Linux stores the random data collected from the physical resources into a random pool, and then uses two devices to turn the randomness into pseudo random numbers. These two devices are /dev/random and /dev/urandom. They have different behaviors. The /dev/random device is a blocking device. Namely, every time a random number is given out by this device, the entropy of the randomness pool will be decreased. When the entropy reaches zero, /dev/random will block, until it gains enough randomness. Let us design an experiment to observe the behavior of the/dev/random device. We will use the cat command for nice printing. s cat /dev/random hexdump to keep reading pseudo random numbers from /dev/random. We pipe the output to hexdump