How does Docker run a Linux kernel under macOS host?

Question

I installed Docker on my macOS Sierra as follows. Note I don\'t have VirtualBox installed.

brew cask uninstall virtualbox
brew cask install docker

Answer 1

While the other answers are correct about the hypervisor, they don't answer your specific question.

The answer is "Docker [Desktop] for Mac" does run a Linux host VM with a replacement for boot2docker - LinuxKit developed and maintained by Docker for the purpose of making lightweight distributions.

https://blog.docker.com/2017/04/introducing-linuxkit-container-os-toolkit/

The uname you saw didn't have the keyword in it, but it seems to be included now, e.g. from Docker for Mac 18.03.1 I see:

Linux a8e079429a51 4.9.87-linuxkit-aufs #1 SMP Wed Mar 14 15:12:16 UTC 2018 x86_64 Linux

You can see links to the included versions on the release pages. https://docs.docker.com/docker-for-mac/release-notes/

So it's not so different from the old days Docker Machine + VirtualBox + boot2docker,

for the new days, it's just the provisioning is done internally by "Docker [Desktop] for Mac" and VirtualBox is replaced by Apple's Hyperkit, and the "default VM" is a bit more tucked away.