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Chapter 22. Persistent Storage Examples

22.1. Overview
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The following sections provide detailed, comprehensive instructions on setting up and configuring common storage use cases. These examples cover both the administration of persistent volumes and their security, and how to claim against the volumes as a user of the system.

22.2.1. Overview
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The following use case describes how a cluster administrator wanting to leverage shared storage for use by two separate containers would configure the solution. This example highlights the use of NFS, but can easily be adapted to other shared storage types, such as GlusterFS. In addition, this example will show configuration of pod security as it relates to shared storage.

Persistent Storage Using NFS provides an explanation of persistent volumes (PVs), persistent volume claims (PVCs), and using NFS as persistent storage. This topic shows and end-to-end example of using an existing NFS cluster and OpenShift Container Platform persistent store, and assumes an existing NFS server and exports exist in your OpenShift Container Platform infrastructure.

Note

All oc commands are executed on the OpenShift Container Platform master host.

22.2.2. Creating the Persistent Volume
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Before creating the PV object in OpenShift Container Platform, the persistent volume (PV) file is defined:

Example 22.1. Persistent Volume Object Definition Using NFS

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv
1 

spec:
  capacity:
    storage: 1Gi
2 

  accessModes:
    - ReadWriteMany
3 

  persistentVolumeReclaimPolicy: Retain
4 

  nfs:
5 

    path: /opt/nfs
6 

    server: nfs.f22
7 

    readOnly: false
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1
The name of the PV, which is referenced in pod definitions or displayed in various oc volume commands.
2
The amount of storage allocated to this volume.
3
accessModes are used as labels to match a PV and a PVC. They currently do not define any form of access control.
4
The volume reclaim policy Retain indicates that the volume will be preserved after the pods accessing it terminates.
5
This defines the volume type being used, in this case the NFS plug-in.
6
This is the NFS mount path.
7
This is the NFS server. This can also be specified by IP address.

Save the PV definition to a file, for example nfs-pv.yaml, and create the persistent volume: 

# oc create -f nfs-pv.yaml
persistentvolume "nfs-pv" created
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Verify that the persistent volume was created: 

# oc get pv
NAME         LABELS    CAPACITY   ACCESSMODES   STATUS      CLAIM     REASON    AGE
nfs-pv       <none>    1Gi        RWX           Available                       37s
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22.2.3. Creating the Persistent Volume Claim
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A persistent volume claim (PVC) specifies the desired access mode and storage capacity. Currently, based on only these two attributes, a PVC is bound to a single PV. Once a PV is bound to a PVC, that PV is essentially tied to the PVC’s project and cannot be bound to by another PVC. There is a one-to-one mapping of PVs and PVCs. However, multiple pods in the same project can use the same PVC. This is the use case we are highlighting in this example.

Example 22.2. PVC Object Definition

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-pvc
1 

spec:
  accessModes:
  - ReadWriteMany
2 

  resources:
     requests:
       storage: 1Gi
3
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1
The claim name is referenced by the pod under its volumes section.
2
As mentioned above for PVs, the accessModes do not enforce access right, but rather act as labels to match a PV to a PVC.
3
This claim will look for PVs offering 1Gi or greater capacity.

Save the PVC definition to a file, for example nfs-pvc.yaml, and create the PVC: 

# oc create -f nfs-pvc.yaml
persistentvolumeclaim "nfs-pvc" created
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Verify that the PVC was created and bound to the expected PV: 

# oc get pvc
NAME            LABELS    STATUS    VOLUME       CAPACITY   ACCESSMODES   AGE
nfs-pvc         <none>    Bound     nfs-pv       1Gi        RWX           24s
1
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1
The claim, nfs-pvc, was bound to the nfs-pv PV.

22.2.4. Ensuring NFS Volume Access
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Access is necessary to a node in the NFS server. On this node, examine the NFS export mount: 

[root@nfs nfs]# ls -lZ /opt/nfs/
total 8
-rw-r--r--. 1 root 100003  system_u:object_r:usr_t:s0     10 Oct 12 23:27 test2b
1
2
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1
the owner has ID 0.
2
the group has ID 100003.

In order to access the NFS mount, the container must match the SELinux label, and either run with a UID of 0, or with 100003 in its supplemental groups range. Gain access to the volume by matching the NFS mount’s groups, which will be defined in the pod definition below.

By default, SELinux does not allow writing from a pod to a remote NFS server. To enable writing to NFS volumes with SELinux enforcing on each node, run: 

# setsebool -P virt_use_nfs on
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22.2.5. Creating the Pod
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A pod definition file or a template file can be used to define a pod. Below is a pod specification that creates a single container and mounts the NFS volume for read-write access:

Example 22.3. Pod Object Definition

apiVersion: v1
kind: Pod
metadata:
  name: hello-openshift-nfs-pod
1 

  labels:
    name: hello-openshift-nfs-pod
spec:
  containers:
    - name: hello-openshift-nfs-pod
      image: openshift/hello-openshift
2 

      ports:
        - name: web
          containerPort: 80
      volumeMounts:
        - name: nfsvol
3 

          mountPath: /usr/share/nginx/html
4 

  securityContext:
      supplementalGroups: [100003]
5 

      privileged: false
  volumes:
    - name: nfsvol
      persistentVolumeClaim:
        claimName: nfs-pvc
6
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1
The name of this pod as displayed by oc get pod.
2
The image run by this pod.
3
The name of the volume. This name must be the same in both the containers and volumes sections.
4
The mount path as seen in the container.
5
The group ID to be assigned to the container.
6
The PVC that was created in the previous step.

