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 Meridian 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

Meridian 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 Meridian 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