Namespaces

In the previous article we found out that the kernel makes all the memory feel like one single big thing, even though underneath it’s split into pieces. Today we go the other way: we’re going to make one machine look like several.

You’ve probably done this already without thinking about it. Start a container, and the processes inside it see their own hostname, their own list of processes, their own network and their own filesystem, as if they had the machine to themselves. But there’s no second machine and no second kernel. It’s the same kernel answering everybody, but when they ask for something like the hostname, each of them can receive a different answer.