Save the pod definition to a file, for example nfs.yaml, and create the pod: 

# oc create -f nfs.yaml
pod "hello-openshift-nfs-pod" created
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Verify that the pod was created: 

# oc get pods
NAME                          READY     STATUS    RESTARTS   AGE
hello-openshift-nfs-pod       1/1       Running   0          4s
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More details are shown in the oc describe pod command: 

[root@ose70 nfs]# oc describe pod hello-openshift-nfs-pod
Name:				hello-openshift-nfs-pod
Namespace:			default
1 

Image(s):			fedora/S3
Node:				ose70.rh7/192.168.234.148
2 

Start Time:			Mon, 21 Mar 2016 09:59:47 -0400
Labels:				name=hello-openshift-nfs-pod
Status:				Running
Reason:
Message:
IP:				10.1.0.4
Replication Controllers:	<none>
Containers:
  hello-openshift-nfs-pod:
    Container ID:	docker://a3292104d6c28d9cf49f440b2967a0fc5583540fc3b062db598557b93893bc6f
    Image:		fedora/S3
    Image ID:		docker://403d268c640894cbd76d84a1de3995d2549a93af51c8e16e89842e4c3ed6a00a
    QoS Tier:
      cpu:		BestEffort
      memory:		BestEffort
    State:		Running
      Started:		Mon, 21 Mar 2016 09:59:49 -0400
    Ready:		True
    Restart Count:	0
    Environment Variables:
Conditions:
  Type		Status
  Ready 	True
Volumes:
  nfsvol:
    Type:	PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:	nfs-pvc
3 

    ReadOnly:	false
  default-token-a06zb:
    Type:	Secret (a secret that should populate this volume)
    SecretName:	default-token-a06zb
Events:
4 

  FirstSeen	LastSeen	Count	From			SubobjectPath				                      Reason		Message
  ─────────	────────	─────	────			─────────────				                      ──────		───────
  4m		4m		1	{scheduler }							                                      Scheduled	Successfully assigned hello-openshift-nfs-pod to ose70.rh7
  4m		4m		1	{kubelet ose70.rh7}	implicitly required container POD	          Pulled		Container image "openshift3/ose-pod:v3.1.0.4" already present on machine
  4m		4m		1	{kubelet ose70.rh7}	implicitly required container POD	          Created		Created with docker id 866a37108041
  4m		4m		1	{kubelet ose70.rh7}	implicitly required container POD	          Started		Started with docker id 866a37108041
  4m		4m		1	{kubelet ose70.rh7}	spec.containers{hello-openshift-nfs-pod}		Pulled		Container image "fedora/S3" already present on machine
  4m		4m		1	{kubelet ose70.rh7}	spec.containers{hello-openshift-nfs-pod}		Created		Created with docker id a3292104d6c2
  4m		4m		1	{kubelet ose70.rh7}	spec.containers{hello-openshift-nfs-pod}		Started		Started with docker id a3292104d6c2
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1
The project (namespace) name.
2
The IP address of the OpenShift Container Platform node running the pod.
3
The PVC name used by the pod.
4
The list of events resulting in the pod being launched and the NFS volume being mounted. The container will not start correctly if the volume cannot mount.

There is more internal information, including the SCC used to authorize the pod, the pod’s user and group IDs, the SELinux label, and more, shown in the oc get pod <name> -o yaml command: 

[root@ose70 nfs]# oc get pod hello-openshift-nfs-pod -o yaml
apiVersion: v1
kind: Pod
metadata:
  annotations:
    openshift.io/scc: restricted
1 

  creationTimestamp: 2016-03-21T13:59:47Z
  labels:
    name: hello-openshift-nfs-pod
  name: hello-openshift-nfs-pod
  namespace: default
2 

  resourceVersion: "2814411"
  selflink: /api/v1/namespaces/default/pods/hello-openshift-nfs-pod
  uid: 2c22d2ea-ef6d-11e5-adc7-000c2900f1e3
spec:
  containers:
  - image: fedora/S3
    imagePullPolicy: IfNotPresent
    name: hello-openshift-nfs-pod
    ports:
    - containerPort: 80
      name: web
      protocol: TCP
    resources: {}
    securityContext:
      privileged: false
    terminationMessagePath: /dev/termination-log
    volumeMounts:
    - mountPath: /usr/share/S3/html
      name: nfsvol
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-a06zb
      readOnly: true
  dnsPolicy: ClusterFirst
  host: ose70.rh7
  imagePullSecrets:
  - name: default-dockercfg-xvdew
  nodeName: ose70.rh7
  restartPolicy: Always
  securityContext:
    supplementalGroups:
    - 100003
3 

  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  volumes:
  - name: nfsvol
    persistentVolumeClaim:
      claimName: nfs-pvc
4 

  - name: default-token-a06zb
    secret:
      secretName: default-token-a06zb
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2016-03-21T13:59:49Z
    status: "True"
    type: Ready
  containerStatuses:
  - containerID: docker://a3292104d6c28d9cf49f440b2967a0fc5583540fc3b062db598557b93893bc6f
    image: fedora/S3
    imageID: docker://403d268c640894cbd76d84a1de3995d2549a93af51c8e16e89842e4c3ed6a00a
    lastState: {}
    name: hello-openshift-nfs-pod
    ready: true
    restartCount: 0
    state:
      running:
        startedAt: 2016-03-21T13:59:49Z
  hostIP: 192.168.234.148
  phase: Running
  podIP: 10.1.0.4
  startTime: 2016-03-21T13:59:47Z
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1
The SCC used by the pod.
2
The project (namespace) name.
3
The supplemental group ID for the pod (all containers).
4
The PVC name used by the pod.

This pod definition, created in the same namespace, uses a different container. However, we can use the same backing storage by specifying the claim name in the volumes section below:

Example 22.4. Pod Object Definition

apiVersion: v1
kind: Pod
metadata:
  name: busybox-nfs-pod
1 

  labels:
    name: busybox-nfs-pod
spec:
  containers:
  - name: busybox-nfs-pod
    image: busybox
2 

    command: ["sleep", "60000"]
    volumeMounts:
    - name: nfsvol-2
3 

      mountPath: /usr/share/busybox
4 

      readOnly: false
  securityContext:
    supplementalGroups: [100003]
5 

    privileged: false
  volumes:
  - name: nfsvol-2
    persistentVolumeClaim:
      claimName: nfs-pvc
6
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1
The name of this pod as displayed by oc get pod.
2
The image run by this pod.
3
The name of the volume. This name must be the same in both the containers and volumes sections.
4
The mount path as seen in the container.
5
The group ID to be assigned to the container.
6
The PVC that was created earlier and is also being used by a different container.

