The default distro is Container Optimised OS: https://cloud.google.com/container-optimized-os/docs/. It's derived from Chromium OS, which means we can take advantage of the team who build images for the many devices which use it, and the security response infrastructure around it.

With 'docker info' on a node you can see we use OverlayFS, which seems a popular choice in the community also: http://burkelibbey.s3.amazonaws.com/dockercon-fs.pdf

So, customized Google OS, but using the official Docker package? Oh wait. How could there be an official docker package for an OS noone known existed?

I assume customized kernel as well? and where does the overlay drivers come from? How much custom back-ports and custom development?

The article is not on point to say GKE replaced docker entirely then... but you are not point to deny and pretend that you are running Docker on anything remotely common.

Chromium OS is open source: https://www.chromium.org/chromium-os. OverlayFS is in the upstream Linux kernel.

CoreOS is a very similar idea, and given that, we don't make builds of the container images available outside GCE.

Customers who need specifics of the OS (that they can't find them by just looking at the kernel config on the node) are welcome to ping us a support ticket.