big production setup you need to modify only a few settings. This is covered in our Multi-Node Setup guide. The Default File Location guide will give you the file you need to modify in your setup.