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Chapter 6. Deploying OpenShift sandboxed containers on IBM Z and IBM LinuxONE

You can deploy OpenShift sandboxed containers on IBM Z® and IBM® LinuxONE.

OpenShift sandboxed containers deploys peer pods. The peer pod design circumvents the need for nested virtualization. For more information, see peer pods.

Important

OpenShift sandboxed containers on IBM Z® and IBM® LinuxONE is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Cluster requirements

  • You have installed Red Hat OpenShift Container Platform 4.14 or later on the cluster where you are installing the OpenShift sandboxed containers Operator.
  • Your cluster has at least one worker node.

6.1. Peer pod resource requirements

You must ensure that your cluster has sufficient resources.

Peer pod virtual machines (VMs) require resources in two locations:

  • The worker node. The worker node stores metadata, Kata shim resources (containerd-shim-kata-v2), remote-hypervisor resources (cloud-api-adaptor), and the tunnel setup between the worker nodes and the peer pod VM.
  • The libvirt virtual machine instance. This is the actual peer pod VM running in the LPAR (KVM host).

The CPU and memory resources used in the Kubernetes worker node are handled by the pod overhead included in the RuntimeClass (kata-remote) definition used for creating peer pods.

The total number of peer pod VMs running in the cloud is defined as Kubernetes Node extended resources. This limit is per node and is set by the limit attribute in the peerpodConfig custom resource (CR).

The peerpodConfig CR, named peerpodconfig-openshift, is created when you create the kataConfig CR and enable peer pods, and is located in the openshift-sandboxed-containers-operator namespace.

The following peerpodConfig CR example displays the default spec values: 

apiVersion: confidentialcontainers.org/v1alpha1
kind: PeerPodConfig
metadata:
  name: peerpodconfig-openshift
  namespace: openshift-sandboxed-containers-operator
spec:
  cloudSecretName: peer-pods-secret
  configMapName: peer-pods-cm
  limit: "10" 1
  nodeSelector:
    node-role.kubernetes.io/kata-oc: ""
1
The default limit is 10 VMs per node.

The extended resource is named kata.peerpods.io/vm, and enables the Kubernetes scheduler to handle capacity tracking and accounting.

You can edit the limit per node based on the requirements for your environment after you install the OpenShift sandboxed containers Operator.

A mutating webhook adds the extended resource kata.peerpods.io/vm to the pod specification. It also removes any resource-specific entries from the pod specification, if present. This enables the Kubernetes scheduler to account for these extended resources, ensuring the peer pod is only scheduled when resources are available.

The mutating webhook modifies a Kubernetes pod as follows:

  • The mutating webhook checks the pod for the expected RuntimeClassName value, specified in the TARGET_RUNTIME_CLASS environment variable. If the value in the pod specification does not match the value in the TARGET_RUNTIME_CLASS, the webhook exits without modifying the pod.

  • If the RuntimeClassName values match, the webhook makes the following changes to the pod spec:

    1. The webhook removes every resource specification from the resources field of all containers and init containers in the pod.
    2. The webhook adds the extended resource (kata.peerpods.io/vm) to the spec by modifying the resources field of the first container in the pod. The extended resource kata.peerpods.io/vm is used by the Kubernetes scheduler for accounting purposes.
Note

The mutating webhook excludes specific system namespaces in OpenShift Container Platform from mutation. If a peer pod is created in those system namespaces, then resource accounting using Kubernetes extended resources does not work unless the pod spec includes the extended resource.

As a best practice, define a cluster-wide policy to only allow peer pod creation in specific namespaces.

6.2. Deploying OpenShift sandboxed containers on IBM Z and IBM LinuxONE

You can deploy OpenShift sandboxed containers on IBM Z® and IBM® LinuxONE by using the command line interface (CLI) to perform the following tasks:

  1. Install the OpenShift sandboxed containers Operator.
  2. Optional: Change the number of virtual machines running on each worker node.
  3. Configure the libvirt volume.
  4. Optional: Create a custom peer pod VM image.
  5. Create the peer pods secret.
  6. Create the peer pods config map.
  7. Create the peer pod VM image config map.
  8. Create the KVM host secret.
  9. Create the KataConfig custom resource.
  10. Configure the OpenShift sandboxed containers workload objects.

6.2.1. Installing the OpenShift sandboxed containers Operator

You can install the OpenShift sandboxed containers Operator by using the CLI.

Prerequisites

  • You have installed the OpenShift CLI (oc).
  • You have access to the cluster as a user with the cluster-admin role.

