Install OpenJDK 11 JRE runtime sudo dnf -y install java-11-openjdk-headless Add repository and import GPG key sudo dnf -y install https://yum.opennms.org/repofiles/opennms-repo-stable-rhel8.noarch.rpm sudo rpm --import https://yum.opennms.org/OPENNMS-GPG-KEY Installing the of Horizon Sentinel sudo dnf -y install opennms-sentinel Disable the OpenNMS Horizon repository after installation to prevent unwanted upgrades when upgrading other packages on the server. After upgrade, Horizon requires manual steps to upgrade configuration files or migrate database schemas to a new version. For this reason, it is recommended to exclude the Horizon packages from update except when you are planning on performing an upgrade. Disable auto updates for Horizon Sentinel sudo dnf config-manager --disable opennms-repo-stable-* Verify directory structure with the tree command sudo dnf -y install tree tree /opt/sentinel -L 1 Directory structure after successful installation /opt/sentinel ├── bin ├── COPYING ├── deploy ├── etc ├── lib └── system Enable Horizon Sentinel on system boot and start immediately sudo systemctl enable --now sentinel