Recently, we have extended OpenSSH so that it also does SSH 2 protocol. The generated numbers should not have repeating patterns which means the PRNG should have a very long cycle length. A PRNG is normally just an algorithm where the same initial starting values will yield the same sequence of outputs. On a multiuser operating system there are many sources which allow seeding the PRNG with random data. The OpenBSD kernel uses the mouse interrupt timing, network data interrupt latency, inter-keypress timing and disk IO information to fill an entropy pool.
Random numbers are available for kernel routines and are exported via devices to userland programs.
PIDs of processes. IP datagram IDs. Randomness added to the TCP ISS value for protection against spoofing attacks. To generate salts for the various password algorithms. In photurisd and isakmpd to provide liveness proof of key exchanges.