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Kernel Module Management Operator | Specialized hardware and driver enablement | OpenShift Container Platform 4.12
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Kernel Module Management Operator

About the Kernel Module Management Operator

The Kernel Module Management (KMM) Operator manages, builds, signs, and deploys out-of-tree kernel modules and device plugins on OpenShift Container Platform clusters.

KMM adds a new Module CRD which describes an out-of-tree kernel module and its associated device plugin. You can use Module resources to configure how to load the module, define ModuleLoader images for kernel versions, and include instructions for building and signing modules for specific kernel versions.

KMM is designed to accommodate multiple kernel versions at once for any kernel module, allowing for seamless node upgrades and reduced application downtime.

Installing the Kernel Module Management Operator

As a cluster administrator, you can install the Kernel Module Management (KMM) Operator by using the OpenShift CLI or the web console.

The KMM Operator is supported on OpenShift Container Platform 4.12 and later. Installing KMM on version 4.11 does not require specific additional steps. For details on installing KMM on version 4.10 and earlier, see the section "Installing the Kernel Module Management Operator on earlier versions of OpenShift Container Platform".

Installing the Kernel Module Management Operator using the web console

As a cluster administrator, you can install the Kernel Module Management (KMM) Operator using the OpenShift Container Platform web console.

Procedure

  1. Log in to the OpenShift Container Platform web console.

  2. Install the Kernel Module Management Operator:

    1. In the OpenShift Container Platform web console, click Operators → OperatorHub.

    2. Select Kernel Module Management Operator from the list of available Operators, and then click Install.

    3. On the Install Operator page, select the Installation mode as A specific namespace on the cluster.

    4. From the Installed Namespace list, select the openshift-kmm namespace.

    5. Click Install.

Verification

To verify that KMM Operator installed successfully:

  1. Navigate to the Operators → Installed Operators page.

  2. Ensure that Kernel Module Management Operator is listed in the openshift-kmm project with a Status of InstallSucceeded.

    During installation, an Operator might display a Failed status. If the installation later succeeds with an InstallSucceeded message, you can ignore the Failed message.
Troubleshooting

  1. To troubleshoot issues with Operator installation:

    1. Navigate to the Operators → Installed Operators page and inspect the Operator Subscriptions and Install Plans tabs for any failure or errors under Status.

    2. Navigate to the Workloads → Pods page and check the logs for pods in the openshift-kmm project.

Installing the Kernel Module Management Operator by using the CLI

As a cluster administrator, you can install the Kernel Module Management (KMM) Operator by using the OpenShift CLI.

Prerequisites

  • You have a running OpenShift Container Platform cluster.

  • You installed the OpenShift CLI (oc).

  • You are logged into the OpenShift CLI as a user with cluster-admin privileges.

Procedure

  1. Install KMM in the openshift-kmm namespace:

    1. Create the following Namespace CR and save the YAML file, for example, kmm-namespace.yaml:

      apiVersion: v1
kind: Namespace
metadata:
  name: openshift-kmm

    2. Create the following OperatorGroup CR and save the YAML file, for example, kmm-op-group.yaml:

      apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: kernel-module-management
  namespace: openshift-kmm

    3. Create the following Subscription CR and save the YAML file, for example, kmm-sub.yaml:

      apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: kernel-module-management
  namespace: openshift-kmm
spec:
  channel: release-1.0
  installPlanApproval: Automatic
  name: kernel-module-management
  source: redhat-operators
  sourceNamespace: openshift-marketplace
  startingCSV: kernel-module-management.v1.0.0

    4. Create the subscription object by running the following command:

      $ oc create -f kmm-sub.yaml
Verification

  • To verify that the Operator deployment is successful, run the following command:

    $ oc get -n openshift-kmm deployments.apps kmm-operator-controller-manager
    Example output
    NAME                              READY UP-TO-DATE  AVAILABLE AGE
kmm-operator-controller-manager   1/1   1           1         97s

    The Operator is available.

Installing the Kernel Module Management Operator on earlier versions of OpenShift Container Platform

The KMM Operator is supported on OpenShift Container Platform 4.12 and later. For version 4.10 and earlier, you must create a new SecurityContextConstraint object and bind it to the Operator’s ServiceAccount. As a cluster administrator, you can install the Kernel Module Management (KMM) Operator by using the OpenShift CLI.

Prerequisites

  • You have a running OpenShift Container Platform cluster.

  • You installed the OpenShift CLI (oc).

  • You are logged into the OpenShift CLI as a user with cluster-admin privileges.

Procedure

  1. Install KMM in the openshift-kmm namespace:

    1. Create the following Namespace CR and save the YAML file, for example, kmm-namespace.yaml file:

      apiVersion: v1
kind: Namespace
metadata:
  name: openshift-kmm

    2. Create the following SecurityContextConstraint object and save the YAML file, for example, kmm-security-constraint.yaml:

      allowHostDirVolumePlugin: false
allowHostIPC: false
allowHostNetwork: false
allowHostPID: false
allowHostPorts: false
allowPrivilegeEscalation: false
allowPrivilegedContainer: false
allowedCapabilities:
  - NET_BIND_SERVICE
apiVersion: security.openshift.io/v1
defaultAddCapabilities: null
fsGroup:
  type: MustRunAs
groups: []
kind: SecurityContextConstraints
metadata:
  name: restricted-v2
priority: null
readOnlyRootFilesystem: false
requiredDropCapabilities:
  - ALL
runAsUser:
  type: MustRunAsRange
seLinuxContext:
  type: MustRunAs
seccompProfiles:
  - runtime/default
supplementalGroups:
  type: RunAsAny
users: []
volumes:
  - configMap
  - downwardAPI
  - emptyDir
  - persistentVolumeClaim
  - projected
  - secret

    3. Bind the SecurityContextConstraint object to the Operator’s ServiceAccount by running the following commands:

      $ oc apply -f kmm-security-constraint.yaml
      $ oc adm policy add-scc-to-user kmm-security-constraint -z kmm-operator-controller-manager -n openshift-kmm

    4. Create the following OperatorGroup CR and save the YAML file, for example, kmm-op-group.yaml:

      apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: kernel-module-management
  namespace: openshift-kmm

    5. Create the following Subscription CR and save the YAML file, for example, kmm-sub.yaml:

      apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: kernel-module-management
  namespace: openshift-kmm
spec:
  channel: release-1.0
  installPlanApproval: Automatic
  name: kernel-module-management
  source: redhat-operators
  sourceNamespace: openshift-marketplace
  startingCSV: kernel-module-management.v1.0.0

    6. Create the subscription object by running the following command:

      $ oc create -f kmm-sub.yaml
Verification

  • To verify that the Operator deployment is successful, run the following command:

    $ oc get -n openshift-kmm deployments.apps kmm-operator-controller-manager
    Example output
    NAME                              READY UP-TO-DATE  AVAILABLE AGE
kmm-operator-controller-manager   1/1   1           1         97s

    The Operator is available.

