Running a stateful container with file system configurations

Use this section as a sample of how to run a stateful container with a file system configuration.

1. Open a command-line terminal.
2. Create an array secret.

   Important: Be sure that the username and password match the same username and password used on the storage system.

   $> cat demo-secret-svc-array.yaml
   kind: Secret
   apiVersion: v1
   metadata:
     name: svc-array
     namespace: csi-ns
   type: Opaque
   stringData:
      management_address: <ADDRESS-1, ADDRESS-2> # replace with valid storage system management address
      username: <USERNAME>                   # replace with valid username
   data:
      password: <PASSWORD base64>            # replace with valid password
     
   $> kubectl create -f demo-secret-svc-array.yaml
   secret/svc-array created
   

3. Create a storage class.

   Note: The SpaceEfficiency values for Spectrum Virtualize Family are: thick, thin, compressed, or deduplicated. These values are not case specific. For DS8000 Family systems, the default value is standard, but can be set to thin, if required. These values are not case specific. For more information, see Creating storage classes. This parameter is not applicable for IBM FlashSystem A9000 and A9000R systems. These systems always include deduplication and compression.

   $> cat demo-storageclass-gold-svc.yaml
   kind: StorageClass
   apiVersion: storage.k8s.io/v1
   metadata:
     name: gold
   provisioner: block.csi.ibm.com
   parameters:
     SpaceEfficiency: deduplicated
     pool: gold
   ​
     csi.storage.k8s.io/provisioner-secret-name: svc-array
     csi.storage.k8s.io/provisioner-secret-namespace: csi-ns
     csi.storage.k8s.io/controller-publish-secret-name: svc-array
     csi.storage.k8s.io/controller-publish-secret-namespace: csi-ns
   ​
     csi.storage.k8s.io/fstype: xfs   # Optional. values ext4\xfs. The default is ext4.
     volume_name_prefix: demo         # Optional.
   
   $> kubectl create -f demo-storageclass-gold-svc.yaml
   storageclass.storage.k8s.io/gold created

4. Create a PVC demo-pvc-file-system.yaml with the size of 1 Gb.

   Note: For more information about creating a PVC yaml file, see Creating a PersistentVolumeClaim (PVC).

   $> cat demo-pvc-file-system.yaml
   kind: PersistentVolumeClaim
   apiVersion: v1
   metadata:
     name: demo-pvc-file-system
   spec:
     volumeMode: Filesystem
     accessModes:
     - ReadWriteOnce
     resources:
       requests:
         storage: 1Gi
     storageClassName: gold
   
   $> kubectl apply -f demo-pvc-file-system.yaml
   persistentvolumeclaim/demo-pvc-file-system created

5. Display the existing PVC and the created persistent volume (PV).

   Note: For more information about creating a PVC yaml file, see Creating a PersistentVolumeClaim (PVC).

   $> kubectl get pv,pvc
   NAME                                                        CAPACITY   ACCESS MODES
   persistentvolume/pvc-828ce909-6eb2-11ea-abc8-005056a49b44   1Gi        RWO
   
   RECLAIM POLICY   STATUS   CLAIM              STORAGECLASS   REASON   AGE
   Delete           Bound    default/demo-pvc-file-system   gold                    109m
   
   NAME                             STATUS   VOLUME                                     CAPACITY   
   persistentvolumeclaim/demo-pvc-file-system   Bound    pvc-828ce909-6eb2-11ea-abc8-005056a49b44   1Gi
   
   ACCESS MODES   STORAGECLASS   AGE
   RWO            gold           78s
   
   $> kubectl describe persistentvolume/pvc-828ce909-6eb2-11ea-abc8-005056a49b44
   Name:            pvc-828ce909-6eb2-11ea-abc8-005056a49b44
   Labels:          <none>
   Annotations:     pv.kubernetes.io/provisioned-by: block.csi.ibm.com
   Finalizers:      [kubernetes.io/pv-protection external-attacher/block-csi-ibm-com]
   StorageClass:    gold
   Status:          Bound
   Claim:           default/demo-pvc-file-system
   Reclaim Policy:  Delete
   Access Modes:    RWO
   VolumeMode:      Filesystem
   Capacity:        1Gi
   Node Affinity:   <none>
   Message:
   Source:
       Type:              CSI (a Container Storage Interface (CSI) volume source)
       Driver:            block.csi.ibm.com
       VolumeHandle:      SVC:60050760718106998000000000000543
       ReadOnly:          false
       VolumeAttributes:      array_address=baremetal10-cluster.xiv.ibm.com
                              pool_name=csi_svcPool
                              storage.kubernetes.io/csiProvisionerIdentity=1585146948772-8081-block.csi.ibm.com
                              storage_type=SVC
                              volume_name=demo_pvc-828ce909-6eb2-11ea-abc8-005056a49b44
   Events:                <none>

6. Create a StatefulSet, using the demo-statefulset-file-system.yaml.

   Note: For more information about creating a StatefulSet, see Creating a StatefulSet.

