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Creating a cluster with multi-architecture compute machines on IBM Z and IBM LinuxONE with RHEL KVM

To create a cluster with multi-architecture compute machines on IBM Z(R) and IBM(R) LinuxONE (s390x) with RHEL KVM, you must have an existing single-architecture x86_64 cluster. You can then add s390x compute machines to your OpenShift Container Platform cluster.

Before you can add s390x nodes to your cluster, you must upgrade your cluster to one that uses the multi-architecture payload. For more information on migrating to the multi-architecture payload, see "Migrating to a cluster with multi-architecture compute machines".

The following procedures explain how to create a RHCOS compute machine using a RHEL KVM instance. This will allow you to add s390x nodes to your cluster and deploy a cluster with multi-architecture compute machines.

To create an IBM Z(R) or IBM(R) LinuxONE (s390x) cluster with multi-architecture compute machines on x86_64, follow the instructions for "Installing a cluster on IBM Z(R) and IBM(R) LinuxONE". You can then add x86_64 compute machines as described in "Creating a cluster with multi-architecture compute machines on bare metal, IBM Power, or IBM Z".

Note

Before adding a secondary architecture node to your cluster, install the Multiarch Tuning Operator and then deploy a ClusterPodPlacementConfig object. For more information, see "Managing workloads on multi-architecture clusters by using the Multiarch Tuning Operator".

Creating RHCOS machines using virt-install

You can create more Red Hat Enterprise Linux CoreOS (RHCOS) compute machines for your cluster by using virt-install.

Prerequisites

  • You have at least one LPAR running on RHEL 8.7 or later with KVM, referred to as RHEL KVM host in this procedure.
  • The KVM/QEMU hypervisor is installed on the RHEL KVM host.
  • You have a domain name server (DNS) that can perform hostname and reverse lookup for the nodes.
  • An HTTP or HTTPS server is set up.

Procedure

  1. Extract the Ignition config file from the cluster by running the following command:

    $ oc extract -n openshift-machine-api secret/worker-user-data-managed --keys=userData --to=- > worker.ign

  2. Upload the worker.ign Ignition config file you exported from your cluster to your HTTP server. Note the URL of this file.

  3. You can validate that the Ignition file is available on the URL. The following example gets the Ignition config file for the compute node:

    $ curl -k http://<HTTP_server>/worker.ign

  4. Download the RHEL live kernel, initramfs, and rootfs files by running the following commands:

     $ curl -LO $(oc -n openshift-machine-config-operator get configmap/coreos-bootimages -o jsonpath='{.data.stream}' \
| jq -r '.architectures.s390x.artifacts.metal.formats.pxe.kernel.location')

    $ curl -LO $(oc -n openshift-machine-config-operator get configmap/coreos-bootimages -o jsonpath='{.data.stream}' \
| jq -r '.architectures.s390x.artifacts.metal.formats.pxe.initramfs.location')

    $ curl -LO $(oc -n openshift-machine-config-operator get configmap/coreos-bootimages -o jsonpath='{.data.stream}' \
| jq -r '.architectures.s390x.artifacts.metal.formats.pxe.rootfs.location')

  5. Move the downloaded RHEL live kernel, initramfs, and rootfs files to an HTTP or HTTPS server before you launch virt-install.

  6. Create the new KVM guest nodes using the RHEL kernel, initramfs, and Ignition files; the new disk image; and adjusted parm line arguments.

    $ virt-install \
   --connect qemu:///system \
   --name <vm_name> \
   --autostart \
   --os-variant rhel9.4 \
   --cpu host \
   --vcpus <vcpus> \
   --memory <memory_mb> \
   --disk <vm_name>.qcow2,size=<image_size> \
   --network network=<virt_network_parm> \
   --location <media_location>,kernel=<rhcos_kernel>,initrd=<rhcos_initrd> \
   --extra-args "rd.neednet=1" \
   --extra-args "coreos.inst.install_dev=/dev/vda" \
   --extra-args "coreos.inst.ignition_url=http://<http_server>/worker.ign " \
   --extra-args "coreos.live.rootfs_url=http://<http_server>/rhcos-<version>-live-rootfs.<architecture>.img" \
   --extra-args "ip=<ip>::<gateway>:<netmask>:<hostname>::none" \
   --extra-args "nameserver=<dns>" \
   --extra-args "console=ttysclp0" \
   --noautoconsole \
   --wait

    where:

    os-variant
    Specifies the RHEL version for the RHCOS compute machine. rhel9.4 is the recommended version. To query the supported RHEL version of your operating system, run the following command:
    $ osinfo-query os -f short-id

    Note

    The os-variant is case sensitive.

    location
    Specifies the location of the kernel/initrd on the HTTP or HTTPS server.
    coreos.inst.ignition_url
    Specifies the location of the worker.ign config file. Only HTTP and HTTPS protocols are supported.
    coreos.live.rootfs_url
    Specifies the location of the rootfs artifact for the kernel and initramfs you are booting. Only HTTP and HTTPS protocols are supported
    hostname
    Optional parameter. Specifies the fully qualified hostname of the client machine.