Procedure

  1. Create an osc-namespace.yaml manifest file: 

    apiVersion: v1
kind: Namespace
metadata:
  name: openshift-sandboxed-containers-operator

  2. Create the namespace by running the following command: 

    $ oc apply -f osc-namespace.yaml

  3. Create an osc-operatorgroup.yaml manifest file: 

    apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: sandboxed-containers-operator-group
  namespace: openshift-sandboxed-containers-operator
spec:
  targetNamespaces:
  - openshift-sandboxed-containers-operator

  4. Create the operator group by running the following command: 

    $ oc apply -f osc-operatorgroup.yaml

  5. Create an osc-subscription.yaml manifest file: 

    apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: sandboxed-containers-operator
  namespace: openshift-sandboxed-containers-operator
spec:
  channel: stable
  installPlanApproval: Automatic
  name: sandboxed-containers-operator
  source: redhat-operators
  sourceNamespace: openshift-marketplace
  startingCSV: sandboxed-containers-operator.v1.8.0

  6. Create the subscription by running the following command: 

    $ oc apply -f osc-subscription.yaml

  7. Verify that the Operator is correctly installed by running the following command: 

    $ oc get csv -n openshift-sandboxed-containers-operator

    This command can take several minutes to complete.

  8. Watch the process by running the following command: 

    $ watch oc get csv -n openshift-sandboxed-containers-operator

    Example output

    NAME                             DISPLAY                                  VERSION             REPLACES                   PHASE
openshift-sandboxed-containers   openshift-sandboxed-containers-operator  1.8.0    1.7.0        Succeeded

Additional resources

6.2.2. Modifying the number of peer pod VMs per node

You can change the limit of peer pod virtual machines (VMs) per node by editing the peerpodConfig custom resource (CR).

Procedure

  1. Check the current limit by running the following command: 

    $ oc get peerpodconfig peerpodconfig-openshift -n openshift-sandboxed-containers-operator \
-o jsonpath='{.spec.limit}{"\n"}'

  2. Modify the limit attribute of the peerpodConfig CR by running the following command: 

    $ oc patch peerpodconfig peerpodconfig-openshift -n openshift-sandboxed-containers-operator \
--type merge --patch '{"spec":{"limit":"<value>"}}' 1
    1
    Replace <value> with the limit you want to define.

6.2.3. Configuring the libvirt volume

You must configure the libvirt volume on your KVM host. Peer pods use the libvirt provider of the Cloud API Adaptor to create and manage virtual machines.

Prerequisites

  • You have installed the OpenShift sandboxed containers Operator on your OpenShift Container Platform cluster by using the OpenShift Container Platform web console or the command line.
  • You have administrator privileges for your KVM host.
  • You have installed podman on your KVM host.
  • You have installed virt-customize on your KVM host.

Procedure

  1. Log in to the KVM host.

  2. Set the name of the libvirt pool by running the following command: 

    $ export LIBVIRT_POOL=<libvirt_pool>

    You need the LIBVIRT_POOL value to create the secret for the libvirt provider.

  3. Set the name of the libvirt pool by running the following command: 

    $ export LIBVIRT_VOL_NAME=<libvirt_volume>

    You need the LIBVIRT_VOL_NAME value to create the secret for the libvirt provider.

  4. Set the path of the default storage pool location, by running the following command: 

    $ export LIBVIRT_POOL_DIRECTORY=<target_directory> 1
    1
    To ensure libvirt has read and write access permissions, use a subdirectory of the libvirt storage directory. The default is /var/lib/libvirt/images/.

  5. Create a libvirt pool by running the following command: 

    $ virsh pool-define-as $LIBVIRT_POOL --type dir --target "$LIBVIRT_POOL_DIRECTORY"

  6. Start the libvirt pool by running the following command: 

    $ virsh pool-start $LIBVIRT_POOL

  7. Create a libvirt volume for the pool by running the following command: 

    $ virsh -c qemu:///system \
  vol-create-as --pool $LIBVIRT_POOL \
  --name $LIBVIRT_VOL_NAME \
  --capacity 20G \
  --allocation 2G \
  --prealloc-metadata \
  --format qcow2

6.2.4. Creating a custom peer pod VM image

You can create a custom peer pod virtual machine (VM) image instead of using the default Operator-built image.

You build an Open Container Initiative (OCI) container with the peer pod QCOW2 image. Later, you add the container registry URL and the image path to the peer pod VM image config map.

Procedure

  1. Create a Dockerfile.podvm-oci file: 

    FROM scratch

ARG PODVM_IMAGE_SRC
ENV PODVM_IMAGE_PATH="/image/podvm.qcow2"

COPY $PODVM_IMAGE_SRC $PODVM_IMAGE_PATH

  2. Build a container with the pod VM QCOW2 image by running the following command: 

    $ docker build -t podvm-libvirt \
  --build-arg PODVM_IMAGE_SRC=<podvm_image_source> \ 1
  --build-arg PODVM_IMAGE_PATH=<podvm_image_path> \ 2
  -f Dockerfile.podvm-oci .
    1
    Specify the QCOW2 image source on the host.
    2
    Optional: Specify the path of the QCOW2 image if you do not use the default, /image/podvm.qcow2.

