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Dry-Run Preview

Dry-Run Preview lets you validate and preview a change before it is applied to the cluster. The Kubernetes API Server performs the full admission and validation pass — so what you see is exactly what would happen — without actually writing anything.

How to Use​

From the YAML Editor​

  1. Open any resource and click Edit YAML (or click Create for a new resource)
  2. Make your changes in the Monaco editor
  3. Click Dry Run instead of Save
  4. A side-by-side diff opens: current spec on the left, proposed spec on the right
  5. Review the diff, then either click Apply to save for real or Cancel to keep editing

What the Diff Shows​

PanelContent
Left (current)The resource YAML as it exists in the cluster right now
Right (proposed)Your edited YAML after the API Server normalizes it (defaults injected, etc.)

The diff highlights only meaningful changes — managedFields and server-assigned metadata are stripped from the comparison.

API Reference​

POST /api/v1/clusters/:cluster/namespaces/:namespace/resources/:resource/:name/dry-run
Content-Type: application/json

{
  "manifest": { /* full resource object */ }
}

Response:

{
  "current":  { /* existing resource */ },
  "proposed": { /* API Server normalized result */ },
  "valid":    true,
  "warnings": []
}

If the API Server rejects the change, valid is false and the error message is surfaced directly in the UI.

Admission Webhook Validation​

Because the dry run goes through the real API Server with dryRun: All, all admission webhooks (OPA/Gatekeeper, Kyverno, etc.) run against your change. Policy violations are reported before anything is written.

# Example: Kyverno policy violation returned in warnings
- "Resource 'api-server' violates policy 'require-resource-limits': container 'app' has no CPU limit"
info

Dry-run is supported for all 26+ resource types KubeVision manages, including CRDs.

Use Cases​

  • Safe production edits — Verify a Deployment image bump won't be rejected by policy
  • Template development — Confirm a new manifest is well-formed before first apply
  • Education — See exactly what fields the API Server adds by default (e.g., defaultMode on volumes)