Save the pod definition to a file, for example nfs-2.yaml, and create the pod: 

# oc create -f nfs-2.yaml
pod "busybox-nfs-pod" created
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Verify that the pod was created: 

# oc get pods
NAME                READY     STATUS    RESTARTS   AGE
busybox-nfs-pod     1/1       Running   0          3s
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More details are shown in the oc describe pod command: 

[root@ose70 nfs]# oc describe pod busybox-nfs-pod
Name:				busybox-nfs-pod
Namespace:			default
Image(s):			busybox
Node:				ose70.rh7/192.168.234.148
Start Time:			Mon, 21 Mar 2016 10:19:46 -0400
Labels:				name=busybox-nfs-pod
Status:				Running
Reason:
Message:
IP:				10.1.0.5
Replication Controllers:	<none>
Containers:
  busybox-nfs-pod:
    Container ID:	docker://346d432e5a4824ebf5a47fceb4247e0568ecc64eadcc160e9bab481aecfb0594
    Image:		busybox
    Image ID:		docker://17583c7dd0dae6244203b8029733bdb7d17fccbb2b5d93e2b24cf48b8bfd06e2
    QoS Tier:
      cpu:		BestEffort
      memory:		BestEffort
    State:		Running
      Started:		Mon, 21 Mar 2016 10:19:48 -0400
    Ready:		True
    Restart Count:	0
    Environment Variables:
Conditions:
  Type		Status
  Ready 	True
Volumes:
  nfsvol-2:
    Type:	PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:	nfs-pvc
    ReadOnly:	false
  default-token-32d2z:
    Type:	Secret (a secret that should populate this volume)
    SecretName:	default-token-32d2z
Events:
  FirstSeen	LastSeen	Count	From			SubobjectPath				Reason		Message
  ─────────	────────	─────	────			─────────────				──────		───────
  4m		4m		1	{scheduler }							Scheduled	Successfully assigned busybox-nfs-pod to ose70.rh7
  4m		4m		1	{kubelet ose70.rh7}	implicitly required container POD	Pulled		Container image "openshift3/ose-pod:v3.1.0.4" already present on machine
  4m		4m		1	{kubelet ose70.rh7}	implicitly required container POD	Created		Created with docker id 249b7d7519b1
  4m		4m		1	{kubelet ose70.rh7}	implicitly required container POD	Started		Started with docker id 249b7d7519b1
  4m		4m		1	{kubelet ose70.rh7}	spec.containers{busybox-nfs-pod}	Pulled		Container image "busybox" already present on machine
  4m		4m		1	{kubelet ose70.rh7}	spec.containers{busybox-nfs-pod}	Created		Created with docker id 346d432e5a48
  4m		4m		1	{kubelet ose70.rh7}	spec.containers{busybox-nfs-pod}	Started		Started with docker id 346d432e5a48
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As you can see, both containers are using the same storage claim that is attached to the same NFS mount on the back end.

22.3. Complete Example Using Ceph RBD
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22.3.1. Overview
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This topic provides an end-to-end example of using an existing Ceph cluster as an OpenShift Container Platform persistent store. It is assumed that a working Ceph cluster is already set up. If not, consult the Overview of Red Hat Ceph Storage.

Persistent Storage Using Ceph Rados Block Device provides an explanation of persistent volumes (PVs), persistent volume claims (PVCs), and using Ceph RBD as persistent storage.

Note

All oc …​ commands are executed on the OpenShift Container Platform master host.

22.3.2. Installing the ceph-common Package
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The ceph-common library must be installed on all schedulable OpenShift Container Platform nodes:

Note

The OpenShift Container Platform all-in-one host is not often used to run pod workloads and, thus, is not included as a schedulable node. 

# yum install -y ceph-common
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22.3.3. Creating the Ceph Secret
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The ceph auth get-key command is run on a Ceph MON node to display the key value for the client.admin user:

Example 22.5. Ceph Secret Definition

apiVersion: v1
kind: Secret
metadata:
  name: ceph-secret
data:
  key: QVFBOFF2SlZheUJQRVJBQWgvS2cwT1laQUhPQno3akZwekxxdGc9PQ==
1
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1
This base64 key is generated on one of the Ceph MON nodes using the ceph auth get-key client.admin | base64 command, then copying the output and pasting it as the secret key’s value.

Save the secret definition to a file, for example ceph-secret.yaml, then create the secret: 

$ oc create -f ceph-secret.yaml
secret "ceph-secret" created
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Verify that the secret was created: 

# oc get secret ceph-secret
NAME          TYPE      DATA      AGE
ceph-secret   Opaque    1         23d
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22.3.4. Creating the Persistent Volume
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Next, before creating the PV object in OpenShift Container Platform, define the persistent volume file:

Example 22.6. Persistent Volume Object Definition Using Ceph RBD

apiVersion: v1
kind: PersistentVolume
metadata:
  name: ceph-pv
1 

spec:
  capacity:
    storage: 2Gi
2 

  accessModes:
    - ReadWriteOnce
3 

  rbd:
4 

    monitors:
5 

      - 192.168.122.133:6789
    pool: rbd
    image: ceph-image
    user: admin
    secretRef:
      name: ceph-secret
6 

    fsType: ext4
7 

    readOnly: false
  persistentVolumeReclaimPolicy: Recycle
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1
The name of the PV, which is referenced in pod definitions or displayed in various oc volume commands.
2
The amount of storage allocated to this volume.
3
accessModes are used as labels to match a PV and a PVC. They currently do not define any form of access control. All block storage is defined to be single user (non-shared storage).
4
This defines the volume type being used. In this case, the rbd plug-in is defined.
5
This is an array of Ceph monitor IP addresses and ports.
6
This is the Ceph secret, defined above. It is used to create a secure connection from OpenShift Container Platform to the Ceph server.
7
This is the file system type mounted on the Ceph RBD block device.

Save the PV definition to a file, for example ceph-pv.yaml, and create the persistent volume: 

# oc create -f ceph-pv.yaml
persistentvolume "ceph-pv" created
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Verify that the persistent volume was created: 

# oc get pv
NAME                     LABELS    CAPACITY     ACCESSMODES   STATUS      CLAIM     REASON    AGE
ceph-pv                  <none>    2147483648   RWO           Available                       2s
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22.3.5. Creating the Persistent Volume Claim
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A persistent volume claim (PVC) specifies the desired access mode and storage capacity. Currently, based on only these two attributes, a PVC is bound to a single PV. Once a PV is bound to a PVC, that PV is essentially tied to the PVC’s project and cannot be bound to by another PVC. There is a one-to-one mapping of PVs and PVCs. However, multiple pods in the same project can use the same PVC.

Example 22.7. PVC Object Definition

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: ceph-claim
spec:
  accessModes:
1 

    - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi
2
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1
As mentioned above for PVs, the accessModes do not enforce access right, but rather act as labels to match a PV to a PVC.
2
This claim will look for PVs offering 2Gi or greater capacity.