6.2.5. Creating the peer pods secret

You must create the peer pods secret for OpenShift sandboxed containers.

The secret stores credentials for creating the pod virtual machine (VM) image and peer pod instances.

By default, the OpenShift sandboxed containers Operator creates the secret based on the credentials used to create the cluster. However, you can manually create a secret that uses different credentials.

Prerequisites

  • LIBVIRT_POOL. Use the value you set when you configured libvirt on the KVM host.
  • LIBVIRT_VOL_NAME. Use the value you set when you configured libvirt on the KVM host.

  • LIBVIRT_URI. This value is the default gateway IP address of the libvirt network. Check your libvirt network setup to obtain this value.

    Note

    If libvirt uses the default bridge virtual network, you can obtain the LIBVIRT_URI by running the following commands: 

    $ virtint=$(bridge_line=$(virsh net-info default | grep Bridge);  echo "${bridge_line//Bridge:/}" | tr -d [:blank:])

$ LIBVIRT_URI=$( ip -4 addr show $virtint | grep -oP '(?<=inet\s)\d+(\.\d+){3}')

$ LIBVIRT_GATEWAY_URI="qemu+ssh://root@${LIBVIRT_URI}/system?no_verify=1"
  • REDHAT_OFFLINE_TOKEN. You have generated this token to download the RHEL image at Red Hat API Tokens.

Procedure

  1. Create a peer-pods-secret.yaml manifest file according to the following example: 

    apiVersion: v1
kind: Secret
metadata:
  name: peer-pods-secret
  namespace: openshift-sandboxed-containers-operator
type: Opaque
stringData:
  CLOUD_PROVIDER: "libvirt"
  LIBVIRT_URI: "<libvirt_gateway_uri>" 1
  LIBVIRT_POOL: "<libvirt_pool>" 2
  LIBVIRT_VOL_NAME: "<libvirt_volume>" 3
  REDHAT_OFFLINE_TOKEN: "<rh_offline_token>" 4
    1
    Specify the libvirt URI.
    2
    Specify the libvirt pool.
    3
    Specify the libvirt volume name.
    4
    Specify the Red Hat offline token, which is required for the Operator-built image.

  2. Create the secret by running the following command: 

    $ oc apply -f peer-pods-secret.yaml

6.2.6. Creating the peer pods config map

You must create the peer pods config map for OpenShift sandboxed containers.

Procedure

  1. Create a peer-pods-cm.yaml manifest file according to the following example: 

    apiVersion: v1
kind: ConfigMap
metadata:
  name: peer-pods-cm
  namespace: openshift-sandboxed-containers-operator
data:
  CLOUD_PROVIDER: "libvirt"
  DISABLECVM: "true"

  2. Create the config map by running the following command: 

    $ oc apply -f peer-pods-cm.yaml

6.2.7. Creating the peer pod VM image config map

You must create the config map for the peer pod VM image.

Procedure

  1. Create a libvirt-podvm-image-cm.yaml manifest according to the following example: 

    apiVersion: v1
kind: ConfigMap
metadata:
  name: libvirt-podvm-image-cm
  namespace: openshift-sandboxed-containers-operator
data:
  PODVM_DISTRO: "rhel"
  CAA_SRC: "https://github.com/confidential-containers/cloud-api-adaptor"
  CAA_REF: "<cloud_api_adaptor_version>" 1
  DOWNLOAD_SOURCES: "no"
  CONFIDENTIAL_COMPUTE_ENABLED: "yes"
  UPDATE_PEERPODS_CM: "yes"
  ORG_ID: "<rhel_organization_id>"
  ACTIVATION_KEY: "<rhel_activation_key>" 2
  IMAGE_NAME: "<podvm_libvirt_image>"
  PODVM_IMAGE_URI: "oci::<image_repo_url>:<image_tag>::<image_path>" 3
  SE_BOOT: "true" 4
  BASE_OS_VERSION: "<rhel_image_os_version>" 5
    1
    Specify the latest version of the Cloud API Adaptor source.
    2
    Specify your RHEL activation key.
    3
    Optional: Specify the following values if you created a container image:
    • image_repo_url: Container registry URL.
    • image_tag: Image tag.
    • image_path: Image path. Default: /image/podvm.qcow2.
    4
    SE_BOOT: "true" enables IBM Secure Execution for an Operator-built image. Set to false if you created a container image.
    5
    Specify the RHEL image operating system version. IBM Z® Secure Execution supports RHEL 9.4 and later versions.

  2. Create the config map by running the following command: 

    $ oc apply -f libvirt-podvm-image-cm.yaml

    The libvirt pod VM image config map is created for your libvirt provider.