Kernel module deployment

For each Module resource, Kernel Module Management (KMM) can create a number of DaemonSet resources:

  • One ModuleLoader DaemonSet per compatible kernel version running in the cluster.

  • One device plugin DaemonSet, if configured.

The module loader daemon set resources run ModuleLoader images to load kernel modules. A module loader image is an OCI image that contains the .ko files and both the modprobe and sleep binaries.

When the module loader pod is created, the pod runs modprobe to insert the specified module into the kernel. It then enters a sleep state until it is terminated. When that happens, the ExecPreStop hook runs modprobe -r to unload the kernel module.

If the .spec.devicePlugin attribute is configured in a Module resource, then KMM creates a device plugin daemon set in the cluster. That daemon set targets:

  • Nodes that match the .spec.selector of the Module resource.

  • Nodes with the kernel module loaded (where the module loader pod is in the Ready condition).

The Module custom resource definition

The Module custom resource definition (CRD) represents a kernel module that can be loaded on all or select nodes in the cluster, through a module loader image. A Module custom resource (CR) specifies one or more kernel versions with which it is compatible, and a node selector.

The compatible versions for a Module resource are listed under .spec.moduleLoader.container.kernelMappings. A kernel mapping can either match a literal version, or use regexp to match many of them at the same time.

The reconciliation loop for the Module resource runs the following steps:

  1. List all nodes matching .spec.selector.

  2. Build a set of all kernel versions running on those nodes.

  3. For each kernel version:

    1. Go through .spec.moduleLoader.container.kernelMappings and find the appropriate container image name. If the kernel mapping has build or sign defined and the container image does not already exist, run the build, the signing job, or both, as needed.

    2. Create a module loader daemon set with the container image determined in the previous step.

    3. If .spec.devicePlugin is defined, create a device plugin daemon set using the configuration specified under .spec.devicePlugin.container.

  4. Run garbage-collect on:

    1. Existing daemon set resources targeting kernel versions that are not run by any node in the cluster.

    2. Successful build jobs.

    3. Successful signing jobs.

Security and permissions

Loading kernel modules is a highly sensitive operation. After they are loaded, kernel modules have all possible permissions to do any kind of operation on the node.

ServiceAccounts and SecurityContextConstraints

Kernel Module Management (KMM) creates a privileged workload to load the kernel modules on nodes. That workload needs ServiceAccounts allowed to use the privileged SecurityContextConstraint (SCC) resource.

The authorization model for that workload depends on the namespace of the Module resource, as well as its spec.

  • If the .spec.moduleLoader.serviceAccountName or .spec.devicePlugin.serviceAccountName fields are set, they are always used.

  • If those fields are not set, then:

    • If the Module resource is created in the operator’s namespace (openshift-kmm by default), then KMM uses its default, powerful ServiceAccounts to run the daemon sets.

    • If the Module resource is created in any other namespace, then KMM runs the daemon sets as the namespace’s default ServiceAccount. The Module resource cannot run a privileged workload unless you manually enable it to use the privileged SCC.

openshift-kmm is a trusted namespace.

When setting up RBAC permissions, remember that any user or ServiceAccount creating a Module resource in the openshift-kmm namespace results in KMM automatically running privileged workloads on potentially all nodes in the cluster.

To allow any ServiceAccount to use the privileged SCC and therefore to run module loader or device plugin pods, use the following command:

$ oc adm policy add-scc-to-user privileged -z "${serviceAccountName}" [ -n "${namespace}" ]

Pod security standards

OpenShift runs a synchronization mechanism that sets the namespace Pod Security level automatically based on the security contexts in use. No action is needed.

Additional resources

Example Module CR

The following is an annotated Module example:

