Docker in a GKE sandbox

Docker is a platform designed to help developers build, share, and run container applications.

In gVisor, all basic docker commands should function as expected. The host network driver and the bridge network driver are supported.

How to run Docker in a GKE Sandbox

Supported Docker version mapping in GKE cluster

GKE standard cluster

Install a GKE standard cluster and deploy a node pool with gVisor enabled. You can view the full documentation here.

GKE Autopilot cluster

Alternatively to GKE standard cluster, you could run docker in gVisor at GKE autopilot cluster. GKE autopilot is a fully managed mode of operation in GKE that automates cluster infrastructure management, including node provisioning, scaling, and security.

When creating the autopilot cluster, please add the option --workload-policies=allow-net-admin to allow NET_ADMIN capability that will be granted by the gVisor sandbox which is needed by docker daemon.

An example command to start an GKE autopilot cluster will be:

gcloud container clusters create-auto [CLUTER_NAME] --workload-policies=allow-net-admin --location=[LOCATION]

Get started

Prepare a container image with pre-installed Docker:

$ docker build -t docker-in-gvisor images/basic/docker/
$ docker push {registry_url}/docker-in-gvisor:latest

Create a Kubernetes pod YAML file (docker.yaml) with the following content:

apiVersion: v1
kind: Pod
metadata:
  name: docker-in-gvisor
spec:
  runtimeClassName: gvisor
  containers:
  - name: docker-in-gvisor
    image: {registry_url}/docker-in-gvisor:latest
    securityContext:
      capabilities:
        # NOTE: This setting does **not** grant any capabilities on the host.
        # gVisor *always* runs with zero privileges and zero capabilities,
        # regardless of this setting.
        add: [
          # Required for Docker daemon to work in the sandbox.
          # This does *NOT* grant any host capabilities. See below.
          NET_ADMIN,SYS_ADMIN,
          # Default set of capabilities granted to any container:
          AUDIT_WRITE,CHOWN,DAC_OVERRIDE,FOWNER,FSETID,KILL,MKNOD,NET_BIND_SERVICE,NET_RAW,SETFCAP,SETGID,SETPCAP,SETUID,SYS_CHROOT,SYS_PTRACE,
        ]
    volumeMounts:
      - name: docker
        # NOTE: This does *not* expose any host directory;
        # this just mounts a tmpfs here.
        mountPath: /var/lib/docker
  volumes:
  - name: docker
    emptyDir: {}  # tmpfs

NOTE: gVisor never runs with capabilities on the host Linux kernel, even when the above securityContext.capabilities fields are specified. These fields only control the capabilities perceived by the in-sandbox application (in this case, the in-sandbox Docker daemon). This does not provide the sandboxed application, nor the gVisor sandbox itself, any host privileges.

This YAML file defines a Kubernetes Pod named docker-in-gvisor that will run a single container from the {registry_url}/docker-in-gvisor:latest image.

Apply the pod YAML to your GKE cluster using the kubectl apply command:

$ kubectl apply -f docker.yaml

Verify that the docker-in-gvisor pid is running successfully: shell $ kubectl get pods | grep docker-in-gvisor

Build and run the image with docker in gVisor

You can access the container by executing a shell inside it. Use the following command:

kubectl exec -it docker-in-gvisor -- bash

Now, we can build and run Docker containers.

$ mkdir whalesay && cd whalesay
$ cat > Dockerfile <<EOF
FROM ubuntu

RUN apt-get update && apt-get install -y cowsay curl
RUN mkdir -p /usr/share/cowsay/cows/
RUN curl -o /usr/share/cowsay/cows/docker.cow https://raw.githubusercontent.com/docker/whalesay/master/docker.cow
ENTRYPOINT ["/usr/games/cowsay", "-f", "docker.cow"]
EOF
$ docker build -t whalesay .
....
Successfully tagged whalesay:latest
$ docker run -it --rm whalesay "Containers do not contain, but gVisor-s do!"
 _________________________________________
/ Containers do not contain, but gVisor-s \
\ do!                                     /
 -----------------------------------------
   \               ##         .
    \        ## ## ##        ==
          ## ## ## ##       ===
       /""""""""""""""""\___/ ===
  ~~~ {~~ ~~~~ ~~~ ~~~~ ~~ ~ /  ===- ~~~
       \______ o          __/
         \    \        __/
          \____\______/