Save the PVC definition to a file, for example ceph-claim.yaml, and create the PVC: 

# oc create -f ceph-claim.yaml
persistentvolumeclaim "ceph-claim" created

#and verify the PVC was created and bound to the expected PV:
# oc get pvc
NAME         LABELS    STATUS    VOLUME    CAPACITY   ACCESSMODES   AGE
ceph-claim   <none>    Bound     ceph-pv   1Gi        RWX           21s
1
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1
the claim was bound to the ceph-pv PV.

22.3.6. Creating the Pod
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A pod definition file or a template file can be used to define a pod. Below is a pod specification that creates a single container and mounts the Ceph RBD volume for read-write access:

Example 22.8. Pod Object Definition

apiVersion: v1
kind: Pod
metadata:
  name: ceph-pod1
1 

spec:
  containers:
  - name: ceph-busybox
    image: busybox
2 

    command: ["sleep", "60000"]
    volumeMounts:
    - name: ceph-vol1
3 

      mountPath: /usr/share/busybox
4 

      readOnly: false
  volumes:
  - name: ceph-vol1
5 

    persistentVolumeClaim:
      claimName: ceph-claim
6
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1
The name of this pod as displayed by oc get pod.
2
The image run by this pod. In this case, we are telling busybox to sleep.
3 5
The name of the volume. This name must be the same in both the containers and volumes sections.
4
The mount path as seen in the container.
6
The PVC that is bound to the Ceph RBD cluster.

Save the pod definition to a file, for example ceph-pod1.yaml, and create the pod: 

# oc create -f ceph-pod1.yaml
pod "ceph-pod1" created

#verify pod was created
# oc get pod
NAME        READY     STATUS    RESTARTS   AGE
ceph-pod1   1/1       Running   0          2m
1
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1
After a minute or so, the pod will be in the Running state.

22.3.7. Defining Group and Owner IDs (Optional)
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When using block storage, such as Ceph RBD, the physical block storage is managed by the pod. The group ID defined in the pod becomes the group ID of both the Ceph RBD mount inside the container, and the group ID of the actual storage itself. Thus, it is usually unnecessary to define a group ID in the pod specifiation. However, if a group ID is desired, it can be defined using fsGroup, as shown in the following pod definition fragment:

Example 22.9. Group ID Pod Definition

...
spec:
  containers:
    - name:
    ...
  securityContext:
1 

    fsGroup: 7777
2 

...
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1
securityContext must be defined at the pod level, not under a specific container.
2
All containers in the pod will have the same fsGroup ID.

22.4. Complete Example Using GlusterFS
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22.4.1. Overview
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This topic provides an end-to-end example of how to use an existing Gluster cluster as an OpenShift Container Platform persistent store. It is assumed that a working Gluster cluster is already set up. If not, consult the Red Hat Gluster Storage Administration Guide.

Persistent Storage Using GlusterFS provides an explanation of persistent volumes (PVs), persistent volume claims (PVCs), and using GlusterFS as persistent storage.

For an end-to-end example of how to dynamically provision GlusterFS volumes, see Complete Example of Dynamic Provisioning Using GlusterFS. The persistent volume (PV) and endpoints are both created dynamically by GlusterFS.

Note

All oc …​ commands are executed on the OpenShift Container Platform master host.

22.4.2. Installing the glusterfs-fuse Package
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The glusterfs-fuse library must be installed on all schedulable OpenShift Container Platform nodes: 

# yum install -y glusterfs-fuse
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Note

The OpenShift Container Platform all-in-one host is often not used to run pod workloads and, thus, is not included as a schedulable node.

The named endpoints define each node in the Gluster-trusted storage pool:

Example 22.10. GlusterFS Endpoint Definition

apiVersion: v1
kind: Endpoints
metadata:
  name: gluster-cluster
1 

subsets:
- addresses:
2 

  - ip: 192.168.122.21
  ports:
3 

  - port: 1
    protocol: TCP
- addresses:
  - ip: 192.168.122.22
  ports:
  - port: 1
    protocol: TCP
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1
The endpoints name. If using a service, then the endpoints name must match the service name.
2
An array of IP addresses for each node in the Gluster pool. Currently, host names are not supported.
3
The port numbers are ignored, but must be legal port numbers. The value 1 is commonly used.

Save the endpoints definition to a file, for example gluster-endpoints.yaml, then create the endpoints object: 

# oc create -f gluster-endpoints.yaml
endpoints "gluster-cluster" created
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Verify that the endpoints were created: 

# oc get endpoints gluster-cluster
NAME                ENDPOINTS                           AGE
gluster-cluster     192.168.122.21:1,192.168.122.22:1   1m
Copy to Clipboard Toggle word wrap
Note

To persist the Gluster endpoints, you also need to create a service.

Note

Endpoints are name-spaced. Each project accessing the Gluster volume needs its own endpoints.

Example 22.11. GlusterFS Service Definition

apiVersion: v1
kind: Service
metadata:
  name: gluster-cluster
1 

spec:
  ports:
  - port: 1
2
Copy to Clipboard Toggle word wrap
1
The name of the service. If using a service, then the endpoints name must match the service name.
2
The port should match the same port used in the endpoints.

Save the service definition to a file, for example gluster-service.yaml, then create the endpoints object: 

# oc create -f gluster-service.yaml
endpoints "gluster-cluster" created
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Verify that the service was created: 

# oc get service gluster-cluster
NAME                CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
gluster-cluster     10.0.0.130   <none>        1/TCP     9s
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22.4.4. Creating the Persistent Volume
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Next, before creating the PV object, define the persistent volume in OpenShift Container Platform:

Persistent Volume Object Definition Using GlusterFS

apiVersion: v1
kind: PersistentVolume
metadata:
  name: gluster-pv
1 

spec:
  capacity:
    storage: 1Gi
2 

  accessModes:
  - ReadWriteMany
3 

  glusterfs:
4 

    endpoints: gluster-cluster
5 

    path: /HadoopVol
6 

    readOnly: false
  persistentVolumeReclaimPolicy: Retain
7
Copy to Clipboard Toggle word wrap

1
The name of the PV, which is referenced in pod definitions or displayed in various oc volume commands.
2
The amount of storage allocated to this volume.
3
accessModes are used as labels to match a PV and a PVC. They currently do not define any form of access control.
4
This defines the volume type being used. In this case, the glusterfs plug-in is defined.
5
This references the endpoints named above.
6
This is the Gluster volume name, preceded by /.
7
The volume reclaim policy Retain indicates that the volume will be preserved after the pods accessing it terminates. For GlusterFS, the accepted values include Retain, and Delete.