apiVersion: kmm.sigs.x-k8s.io/v1beta1
kind: Module
metadata:
  name: <my_kmod>
spec:
  moduleLoader:
    container:
      modprobe:
        moduleName: <my_kmod> (1)
        dirName: /opt (2)
        firmwarePath: /firmware (3)
        parameters:  (4)
          - param=1
      kernelMappings:  (5)
        - literal: 6.0.15-300.fc37.x86_64
          containerImage: some.registry/org/my-kmod:6.0.15-300.fc37.x86_64
        - regexp: '^.+\fc37\.x86_64$' (6)
          containerImage: "some.other.registry/org/<my_kmod>:${KERNEL_FULL_VERSION}"
        - regexp: '^.+$' (7)
          containerImage: "some.registry/org/<my_kmod>:${KERNEL_FULL_VERSION}"
          build:
            buildArgs:  (8)
              - name: ARG_NAME
                value: <some_value>
            secrets:
              - name: <some_kubernetes_secret>  (9)
            baseImageRegistryTLS: (10)
              insecure: false
              insecureSkipTLSVerify: false (11)
            dockerfileConfigMap:  (12)
              name: <my_kmod_dockerfile>
          sign:
            certsecret:
              name: <cert_secret>  (13)
            keysecret:
              name: <key_secret>  (14)
            filesToSign:
              - /opt/lib/modules/${KERNEL_FULL_VERSION}/<my_kmod>.ko
          registryTLS: (15)
            insecure: false (16)
            insecureSkipTLSVerify: false
    serviceAccountName: <sa_module_loader>  (17)
  devicePlugin:  (18)
    container:
      image: some.registry/org/device-plugin:latest  (19)
      env:
        - name: MY_DEVICE_PLUGIN_ENV_VAR
          value: SOME_VALUE
      volumeMounts:  (20)
        - mountPath: /some/mountPath
          name: <device_plugin_volume>
    volumes:  (21)
      - name: <device_plugin_volume>
        configMap:
          name: <some_configmap>
    serviceAccountName: <sa_device_plugin> (22)
  imageReposecret:  (23)
    name: <secret_name>
  selector:
    node-role.kubernetes.io/worker: ""
1 Required.
2 Optional.
3 Optional: Copies /firmware/* into /var/lib/firmware/ on the node.
4 Optional.
5 At least one kernel item is required.
6 For each node running a kernel matching the regular expression, KMM creates a DaemonSet resource running the image specified in containerImage with ${KERNEL_FULL_VERSION} replaced with the kernel version.
7 For any other kernel, build the image using the Dockerfile in the my-kmod ConfigMap.
8 Optional.
9 Optional: A value for some-kubernetes-secret can be obtained from the build environment at /run/secrets/some-kubernetes-secret.
10 Optional: Avoid using this parameter. If set to true, the build is allowed to pull the image in the Dockerfile FROM instruction using plain HTTP.
11 Optional: Avoid using this parameter. If set to true, the build will skip any TLS server certificate validation when pulling the image in the Dockerfile FROM instruction using plain HTTP.
12 Required.
13 Required: A secret holding the public secureboot key with the key 'cert'.
14 Required: A secret holding the private secureboot key with the key 'key'.
15 Optional: Avoid using this parameter. If set to true, KMM will be allowed to check if the container image already exists using plain HTTP.
16 Optional: Avoid using this parameter. If set to true, KMM will skip any TLS server certificate validation when checking if the container image already exists.
17 Optional.
18 Optional.
19 Required: If the device plugin section is present.
20 Optional.
21 Optional.
22 Optional.
23 Optional: Used to pull module loader and device plugin images.

Using a ModuleLoader image

Kernel Module Management (KMM) works with purpose-built module loader images. These are standard OCI images that must satisfy the following requirements:

  • .ko files must be located in /opt/lib/modules/${KERNEL_VERSION}.

  • modprobe and sleep binaries must be defined in the $PATH variable.

Running depmod

If your module loader image contains several kernel modules and if one of the modules depends on another module, it is best practice to run depmod at the end of the build process to generate dependencies and map files.

You must have a Red Hat subscription to download the kernel-devel package.
Procedure

  1. To generate modules.dep and .map files for a specific kernel version, run depmod -b /opt ${KERNEL_VERSION}.

Example Dockerfile

If you are building your image on OpenShift Container Platform, consider using the Driver Tool Kit (DTK).

For further information, see using an entitled build.

apiVersion: v1
kind: ConfigMap
metadata:
  name: kmm-ci-dockerfile
data:
  dockerfile: |
    ARG DTK_AUTO
    FROM ${DTK_AUTO} as builder
    ARG KERNEL_VERSION
    WORKDIR /usr/src
    RUN ["git", "clone", "https://github.com/rh-ecosystem-edge/kernel-module-management.git"]
    WORKDIR /usr/src/kernel-module-management/ci/kmm-kmod
    RUN KERNEL_SRC_DIR=/lib/modules/${KERNEL_VERSION}/build make all
    FROM registry.redhat.io/ubi8/ubi-minimal
    ARG KERNEL_VERSION
    RUN microdnf install kmod
    COPY --from=builder /usr/src/kernel-module-management/ci/kmm-kmod/kmm_ci_a.ko /opt/lib/modules/${KERNEL_VERSION}/
    COPY --from=builder /usr/src/kernel-module-management/ci/kmm-kmod/kmm_ci_b.ko /opt/lib/modules/${KERNEL_VERSION}/
    RUN depmod -b /opt ${KERNEL_VERSION}
Additional resources

Building in the cluster

KMM can build module loader images in the cluster. Follow these guidelines:

  • Provide build instructions using the build section of a kernel mapping.

  • Copy the Dockerfile for your container image into a ConfigMap resource, under the dockerfile key.

  • Ensure that the ConfigMap is located in the same namespace as the Module.

KMM checks if the image name specified in the containerImage field exists. If it does, the build is skipped.

Otherwise, KMM creates a Build resource to build your image. After the image is built, KMM proceeds with the Module reconciliation. See the following example.

# ...
- regexp: '^.+$'
  containerImage: "some.registry/org/<my_kmod>:${KERNEL_FULL_VERSION}"
  build:
    buildArgs:  (1)
      - name: ARG_NAME
        value: <some_value>
    secrets: (2)
      - name: <some_kubernetes_secret> (3)
    baseImageRegistryTLS:
      insecure: false (4)
      insecureSkipTLSVerify: false (5)
    dockerfileConfigMap:  (6)
      name: <my_kmod_dockerfile>
  registryTLS:
    insecure: false (7)
    insecureSkipTLSVerify: false (8)
1 Optional.
2 Optional.
3 Will be mounted in the build pod as /run/secrets/some-kubernetes-secret.
4 Optional: Avoid using this parameter. If set to true, the build will be allowed to pull the image in the Dockerfile FROM instruction using plain HTTP.
5 Optional: Avoid using this parameter. If set to true, the build will skip any TLS server certificate validation when pulling the image in the Dockerfile FROM instruction using plain HTTP.
6 Required.
7 Optional: Avoid using this parameter. If set to true, KMM will be allowed to check if the container image already exists using plain HTTP.
8 Optional: Avoid using this parameter. If set to true, KMM will skip any TLS server certificate validation when checking if the container image already exists.
Additional resources

Using the Driver Toolkit

The Driver Toolkit (DTK) is a convenient base image for building build module loader images. It contains tools and libraries for the OpenShift version currently running in the cluster.

Procedure

Use DTK as the first stage of a multi-stage Dockerfile.

