Kyverno Mutation Templates

When to Use This Skill

Mutation policies modify resources at admission time, before they're persisted to etcd. This approach enforces standards without blocking deployments or requiring manual manifest updates.

Implementation

See the full implementation guide in the source documentation.

Techniques

Common Patterns

Conditional Mutations

Only mutate resources that match specific criteria:

• Namespace-scoped mutations (dev vs prod)
• Label-based mutations (inject monitoring only for app.kubernetes.io/monitored=true)
• Resource type mutations (different rules for Deployments vs StatefulSets)

Mutation Conflicts

When multiple policies mutate the same field:

• Last-write-wins - Policies execute in alphabetical order by name
• Merge strategies - Use patchStrategicMerge or patchesJson6902 for predictable merging
• Exclusions - Use exclude blocks to prevent conflicting mutations

Security Boundaries

Never mutate security-critical fields:

• Security contexts (runAsUser, capabilities, privileged)
• Resource limits (mutations can escalate privileges)
• Host paths or volumes (mutations can grant filesystem access)

Use validation policies for security boundaries. Use mutations for operational standards.

Examples

See examples.md for code examples.

Related Patterns

• Kyverno Templates Overview
• Kyverno Generation Templates
• Kyverno Image Security

References

• Source Documentation
• AEL Enforce