   $> kubectl create -f demo-statefulset-file-system.yaml
   statefulset/demo-statefulset-file-system created

   $> cat demo-statefulset-file-system.yaml
   kind: StatefulSet
   apiVersion: apps/v1
   metadata:
     name: demo-statefulset-file-system
   spec:
     selector:
       matchLabels:
         app: demo-statefulset
     serviceName: demo-statefulset
     replicas: 1
     template:
       metadata:
         labels:
           app: demo-statefulset
       spec:
         containers:
         - name: container-demo
           image: registry.access.redhat.com/ubi8/ubi:latest
           command: [ "/bin/sh", "-c", "--" ]
           args: [ "while true; do sleep 30; done;" ]
           volumeMounts:
             - name: demo-volume
               mountPath: "/data"
         volumes:
         - name: demo-volume
           persistentVolumeClaim:
             claimName: demo-pvc-file-system
   ​
   #      nodeSelector:
   #        kubernetes.io/hostname: NODESELECTOR

7. Check the newly created pod.
   Display the newly created pod (make sure the pod status is Running).

   $> kubectl get pod demo-statefulset-file-system-0
   NAME                 READY   STATUS    RESTARTS   AGE
   demo-statefulset-file-system-0   1/1     Running   0          43s

8. Write data to the persistent volume of the pod.
   The PV should be mounted inside the pod at /data.

   $> kubectl exec demo-statefulset-0 touch /data/FILE
   $> kubectl exec demo-statefulset-0 ls /data/FILE
   /data/FILE

9. Log into the worker node that has the running pod and display the newly attached volume on the node.
   1. Verify which worker node is running the pod demo-statefulset-0.

      $> kubectl describe pod demo-statefulset-0| grep "^Node:"
      Node: k8s-node1/hostname

   2. Establish an SSH connection and log into the worker node.

      $> ssh root@k8s-node1

   3. List the multipath devices on the worker node.

      $>[k8s-node1]  multipath -ll
      mpathz (828ce9096eb211eaabc8005056a49b44) dm-3 IBM     ,2145 (for SVC)         
      size=1.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
      `-+- policy='service-time 0' prio=1 status=active
        |- 37:0:0:12 sdc 8:32 active ready running
        `- 36:0:0:12 sdb 8:16 active ready running
      
      $>[k8s-node1] ls -l /dev/mapper/mpathz
      lrwxrwxrwx. 1 root root 7 Aug 12 19:29 /dev/mapper/mpathz -> ../dm-3

   4. List the physical devices of the multipath mpathz and its mountpoint on the host. (This is the /data inside the stateful pod).

      $>[k8s-node1]  lsblk /dev/sdb /dev/sdc
      NAME     MAJ:MIN RM SIZE RO TYPE  MOUNTPOINT
      sdb        8:16   0   1G  0 disk  
      └─mpathz 253:3    0   1G  0 mpath /var/lib/kubelet/pods/d67d22b8-bd10-11e9-a1f5-005056a45d5f/volumes/kubernetes.io~csi/pvc-828ce909-6eb2-11ea-abc8-005056a49b44
      sdc        8:32   0   1G  0 disk  
      └─mpathz 253:3    0   1G  0 mpath /var/lib/kubelet/pods/d67d22b8-bd10-11e9-a1f5-005056a45d5f/volumes/kubernetes.io~csi/pvc-828ce909-6eb2-11ea-abc8-005056a49b44

   5. View the PV mounted on this host.

      Note: All PV mountpoints look like: /var/lib/kubelet/pods/*/volumes/kubernetes.io~csi/pvc-*/mount

      $>[k8s-node1]  df | egrep pvc
      /dev/mapper/mpathz      1038336    32944   1005392   4% /var/lib/kubelet/pods/d67d22b8-bd10-11e9-a1f5-005056a45d5f/volumes/kubernetes.io~csi/pvc-828ce909-6eb2-11ea-abc8-005056a49b44/mount

   6. Details about the driver internal metadata file .stageInfo.json is stored in the k8s PV node stage path /var/lib/kubelet/plugins/kubernetes.io/csi/pv/<PVC-ID>/globalmount/.stageInfo.json. The CSI driver creates the metadata file during the NodeStage API and is used at later stages by the NodePublishVolume, NodeUnPublishVolume and NodeUnStage CSI APIs later on.

      $> cat /var/lib/kubelet/plugins/kubernetes.io/csi/pv/pvc-828ce909-6eb2-11ea-abc8-005056a49b44/globalmount/.stageInfo.json
      {"connectivity":"iscsi","mpathDevice":"dm-3","sysDevices":",sdb,sdc"}

10. Delete StatefulSet and then recreate, in order to validate data (/data/FILE) remains in the persistent volume.

    $> kubectl delete statefulset/demo-statefulset-file-system
    statefulset/demo-statefulset-file-system deleted
    
    ### Wait until the pod is deleted. Once deleted the '"demo-statefulset-file-system" not found' is returned.
    $> kubectl get statefulset/demo-statefulset-file-system
    NAME                 READY   STATUS        RESTARTS   AGE
    demo-statefulset-file-system-0   0/1     Terminating   0          91m
    
    
    ###### Establish an SSH connection and log into the worker node in order to see that the multipath was deleted and that the PV mountpoint no longer exists.
    
    $> ssh root@k8s-node1
    
    $>[k8s-node1] df | egrep pvc
    $>[k8s-node1] multipath -ll
    $>[k8s-node1] lsblk /dev/sdb /dev/sdc
    lsblk: /dev/sdb: not a block device
    lsblk: /dev/sdc: not a block device
    
    
    ###### Recreate the statefulset and verify that /data/FILE exists.
    $> kubectl create -f demo-statefulset-file-system.yml
    statefulset/demo-statefulset-file-system created
    
    $> kubectl exec demo-statefulset-file-system-0 ls /data/FILE
    File

11. Delete StatefulSet and the PVC.

    $> kubectl delete statefulset/demo-statefulset-file-system
    statefulset/demo-statefulset-file-system deleted
    
    $> kubectl get statefulset/demo-statefulset-file-system
    No resources found.
    
    $> kubectl delete pvc/demo-pvc-file-system
    persistentvolumeclaim/demo-pvc-file-system deleted
    
    $> kubectl get pv,pvc
    No resources found.