While the kernel offers all sorts of APIs to manipulate namespaces and processes at a fine-grained level, that is often not especially helpful when trying to build systems at a more coarse-grained level, such as a macro container. As is common practice in programming, therefore, various other tools have sprung up to abstract those low-level APIs into easier to use higher-level APIs.

.@Crell's article on containers, unix processes and the fact that everything we've ever built is a lie in february's @phparch is super interesting. You should check it out if you haven't already #php

— James Mallison (@J7mbo) March 2, 2018