Containers

Containers is a virtualization method that allows an operating system to run an application in isolated user space, controlling and limiting the resources for each contained application. For an application that runs on a container, it will work as if it is running in its own operating system. Most of the containers will not know that they are hosted on another operating system. This allows the host operating system to spawn or destroy those applications without affecting any part of the system and preventing impacts of one container to another.

Since these containers are running on a hosted system, when they need to start they will be faster than in a normal virtualization that requires a new operating system to boot. However, this implied that we could not spawn a container with a different system than the running host, so we could not run a Windows application as a process in a Linux host. Docker is probably the most used container system for cloud applications, however different cloud providers may choose different systems to run their applications. We will learn more about this topic in Chapter 7, Creating Dockers.