Before we get too deep into Docker itself, let us also cover some of the current competitors in broad strokes and see how they differ from Docker itself. The curious thing about almost all of them is that they are generally a form of abstraction around Linux control groups (cgroups) and namespaces that limit the use of Linux host's physical resources and isolate groups of processes from each other, respectively. While almost every tooling mentioned here provides some sort of containerization of resources, it can differ greatly in the depth of isolation, implementation security, and/or the container distribution.