[geofft]

Ugh, yes, the practice of short-lived machines throws off the assumption of "when it was last shut down." You are totally right that this is a concern.

The ideal solution to this would be for hypervisors to just pass a random seed to their guests. (There is even a full virtio-rng device in qemu, it just seems to have /dev/random semantics from a quick glance.) I don't know how we get to the point of convincing the big cloud providers to start doing this, though.

[jasonvorhe]

Wouldn't it help to run something like havaged on the virtualization host that's feeding entropy to the virtualized nodes?

[jquast]

yes