A guest image is technically just another Nova template on which some additional customization has been performed. The guest image technically has to fulfill the following aspects:
It should have an operating system, and a database engine (installed or the ability to install it) format that Trove supports
It should be in a format that Nova can boot – which means it should be of the same format of the hypervisor that we are trying to use with Nova
It should have the Trove guest agent installed (or a way to install and configure the Trove guest agent)
The image, like all the other OpenStack images, will be stored in Glance so that it can be called and used by Nova and finally by Trove to orchestrate and manage the database engine that will be installed in the system itself.
As we have already seen in the previous chapters, the guest agent is different for different database engines, and hence the correct version of the guest agent needs to be installed on the system...