Docker is not a VM, why does a container need a basic OS?

Question

They say that docker is not a virtual machine, and containers run directly on the host.

But why do containers need an OS?

If the process in containers runs on the base image OS, what is the difference between a virtual machine and docker (only the base image OS can be reused and read-only?)

And why does it load faster than VM?

What is an OS OS? kernel, rootfs, or both?

Answer 1

You might want to refer to this blog post: http://www.activestate.com/blog/2013/06/solomon-hykes-explains-docker

Simply put, Docker makes process isolation using LXC (a kind of lightweight virtualization built into the Linux kernel). The main difference between LXC and virtual machines is that only one instance of the Linux kernel works with LXC. The base image OS is used for the file system, binary files, etc.