  1. Build the kernel modules.

  2. Copy the .ko files into a smaller end-user image such as ubi-minimal.

  3. To leverage DTK in your in-cluster build, use the DTK_AUTO build argument. The value is automatically set by KMM when creating the Build resource. See the following example.

    ARG DTK_AUTO
FROM ${DTK_AUTO} as builder
ARG KERNEL_VERSION
WORKDIR /usr/src
RUN ["git", "clone", "https://github.com/rh-ecosystem-edge/kernel-module-management.git"]
WORKDIR /usr/src/kernel-module-management/ci/kmm-kmod
RUN KERNEL_SRC_DIR=/lib/modules/${KERNEL_VERSION}/build make all
FROM registry.redhat.io/ubi8/ubi-minimal
ARG KERNEL_VERSION
RUN microdnf install kmod
COPY --from=builder /usr/src/kernel-module-management/ci/kmm-kmod/kmm_ci_a.ko /opt/lib/modules/${KERNEL_VERSION}/
COPY --from=builder /usr/src/kernel-module-management/ci/kmm-kmod/kmm_ci_b.ko /opt/lib/modules/${KERNEL_VERSION}/
RUN depmod -b /opt ${KERNEL_VERSION}
Additional resources

Using signing with Kernel Module Management (KMM)

On a Secure Boot enabled system, all kernel modules (kmods) must be signed with a public/private key-pair enrolled into the Machine Owner’s Key (MOK) database. Drivers distributed as part of a distribution should already be signed by the distribution’s private key, but for kernel modules build out-of-tree, KMM supports signing kernel modules using the sign section of the kernel mapping.

For more details on using Secure Boot, see Generating a public and private key pair

Prerequisites

  • A public private key pair in the correct (DER) format.

  • At least one secure-boot enabled node with the public key enrolled in its MOK database.

  • Either a pre-built driver container image, or the source code and Dockerfile needed to build one in-cluster.

Adding the keys for secureboot

To use KMM Kernel Module Management (KMM) to sign kernel modules, a certificate and private key are required. For details on how to create these, see Generating a public and private key pair.

For details on how to extract the public and private key pair, see Signing kernel modules with the private key. Use steps 1 through 4 to extract the keys into files.

Procedure

  1. Create the sb_cert.cer file that contains the certificate and the sb_cert.priv file that contains the private key:

    $ openssl req -x509 -new -nodes -utf8 -sha256 -days 36500 -batch -config configuration_file.config -outform DER -out my_signing_key_pub.der -keyout my_signing_key.priv

  2. Add the files by using one of the following methods:

    • Add the files as secrets directly:

      $ oc create secret generic my-signing-key --from-file=key=<my_signing_key.priv>
      $ oc create secret generic my-signing-key-pub --from-file=cert=<my_signing_key_pub.der>

    • Add the files by base64 encoding them:

      $ cat sb_cert.priv | base64 -w 0 > my_signing_key2.base64
      $ cat sb_cert.cer | base64 -w 0 > my_signing_key_pub.base64

  3. Add the encoded text to a YAML file:

    apiVersion: v1
kind: secret
metadata:
  name: my-signing-key-pub
  namespace: default (1)
type: Opaque
data:
  cert: <base64_encoded_secureboot_public_key>

---
apiVersion: v1
kind: secret
metadata:
  name: my-signing-key
  namespace: default (1)
type: Opaque
data:
  key: <base64_encoded_secureboot_private_key>
    1 namespace - Replace default with a valid namespace.

  4. Apply the YAML file:

    $ oc apply -f <yaml_filename>

Checking the keys

After you have added the keys, you must check them to ensure they are set correctly.

Procedure

  1. Check to ensure the public key secret is set correctly:

    $ oc get secret -o yaml <certificate secret name> | awk '/cert/{print $2; exit}' | base64 -d  | openssl x509 -inform der -text

    This should display a certificate with a Serial Number, Issuer, Subject, and more.

  2. Check to ensure the private key secret is set correctly:

    $ oc get secret -o yaml <private key secret name> | awk '/key/{print $2; exit}' | base64 -d

    This should display the key enclosed in the -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY----- lines.

Signing a pre-built driver container

Use this procedure if you have a pre-built image, such as an image either distributed by a hardware vendor or built elsewhere.

The following YAML file adds the public/private key-pair as secrets with the required key names - key for the private key, cert for the public key. The cluster then pulls down the unsignedImage image, opens it, signs the kernel modules listed in filesToSign, adds them back, and pushes the resulting image as containerImage.

Kernel Module Management (KMM) should then deploy the DaemonSet that loads the signed kmods onto all the nodes that match the selector. The driver containers should run successfully on any nodes that have the public key in their MOK database, and any nodes that are not secure-boot enabled, which ignore the signature. They should fail to load on any that have secure-boot enabled but do not have that key in their MOK database.

Prerequisites

  • The keysecret and certsecret secrets have been created.

Procedure

  1. Apply the YAML file:

    ---
apiVersion: kmm.sigs.x-k8s.io/v1beta1
kind: Module
metadata:
  name: example-module
spec:
  moduleLoader:
    serviceAccountName: default
    container:
      modprobe: (1)
        moduleName: '<your module name>'
      kernelMappings:
        # the kmods will be deployed on all nodes in the cluster with a kernel that matches the regexp
        - regexp: '^.*\.x86_64$'
          # the container to produce containing the signed kmods
          containerImage: <image name e.g. quay.io/myuser/my-driver:<kernelversion>-signed>
          sign:
            # the image containing the unsigned kmods (we need this because we are not building the kmods within the cluster)
            unsignedImage: <image name e.g. quay.io/myuser/my-driver:<kernelversion> >
            keysecret: # a secret holding the private secureboot key with the key 'key'
              name: <private key secret name>
            certsecret: # a secret holding the public secureboot key with the key 'cert'
              name: <certificate secret name>
            filesToSign: # full path within the unsignedImage container to the kmod(s) to sign
              - /opt/lib/modules/4.18.0-348.2.1.el8_5.x86_64/kmm_ci_a.ko
  imageReposecret:
    # the name of a secret containing credentials to pull unsignedImage and push containerImage to the registry
    name: repo-pull-secret
  selector:
    kubernetes.io/arch: amd64
1 modprobe - The name of the kmod to load.

