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Migrating to Helm 3

Helm supports in-place migrations using the 2to3 plugin. The migration involves converting the Helm 2 release information (stored in ConfigMaps/Secrets in the Tiller namespace) to Helm 3 releases, cleaning up Helm 2 releases afterwards and then removing Tiller and its associated resources in the final step.

During the migration, existing resources are not modified, so LoadBalancers will for example not potentially trigger an IP change.

Example

Make sure that during a migration no other operations are performed using Helm 2, for example due to “accidental” automated deployment jobs. Ideally, all charts are migrated sequentially and then Tiller is removed.

In this example, the cert-manager chart is migrated to Helm 3.

Before we begin, we have to install the 2to3 plugin. Throughout the example, we’re using Helm 3 exclusively.

helm plugin install https://github.com/helm/helm-2to3.git
#Downloading and installing helm-2to3 v0.6.0 ...
#https://github.com/helm/helm-2to3/releases/download/v0.6.0/helm-2to3_0.6.0_linux_amd64.tar.gz
#Installed plugin: 2to3

Next you need a kubeconfig for the cluster in which the releases should be migrated. The kubeconfig can either be specified explicitly for each 2to3 call (e.g. helm 2to3 convert --kubeconfig=<path>) or set as a KUBECONFIG environment variable.

export KUBECONFIG=/path/to/kubeconfig

We can now convert the release information from version 2 to 3. This will by default only convert (and delete) the 10 most recent releases, so a cleanup is later required to remove the remaining releases (if there were more than 10).

Remove --dry-run to actually perform the conversion.

helm 2to3 convert \
  --dry-run \
  --tiller-ns kubermatic \
  --delete-v2-releases \
  cert-manager

Now the remaining Helm 2 releases can be removed:

helm 2to3 cleanup \
  --dry-run \
  --tiller-ns kubermatic \
  --name cert-manager

This completes the migration for the cert-manager chart.

After all migrations have completed, Tiller can then also be removed by running the cleanup command again without a --name flag (see --help):

helm 2to3 cleanup \
  --dry-run \
  --tiller-ns kubermatic