Driver Toolkit

The Driver Toolkit (DTK from now on) is a container image in the OpenShift payload which is meant to be used as a base image on which to build driver containers. The Driver Toolkit image contains the kernel packages commonly required as dependencies to build or install kernel modules as well as a few tools needed in driver containers. The version of these packages will match the kernel version running on the RHCOS nodes in the corresponding OpenShift release.

Driver containers are container images used for building and deploying out-of-tree kernel modules and drivers on container OSs like Red Hat Enterprise Linux CoreOS (RHCOS). Kernel modules and drivers are software libraries running with a high level of privilege in the operating system kernel. They extend the kernel functionalities or provide the hardware-specific code required to control new devices. Examples include hardware devices like FPGAs or GPUs, and software defined storage (SDS) solutions like Lustre parallel filesystem, which all require kernel modules on client machines. Driver containers are the first layer of the software stack used to enable these technologies on Kubernetes.

The list of the packages installed in the DTK can be found in the Dockerfile.

Purpose

Prior to the Driver Toolkit's existence, you could install kernel packages in a pod or build config on OpenShift using entitled builds or by installing from the kernel RPMs in the hosts machine-os-content. The Driver Toolkit simplifies the process by removing the entitlement step, and avoids the privileged operation of accessing the machine-os-content in a pod. The Driver Toolkit can also be used by partners who have access to pre-released OpenShift versions to prebuild driver-containers for their hardware devices for future OpenShift releases.

The Driver Toolkit is also used by the Kernel Module Management (KMM), which is currently available as a community Operator on OperatorHub. KMM supports out-of-tree and third-party kernel drivers and the support software for the underlying operating system. Users can create modules for KMM to build and deploy a driver container, as well as support software like a device plug-in, or metrics. Modules can include a build config to build a driver container based on the Driver Toolkit, or KMM can deploy a prebuilt driver container.

Pulling the image

How to get the image from the Red Hat Ecosystem Catalog

The driver-toolkit image is available from the Container images section of the Red Hat Ecosystem Catalog and in the OpenShift release payload. The image corresponding to the most recent minor release of OpenShift will be tagged with the version number in the catalog. The image URL for a specific release can be found using the oc adm CLI command.

Instructions for pulling the driver-toolkit image from registry.redhat.io with podman, or in OpenShift can be found on the Red Hat Ecosystem Catalog.

The driver-toolkit image for the latest minor release will be tagged with the minor release version on registry.redhat.io for example registry.redhat.io/openshift4/driver-toolkit-rhel8:v4.8.

Finding the Driver Toolkit image URL in the payload

The following steps require the image pull secret needed to perform an installation of OpenShift, and the oc CLI.

The image URL of the driver-toolkit corresponding to a certain release can be extracted from the release image using the oc adm command:

# For x86 image:
$ oc adm release info quay.io/openshift-release-dev/ocp-release:4.8.0-x86_64 --image-for=driver-toolkit

# For ARM image:
$ oc adm release info quay.io/openshift-release-dev/ocp-release:4.8.0-aarch64 --image-for=driver-toolkit

Example output:

quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:0fd84aee79606178b6561ac71f8540f404d518ae5deff45f6d6ac8f02636c7f4

This image can be pulled using a valid pull secret.

$ podman pull --authfile=path/to/pullsecret.json <image from previous output>

Example usage

The Driver Toolkit can be used as the base image for building a very simple kernel module called simple-kmod. For these steps, you will need to be logged into an OpenShift cluster as a user with cluster-admin privileges, and access to the oc CLI.

