CentOS installation

This guide describes the fastest way to install Graylog on CentOS 8. All links and packages are present at the time of writing but might need to be updated later on.

Prerequisites

Taking a minimal server setup as base will need these additional packages:

sudo yum install java-<version_number>-openjdk-headless.x86_64

If you want to use pwgen later on you need to Setup EPEL on your system with sudo yum install epel-release and install the package with sudo yum install pwgen.

MongoDB

Installing MongoDB on CentOS should follow the tutorial for RHEL and CentOS from the MongoDB documentation. First add the repository file /etc/yum.repos.d/mongodb-org.repo with the following contents:

[mongodb-org-4.2]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.2/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-4.2.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:

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

Elasticsearch

Graylog currently supports all Elasticsearch versions up to 7.10.2. Follow the instructions below to begin the installation. 

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:

[elasticsearch-7.x]
name=Elasticsearch repository for 7.x 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:

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:

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:

sudo rpm -Uvh https://packages.graylog2.org/repo/packages/graylog-4.2-repository_latest.rpm
sudo yum install graylog-server graylog-enterprise-plugins graylog-integrations-plugins graylog-enterprise-integrations-plugins

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:

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.

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

sudo systemctl daemon-reload
sudo systemctl enable graylog-server.service
sudo systemctl start graylog-server.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

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.

Further reading

• https://www.nginx.com/blog/nginx-se-linux-changes-upgrading-rhel-6-6/
• https://wiki.centos.org/HowTos/SELinux
• https://wiki.centos.org/TipsAndTricks/SelinuxBooleans
• http://www.serverlab.ca/tutorials/linux/administration-linux/troubleshooting-selinux-centos-red-hat/
• https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/SELinux_Users_and_Administrators_Guide/
• https://www.digitalocean.com/community/tutorials/an-introduction-to-selinux-on-centos-7-part-1-basic-concepts

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.