# Rendering, Linting and Dry Runs — Helm

Source: https://www.skillbyai.com/en/helm/c-render

> Inspect the YAML Helm will produce before it reaches a cluster.

## See the output before you apply it

Most chart bugs are visible in the rendered YAML, so make rendering a habit. **`helm template`** renders a chart locally and prints manifests without contacting the cluster; it is ideal for reviews, CI checks and diffing. Note that it does not know the cluster's real state: `lookup` returns nothing and `.Capabilities` uses defaults unless you pass `--kube-version` or `--api-versions`. **`helm install` or `upgrade` with `--dry-run`** renders and validates against the cluster without changing it (`--dry-run=server` also lets `lookup` query the cluster). **`helm lint`** checks chart structure and common mistakes. Adding `--debug` prints rendered output even when it fails to parse, which helps locate a broken template. The **helm-diff** plugin (`helm diff upgrade`) shows exactly what an upgrade would change in a live release.

## Render, lint and diff

Run these locally and in CI before any upgrade.

```bash
helm lint ./charts/shop-api -f values-prod.yaml

helm template shop-api ./charts/shop-api -f values-prod.yaml \
  --namespace shop > rendered.yaml

# render only one template while debugging
helm template shop-api ./charts/shop-api -s templates/deployment.yaml --debug

# against a live cluster, no changes applied
helm upgrade --install shop-api ./charts/shop-api -n shop -f values-prod.yaml --dry-run=server

# with the helm-diff plugin installed
helm diff upgrade shop-api ./charts/shop-api -n shop -f values-prod.yaml
```

## Read the rendered YAML in review

Reviewing template diffs is hard; reviewing rendered manifests is easy. Many teams commit or attach `helm template` output per environment to pull requests so reviewers see what will actually change.

**Quiz:** Which command renders manifests locally without contacting the cluster?

- [ ] helm upgrade --wait
- [ ] helm rollback
- [x] helm template
- [ ] helm status

*Answer:* helm template. helm template renders charts offline; dry runs of install/upgrade can contact the cluster.