OpenShift Container Platform

Configuring Discovery ISO kernel arguments for installations using GitOps ZTP

The GitOps Zero Touch Provisioning (ZTP) workflow uses the Discovery ISO as part of the OpenShift Container Platform installation process on managed bare-metal hosts. You can edit the InfraEnv resource to specify kernel arguments for the Discovery ISO. This is useful for cluster installations with specific environmental requirements.

For example, configure the rd.net.timeout.carrier kernel argument for the Discovery ISO to facilitate static networking for the cluster or to receive a DHCP address before downloading the root file system during installation.

In OpenShift Container Platform {product-version}, you can only add kernel arguments. You can not replace or delete kernel arguments.

Prerequisites

You have installed the OpenShift CLI (oc).
You have logged in to the hub cluster as a user with cluster-admin privileges.

Procedure

Create the InfraEnv CR and edit the spec.kernelArguments specification to configure kernel arguments.

Save the following YAML in an InfraEnv-example.yaml file:

The InfraEnv CR in this example uses template syntax such as {{ .Cluster.ClusterName }} that is populated based on values in the ClusterInstance CR. The ClusterInstance CR automatically populates values for these templates during deployment. Do not edit the templates manually.

apiVersion: agent-install.openshift.io/v1beta1
kind: InfraEnv
metadata:
  annotations:
    argocd.argoproj.io/sync-wave: "1"
  name: "{{ .Cluster.ClusterName }}"
  namespace: "{{ .Cluster.ClusterName }}"
spec:
  clusterRef:
    name: "{{ .Cluster.ClusterName }}"
    namespace: "{{ .Cluster.ClusterName }}"
  kernelArguments:
    - operation: append
      value: audit=0
    - operation: append
      value: trace=1
  sshAuthorizedKey: "{{ .Site.SshPublicKey }}"
  proxy: "{{ .Cluster.ProxySettings }}"
  pullSecretRef:
    name: "{{ .Site.PullSecretRef.Name }}"
  ignitionConfigOverride: "{{ .Cluster.IgnitionConfigOverride }}"
  nmStateConfigLabelSelector:
    matchLabels:
      nmstate-label: "{{ .Cluster.ClusterName }}"
  additionalNTPSources: "{{ .Cluster.AdditionalNTPSources }}"

kernelArguments.operation specifies the append operation to add a kernel argument.
kernelArguments.value specifies the kernel argument you want to configure. This example configures the audit kernel argument and the trace kernel argument.

Commit the InfraEnv-example.yaml file to your Git repository and push your changes. The following example shows a sample Git repository structure:

~/example-ztp/install
          └── site-install
               ├── clusterinstance-example.yaml
               ├── InfraEnv-example.yaml
               └── kustomization.yaml

Update the kustomization.yaml file to use the configMapGenerator field to package the InfraEnv CR into a ConfigMap:
```
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - clusterinstance-example.yaml
configMapGenerator:
  - name: custom-infraenv-cm
    namespace: example-cluster
    files:
      - InfraEnv-example.yaml
generatorOptions:
  disableNameSuffixHash: true
```
- clusterinstance-example.yaml specifies the name of the ClusterInstance CR.
- configMapGenerator.name specifies the name of the ConfigMap that contains the custom InfraEnv CR.
- configMapGenerator.namespace must match the ClusterInstance namespace.

In your ClusterInstance CR, reference the ConfigMap in the spec.templateRefs field:

apiVersion: siteconfig.open-cluster-management.io/v1alpha1
kind: ClusterInstance
metadata:
  name: "example-cluster"
  namespace: "example-cluster"
spec:
  clusterName: "example-cluster"
  templateRefs:
    - name: custom-infraenv-cm
      namespace: example-cluster
# ...

spec.templateRefs specifies the ConfigMap CR that contains the custom InfraEnv CR template.

Commit the ClusterInstance CR and kustomization.yaml to your Git repository and push your changes.

When the Argo CD pipeline syncs the changes, the SiteConfig Operator uses the custom InfraEnv-example CR from the generated ConfigMap to configure the infrastructure environment, including the custom kernel arguments.

Verification

To verify that the kernel arguments are applied, after the Discovery image verifies that OpenShift Container Platform is ready for installation, you can SSH to the target host before the installation process begins. At that point, you can view the kernel arguments for the Discovery ISO in the /proc/cmdline file.

Begin an SSH session with the target host:

$ ssh -i /path/to/privatekey core@<host_name>

View the system’s kernel arguments by using the following command:
```
$ cat /proc/cmdline
```