Migrate releases from helm2 to helm3

script.sh

#!/bin/bash

# You need both helm v2 and v3, also helm "2to3" plugin should be installed in helm3
HELM2_BINARY=/usr/local/bin/helm
HELM3_BINARY=/usr/local/bin/helm3

KUBE_CONTEXT="mycontext"
kubectl config use-context ${KUBE_CONTEXT}

# Get available resource definitions in the CONTEXT
RESOURCES=$(kubectl api-resources --no-headers | awk '{print $1}' | xargs | sed 's; ;,;g')

comm -3 \
        <(${HELM2_BINARY} list | grep -v 'NAMESPACE' | awk -F"\t" '$7 != "" {print $7 "\t" $1}' | sort -k1,2) \
        <(${HELM3_BINARY} list --all-namespaces | grep -v 'NAMESPACE' | awk -F"\t" '{print $2 "\t" $1}' | sort -k1,2) |
  awk '{print $1 "\t" $2}' |
    while IFS= read -r line
    do
      while IFS=$'\t' read -r NAMESPACE RELEASE
      do
        echo "$NAMESPACE        $RELEASE"
        helm3 2to3 convert $RELEASE
        # Label resources from charts
        kubectl label $RESOURCES \
                -n $NAMESPACE \
                --overwrite \
                -l "heritage=Tiller, release=$RELEASE" \
                "app.kubernetes.io/managed-by=Helm"

        # Annotate resources from chart
        kubectl annotate $RESOURCES \
                -n $NAMESPACE \
                --overwrite \
                -l "heritage=Tiller, release=$RELEASE" \
                "meta.helm.sh/release-name=$RELEASE" \
                "meta.helm.sh/release-namespace=$NAMESPACE"
      done < <(echo "$line")
    done

### If something went wrong you can delete all generated helm3 releases with command
# kubectl --context ${KUBE_CONTEXT} get secrets --all-namespaces \
#   | grep sh.helm.release \
#   | awk '{print "kubectl --context ${KUBE_CONTEXT} -n " $1 " delete secrets " $2}' \
#   | parallel