During vCenter Server Reduced Downtime Upgrades the user may see an error like:
Previous Error Found the following RPMs that are not part of the vCenter Server installation: [oniguruma, vsphere-ui-config, VMware-spherelet_1_29]
Resolution The upgrade process does not preserve any 3rd party RPMs installed on the vCenter Server Appliance. Please re-install any non-standard packages again after the upgrade.
VMware vCenter Server 8.x
The RPM pre-check is designed to find RPMs installed by the customer that are not part of the regular vCenter deployment. In this case, the pre-check is reporting packages which are part of the standard vCenter installation.
This message is a false positive and can be ignored. There is no impact to the vCenter upgrade due to this error.