[$] Containers, pseudo TTYs, and backward compatibility
There is no doubt that the addition of container technologies to Linux has created a lot of value, allowing workloads to be effectively and efficiently isolated from each other. Implementing these technologies presents a number of challenges, particularly as much of Linux and Unix was designed to use singletons: objects of which there could never ever be more than one, such as host names, network routing tables, or process-ID namespaces. Containers require this design approach to be revised as they need multiple instances of these objects. A singleton that has been causing problems recently is the set of pseudo terminals (TTYs).

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