Single-Node OpenShift Deployment on LinuxONE with RHEL KVM

Prerequisites

Before you begin, ensure the following:

• RHEL KVM host with virtualization enabled
• Podman installed
• HTTP/HTTPS server running (e.g., Apache/httpd )
• Static IP, DNS, and hostname reserved for the VM
• OpenShift CLI and Installer downloaded for s390x
• RHCOS boot artifacts:
• rhcos-4.16.36-s390x-live-kernel-s390x
• rhcos-4.16.36-s390x-live-initramfs.s390x.img
• rhcos-4.16.36-s390x-live-rootfs.s390x.img
• Ignition file: bootstrap-in-place-for-live-iso.ign
• VM created with required CPU, memory, disk, and network resources

Step 1: Create a VM

Before running virt-install, create a VM with:

• CPU and memory allocation
• Pre-attached virtual disk (e.g., 500GB)
• Network interface mapped to appropriate bridge
• Boot device set to disk

Step 2: Installation Workflow

2.1 Set Environment Variables

export OCP_VERSION=latest-4.16
export ARCH=s390x

2.2 Download CLI Tools

curl -k https://mirror.openshift.com/pub/openshift-v4/${ARCH}/clients/ocp/${OCP_VERSION}/openshift-client-linux.tar.gz -o oc.tar.gz
tar zxf oc.tar.gz && chmod +x oc

2.3 Download Installer

curl -k https://mirror.openshift.com/pub/openshift-v4/${ARCH}/clients/ocp/${OCP_VERSION}/openshift-install-linux.tar.gz -o openshift-install-linux.tar.gz
tar zxvf openshift-install-linux.tar.gz && chmod +x openshift-install

2.4 Prepare install-config.yaml

apiVersion:
baseDomain: <domain> 
compute:
- name: worker
  replicas: 0
controlPlane:
  name: master
  replicas: 1 
metadata:
  name: <name> 
networking: 
  clusterNetwork:
  - cidr: 10.128.0.0/14
    hostPrefix: 23
  machineNetwork:
  - cidr: 10.0.0.0/16 
  networkType: OVNKubernetes
  serviceNetwork:
  - 172.30.0.0/16
platform:
  none: {}
bootstrapInPlace:
  installationDisk: /dev/vda 
pullSecret: '<pull_secret>' 
sshKey: |
  <ssh_key>

2.5 Generate Ignition Configs

mkdir ocp
cp install-config.yaml ocp/
./openshift-install --dir=ocp create single-node-ignition-config

2.6 Host Boot Files

Place the following in /var/www/html/:

• RHCOS kernel/initramfs/rootfs
• Ignition file: bootstrap-in-place-for-live-iso.ign

Step 3: Deploy VM Using virt-install

virt-install \
  --connect qemu:///system \
  --reinstall <VM-Name>\
  --boot hd \
  --location /var/www/html/iso,\
kernel=/var/www/html/rhcos-4.16.36-s390x-live-kernel-s390x,\
initrd=/var/www/html/rhcos-4.16.36-s390x-live-initramfs.s390x.img \
  --extra-args "rd.neednet=1 coreos.inst=yes coreos.inst.install_dev=vda \
coreos.live.rootfs_url=http://<http-host>:<port>/rhcos-4.16.36-s390x-live-rootfs.s390x.img \
ip=<IP>::<Gateway>:<mask>:<Hostname>::<network-interface>:none \
nameserver=<DNS Server> \
coreos.inst.ignition_url=http://<http-host>:<port>/bootstrap-in-place-for-live-iso.ign" \
  --osinfo detect=on

Understanding the virt-install Command for OpenShift SNO on LinuxONE

When deploying a Single-Node OpenShift (SNO) cluster on IBM LinuxONE using RHEL KVM, the virt-install command plays a central role in provisioning the virtual machine with the correct boot artifacts, networking, and Ignition configuration.

Let’s break down the command and understand each component.

Connection & VM Setup

--connect qemu:///system
--reinstall <VM-Name>
--boot hd

• Connects to the system-wide libvirt daemon
• Re-installs an existing VM definition (useful when templating)
• Boots from hard disk after installation

Boot Artifacts

--location /var/www/html/iso,\
kernel=/var/www/html/rhcos-4.16.36-s390x-live-kernel-s390x,\
initrd=/var/www/html/rhcos-4.16.36-s390x-live-initramfs.s390x.img

• Specifies the location of the RHCOS live kernel and initramfs
• These are served via HTTP from the bastion or KVM host

Installation Parameters

--extra-args "rd.neednet=1 coreos.inst=yes coreos.inst.install_dev=vda \
coreos.live.rootfs_url=http://<http-host>:<port>/rhcos-4.16.36-s390x-live-rootfs.s390x.img \
ip=<IP>::<Gateway>:<mask>:<Hostname>::<network-interface>:none \
nameserver=<DNS Server> \
coreos.inst.ignition_url=http://<http-host>:<port>/bootstrap-in-place-for-live-iso.ign"

• rd.neednet=1: Ensures networking is initialized during boot
• coreos.inst=yes: Triggers RHCOS installation
• coreos.inst.install_dev=vda: Specifies the target disk
• coreos.live.rootfs_url: Points to the rootfs image
• ip=...: Static IP configuration for the VM
• nameserver=...: DNS server
• coreos.inst.ignition_url: URL to the Ignition config (bootstrap or master)

OS Detection

--osinfo detect=on

• Enables automatic detection of OS type for better compatibility

Step 4: Bootstrap Recovery (If Needed)

Symptom

If the VM fails to reboot and journalctl shows:

systemd[1]: Bootstrap a Kubernetes cluster was skipped because of an unmet condition check (ConditionPathExists=!/opt/openshift/.bootkube.done)

Recovery Steps

# Check for master.ign on bootstrap node

ssh core@<bootstrap-node-ip/FQDN>

ls /opt/openshift/master.ign

# Copy to bastion server
scp /opt/openshift/master.ign <bastion_user>@<bastion_ip>:/var/www/html/

# Stop the VM
virsh destroy <VM Name>

Update the virt-install command to use master.ign:

virt-install \
  --connect qemu:///system \
  --reinstall <Same-VM-Name>\
  --boot hd \
  --location /var/www/html/iso,\
kernel=/var/www/html/rhcos-4.16.36-s390x-live-kernel-s390x,\
initrd=/var/www/html/rhcos-4.16.36-s390x-live-initramfs.s390x.img \
  --extra-args "rd.neednet=1 coreos.inst=yes coreos.inst.install_dev=vda \
coreos.live.rootfs_url=http://<http-host>:<port>/rhcos-4.16.36-s390x-live-rootfs.s390x.img \
ip=<IP>::<Gateway>:<mask>:<Hostname>::<network-interface>:none \
nameserver=<DNS Server> \
coreos.inst.ignition_url=http://<http-host>:<port>/master.ign" \
  --osinfo detect=on

Re-run the VM creation and monitor via virsh console.

Step 5: Post-Install Validation

Export Kubeconfig

export KUBECONFIG=ocp/auth/kubeconfig

Verify Cluster Health

oc get nodes
oc get clusterversion
oc get co

Confirm Installation Completion

openshift-install --dir=ocp wait-for install-complete --log-level=debug

Reference:

https://docs.redhat.com/en/documentation/openshift_container_platform/4.16/html/installing_on_a_single_node/install-sno-installing-sno#install-sno-with-ibmz