[Panino]

OpenBSD has two seed files but random number generation isn't limited to them. OpenBSD has more random sources (such as from jitter) than other systems and regularly reseeds itself. Both seed files are re-written multiple times during the boot process, each time incorporating new random. So by the time sshd starts for the very first time and creates host keys (like ssh-keygen -A), those keys should have access to good random.

The first file, /etc/random.seed is 512 bytes and is available very early as it's on the root filesystem. This file is re-written by rc(8) at every boot, halt, shutdown, and reboot.

Second, /var/db/host.random is 65536 bytes. It is also re-written by rc at every boot, halt, shutdown and reboot.

In addition to all that, rc includes:

  # If bootblocks failed to give us random, try to cause some churn
  (dmesg; sysctl hw.{uuid,serialno,sensors} ) >/dev/random 2>&1

I just checked my VMs and they all print unique values for dmesg, hw.uuid and hw.serialno. I can guess but I don't know how hw.uuid and hw.serialno are set.