[derobert]

A lot of these things do exist. Desktop/server Linux systems (used to at least) save some output from the PRNG to disk on shutdown and load it back on boot.

But of course snapshots, cloning, etc. can foil that badly, causing the same seed to be used multiple times. And on initial install you're not going to have any of that (but initial install is also when you may need to generate long-lived random numbers like ssh host keys).

Embedded devices it can be a real challenge. You must not re-use the seed data, so you effectively have to erase it from NVRAM/flash before use. But then if you lose power before you can generate a new one, you won't have one next boot. And you're adding flash writes, which decreases longevity and increases the chance of power failure in the middle of a write.

Qemu/KVM has a virtual RNG so you can feed host randomness into the guests if you want. So there are hypervisor calls available.