Save the PV definition to a file, for example gluster-pv.yaml, and create the persistent volume: 

# oc create -f gluster-pv.yaml
persistentvolume "gluster-pv" created
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Verify that the persistent volume was created: 

# oc get pv
NAME         LABELS    CAPACITY   ACCESSMODES   STATUS      CLAIM     REASON    AGE
gluster-pv   <none>    1Gi        RWX           Available                       37s
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22.4.5. Creating the Persistent Volume Claim
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A persistent volume claim (PVC) specifies the desired access mode and storage capacity. Currently, based on only these two attributes, a PVC is bound to a single PV. Once a PV is bound to a PVC, that PV is essentially tied to the PVC’s project and cannot be bound to by another PVC. There is a one-to-one mapping of PVs and PVCs. However, multiple pods in the same project can use the same PVC.

Example 22.12. PVC Object Definition

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: gluster-claim
1 

spec:
  accessModes:
  - ReadWriteMany
2 

  resources:
     requests:
       storage: 1Gi
3
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1
The claim name is referenced by the pod under its volumes section.
2
As mentioned above for PVs, the accessModes do not enforce access rights, but rather act as labels to match a PV to a PVC.
3
This claim will look for PVs offering 1Gi or greater capacity.

Save the PVC definition to a file, for example gluster-claim.yaml, and create the PVC: 

# oc create -f gluster-claim.yaml
persistentvolumeclaim "gluster-claim" created
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Verify the PVC was created and bound to the expected PV: 

# oc get pvc
NAME            LABELS    STATUS    VOLUME       CAPACITY   ACCESSMODES   AGE
gluster-claim   <none>    Bound     gluster-pv   1Gi        RWX           24s
1
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1
The claim was bound to the gluster-pv PV.

22.4.6. Defining GlusterFS Volume Access
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Access is necessary to a node in the Gluster-trusted storage pool. On this node, examine the glusterfs-fuse mount: 

# ls -lZ /mnt/glusterfs/
drwxrwx---. yarn hadoop system_u:object_r:fusefs_t:s0    HadoopVol

# id yarn
uid=592(yarn) gid=590(hadoop) groups=590(hadoop)
1
2
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1
The owner has ID 592.
2
The group has ID 590.

In order to access the HadoopVol volume, the container must match the SELinux label, and either run with a UID of 592, or with 590 in its supplemental groups. It is recommended to gain access to the volume by matching the Gluster mount’s groups, which is defined in the pod definition below.

By default, SELinux does not allow writing from a pod to a remote Gluster server. To enable writing to GlusterFS volumes with SELinux enforcing on each node, run: 

# setsebool -P virt_sandbox_use_fusefs on
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Note

The virt_sandbox_use_fusefs boolean is defined by the docker-selinux package. If you get an error saying it is not defined, ensure that this package is installed.

A pod definition file or a template file can be used to define a pod. Below is a pod specification that creates a single container and mounts the Gluster volume for read-write access:

Note

The NGINX image may require to run in privileged mode to create the mount and run properly. An easy way to accomplish this is to simply add your user to the privileged Security Context Constraint (SCC): 

$ oc adm policy add-scc-to-user privileged myuser
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Then, add the privileged: true to the containers securityContext: section of the YAML file (as seen in the example below).

Managing Security Context Constraints provides additional information regarding SCCs.

Example 22.13. Pod Object Definition using NGINX image

apiVersion: v1
kind: Pod
metadata:
  name: gluster-pod1
  labels:
    name: gluster-pod1
1 

spec:
  containers:
  - name: gluster-pod1
    image: nginx
2 

    ports:
    - name: web
      containerPort: 80
    securityContext:
      privileged: true
    volumeMounts:
    - name: gluster-vol1
3 

      mountPath: /usr/share/nginx/html
4 

      readOnly: false
  securityContext:
    supplementalGroups: [590]
5 

  volumes:
  - name: gluster-vol1
6 

    persistentVolumeClaim:
      claimName: gluster-claim
7
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1
The name of this pod as displayed by oc get pod.
2
The image run by this pod. In this case, we are using a standard NGINX image.
3 6
The name of the volume. This name must be the same in both the containers and volumes sections.
4
The mount path as seen in the container.
5
The SupplementalGroup ID (Linux Groups) to be assigned at the pod level and as discussed this should match the POSIX permissions on the Gluster volume.
7
The PVC that is bound to the Gluster cluster.

Save the pod definition to a file, for example gluster-pod1.yaml, and create the pod: 

# oc create -f gluster-pod1.yaml
pod "gluster-pod1" created
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Verify the pod was created: 

# oc get pod
NAME           READY     STATUS    RESTARTS   AGE
gluster-pod1   1/1       Running   0          31s
1
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1
After a minute or so, the pod will be in the Running state.

More details are shown in the oc describe pod command: 

# oc describe pod gluster-pod1
Name:			gluster-pod1
Namespace:		default
1 

Security Policy:	privileged
Node:			ose1.rhs/192.168.122.251
Start Time:		Wed, 24 Aug 2016 12:37:45 -0400
Labels:			name=gluster-pod1
Status:			Running
IP:			172.17.0.2
2 

Controllers:		<none>
Containers:
  gluster-pod1:
    Container ID:	docker://e67ed01729e1dc7369c5112d07531a27a7a02a7eb942f17d1c5fce32d8c31a2d
    Image:		nginx
    Image ID:		docker://sha256:4efb2fcdb1ab05fb03c9435234343c1cc65289eeb016be86193e88d3a5d84f6b
    Port:		80/TCP
    State:		Running
      Started:		Wed, 24 Aug 2016 12:37:52 -0400
    Ready:		True
    Restart Count:	0
    Volume Mounts:
      /usr/share/nginx/html/test from glustervol (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-1n70u (ro)
    Environment Variables:	<none>
Conditions:
  Type		Status
  Initialized 	True
  Ready 	True
  PodScheduled 	True
Volumes:
  glustervol:
    Type:	PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:	gluster-claim
3 

    ReadOnly:	false
  default-token-1n70u:
    Type:	Secret (a volume populated by a Secret)
    SecretName:	default-token-1n70u
QoS Tier:	BestEffort
Events:
4 

  FirstSeen	LastSeen	Count	From			SubobjectPath			Type		Reason		Message
  ---------	--------	-----	----			-------------			--------	------		-------
  10s		10s		1	{default-scheduler }					Normal		Scheduled	Successfully assigned gluster-pod1 to ose1.rhs
  9s		9s		1	{kubelet ose1.rhs}	spec.containers{gluster-pod1}	Normal		Pulling		pulling image "nginx"
  4s		4s		1	{kubelet ose1.rhs}	spec.containers{gluster-pod1}	Normal		Pulled		Successfully pulled image "nginx"
  3s		3s		1	{kubelet ose1.rhs}	spec.containers{gluster-pod1}	Normal		Created		Created container with docker id e67ed01729e1
  3s		3s		1	{kubelet ose1.rhs}	spec.containers{gluster-pod1}	Normal		Started		Started container with docker id e67ed01729e1
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1
The project (namespace) name.
2
The IP address of the OpenShift Container Platform node running the pod.
3
The PVC name used by the pod.
4
The list of events resulting in the pod being launched and the Gluster volume being mounted.

