Introduction The Linux Kernel supplies two sources of random numbers, /dev/random and /dev/urandom. Theses character devices can supply random numbers to any application running on your machine. The random numbers supplied by the kernel on these devices come from the Linux kernel’s random-number entropy pool. The random-number entropy pool contains “sufficiently random” numbers meaning they are good for use in things like secure communications. But what happens if the random-number entropy pool runs out of numbers?