How does Docker run a Linux kernel under macOS host?
I installed Docker on my macOS Sierra as follows. Note I don't have VirtualBox installed.
brew cask uninstall virtualbox
brew cask install docker
My macOS details.
$ uname -a
Darwin m-C02QG7TRG8WN.local 16.5.0 Darwin Kernel Version 16.5.0: Fri Mar 3 16:52:33 PST 2017; root:xnu-3789.51.2~3/RELEASE_X86_64 x86_64
$ docker version
Client:
Version: 17.03.1-ce
API version: 1.27
Go version: go1.7.5
Git commit: c6d412e
Built: Tue Mar 28 00:40:02 2017
OS/Arch: darwin/amd64
Server:
Version: 17.03.1-ce
API version: 1.27 (minimum version 1.12)
Go version: go1.7.5
Git commit: c6d412e
Built: Fri Mar 24 00:00:50 2017
OS/Arch: linux/amd64
Experimental: true
Once I run Docker from launchpad, I am able to run Docker containers.
$ docker run -it ubuntu
root@2351d4222a4e:/# uname -a
Linux 2351d4222a4e 4.9.13-moby #1 SMP Sat Mar 25 02:48:44 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
My question is how does Docker manage to run a Linux kernel within macOS? I thought Docker would at least require boot2docker or some other such Linux kernel running so that it can create the Ubuntu's filesystem with the help of it. But the above output seems to indicate that it is not so. Where does the Linux kernel come from then?
The early version Docker used VirtualBox to run virtual machine for Docker. Since June 2016, the way to run Docker on Mac and Windows became mush simpler, there's the official release introduction blog for Docker on Mac/Windows, and there's also some introduction from docker mac website:
Docker for Mac is a complete development environment deeply integrated with the MacOS Hypervisor framework, networking and filesystem.
And with the structure looks like:
Docker is using Apple's Hypervisor Framework: https://developer.apple.com/reference/hypervisor
More reading on the Docker blogs for when then came out last year: https://blog.docker.com/2016/05/docker-unikernels-open-source/
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