Getting Started with Kyverno: Kubernetes Policy Made Simple

What is Kyverno?

Kyverno is a policy admission controller that helps you manage and enforce rules across your clusters. It works by validating, mutating, or even blocking incoming requests to the Kubernetes API server based on a set of policies. In simple terms, Kyverno lets you automatically check whether resources meet certain standards before they’re created or updated. This helps ensure consistency, improve security, and catch misconfigurations early — without writing custom code.

Why Do We Need Kyverno?

As Kubernetes environments grow more complex, maintaining security and consistency becomes harder. Kyverno helps by providing a structured way to enforce policies that define what’s allowed and what’s not — making it easier to follow security best practices and organizational standards.

For instance, you can create a policy that only permits pods to use images from an approved container registry. This ensures that teams deploy trusted, verified images — while blocking unapproved or potentially harmful workloads before they even start.

Kyverno Custom Resources

Kyverno uses Custom Resource Definitions (CRDs) to define and manage policies within Kubernetes environments. These CRDs help you control how resources are created, modified, or validated — ensuring that workloads follow security and operational standards. Whether you’re working at the namespace level or managing your entire cluster, Kyverno provides flexible tools to help you enforce rules consistently.

Policy vs ClusterPolicy

Kyverno provides two main types of policy resources:

• Policy — Applied within a specific namespace.
• ClusterPolicy — Applied cluster-wide and not tied to any particular namespace.

Both types allow you to define one or more rules, each of which includes:

• Match conditions: which resources the rule applies to.
• Exclude conditions: which resources to ignore.

Each rule can perform actions such as:

• Mutate resources (e.g., add a label to a pod).
• Validate values (e.g., ensure a label or annotation exists).
• Verify images (e.g., check if a container uses an approved image hash).
• Generate other resources (e.g., auto-create ConfigMaps or roles).

You can run these policies in two modes:

• Audit mode: Logs violations without blocking the request — ideal for testing.
• Enforce mode: Actively blocks resources that don’t meet policy requirements.

Tip: Kyverno also supports PolicyExceptions to allow specific resources to bypass a policy when needed — useful for controlled flexibility.

Audit Mode

In audit mode, Kyverno scans existing resources across namespaces to check if they comply with defined policies. This mode doesn’t block or modify anything — it simply reports violations. It’s a safe and practical way to test new policies before enforcing them in production, helping teams understand the potential impact without disrupting workloads.

Enforce Mode

Enforce mode is used to apply policies to newly created or modified resources. When a resource doesn’t meet policy requirements, Kyverno will block it. This ensures that all new workloads follow security and operational standards from the start.

Note that enforce mode does not affect existing resources. Even if something already running violates a policy, it won’t be removed or changed unless the policy is also applied in another way.

Some namespaces can be excluded from enforcement if needed — for example, system or exempted dev namespaces.

PolicyException

There may be cases where a workload intentionally needs to bypass a policy — for example, a temporary or special-use deployment. That’s where PolicyException comes in.

A PolicyException lets you create a rule to skip validation or mutation for specific resources. These exceptions are defined using match selectors based on namespace, resource type, or resource name.

Tip: Use exceptions sparingly. If you find yourself needing too many exceptions, it may be a sign that the policy itself needs to be updated or made more flexible.

Understanding PolicyReport in Kyverno

Kyverno automatically generates PolicyReports that summarize which resources in your cluster are compliant or non-compliant with the defined policies. These reports help you track which workloads pass or fail validation checks based on your current policies.

Note: PolicyReports only reflect results from audit mode. Since audit mode evaluates existing resources without blocking them, the reports provide a live snapshot of what’s happening in the cluster.

Resources blocked in enforce mode don’t appear in these reports — because they never get created in the first place.

PolicyReports are especially helpful when testing new policies, as they show the potential impact before enforcement is turned on.

Final Thoughts

Kyverno makes Kubernetes policy management approachable by using familiar YAML syntax and integrating seamlessly with cluster operations. Whether you’re just starting with audit mode or rolling out enforcement in production, Kyverno helps teams maintain consistency, security, and governance — without introducing unnecessary complexity.

As you begin experimenting with Kyverno, start small: test your policies in audit mode, review PolicyReports, and gradually move toward enforcement. And remember — policies are not just guardrails, they’re a powerful way to encode best practices into your infrastructure.

Resources

About Kyverno — Official Website: https://kyverno.io/#about-kyverno
Kyverno Policy Samples: https://kyverno.io/policies/