We learnt from functional programming that state is something we need to control to make maintainable code. Systems where state is changed in an uncontrolled and hard to debug way are fortunately becoming less common. Until you install a Linux distribution that is: then you discover a system that is full of mutable state scattered all over the filesystem, which gradually bitrots over time. LinuxKit is a new alternative based on immutability, built from containers, with controlled state management. And it is quick and easy to run in your continuous delivery pipeline, building an operating system in a minute or so.
Justin Cormack is an engineer at Docker, based in Cambridge UK. He works largely on Docker's open source projects. He used to be a sysadmin in a past life.