Create a configuration file for gRPC settings sudo vi etc/opennms.properties.d/grpc.properties Set OSGi as IPC strategy org.opennms.core.ipc.strategy=osgi Create a file to install gRPC features on startup sudo vi etc/featuresBoot.d/grpc.boot Add the gRPC server features opennms-core-ipc-grpc-server Apply the changes with Horizon Core instance restart sudo systemctl restart opennms The gRPC server listens on port 8990/tcp by default. Use ss -lnpt = :8990 to verify the port is listening. Optional: to enable TLS for gRPC, you must provide certificate files and enable it. See below for TLS commands. Connect to the Karaf shell ssh -p 8101 admin@localhost Configure TLS and certificate parameters config:edit org.opennms.core.ipc.grpc.server config:property-set tls.enabled true(1) config:property-set server.cert.filepath /custom-path/server.crt(2) config:property-set server.private.key.filepath /custom-path/server.pem(3) config:property-set trust.cert.filepath /custom-path/ca.crt(4) config:update(5) 1 Enable TLS for the gRPC server. 2 Set the path to your CA certificate file. 3 Set the path to the server certificate private key file. 4 Set the path to your server certificate file 5 Save and update the configuration. This is optional and you can set a maximum message size for gRPC. The maximum size must be the same on the Minion. Default maximum message size is 10 MiB. Configure maximum message size for gRPC in the Karaf shell config:edit org.opennms.core.ipc.grpc.client config:property-set max.message.size 10485760 config:update Apply the changes with Horizon Core instance restart sudo systemctl restart opennms