    Note

    If you are using HAProxy as a load balancer, update your HAProxy rules for ingress-router-443 and ingress-router-80 in the /etc/haproxy/haproxy.cfg configuration file.

  7. Continue to create more compute machines for your cluster.

Approve the certificate signing requests for your machines

To allow newly added machines to join your OpenShift Container Platform cluster, confirm that the cluster approves pending certificate signing requests (CSRs), or approve them yourself. Approve client requests first, then server requests.

Prerequisites

  • You added machines to your cluster.

Procedure

  1. Confirm that the cluster recognizes the machines:

    $ oc get nodes
    Example output
    NAME      STATUS    ROLES   AGE  VERSION
master-0  Ready     master  63m  v1.35.4
master-1  Ready     master  63m  v1.35.4
master-2  Ready     master  64m  v1.35.4

    The output lists all of the machines that you created.

    Note

    The preceding output might not include the compute nodes until you approve some CSRs.

  2. Review the pending CSRs and ensure that you see the client requests with the Pending or Approved status for each machine that you added to the cluster:

    $ oc get csr
    Example output
    NAME        AGE     REQUESTOR                                                                   CONDITION
csr-8b2br   15m     system:serviceaccount:openshift-machine-config-operator:node-bootstrapper   Pending
csr-8vnps   15m     system:serviceaccount:openshift-machine-config-operator:node-bootstrapper   Pending
...

    In this example, two machines are joining the cluster. You might see more approved CSRs in the list.

  3. If the CSRs were not approved, after all of the pending CSRs for the machines you added are in Pending status, approve the CSRs for your cluster machines:

    Note

    You must approve your CSRs within an hour of adding the machines to the cluster. If you do not approve them within an hour, the certificates rotate, and more than two certificates are present for each node. You must approve all of these certificates. After you approve the client CSR, the kubelet creates a secondary CSR for the serving certificate, which requires manual approval. The machine-approver then automatically approves later serving certificate renewal requests if the kubelet requests a new certificate with the same parameters.

    Note

    For clusters running on platforms that are not machine API enabled, such as bare metal and other user-provisioned infrastructure, you must implement a method of automatically approving the kubelet serving certificate requests (CSRs). If you do not approve a request, the oc exec, oc rsh, and oc logs commands cannot succeed, because the API server requires a serving certificate when it connects to the kubelet. Any operation that contacts the kubelet endpoint requires this certificate approval to be in place. The method must watch for new CSRs, confirm that the node-bootstrapper service account in the system:node or system:admin groups submitted the CSR, and confirm the identity of the node.

    • To approve them individually, run the following command for each valid CSR:

      $ oc adm certificate approve <csr_name>

      where:

      <csr_name>
      Specifies the name of a CSR from the list of current CSRs.

    • To approve all pending CSRs, run the following command:

      $ oc get csr -o go-template='{{range .items}}{{if not .status}}{{.metadata.name}}{{"\n"}}{{end}}{{end}}' | xargs --no-run-if-empty oc adm certificate approve

      Note

      Some Operators might not become available until you approve some CSRs. Each node submits two CSRs, so you might need to run the command to approve CSRs many times.

  4. After you approve your client requests, review the server requests for each machine that you added to the cluster:

    $ oc get csr
    Example output
    NAME        AGE     REQUESTOR                                                                   CONDITION
csr-bfd72   5m26s   system:node:ip-10-0-50-126.us-east-2.compute.internal                       Pending
csr-c57lv   5m26s   system:node:ip-10-0-95-157.us-east-2.compute.internal                       Pending
...

  5. If the remaining CSRs are not approved, and are in the Pending status, approve the CSRs for your cluster machines:

    • To approve them individually, run the following command for each valid CSR:

      $ oc adm certificate approve <csr_name>

      where:

      <csr_name>
      Specifies the name of a CSR from the list of current CSRs.

    • To approve all pending CSRs, run the following command:

      $ oc get csr -o go-template='{{range .items}}{{if not .status}}{{.metadata.name}}{{"\n"}}{{end}}{{end}}' | xargs oc adm certificate approve

  6. After you approve all client and server CSRs, the machines have the Ready status. Verify this by running the following command:

    $ oc get nodes
    Example output
    NAME      STATUS    ROLES   AGE  VERSION
master-0  Ready     master  73m  v1.35.4
master-1  Ready     master  73m  v1.35.4
master-2  Ready     master  74m  v1.35.4
worker-0  Ready     worker  11m  v1.35.4
worker-1  Ready     worker  11m  v1.35.4

    Note

    You might need to wait a few minutes after approval of the server CSRs for the machines to reach the Ready status.

Additional resources