Due to the flexibility of the public cloud its an useful platform to use it as an development area where by you may reinstall the OS many times. To complete the reinstall, you can do it from the OpenStack API directly and at the same time, you can change the OS of the instance if needed.
firstname.lastname@example.org:~# nova rebuild instanceName f69c46bb-7301-4d03-8aa0-45ca273677f2 The instanceName is the instance name listed in OpenStack. The last value is the image ID of the OS template. This can be the same OS you already have on the instance or a new OS to be applied to the instance.