Building and signing a ModuleLoader container image

Use this procedure if you have source code and must build your image first.

The following YAML file builds a new container image using the source code from the repository. The image produced is saved back in the registry with a temporary name, and this temporary image is then signed using the parameters in the sign section.

The temporary image name is based on the final image name and is set to be <containerImage>:<tag>-<namespace>_<module name>_kmm_unsigned.

For example, using the following YAML file, Kernel Module Management (KMM) builds an image named example.org/repository/minimal-driver:final-default_example-module_kmm_unsigned containing the build with unsigned kmods and push it to the registry. Then it creates a second image named example.org/repository/minimal-driver:final that contains the signed kmods. It is this second image that is loaded by the DaemonSet object and deploys the kmods to the cluster nodes.

After it is signed, the temporary image can be safely deleted from the registry. It will be rebuilt, if needed.

Prerequisites

  • The keysecret and certsecret secrets have been created.

Procedure

  1. Apply the YAML file:

    ---
apiVersion: v1
kind: ConfigMap
metadata:
  name: example-module-dockerfile
  namespace: default (1)
data:
  Dockerfile: |
    ARG DTK_AUTO
    ARG KERNEL_VERSION
    FROM ${DTK_AUTO} as builder
    WORKDIR /build/
    RUN git clone -b main --single-branch https://github.com/rh-ecosystem-edge/kernel-module-management.git
    WORKDIR kernel-module-management/ci/kmm-kmod/
    RUN make
    FROM registry.access.redhat.com/ubi8/ubi:latest
    ARG KERNEL_VERSION
    RUN yum -y install kmod && yum clean all
    RUN mkdir -p /opt/lib/modules/${KERNEL_VERSION}
    COPY --from=builder /build/kernel-module-management/ci/kmm-kmod/*.ko /opt/lib/modules/${KERNEL_VERSION}/
    RUN /usr/sbin/depmod -b /opt
---
apiVersion: kmm.sigs.x-k8s.io/v1beta1
kind: Module
metadata:
  name: example-module
  namespace: default (1)
spec:
  moduleLoader:
    serviceAccountName: default (2)
    container:
      modprobe:
        moduleName: simple_kmod
      kernelMappings:
        - regexp: '^.*\.x86_64$'
          containerImage: < the name of the final driver container to produce>
          build:
            dockerfileConfigMap:
              name: example-module-dockerfile
          sign:
            keysecret:
              name: <private key secret name>
            certsecret:
              name: <certificate secret name>
            filesToSign:
              - /opt/lib/modules/4.18.0-348.2.1.el8_5.x86_64/kmm_ci_a.ko
  imageReposecret: (3)
    name: repo-pull-secret
  selector: # top-level selector
    kubernetes.io/arch: amd64
1 namespace - Replace default with a valid namespace.
2 serviceAccountName - The default serviceAccountName does not have the required permissions to run a module that is privileged. For information on creating a service account, see "Creating service accounts" in the "Additional resources" of this section.
3 imageReposecret - Used as imagePullsecrets in the DaemonSet object and to pull and push for the build and sign features.
Additional resources

For information on creating a service account, see Creating service accounts.

Debugging and troubleshooting

If the kmods in your driver container are not signed or are signed with the wrong key, then the container can enter a PostStartHookError or CrashLoopBackOff status. You can verify by running the oc describe command on your container, which displays the following message in this scenario:

modprobe: ERROR: could not insert '<your_kmod_name>': Required key not available

KMM firmware support

Kernel modules sometimes need to load firmware files from the file system. KMM supports copying firmware files from the ModuleLoader image to the node’s file system.

The contents of .spec.moduleLoader.container.modprobe.firmwarePath are copied into the /var/lib/firmware path on the node before running the modprobe command to insert the kernel module.

All files and empty directories are removed from that location before running the modprobe -r command to unload the kernel module, when the pod is terminated.

Additional resources

Configuring the lookup path on nodes

On OpenShift Container Platform nodes, the set of default lookup paths for firmwares does not include the /var/lib/firmware path.

Procedure

  1. Use the Machine Config Operator to create a MachineConfig custom resource (CR) that contains the /var/lib/firmware path:

    apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker (1)
  name: 99-worker-kernel-args-firmware-path
spec:
  kernelArguments:
    - 'firmware_class.path=/var/lib/firmware'
    1 You can configure the label based on your needs. In the case of single-node OpenShift, use either control-pane or master objects.

  2. By applying the MachineConfig CR, the nodes are automatically rebooted.

Additional resources

Building a ModuleLoader image

Procedure

  • In addition to building the kernel module itself, include the binary firmware in the builder image:

    FROM registry.redhat.io/ubi8/ubi-minimal as builder

# Build the kmod

RUN ["mkdir", "/firmware"]
RUN ["curl", "-o", "/firmware/firmware.bin", "https://artifacts.example.com/firmware.bin"]

FROM registry.redhat.io/ubi8/ubi-minimal

# Copy the kmod, install modprobe, run depmod

COPY --from=builder /firmware /firmware

Tuning the Module resource

Procedure

  • Set .spec.moduleLoader.container.modprobe.firmwarePath in the Module custom resource (CR):

    apiVersion: kmm.sigs.x-k8s.io/v1beta1
kind: Module
metadata:
  name: my-kmod
spec:
  moduleLoader:
    container:
      modprobe:
        moduleName: my-kmod  # Required

        firmwarePath: /firmware (1)
    1 Optional: Copies /firmware/* into /var/lib/firmware/ on the node.

Troubleshooting KMM

When troubleshooting KMM installation issues, you can monitor logs to determine at which stage issues occur. Then, retrieve diagnostic data relevant to that stage.

Using the must-gather tool

The oc adm must-gather command is the preferred way to collect a support bundle and provide debugging information to Red Hat Support. Collect specific information by running the command with the appropriate arguments as described in the following sections.

