Entropy is a measurement of the amount of randomness in a system. All systems need entropy to run in a secure fashion. We'll do a deep dive into entropy; what entropy is, how it's used, and how it's generated and kept in a pool in the linux kernel. We'll also give some important safety tips.Entropy is a tricky subject. It measures something, but what it measures is sometimes not quite clear. It's also not very clear how the linux kernel gathers entropy and when and how it uses it.