There is more internal information, including the SCC used to authorize the pod, the pod’s user and group IDs, the ⁠SELinux label, and more shown in the oc get pod <name> -o yaml command: 

# oc get pod gluster-pod1 -o yaml
apiVersion: v1
kind: Pod
metadata:
  annotations:
    openshift.io/scc: privileged
1 

  creationTimestamp: 2016-08-24T16:37:45Z
  labels:
    name: gluster-pod1
  name: gluster-pod1
  namespace: default
2 

  resourceVersion: "482"
  selfLink: /api/v1/namespaces/default/pods/gluster-pod1
  uid: 15afda77-6a19-11e6-aadb-525400f7256d
spec:
  containers:
  - image: nginx
    imagePullPolicy: Always
    name: gluster-pod1
    ports:
    - containerPort: 80
      name: web
      protocol: TCP
    resources: {}
    securityContext:
      privileged: true
3 

    terminationMessagePath: /dev/termination-log
    volumeMounts:
    - mountPath: /usr/share/nginx/html
      name: glustervol
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-1n70u
      readOnly: true
  dnsPolicy: ClusterFirst
  host: ose1.rhs
  imagePullSecrets:
  - name: default-dockercfg-20xg9
  nodeName: ose1.rhs
  restartPolicy: Always
  securityContext:
    supplementalGroups:
    - 590
4 

  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  volumes:
  - name: glustervol
    persistentVolumeClaim:
      claimName: gluster-claim
5 

  - name: default-token-1n70u
    secret:
      secretName: default-token-1n70u
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2016-08-24T16:37:45Z
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: 2016-08-24T16:37:53Z
    status: "True"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: 2016-08-24T16:37:45Z
    status: "True"
    type: PodScheduled
  containerStatuses:
  - containerID: docker://e67ed01729e1dc7369c5112d07531a27a7a02a7eb942f17d1c5fce32d8c31a2d
    image: nginx
    imageID: docker://sha256:4efb2fcdb1ab05fb03c9435234343c1cc65289eeb016be86193e88d3a5d84f6b
    lastState: {}
    name: gluster-pod1
    ready: true
    restartCount: 0
    state:
      running:
        startedAt: 2016-08-24T16:37:52Z
  hostIP: 192.168.122.251
  phase: Running
  podIP: 172.17.0.2
  startTime: 2016-08-24T16:37:45Z
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1
The SCC used by the pod.
2
The project (namespace) name.
3
The security context level requested, in this case privileged
4
The supplemental group ID for the pod (all containers).
5
The PVC name used by the pod.
Note

This example assumes a working OpenShift Container Platform installed and functioning along with Heketi and GlusterFS.

All oc commands are executed on the OpenShift Container Platform master host.

22.5.1. Overview
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This topic provides an end-to-end example of how to dynamically provision GlusterFS volumes. In this example, a simple NGINX HelloWorld application is deployed using the Red Hat Container Native Storage (CNS) solution. CNS hyper-converges GlusterFS storage by containerizing it into the OpenShift Container Platform cluster.

The Red Hat Gluster Storage Administration Guide can also provide additional information about GlusterFS.

To get started, follow the gluster-kubernetes quickstart guide for an easy Vagrant-based installation and deployment of a working OpenShift Container Platform cluster with Heketi and GlusterFS containers.

Note

At this point, there should be a working OpenShift Container Platform cluster deployed, and a working Heketi server with GlusterFS.

  1. Verify and view the cluster environment, including nodes and pods: 

    $ oc get nodes,pods
NAME      STATUS    AGE
master    Ready     22h
node0     Ready     22h
node1     Ready     22h
node2     Ready     22h
NAME                               READY     STATUS              RESTARTS   AGE           1/1       Running             0          1d
glusterfs-node0-2509304327-vpce1   1/1       Running   0          1d        192.168.10.100   node0
glusterfs-node1-3290690057-hhq92   1/1       Running   0          1d        192.168.10.101   node1
    1 
    
glusterfs-node2-4072075787-okzjv   1/1       Running   0          1d        192.168.10.102   node2
heketi-3017632314-yyngh            1/1       Running   0          1d        10.42.0.0        node0
    2
    Copy to Clipboard Toggle word wrap
    1
    Example of GlusterFS storage pods running. There are three in this example.
    2
    Heketi server pod.

  2. If not already set in the environment, export the HEKETI_CLI_SERVER: 

    $ export HEKETI_CLI_SERVER=$(oc describe svc/heketi | grep "Endpoints:" | awk '{print "http://"$2}')
    Copy to Clipboard Toggle word wrap

  3. Identify the Heketi REST URL and server IP address: 

    $ echo $HEKETI_CLI_SERVER
http://10.42.0.0:8080
    Copy to Clipboard Toggle word wrap

  4. Identify the Gluster endpoints that are needed to pass in as a parameter into the storage class, which is used in a later step (heketi-storage-endpoints). 

    $ oc get endpoints
NAME                       ENDPOINTS                                            AGE
heketi                     10.42.0.0:8080                                       22h
heketi-storage-endpoints   192.168.10.100:1,192.168.10.101:1,192.168.10.102:1   22h
    1 
    
kubernetes                 192.168.10.90:6443                                   23h
    Copy to Clipboard Toggle word wrap
    1
    The defined GlusterFS endpoints. In this example, they are called heketi-storage-endpoints.
Note

By default, user_authorization is disabled. If enabled, you may need to find the rest user and rest user secret key. (This is not applicable for this example, as any values will work).