Additional resources

Gathering data for KMM

Procedure

  1. Gather the data for the KMM Operator controller manager:

    1. Set the MUST_GATHER_IMAGE variable:

      $ export MUST_GATHER_IMAGE=$(oc get deployment -n openshift-kmm kmm-operator-controller-manager -ojsonpath='{.spec.template.spec.containers[?(@.name=="manager")].env[?(@.name=="RELATED_IMAGES_MUST_GATHER")].value}')

      Use the -n <namespace> switch to specify a namespace if you installed KMM in a custom namespace.

    2. Run the must-gather tool:

      $ oc adm must-gather --image="${MUST_GATHER_IMAGE}" -- /usr/bin/gather

  2. View the Operator logs:

    $ oc logs -fn openshift-kmm deployments/kmm-operator-controller-manager
    Example output 
    I0228 09:36:37.352405       1 request.go:682] Waited for 1.001998746s due to client-side throttling, not priority and fairness, request: GET:https://172.30.0.1:443/apis/machine.openshift.io/v1beta1?timeout=32s
I0228 09:36:40.767060       1 listener.go:44] kmm/controller-runtime/metrics "msg"="Metrics server is starting to listen" "addr"="127.0.0.1:8080"
I0228 09:36:40.769483       1 main.go:234] kmm/setup "msg"="starting manager"
I0228 09:36:40.769907       1 internal.go:366] kmm "msg"="Starting server" "addr"={"IP":"127.0.0.1","Port":8080,"Zone":""} "kind"="metrics" "path"="/metrics"
I0228 09:36:40.770025       1 internal.go:366] kmm "msg"="Starting server" "addr"={"IP":"::","Port":8081,"Zone":""} "kind"="health probe"
I0228 09:36:40.770128       1 leaderelection.go:248] attempting to acquire leader lease openshift-kmm/kmm.sigs.x-k8s.io...
I0228 09:36:40.784396       1 leaderelection.go:258] successfully acquired lease openshift-kmm/kmm.sigs.x-k8s.io
I0228 09:36:40.784876       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="Module" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="Module" "source"="kind source: *v1beta1.Module"
I0228 09:36:40.784925       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="Module" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="Module" "source"="kind source: *v1.DaemonSet"
I0228 09:36:40.784968       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="Module" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="Module" "source"="kind source: *v1.Build"
I0228 09:36:40.785001       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="Module" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="Module" "source"="kind source: *v1.Job"
I0228 09:36:40.785025       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="Module" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="Module" "source"="kind source: *v1.Node"
I0228 09:36:40.785039       1 controller.go:193] kmm "msg"="Starting Controller" "controller"="Module" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="Module"
I0228 09:36:40.785458       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="PodNodeModule" "controllerGroup"="" "controllerKind"="Pod" "source"="kind source: *v1.Pod"
I0228 09:36:40.786947       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="PreflightValidation" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidation" "source"="kind source: *v1beta1.PreflightValidation"
I0228 09:36:40.787406       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="PreflightValidation" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidation" "source"="kind source: *v1.Build"
I0228 09:36:40.787474       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="PreflightValidation" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidation" "source"="kind source: *v1.Job"
I0228 09:36:40.787488       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="PreflightValidation" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidation" "source"="kind source: *v1beta1.Module"
I0228 09:36:40.787603       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="NodeKernel" "controllerGroup"="" "controllerKind"="Node" "source"="kind source: *v1.Node"
I0228 09:36:40.787634       1 controller.go:193] kmm "msg"="Starting Controller" "controller"="NodeKernel" "controllerGroup"="" "controllerKind"="Node"
I0228 09:36:40.787680       1 controller.go:193] kmm "msg"="Starting Controller" "controller"="PreflightValidation" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidation"
I0228 09:36:40.785607       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="imagestream" "controllerGroup"="image.openshift.io" "controllerKind"="ImageStream" "source"="kind source: *v1.ImageStream"
I0228 09:36:40.787822       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="preflightvalidationocp" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidationOCP" "source"="kind source: *v1beta1.PreflightValidationOCP"
I0228 09:36:40.787853       1 controller.go:193] kmm "msg"="Starting Controller" "controller"="imagestream" "controllerGroup"="image.openshift.io" "controllerKind"="ImageStream"
I0228 09:36:40.787879       1 controller.go:185] kmm "msg"="Starting EventSource" "controller"="preflightvalidationocp" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidationOCP" "source"="kind source: *v1beta1.PreflightValidation"
I0228 09:36:40.787905       1 controller.go:193] kmm "msg"="Starting Controller" "controller"="preflightvalidationocp" "controllerGroup"="kmm.sigs.x-k8s.io" "controllerKind"="PreflightValidationOCP"
I0228 09:36:40.786489       1 controller.go:193] kmm "msg"="Starting Controller" "controller"="PodNodeModule" "controllerGroup"="" "controllerKind"="Pod"

Gathering data for KMM-Hub

Procedure

  1. Gather the data for the KMM Operator hub controller manager:

    1. Set the MUST_GATHER_IMAGE variable:

      $ export MUST_GATHER_IMAGE=$(oc get deployment -n openshift-kmm-hub kmm-operator-hub-controller-manager -ojsonpath='{.spec.template.spec.containers[?(@.name=="manager")].env[?(@.name=="RELATED_IMAGES_MUST_GATHER")].value}')

      Use the -n <namespace> switch to specify a namespace if you installed KMM in a custom namespace.

