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Migrating from Helm

Move a Helm release to a kro instance without downtime: design the API, install it, turn `helm get values` into an instance, switch over, and go back to Helm if needed.

1. Design the API

chart2kro inspect ./mychart                       # what can be exposed, and what cannot
chart2kro convert ./mychart \
  -f platform-defaults.yaml \
  --expose 'replicaCount,image.tag,resources,ingress.*' \
  --group apps.example.com --kind WebApp \
  -o api/

Commit api/ and run chart2kro convert … -o api/ --check in CI (exit 9 if stale). Before upgrading the chart, run chart2kro diff ./mychart --version NEW --against api/rgd.yaml: it exits 8 if existing instances would break.

2. Install the API

kubectl apply -f api/prerequisites.yaml   # only if the file exists: CRDs and shared cluster objects
kubectl apply -f api/rgd.yaml
kubectl get rgd                           # STATE Active

3. Turn releases into instances

helm get values my-release -n prod -o yaml > release.yaml
chart2kro instance ./mychart -f platform-defaults.yaml \
  --expose 'replicaCount,image.tag,resources,ingress.*' \
  --from release.yaml --name my-release --namespace prod > my-release.yaml

Pass the same conversion flags as in step 1. If the release sets values the API does not expose, the command fails and lists them: expose them, or accept their defaults with --allow-unexposed.

4. Switch over

kro creates objects named after the instance: my-release-mychart, like Helm's fullname for a release called my-release.

  • New installs: apply the instance.
  • Existing releases: objects created by Helm carry Helm's labels and ownership metadata. The safe path is to create the instance under a new name (or in a new namespace), move traffic, and then helm uninstall the release.

Adopting running Helm objects in place is not supported.

Going back to Helm

An instance's spec uses the chart's value paths, so it is already a values file. To move an app back to Helm:

yq '.spec | del(.chart2kroGenerated)' my-release.yaml > values.yaml
helm install my-release-helm ./mychart -n prod -f platform-defaults.yaml -f values.yaml
# move traffic, then:
kubectl delete mychart my-release -n prod
  • Pass the same -f files you used for the conversion: they hold the API's defaults.
  • Use a new release name (or namespace). The instance's objects have the names Helm would use for my-release, so installing under that name fails while the instance exists.
  • chart2kroGenerated.* inputs are values the chart generates itself (passwords, keys). Helm generates new ones on install. If data depends on them, set the chart's own value for them (for example auth.password) or its existingSecret option.