6.2.8. Creating the KVM host secret

You must create the secret for your KVM host.

Procedure

  1. Generate an SSH key pair by running the following command: 

    $ ssh-keygen -f ./id_rsa -N ""

  2. Copy the public SSH key to your KVM host: 

    $ ssh-copy-id -i ./id_rsa.pub <KVM_HOST_IP>

  3. Create the Secret object by running the following command: 

    $ oc create secret generic ssh-key-secret \
  -n openshift-sandboxed-containers-operator \
  --from-file=id_rsa.pub=./id_rsa.pub \
  --from-file=id_rsa=./id_rsa

  4. Delete the SSH keys you created: 

    $ shred --remove id_rsa.pub id_rsa

6.2.9. Creating the KataConfig custom resource

You must create the KataConfig custom resource (CR) to install kata-remote as a runtime class on your worker nodes.

Creating the KataConfig CR triggers the OpenShift sandboxed containers Operator to do the following:

  • Create a RuntimeClass CR named kata-remote with a default configuration. This enables users to configure workloads to use kata-remote as the runtime by referencing the CR in the RuntimeClassName field. This CR also specifies the resource overhead for the runtime.

OpenShift sandboxed containers installs kata-remote as a secondary, optional runtime on the cluster and not as the primary runtime.

Important

Creating the KataConfig CR automatically reboots the worker nodes. The reboot can take from 10 to more than 60 minutes. Factors that impede reboot time are as follows:

  • A larger OpenShift Container Platform deployment with a greater number of worker nodes.
  • Activation of the BIOS and Diagnostics utility.
  • Deployment on a hard disk drive rather than an SSD.
  • Deployment on physical nodes such as bare metal, rather than on virtual nodes.
  • A slow CPU and network.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin role.

Procedure

  1. Create an example-kataconfig.yaml manifest file according to the following example: 

    apiVersion: kataconfiguration.openshift.io/v1
kind: KataConfig
metadata:
  name: example-kataconfig
spec:
  enablePeerPods: true
  logLevel: info
#  kataConfigPoolSelector:
#    matchLabels:
#      <label_key>: '<label_value>' 1
    1
    Optional: If you have applied node labels to install kata-remote on specific nodes, specify the key and value, for example, osc: 'true'.

  2. Create the KataConfig CR by running the following command: 

    $ oc apply -f example-kataconfig.yaml

    The new KataConfig CR is created and installs kata-remote as a runtime class on the worker nodes.

    Wait for the kata-remote installation to complete and the worker nodes to reboot before verifying the installation.

  3. Monitor the installation progress by running the following command: 

    $ watch "oc describe kataconfig | sed -n /^Status:/,/^Events/p"

    When the status of all workers under kataNodes is installed and the condition InProgress is False without specifying a reason, the kata-remote is installed on the cluster.

  4. Verify that you have built the peer pod image and uploaded it to the libvirt volume by running the following command: 

    $ oc describe configmap peer-pods-cm -n openshift-sandboxed-containers-operator

    Example output

    Name: peer-pods-cm
Namespace: openshift-sandboxed-containers-operator
Labels: <none>
Annotations: <none>

Data
====
CLOUD_PROVIDER: libvirt

BinaryData
====
Events: <none>

  5. Monitor the kata-oc machine config pool progress to ensure that it is in the UPDATED state, when UPDATEDMACHINECOUNT equals MACHINECOUNT, by running the following command: 

    $ watch oc get mcp/kata-oc

  6. Verify the daemon set by running the following command: 

    $ oc get -n openshift-sandboxed-containers-operator ds/peerpodconfig-ctrl-caa-daemon

  7. Verify the runtime classes by running the following command: 

    $ oc get runtimeclass

    Example output

    NAME             HANDLER          AGE
kata             kata             152m
kata-remote      kata-remote      152m

6.2.10. Configuring workload objects

You must configure OpenShift sandboxed containers workload objects by setting kata-remote as the runtime class for the following pod-templated objects:

  • Pod objects
  • ReplicaSet objects
  • ReplicationController objects
  • StatefulSet objects
  • Deployment objects
  • DeploymentConfig objects
Important

Do not deploy workloads in an Operator namespace. Create a dedicated namespace for these resources.

Prerequisites

  • You have created the KataConfig custom resource (CR).

Procedure

  1. Add spec.runtimeClassName: kata-remote to the manifest of each pod-templated workload object as in the following example: 

    apiVersion: v1
kind: <object>
# ...
spec:
  runtimeClassName: kata-remote
# ...

    OpenShift Container Platform creates the workload object and begins scheduling it.

Verification

  • Inspect the spec.runtimeClassName field of a pod-templated object. If the value is kata-remote, then the workload is running on OpenShift sandboxed containers, using peer pods.
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