    2. Run the must-gather tool:

      $ oc adm must-gather --image="${MUST_GATHER_IMAGE}" -- /usr/bin/gather -u

  2. View the Operator logs:

    $ oc logs -fn openshift-kmm-hub deployments/kmm-operator-hub-controller-manager
    Example output 
    I0417 11:34:08.807472       1 request.go:682] Waited for 1.023403273s due to client-side throttling, not priority and fairness, request: GET:https://172.30.0.1:443/apis/tuned.openshift.io/v1?timeout=32s
I0417 11:34:12.373413       1 listener.go:44] kmm-hub/controller-runtime/metrics "msg"="Metrics server is starting to listen" "addr"="127.0.0.1:8080"
I0417 11:34:12.376253       1 main.go:150] kmm-hub/setup "msg"="Adding controller" "name"="ManagedClusterModule"
I0417 11:34:12.376621       1 main.go:186] kmm-hub/setup "msg"="starting manager"
I0417 11:34:12.377690       1 leaderelection.go:248] attempting to acquire leader lease openshift-kmm-hub/kmm-hub.sigs.x-k8s.io...
I0417 11:34:12.378078       1 internal.go:366] kmm-hub "msg"="Starting server" "addr"={"IP":"127.0.0.1","Port":8080,"Zone":""} "kind"="metrics" "path"="/metrics"
I0417 11:34:12.378222       1 internal.go:366] kmm-hub "msg"="Starting server" "addr"={"IP":"::","Port":8081,"Zone":""} "kind"="health probe"
I0417 11:34:12.395703       1 leaderelection.go:258] successfully acquired lease openshift-kmm-hub/kmm-hub.sigs.x-k8s.io
I0417 11:34:12.396334       1 controller.go:185] kmm-hub "msg"="Starting EventSource" "controller"="ManagedClusterModule" "controllerGroup"="hub.kmm.sigs.x-k8s.io" "controllerKind"="ManagedClusterModule" "source"="kind source: *v1beta1.ManagedClusterModule"
I0417 11:34:12.396403       1 controller.go:185] kmm-hub "msg"="Starting EventSource" "controller"="ManagedClusterModule" "controllerGroup"="hub.kmm.sigs.x-k8s.io" "controllerKind"="ManagedClusterModule" "source"="kind source: *v1.ManifestWork"
I0417 11:34:12.396430       1 controller.go:185] kmm-hub "msg"="Starting EventSource" "controller"="ManagedClusterModule" "controllerGroup"="hub.kmm.sigs.x-k8s.io" "controllerKind"="ManagedClusterModule" "source"="kind source: *v1.Build"
I0417 11:34:12.396469       1 controller.go:185] kmm-hub "msg"="Starting EventSource" "controller"="ManagedClusterModule" "controllerGroup"="hub.kmm.sigs.x-k8s.io" "controllerKind"="ManagedClusterModule" "source"="kind source: *v1.Job"
I0417 11:34:12.396522       1 controller.go:185] kmm-hub "msg"="Starting EventSource" "controller"="ManagedClusterModule" "controllerGroup"="hub.kmm.sigs.x-k8s.io" "controllerKind"="ManagedClusterModule" "source"="kind source: *v1.ManagedCluster"
I0417 11:34:12.396543       1 controller.go:193] kmm-hub "msg"="Starting Controller" "controller"="ManagedClusterModule" "controllerGroup"="hub.kmm.sigs.x-k8s.io" "controllerKind"="ManagedClusterModule"
I0417 11:34:12.397175       1 controller.go:185] kmm-hub "msg"="Starting EventSource" "controller"="imagestream" "controllerGroup"="image.openshift.io" "controllerKind"="ImageStream" "source"="kind source: *v1.ImageStream"
I0417 11:34:12.397221       1 controller.go:193] kmm-hub "msg"="Starting Controller" "controller"="imagestream" "controllerGroup"="image.openshift.io" "controllerKind"="ImageStream"
I0417 11:34:12.498335       1 filter.go:196] kmm-hub "msg"="Listing all ManagedClusterModules" "managedcluster"="local-cluster"
I0417 11:34:12.498570       1 filter.go:205] kmm-hub "msg"="Listed ManagedClusterModules" "count"=0 "managedcluster"="local-cluster"
I0417 11:34:12.498629       1 filter.go:238] kmm-hub "msg"="Adding reconciliation requests" "count"=0 "managedcluster"="local-cluster"
I0417 11:34:12.498687       1 filter.go:196] kmm-hub "msg"="Listing all ManagedClusterModules" "managedcluster"="sno1-0"
I0417 11:34:12.498750       1 filter.go:205] kmm-hub "msg"="Listed ManagedClusterModules" "count"=0 "managedcluster"="sno1-0"
I0417 11:34:12.498801       1 filter.go:238] kmm-hub "msg"="Adding reconciliation requests" "count"=0 "managedcluster"="sno1-0"
I0417 11:34:12.501947       1 controller.go:227] kmm-hub "msg"="Starting workers" "controller"="imagestream" "controllerGroup"="image.openshift.io" "controllerKind"="ImageStream" "worker count"=1
I0417 11:34:12.501948       1 controller.go:227] kmm-hub "msg"="Starting workers" "controller"="ManagedClusterModule" "controllerGroup"="hub.kmm.sigs.x-k8s.io" "controllerKind"="ManagedClusterModule" "worker count"=1
I0417 11:34:12.502285       1 imagestream_reconciler.go:50] kmm-hub "msg"="registered imagestream info mapping" "ImageStream"={"name":"driver-toolkit","namespace":"openshift"} "controller"="imagestream" "controllerGroup"="image.openshift.io" "controllerKind"="ImageStream" "dtkImage"="quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:df42b4785a7a662b30da53bdb0d206120cf4d24b45674227b16051ba4b7c3934" "name"="driver-toolkit" "namespace"="openshift" "osImageVersion"="412.86.202302211547-0" "reconcileID"="e709ff0a-5664-4007-8270-49b5dff8bae9"

KMM hub and spoke

In hub and spoke scenarios, many spoke clusters are connected to a central, powerful hub cluster. Kernel Module Management (KMM) depends on Red Hat Advanced Cluster Management (RHACM) to operate in hub and spoke environments.

KMM is compatible with hub and spoke environments through decoupling KMM features. A ManagedClusterModule Custom Resource Definition (CRD) is provided to wrap the existing Module CRD and extend it to select Spoke clusters. Also provided is KMM-Hub, a new standalone controller that builds images and signs modules on the hub cluster.

In hub and spoke setups, spokes are focused, resource-constrained clusters that are centrally managed by a hub cluster. Spokes run the single-cluster edition of KMM, with those resource-intensive features disabled. To adapt KMM to this environment, you should reduce the workload running on the spokes to the minimum, while the hub takes care of the expensive tasks.

