Install gnupg and add OpenNMS repository GPG key
sudo apt -y install gnupg ca-certificates
sudo apt-key adv --fetch-keys https://debian.opennms.org/OPENNMS-GPG-KEY
Add apt repository
sudo apt -y install software-properties-common
sudo add-apt-repository -s 'deb https://debian.opennms.org stable main'
sudo apt update
You can safely ignore the message about conflicting distributions (expected stable but got opennms-xx).
Installing the of Horizon Sentinel
sudo apt -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.
sudo apt-mark hold opennms-sentinel
Verify directory structure with the tree command
sudo apt -y install tree
tree /usr/share/sentinel -L 1
Directory structure after successful installation
/usr/share/sentinel
├── bin
├── data -> /var/lib/sentinel/data
├── deploy -> /var/lib/sentinel/deploy
├── etc -> /etc/sentinel
├── lib
└── system
Enable Horizon Sentinel on system boot and start immediately
sudo systemctl enable --now sentinel