Migrate FlexVolume to CSI for clusters without data

Plug-in comparison

The following table compares the CSI and FlexVolume storage plug-ins.

Use cases

The CSI plug-in is more stable and efficient than the FlexVolume plug-in. We recommend that you migrate from the FlexVolume plug-in to the CSI plug-in if your cluster meets one of the following conditions:

• No volumes have been mounted in the cluster using FlexVolume.

• Volumes were previously mounted using FlexVolume, but their associated data has been deleted.

Step 1: Uninstall FlexVolume

1. Log on to the OpenAPI Explorer console and call the UnInstallClusterAddons operation to uninstall the FlexVolume plug-in.

   • ClusterId: Your cluster ID. You can find the cluster ID on the Basic Information page of your cluster.

   • name: Flexvolume.

   For more information, see Uninstall cluster add-ons.

2. Delete the alicloud-disk-controller and alicloud-nas-controller Deployments.

   kubectl delete deploy -n kube-system alicloud-disk-controller alicloud-nas-controller

3. Verify that the FlexVolume plug-in is uninstalled.

   kubectl get pods -n kube-system | grep 'flexvolume\|alicloud-disk-controller\|alicloud-nas-controller'

   If the command returns no output, the FlexVolume plug-in is uninstalled.

4. Delete the FlexVolume StorageClass resources. The provisioner for these resources is alicloud/disk.

   kubectl delete storageclass alicloud-disk-available alicloud-disk-efficiency alicloud-disk-essd alicloud-disk-ssd

   Expected output:

   storageclass.storage.k8s.io "alicloud-disk-available" deleted
   storageclass.storage.k8s.io "alicloud-disk-efficiency" deleted
   storageclass.storage.k8s.io "alicloud-disk-essd" deleted
   storageclass.storage.k8s.io "alicloud-disk-ssd" deleted

   The output indicates that the StorageClasses are deleted.

Step 2: Install CSI

• If your cluster uses the csi-compatible-controller plug-in, a custom CSI plug-in is already installed. This plug-in is not the standard CSI plug-in. You must delete the custom CSI components by running the following commands before you install the standard CSI plug-in.

  kubectl delete deploy csi-provisioner -n kube-system
  kubectl delete ds csi-plugin -n kube-system
  kubectl delete csidriver diskplugin.csi.alibabacloud.com nasplugin.csi.alibabacloud.com ossplugin.csi.alibabacloud.com

  Note

  These deletion operations do not affect existing pods in the cluster. However, after you delete the custom components and before you install the standard CSI plug-in, do not make changes to any pods.

• If the csi-compatible-controller plug-in is not used, you can directly call the OpenAPI to install the standard CSI plug-in.

1. Log on to the OpenAPI Explorer console and call the InstallClusterAddons operation to install the CSI plug-in.

   • ClusterId: Your cluster ID.

   • name: csi-provisioner.

   • version: The latest version of the CSI plug-in. For more information about CSI versions, see csi-provisioner.

   For more information, see Install cluster add-ons.

2. Verify that the CSI plug-in is running correctly.

   kubectl get pods -n kube-system | grep csi

   Expected output:

   csi-plugin-577mm                              4/4     Running   0          3d20h
   csi-plugin-k9mzt                              4/4     Running   0          41d
   csi-provisioner-6b58f46989-8wwl5              9/9     Running   0          41d
   csi-provisioner-6b58f46989-qzh8l              9/9     Running   0          6d20h

   The output indicates that the CSI plug-in is running as expected.

Step 3: Modify node pool configurations

Node pool configurations depend on the cluster's storage components. After you install the standard CSI components, the configurations of existing node pools are not automatically updated. You must manually modify the node pool configurations to trigger an update. After a successful update, the --enable-controller-attach-detach kubelet parameter for new nodes in the node pool is updated from false to true.

To trigger the update, you can modify all node pools by either adding an instance type or changing the logon password. This action updates the storage plug-in type in the backend, triggers a refresh of the node initialization script, and ensures that new nodes are configured with the correct parameters.

1. Log on to the ACK console. In the left navigation pane, click Clusters.

2. On the Clusters page, click the name of your cluster. In the left navigation pane, click Nodes > Node Pools.

3. On the Node Pools page, find the target node pool and click Edit in the Actions column.

4. In the dialog box that appears, modify the instance type configuration of the node pool and click OK.

   Note

   This modification only triggers an update of the backend storage plug-in type. After the update takes effect, you can revert this change.

Step 4: Modify existing node configurations

Apply the following YAML to update kubelet parameters to meet CSI requirements. This DaemonSet sets the --enable-controller-attach-detach parameter to true on existing nodes. After the operation is complete, you can delete the DaemonSet.

kind: DaemonSet
apiVersion: apps/v1
metadata:
  name: kubelet-set
spec:
  selector:
    matchLabels:
      app: kubelet-set
  template:
    metadata:
      labels:
        app: kubelet-set
    spec:
      tolerations:
        - operator: "Exists"
      hostNetwork: true
      hostPID: true
      containers:
        - name: kubelet-set
          securityContext:
            privileged: true
            capabilities:
              add: ["SYS_ADMIN"]
            allowPrivilegeEscalation: true
          image: registry.cn-hangzhou.aliyuncs.com/acs/csi-plugin:v1.26.5-56d1e30-aliyun
          imagePullPolicy: "Always"
          env:
          - name: enableADController
            value: "true"
          command: ["sh", "-c"]
          args:
          - echo "Starting kubelet flag set to $enableADController";
            ifFlagTrueNum=`cat /host/etc/systemd/system/kubelet.service.d/10-kubeadm.conf | grep enable-controller-attach-detach=$enableADController | grep -v grep | wc -l`;
            echo "ifFlagTrueNum is $ifFlagTrueNum";
            if [ "$ifFlagTrueNum" = "0" ]; then
                curValue="true";
                if [ "$enableADController" = "true" ]; then
                    curValue="false";
                fi;
                sed -i "s/enable-controller-attach-detach=$curValue/enable-controller-attach-detach=$enableADController/" /host/etc/systemd/system/kubelet.service.d/10-kubeadm.conf;
                restartKubelet="true";
                echo "current value is $curValue, change to expect "$enableADController;
            fi;
            if [ "$restartKubelet" = "true" ]; then
                /nsenter --mount=/proc/1/ns/mnt systemctl daemon-reload;
                /nsenter --mount=/proc/1/ns/mnt service kubelet restart;
                echo "restart kubelet";
            fi;
            while true;
            do
                sleep 5;
            done;
          volumeMounts:
          - name: etc
            mountPath: /host/etc
      volumes:
        - name: etc
          hostPath:
            path: /etc