Container Service for Kubernetes:Upgrade from FlexVolume to CSI for clusters where no data is stored

Differences between CSI and FlexVolume

The following table describes the differences between CSI and FlexVolume.

Scenarios

The CSI plug-in is more stable and efficient than the FlexVolume plug-in. In the following scenarios, we recommend that you upgrade from FlexVolume to CSI:

• No volume has been mounted to the cluster by using FlexVolume and no data is stored in the cluster by using FlexVolume.
• Volumes were mounted to the cluster by using FlexVolume but the relevant data in the volumes is deleted. No data is stored in the cluster by using FlexVolume.

Step 1: Uninstall FlexVolume

1. Log on to the OpenAPI Explorer platform and call the UnInstallClusterAddons operation to uninstall the FlexVolume plug-in.
   • ClusterId: Set the value to the ID of your cluster. You can view the ID of your cluster on the Basic Information page.
   • name: Set the value to Flexvolume.

   Fore more information, see UnInstallClusterAddons.
2. Run the following command to delete the alicloud-disk-controller and alicloud-nas-controller components:

   kubectl delete deploy -nkube-system alicloud-disk-controller alicloud-nas-controller

3. Run the following command to check whether the FlexVolume plug-in is uninstalled from your cluster:

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

   If the output is empty, the FlexVolume plug-in is uninstalled from your cluster.

Step 2: Install the CSI plug-in

1. Log on to the OpenAPI Explorer platform and call the InstallClusterAddons operation to install the CSI plug-in.
   • ClusterId: Set the value to the ID of your cluster.
   • name: Set the value to csi-provisioner.
   • version: The latest version is automatically specified. For more information about CSI versions, see csi-provisioner.

   Fore more information, see Install a component in an ACK cluster.
2. Run the following command to check whether the CSI plug-in runs as expected in the cluster:

   kubectl get pods -nkube-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

   If the preceding output is returned, the CSI plug-in runs as expected in the cluster.

Step 3: Modify the configurations of all node pools in the cluster

You can modify the configuration of each node pool to update the volume plug-in by adding a new instance type for the node pool or changing the logon password of the node pool. This way, the system automatically updates the node initialization script in the background to ensure that newly added nodes use the new configurations.

1. Log on to the ACK console and click Clusters in the left-side navigation pane.
2. On the Clusters page, click the name of a cluster and choose Nodes > Node Pools in the left-side navigation pane.
3. On the Node Pools page, find the node pool that you want to manage and click Edit in the Actions column.
4. On the node pool details page, use one of the following methods to modify the configurations of the node pool:
   • Add a new instance type.

     After you add a node, the system automatically updates the volume plug-in of the cluster in the background. You can delete the node after the new node pool configurations take effect.

   • Change the logon password of the node pool.
5. Click Confirm.

Step 4: Modify the configurations of existing nodes

Create a YAML based on the following code block. Then, deploy the YAML file to modify the kubelet parameters on which the CSI plug-in relies.

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:v1.16.9.43-f36bb540-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