Storage classes manage and enable persistent storage in OpenShift Container Platform. Below is an example of a Storage class requesting 5GB of on-demand storage to be used with your HelloWorld application. 

apiVersion: storage.k8s.io/v1beta1
kind: StorageClass
metadata:
  name: gluster-heketi
1 

provisioner: kubernetes.io/glusterfs
2 

 parameters:
  endpoint: "heketi-storage-endpoints"
3 

  resturl: "http://10.42.0.0:8080"
4 

  restuser: "joe"
5 

  restuserkey: "My Secret Life"
6
Copy to Clipboard Toggle word wrap
1
Name of the storage class.
2
The provisioner.
3
The GlusterFS-defined endpoint (oc get endpoints).
4
Heketi REST URL, taken from Step 1 above (echo $HEKETI_CLI_SERVER).
5
Rest username. This can be any value since authorization is turned off.
6
Rest user key. This can be any value.

  1. Create the Storage Class YAML file, save it, then submit it to OpenShift Container Platform: 

    $ oc create -f gluster-storage-class.yaml
storageclass "gluster-heketi" created
    Copy to Clipboard Toggle word wrap

  2. View the storage class: 

    $ oc get storageclass
NAME              TYPE
gluster-heketi    kubernetes.io/glusterfs
    Copy to Clipboard Toggle word wrap

  1. Create a persistent volume claim (PVC) requesting 5GB of storage.

    During that time, the Dynamic Provisioning Framework and Heketi will automatically provision a new GlusterFS volume and generate the persistent volume (PV) object: 

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: gluster1
 annotations:
   volume.beta.kubernetes.io/storage-class: gluster-heketi
1 

spec:
 accessModes:
  - ReadWriteOnce
 resources:
   requests:
     storage: 5Gi
2
Copy to Clipboard Toggle word wrap
1
The Kubernetes storage class annotation and the name of the storage class.
2
The amount of storage requested.

  1. Create the PVC YAML file, save it, then submit it to OpenShift Container Platform: 

    $ oc create -f gluster-pvc.yaml
persistentvolumeclaim "gluster1" created
    Copy to Clipboard Toggle word wrap

  2. View the PVC: 

    $ oc get pvc
NAME       STATUS    VOLUME                                     CAPACITY   ACCESSMODES   AGE
gluster1   Bound     pvc-7d37c7bd-bb5b-11e6-b81e-525400d87180   5Gi        RWO           14h
    Copy to Clipboard Toggle word wrap

    Notice that the PVC is bound to a dynamically created volume.

  3. View the persistent volume (PV): 

    $ oc get pv
NAME                                       CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM              REASON    AGE
pvc-7d37c7bd-bb5b-11e6-b81e-525400d87180   5Gi        RWO           Delete          Bound     default/gluster1             14h
    Copy to Clipboard Toggle word wrap

22.5.5. Create a NGINX Pod That Uses the PVC
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At this point, you have a dynamically created GlusterFS volume, bound to a PVC. Now, you can use this claim in a pod. Create a simple NGINX pod: 

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    name: nginx-pod
spec:
  containers:
  - name: nginx-pod
    image: gcr.io/google_containers/nginx-slim:0.8
    ports:
    - name: web
      containerPort: 80
    securityContext:
      privileged: true
    volumeMounts:
    - name: gluster-vol1
      mountPath: /usr/share/nginx/html
  volumes:
  - name: gluster-vol1
    persistentVolumeClaim:
      claimName: gluster1
1
Copy to Clipboard Toggle word wrap
1
The name of the PVC created in the previous step.

  1. Create the Pod YAML file, save it, then submit it to OpenShift Container Platform: 

    $ oc create -f nginx-pod.yaml
pod "gluster-pod1" created
    Copy to Clipboard Toggle word wrap

  2. View the pod: 

    $ oc get pods -o wide
NAME                               READY     STATUS    RESTARTS   AGE       IP               NODE
nginx-pod                          1/1       Running   0          9m        10.38.0.0        node1
glusterfs-node0-2509304327-vpce1   1/1       Running   0          1d        192.168.10.100   node0
glusterfs-node1-3290690057-hhq92   1/1       Running   0          1d        192.168.10.101   node1
glusterfs-node2-4072075787-okzjv   1/1       Running   0          1d        192.168.10.102   node2
heketi-3017632314-yyngh            1/1       Running   0          1d        10.42.0.0        node0
    Copy to Clipboard Toggle word wrap
    Note

    This may take a few minutes, as the the pod may need to download the image if it does not already exist.

  3. oc exec into the container and create an index.html file in the mountPath definition of the pod: 

    $ oc exec -ti nginx-pod /bin/sh
$ cd /usr/share/nginx/html
$ echo 'Hello World from GlusterFS!!!' > index.html
$ ls
index.html
$ exit
    Copy to Clipboard Toggle word wrap

  4. Using the curl command from the master node, curl the URL of the pod: 

    $ curl http://10.38.0.0
Hello World from GlusterFS!!!
    Copy to Clipboard Toggle word wrap

  5. Check your Gluster pod to ensure that the index.html file was written. Choose any of the Gluster pods: 

    $ oc exec -ti glusterfs-node1-3290690057-hhq92 /bin/sh
$ mount | grep heketi
/dev/mapper/VolGroup00-LogVol00 on /var/lib/heketi type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
/dev/mapper/vg_f92e09091f6b20ab12b02a2513e4ed90-brick_1e730a5462c352835055018e1874e578 on /var/lib/heketi/mounts/vg_f92e09091f6b20ab12b02a2513e4ed90/brick_1e730a5462c352835055018e1874e578 type xfs (rw,noatime,seclabel,nouuid,attr2,inode64,logbsize=256k,sunit=512,swidth=512,noquota)
/dev/mapper/vg_f92e09091f6b20ab12b02a2513e4ed90-brick_d8c06e606ff4cc29ccb9d018c73ee292 on /var/lib/heketi/mounts/vg_f92e09091f6b20ab12b02a2513e4ed90/brick_d8c06e606ff4cc29ccb9d018c73ee292 type xfs (rw,noatime,seclabel,nouuid,attr2,inode64,logbsize=256k,sunit=512,swidth=512,noquota)

$ cd /var/lib/heketi/mounts/vg_f92e09091f6b20ab12b02a2513e4ed90/brick_d8c06e606ff4cc29ccb9d018c73ee292/brick
$ ls
index.html
$ cat index.html
Hello World from GlusterFS!!!
    Copy to Clipboard Toggle word wrap

22.6. Mounting Volumes on Privileged Pods
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22.6.1. Overview
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Persistent volumes can be mounted to pods with the privileged security context constraint (SCC) attached.

