k8s-cluster-export

I wrote this quick and dirty bash script to export Kubernetes resources from a cluster in order to migrate to a new one. In my case we had to migrate multiple self-hosted Kubernetes cluster (including EBS PVCs) to AWS EKS.

Since on one hand the --export kubectl parameter is depreciated and on the other hand the goal from that server side export was more focused on a namespace migration on the same cluster (namespace removed while keeping for example clusterips) I decided to use the yaml export and remove unnecessary keys with yq.

Supported resource types

Right now not all resources types are implemented.

available_resources=(
  pvc
  sts
  deploy
  svc
  cm
  ing
  secrets
)

Usage

export all resource types for a namespace

./k8s-cluster-export -n test-ns

export all resources types and change the namespace

./k8s-cluster-export -n old-ns -c new-ns

export only PVCs and PVs

./k8s-cluster-export -n test-ns -r pvc

export only a limited list of PVCs and Deployments

This limitation is possible for all available resource types. The input file must match the resources type.

./k8s-cluster-export -n test-ns -r pvc -i pvc -r deploy -i deploy

deploy file

test-deploy-name1
test-deploy-name2

pvc file

pvc-name-1
pvc-name-2

Migration procedure (on AWS with EBS PVCs)

Disclosure: even if this is working in my case, this has to be tested carfully. Since Kubernetes has the permission to delete you're EBS volumes such a migration should be planned with great caution.

1. export configs

./k8s-cluster-export -n test-ns

2. scale down deployments / statefulsets on old Cluster

for i in */5_deploy/*; do
  deploy=$(yq r $i metadata.name)
  kubectl scale deployment --replicas 0 $deploy
done

for i in */6_sts/*; do
  sts=$(yq r $i metadata.name)
  kubectl scale statefulset --replicas 0 $sts
done

3. check if all volumes are available

for i in /2_pv/; do vol=$(yq r $i spec.awsElasticBlockStore.volumeID | cut -f4 -d'/') echo $vol aws ec2 describe-volumes --volume-id $vol | jq -r ".Volumes[].State" done

4. set tags for EBS volumes

OLD_CLUSTER=old-cluster-123
NEW_CLUSTER=new-cluster-123

for i in */2_pv/*; do
  vol=$(yq r $i spec.awsElasticBlockStore.volumeID | cut -f4 -d'/')
  aws ec2 delete-tags --resources $vol --tags Key=kubernetes.io/cluster/$OLD_CLUSTER
  aws ec2 delete-tags --resources $vol --tags Key=KubernetesCluster
  aws ec2 create-tags --resources $vol --tags Key=kubernetes.io/cluster/$NEW_CLUSTER,Value=owned
done

5. crate snapshot from ebs volume and check status

for i in */2_pv/*; do
  vol=$(yq r $i spec.awsElasticBlockStore.volumeID | cut -f4 -d'/')
  aws ec2 create-snapshot --volume-id $vol --description before-migration >> snap-output
done

for i in $(cat snap-output | jq -r ".SnapshotId"); do
  echo $i
  aws ec2 describe-snapshots --snapshot-ids $i | jq -r ".Snapshots[].State"
done

6. import config in new cluster

Take care to import PVCs first followed by PVs.

kubectl apply -f default/1_pvc/.

kubectl apply -f default/2_pv/.

check the pvc status and deploy all other resources after that.

kubectl apply -f default/3_cm/.
...
kubectl apply -f default/8_ing/.

---

Namespace to Namespace pvc migration

1. export configs

./k8s-cluster-export -n old-ns -c new-ns

2. Scale down and create snapshots

See cluster migration

3. Set PV ReclaimPolicy to Retain

for i in */2_pv/*; do
  pv=$(yq r $i metadata.name)
  kubectl patch pv $pv -p '{"spec":{"persistentVolumeReclaimPolicy":"Retain"}}'
done

4. Delete PVCs in old namespace

for i in */1_pvc/*; do
  pvc=$(yq r $i metadata.name)
  kubectl delete pvc -n old-ns $pvc
done

5. Remove claimRef from PVs

Check if the PVs are all in state Released and remove the claimRef from the PV

for i in */2_pv/*; do
  pv=$(yq r $i metadata.name)
  k get pv $pv
done

for i in */2_pv/*; do
  pv=$(yq r $i metadata.name)
  kubectl patch pv $pv --type=json -p='[{"op": "remove", "path": "/spec/claimRef"}]'
done

6. import config in new namespace

Don't reimporte the PVs because they are still there

kubectl apply -f old-ns/1_pvc/.
kubectl apply -f old-ns/5_deploy/.
...