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Cloud Native / Kubernetes

Kyverno: Kubernetes-Native Policy-as-Code for Platform Governance

•Stackxx•Cloud Native, Kubernetes
Kyverno: Kubernetes-Native Policy-as-Code for Platform Governance

Kyverno, the Kubernetes-native policy engine, offers a simpler alternative to Rego-based solutions for cluster governance. With policies written in familiar YAML and tightly integrated into the Kubernetes API, it lowers the barrier to Policy-as-Code adoption while providing robust validation, mutation, and generation capabilities.

Goal

Implement cluster-wide policies using Kyverno to enforce security, compliance, and operational standards without specialized policy languages.

Prerequisites

  • Kubernetes cluster (v1.25+ recommended)
  • Kyverno installed via Helm or manifests
  • kubectl access with permissions to create ClusterPolicy resources
  • Basic understanding of Kubernetes RBAC and admission controllers

Why Kyverno Over Alternatives?

Kyverno addresses a common pain point in Kubernetes governance: the learning curve of policy languages. Instead of Rego or custom DSLs, Kyverno uses standard YAML with Kubernetes-style manifests:

  • YAML-native: Policies look like any other Kubernetes resource
  • CRD-based: Standard Kubernetes tooling works (kubectl, GitOps, RBAC)
  • No special syntax: Uses CEL expressions with an extended function library
  • Rich feature set: Validate, Mutate, Generate, and Cleanup policies supported natively

Installing Kyverno

Deploy Kyverno via Helm:

helm repo add kyverno https://kyverno.github.io/kyverno/
helm repo update

helm install kyverno kyverno/kyverno \
  --namespace kyverno \
  --create-namespace

Verify the installation:

kubectl get pods -n kyverno

Your First Validation Policy

Create a ClusterPolicy that requires resource limits on all pods:

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-resources
spec:
  validationFailureAction: Enforce
  rules:
  - name: check-memory-limits
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "Memory limits are required"
      pattern:
        spec:
          containers:
          - name: "*"
            resources:
              limits:
                memory: "?*"

Apply and test:

kubectl apply -f require-resources.yaml

# This should fail:
kubectl run test --image=nginx

Mutation Policies

Automatically add labels or defaults without user intervention:

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: add-namespace-label
spec:
  rules:
  - name: mutate-labels
    match:
      resources:
        kinds:
        - Namespace
    mutate:
      patchStrategicMerge:
        metadata:
          labels:
            managed-by: kyverno

Common Pitfalls

  • Validation mode: Policies default to Audit mode. Use Enforce with caution and test first.
  • Resource ownership: Generated resources may have unexpected owners. Verify cleanup behavior.
  • Cascading policies: Mutations can trigger other policies—order matters.
  • Admission webhook latency: Complex policies add API latency. Monitor webhook response times.

Steps to Verify

Confirm Kyverno is enforcing policies:

# Check policy status
kubectl get clusterpolicy

# Review policy reports
kubectl get policyreport -A

Sources

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