Your Horizon repository is defined in a file in /etc/yum.repos.d/. It most likely will be named opennms-repo-stable-<OSversion>.repo, but is not guaranteed to be. Become root. Enable auto updates: yum -y install yum-utils yum-config-manager --enable opennms-repo-stable-* Purge any cached yum data: yum clean all Make a backup copy of your OpenNMS config: rsync -Ppav ${OPENNMS_HOME}/etc /tmp/etc.orig rsync -Ppav${OPENNMS_HOME}/jetty-webapps/opennms/WEB-INF /tmp/opennms-web-inf Upgrade the Horizon packages to the new version: yum -y upgrade opennms Disable auto updates: yum-config-manager --disable opennms-repo-stable-* Upgrade Java 11 to the latest release: yum -y install java-11-openjdk java-11-openjdk-devel Execute runjava to update which JVM Horizon will use: ${OPENNMS_HOME}/bin/runjava -s Check for configuration file changes, and update accordingly, using the files you backed up in Idenfity Changed Configuration Files. If you upgrade in place, OpenNMS renames any shipped config that conflicts with an existing user-modified config to .rpmnew or .rpmsave. Inspect these files manually and reconcile the differences. Use diff -Bbw and diff -y to look for changes. If any .rpmnew or .rpmsave files exist within the configuration directory, services will not start. Run the Horizon installer: ${OPENNMS_HOME}/bin/install -dis The upgrade may take some time. The message Upgrade completed successfully! will confirm the upgrade has completed. If you do not get this message, check the output of the install command for any error messages. Clear the Karaf cache: yes | ${OPENNMS_HOME}/bin/fix-karaf-setup.sh Start OpenNMS Horizon: systemctl start opennms.service tail -F ${OPENNMS_HOME}/logs/manager.log can illustrate the current point in the startup process Horizon is. Upgrade is complete and operation is resumed.