I think how you are asking candidates the question might be unfortunate. A FreeBSD, MacOSX, or Windows dev that know their OSes might never tell you "namespace + cgroup".
Hell if you try to explain containers to 99% of the world programmers by saying "namespace + cgroup", I'd bet you that 0% of them will understand what you mean.
Instead, if you tell them that's "like a VM, but faster, because it "reuses" the host's kernel", you might be able to reach a substantial amount of them, and that level of abstraction would be enough for most of them to do something useful with containers.
Maybe the question you should be asking your candidates is: "How would you implement a Docker-like container app on Linux?". That's a question that specifically constraints the level of abstraction of the answer to at least one layer below Docker, and also specifies that you are interested on hearing the details for Linux.
Hell if you try to explain containers to 99% of the world programmers by saying "namespace + cgroup", I'd bet you that 0% of them will understand what you mean.
Instead, if you tell them that's "like a VM, but faster, because it "reuses" the host's kernel", you might be able to reach a substantial amount of them, and that level of abstraction would be enough for most of them to do something useful with containers.
Maybe the question you should be asking your candidates is: "How would you implement a Docker-like container app on Linux?". That's a question that specifically constraints the level of abstraction of the answer to at least one layer below Docker, and also specifies that you are interested on hearing the details for Linux.