Building kernel module images and signing the .ko files, should run on the hub. The scheduling of the Module Loader and Device Plugin DaemonSets can only happen on the spokes.

Additional resources

KMM-Hub

The KMM project provides KMM-Hub, an edition of KMM dedicated to hub clusters. KMM-Hub monitors all kernel versions running on the spokes and determines the nodes on the cluster that should receive a kernel module.

KMM-Hub runs all compute-intensive tasks such as image builds and kmod signing, and prepares the trimmed-down Module to be transferred to the spokes through RHACM.

KMM-Hub cannot be used to load kernel modules on the hub cluster. Install the regular edition of KMM to load kernel modules.
Additional resources

Installing KMM-Hub

You can use one of the following methods to install KMM-Hub:

  • Using the Operator Lifecycle Manager (OLM)

  • Creating KMM resources

Additional resources

Installing KMM-Hub using the Operator Lifecycle Manager

Use the Operators section of the OpenShift console to install KMM-Hub.

Installing KMM-Hub by creating KMM resources

Procedure

  • If you want to install KMM-Hub programmatically, you can use the following resources to create the Namespace, OperatorGroup and Subscription resources:

---
apiVersion: v1
kind: Namespace
metadata:
  name: openshift-kmm-hub
---
apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: kernel-module-management-hub
  namespace: openshift-kmm-hub
---
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: kernel-module-management-hub
  namespace: openshift-kmm-hub
spec:
  channel: stable
  installPlanApproval: Automatic
  name: kernel-module-management-hub
  source: redhat-operators
  sourceNamespace: openshift-marketplace

Using the ManagedClusterModule CRD

Use the ManagedClusterModule Custom Resource Definition (CRD) to configure the deployment of kernel modules on spoke clusters. This CRD is cluster-scoped, wraps a Module spec and adds the following additional fields:

apiVersion: hub.kmm.sigs.x-k8s.io/v1beta1
kind: ManagedClusterModule
metadata:
  name: <my-mcm>
  # No namespace, because this resource is cluster-scoped.
spec:
  moduleSpec: (1)
    selector: (2)
      node-wants-my-mcm: 'true'

  spokeNamespace: <some-namespace> (3)

  selector: (4)
    wants-my-mcm: 'true'
1 moduleSpec: Contains moduleLoader and devicePlugin sections, similar to a Module resource.
2 Selects nodes within the ManagedCluster.
3 Specifies in which namespace the Module should be created.
4 Selects ManagedCluster objects.

If build or signing instructions are present in .spec.moduleSpec, those pods are run on the hub cluster in the operator’s namespace.

When the .spec.selector matches one or more ManagedCluster resources, then KMM-Hub creates a ManifestWork resource in the corresponding namespace(s). ManifestWork contains a trimmed-down Module resource, with kernel mappings preserved but all build and sign subsections are removed. containerImage fields that contain image names ending with a tag are replaced with their digest equivalent.

Running KMM on the spoke

After installing KMM on the spoke, no further action is required. Create a ManagedClusterModule object from the hub to deploy kernel modules on spoke clusters.

Procedure

You can install KMM on the spokes cluster through a RHACM Policy object. In addition to installing KMM from the Operator hub and running it in a lightweight spoke mode, the Policy configures additional RBAC required for the RHACM agent to be able to manage Module resources.

  • Use the following RHACM policy to install KMM on spoke clusters:

    ---
apiVersion: policy.open-cluster-management.io/v1
kind: Policy
metadata:
  name: install-kmm
spec:
  remediationAction: enforce
  disabled: false
  policy-templates:
    - objectDefinition:
        apiVersion: policy.open-cluster-management.io/v1
        kind: ConfigurationPolicy
        metadata:
          name: install-kmm
        spec:
          severity: high
          object-templates:
          - complianceType: mustonlyhave
            objectDefinition:
              apiVersion: v1
              kind: Namespace
              metadata:
                name: openshift-kmm
          - complianceType: mustonlyhave
            objectDefinition:
              apiVersion: operators.coreos.com/v1
              kind: OperatorGroup
              metadata:
                name: kmm
                namespace: openshift-kmm
              spec:
                upgradeStrategy: Default
          - complianceType: mustonlyhave
            objectDefinition:
              apiVersion: operators.coreos.com/v1alpha1
              kind: Subscription
              metadata:
                name: kernel-module-management
                namespace: openshift-kmm
              spec:
                channel: stable
                config:
                  env:
                    - name: KMM_MANAGED
                      value: "1"
                installPlanApproval: Automatic
                name: kernel-module-management
                source: redhat-operators
                sourceNamespace: openshift-marketplace
          - complianceType: mustonlyhave
            objectDefinition:
              apiVersion: rbac.authorization.k8s.io/v1
              kind: ClusterRole
              metadata:
                name: kmm-module-manager
              rules:
                - apiGroups: [kmm.sigs.x-k8s.io]
                  resources: [modules]
                  verbs: [create, delete, get, list, patch, update, watch]
          - complianceType: mustonlyhave
            objectDefinition:
              apiVersion: rbac.authorization.k8s.io/v1
              kind: ClusterRoleBinding
              metadata:
                name: klusterlet-kmm
              subjects:
              - kind: ServiceAccount
                name: klusterlet-work-sa
                namespace: open-cluster-management-agent
              roleRef:
                kind: ClusterRole
                name: kmm-module-manager
                apiGroup: rbac.authorization.k8s.io
---
apiVersion: apps.open-cluster-management.io/v1
kind: PlacementRule
metadata:
  name: all-managed-clusters
spec:
  clusterSelector: (1)
    matchExpressions: []
---
apiVersion: policy.open-cluster-management.io/v1
kind: PlacementBinding
metadata:
  name: install-kmm
placementRef:
  apiGroup: apps.open-cluster-management.io
  kind: PlacementRule
  name: all-managed-clusters
subjects:
  - apiGroup: policy.open-cluster-management.io
    kind: Policy
    name: install-kmm
    1 The spec.clusterSelector field can be customized to target select clusters only.