Configure PostgreSQL database access sudo -u opennms vi /opt/opennms/etc/opennms-datasources.xml Set credentials to access the PostgreSQL database <jdbc-data-source name="opennms" database-name="opennms"(1) class-name="org.postgresql.Driver" url="jdbc:postgresql://localhost:5432/opennms" user-name="** YOUR-OPENNMS-USERNAME **"(2) password="** YOUR-OPENNMS-PASSWORD **" />(3) <jdbc-data-source name="opennms-admin" database-name="template1" class-name="org.postgresql.Driver" url="jdbc:postgresql://localhost:5432/template1" user-name="postgres"(4) password="** YOUR-POSTGRES-PASSWORD **" />(5) 1 Set the database name Horizon should use. 2 Set the user name to access the opennms database table. 3 Set the password to access the opennms database table. 4 Set the postgres user for administrative access to PostgreSQL. 5 Set the password for administrative access to PostgreSQL. Detect and assign Java environment and persist in /opt/opennms/etc/java.conf sudo /opt/opennms/bin/runjava -s Initialize the database and detect system libraries persisted in /opt/opennms/etc/libraries.properties sudo /opt/opennms/bin/install -dis Assign CAP_NET_RAW capabilities Horizon runs as a non-root user, which requires having a Linux kernel greater than 3.10. If you run on an older kernel, and are unable to upgrade your OS, you need to assign CAP_NET_RAW capabilities: Run systemctl edit --full opennms.service and add the following line to the [Service] section: AmbientCapabilities=CAP_NET_RAW CAP_NET_BIND_SERVICE Reload the systemd unit with systemctl daemon-reload and restart the service with systemctl restart opennms. (For more background on this issue, see H29+ won’t start with permission error to open ICMP socket on Discourse.) Enable Horizon core instance on system boot and start immediately sudo systemctl enable --now opennms Allow connection to the web UI from your network sudo firewall-cmd --permanent --add-port=8980/tcp sudo systemctl reload firewalld