Most cloud providers grant instances that run in KVM or Xen, which usually or always implies that the owner of the instance doesn't have low-level access to the hypervisor that would be needed in order to create a OS image from scratch, for instance.
This makes me think something like Bochs might be useful for building and testing OS images within a cloud/CI environment, an emulator like Bochs should be able to run within a VM, but would be more slow. Though as an advantage, Bochs would let you test on different hardware, but I don't consider this a requirement at this time.
Is there a somewhat standard solution to this problem? There are many open source distributions and operating systems out there - I'd be interested to know the more elegant approaches taken that might satisfy this requirement (even if they aren't really standard).
Note that containers don't seem like the answer - you may be testing for kernel-specific features in some cases, or even testing a different OS. (However, maybe containers could be useful for instantiating a portable and fast build environment!)
