A standard upgrade of an earlier virtual SMU to version 15.4.8300.00 or later will not upgrade the operating system version. If you want to upgrade an existing CentOS 6 or CentOS Stream 8 SMU to run on CentOS Stream 9, while preserving the existing network address, it is necessary to deploy a new virtual SMU and migrate the settings from the existing SMU to the new one by performing a backup and restore.
Note: The SMU will be temporarily unavailable while following this procedure.