Create a namespace for the resources:

$ oc new-project simple-kmod-demo

The following YAML defines an ImageStream for storing the simple-kmod driver container image, and a BuildConfig for building the container. You can apply the following yaml:

apiVersion: image.openshift.io/v1
kind: ImageStream
metadata:
  labels:
    app: simple-kmod-driver-container
  name: simple-kmod-driver-container
  namespace: simple-kmod-demo
spec: {}
---
apiVersion: build.openshift.io/v1
kind: BuildConfig
metadata:
  labels:
    app: simple-kmod-driver-build
  name: simple-kmod-driver-build
  namespace: simple-kmod-demo
spec:
  nodeSelector:
    node-role.kubernetes.io/worker: ""
  runPolicy: "Serial"
  triggers:
    - type: "ConfigChange"
    - type: "ImageChange"
  source:
    dockerfile: |
      ARG DTK
      FROM ${DTK} as builder

      ARG KVER

      WORKDIR /build/

      RUN git clone https://github.com/openshift-psap/simple-kmod.git

      WORKDIR /build/simple-kmod

      RUN make all install KVER=${KVER}

      FROM registry.redhat.io/ubi9/ubi-minimal

      ARG KVER

      # Required for installing `modprobe`
      RUN microdnf install kmod

      COPY --from=builder /lib/modules/${KVER}/simple-kmod.ko /lib/modules/${KVER}/
      COPY --from=builder /lib/modules/${KVER}/simple-procfs-kmod.ko /lib/modules/${KVER}/
      RUN depmod ${KVER}
  strategy:
    dockerStrategy:
      buildArgs:
        - name: KMODVER
          value: DEMO
          # $ oc adm release info quay.io/openshift-release-dev/ocp-release:<cluster version>-x86_64 --image-for=driver-toolkit
        - name: DTK
          value: quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:34864ccd2f4b6e385705a730864c04a40908e57acede44457a783d739e377cae
        - name: KVER
          value: 4.18.0-372.26.1.el8_6.x86_64
  output:
    to:
      kind: ImageStreamTag
      name: simple-kmod-driver-container:demo

You can replace the buildArgs in order to cusomize it as you need.

Once the builder pod completes successfully, deploy the driver container image as a DaemonSet. The driver container needs to run with the privileged security context in order to load the kernel modules on the host. The following .yaml file contains the RBAC rules and the DaemonSet for running the driver container. Apply the following yaml:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: simple-kmod-driver-container
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: simple-kmod-driver-container
rules:
- apiGroups:
  - security.openshift.io
  resources:
  - securitycontextconstraints
  verbs:
  - use
  resourceNames:
  - privileged
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: simple-kmod-driver-container
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: simple-kmod-driver-container
subjects:
- kind: ServiceAccount
  name: simple-kmod-driver-container
userNames:
- system:serviceaccount:simple-kmod-demo:simple-kmod-driver-container
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: simple-kmod-driver-container
spec:
  selector:
    matchLabels:
      app: simple-kmod-driver-container
  template:
    metadata:
      labels:
        app: simple-kmod-driver-container
    spec:
      serviceAccount: simple-kmod-driver-container
      serviceAccountName: simple-kmod-driver-container
      containers:
      - image: image-registry.openshift-image-registry.svc:5000/simple-kmod-demo/simple-kmod-driver-container:demo
        name: simple-kmod-driver-container
        imagePullPolicy: Always
        command: [sleep, infinity]
        lifecycle:
          postStart:
            exec:
              command: ["modprobe", "-v", "-a" , "simple-kmod", "simple-procfs-kmod"]
          preStop:
            exec:
              command: ["modprobe", "-r", "-a" , "simple-kmod", "simple-procfs-kmod"]
        securityContext:
          privileged: true
      nodeSelector:
        node-role.kubernetes.io/worker: ""

Once the pods are running on the worker nodes, we can verify that the simple_kmod kernel module is loaded successfully on the host machines with lsmod.

Verify the pods are running:

$ oc get pod -n simple-kmod-demo

Example output:

NAME                                  READY       STATUS       RESTARTS    AGE
simple-kmod-driver-build-1-build      0/1         Completed    0           6m
simple-kmod-driver-container-b22fd    1/1         Running      0           40s
simple-kmod-driver-container-jz9vn    1/1         Running      0           40s
simple-kmod-driver-container-p45cc    1/1         Running      0           40s

Execute the lsmod command in the driver container pod:

$ oc exec -it pod/simple-kmod-driver-container-p45cc -- lsmod | grep simple

Example output

simple_procfs_kmod     16384  0
simple_kmod            16384  0