Note

While this topic uses GlusterFS as a sample use-case for mounting volumes onto privileged pods, it can be adapted to use any supported storage plug-in.

22.6.2. Prerequisites
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22.6.3. Creating the Persistent Volume
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Creating the PersistentVolume makes the storage accessible to users, regardless of projects.

  1. As the admin, create the service, endpoint object, and persistent volume: 

    $ oc create -f gluster-endpoints-service.yaml
$ oc create -f gluster-endpoints.yaml
$ oc create -f gluster-pv.yaml
    Copy to Clipboard Toggle word wrap

  2. Verify that the objects were created: 

    $ oc get svc
NAME              CLUSTER_IP      EXTERNAL_IP   PORT(S)   SELECTOR   AGE
gluster-cluster   172.30.151.58   <none>        1/TCP     <none>     24s
    Copy to Clipboard Toggle word wrap 
    $ oc get ep
NAME              ENDPOINTS                           AGE
gluster-cluster   192.168.59.102:1,192.168.59.103:1   2m
    Copy to Clipboard Toggle word wrap 
    $ oc get pv
NAME                     LABELS    CAPACITY   ACCESSMODES   STATUS      CLAIM     REASON    AGE
gluster-default-volume   <none>    2Gi        RWX           Available                       2d
    Copy to Clipboard Toggle word wrap

22.6.4. Creating a Regular User
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Adding a regular user to the privileged SCC (or to a group given access to the SCC) allows them to run privileged pods:

  1. As the admin, add a user to the SCC: 

    $ oc adm policy add-scc-to-user privileged <username>
    Copy to Clipboard Toggle word wrap

  2. Log in as the regular user: 

    $ oc login -u <username> -p <password>
    Copy to Clipboard Toggle word wrap

  3. Then, create a new project: 

    $ oc new-project <project_name>
    Copy to Clipboard Toggle word wrap

22.6.5. Creating the Persistent Volume Claim
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  1. As a regular user, create the PersistentVolumeClaim to access the volume: 

    $ oc create -f gluster-pvc.yaml -n <project_name>
    Copy to Clipboard Toggle word wrap

  2. Define your pod to access the claim:

    Example 22.14. Pod Definition

    apiVersion: v1
id: gluster-S3-pvc
kind: Pod
metadata:
  name: gluster-nginx-priv
spec:
  containers:
    - name: gluster-nginx-priv
      image: fedora/nginx
      volumeMounts:
        - mountPath: /mnt/gluster
    1 
    
          name: gluster-volume-claim
      securityContext:
        privileged: true
  volumes:
    - name: gluster-volume-claim
      persistentVolumeClaim:
        claimName: gluster-claim
    2
    Copy to Clipboard Toggle word wrap
    1
    Volume mount within the pod.
    2
    The gluster-claim must reflect the name of the PersistentVolume.

  3. Upon pod creation, the mount directory is created and the volume is attached to that mount point.

    As regular user, create a pod from the definition: 

    $ oc create -f gluster-S3-pod.yaml
    Copy to Clipboard Toggle word wrap

  4. Verify that the pod created successfully: 

    $ oc get pods
NAME                 READY     STATUS    RESTARTS   AGE
gluster-S3-pod   1/1       Running   0          36m
    Copy to Clipboard Toggle word wrap

    It can take several minutes for the pod to create.

22.6.6. Verifying the Setup
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22.6.6.1. Checking the Pod SCC
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  1. Export the pod configuration: 

    $ oc export pod <pod_name>
    Copy to Clipboard Toggle word wrap

  2. Examine the output. Check that openshift.io/scc has the value of privileged:

    Example 22.15. Export Snippet

    metadata:
  annotations:
    openshift.io/scc: privileged
    Copy to Clipboard Toggle word wrap

22.6.6.2. Verifying the Mount
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  1. Access the pod and check that the volume is mounted: 

    $ oc rsh <pod_name>
[root@gluster-S3-pvc /]# mount
    Copy to Clipboard Toggle word wrap

  2. Examine the output for the Gluster volume:

    Example 22.16. Volume Mount

    192.168.59.102:gv0 on /mnt/gluster type fuse.gluster (rw,relatime,user_id=0,group_id=0,default_permissions,allow_other,max_read=131072)
    Copy to Clipboard Toggle word wrap

22.7.1. Overview
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This topic reviews how to attach a GlusterFS persistent volume to the Docker Registry.

It is assumed that the Docker registry service has already been started and the Gluster volume has been created.

22.7.2. Prerequisites
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Note

All oc commands are executed on the master node as the admin user.

22.7.3. Create the Gluster Persistent Volume
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First, make the Gluster volume available to the registry. 

$ oc create -f gluster-endpoints-service.yaml
$ oc create -f gluster-endpoints.yaml
$ oc create -f gluster-pv.yaml
$ oc create -f gluster-pvc.yaml
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Check to make sure the PV and PVC were created and bound successfully. The expected output should resemble the following. Note that the PVC status is Bound, indicating that it has bound to the PV. 

$ oc get pv
NAME         LABELS    CAPACITY   ACCESSMODES   STATUS      CLAIM     REASON    AGE
gluster-pv   <none>    1Gi        RWX           Available                       37s
$ oc get pvc
NAME            LABELS    STATUS    VOLUME       CAPACITY   ACCESSMODES   AGE
gluster-claim   <none>    Bound     gluster-pv   1Gi        RWX           24s
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Note

If either the PVC or PV failed to create or the PVC failed to bind, refer back to the GlusterFS Persistent Storage guide. Do not proceed until they initialize and the PVC status is Bound.

22.7.4. Attach the PVC to the Docker Registry
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Before moving forward, ensure that the docker-registry service is running. 

$ oc get svc
NAME              CLUSTER_IP       EXTERNAL_IP   PORT(S)                 SELECTOR                  AGE
docker-registry   172.30.167.194   <none>        5000/TCP                docker-registry=default   18m
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Note

If either the docker-registry service or its associated pod is not running, refer back to the docker-registry setup instructions for troubleshooting before continuing.

Then, attach the PVC: 

$ oc volume deploymentconfigs/docker-registry --add --name=registry-storage -t pvc \
     --claim-name=gluster-claim --overwrite
Copy to Clipboard Toggle word wrap

Deploying a Docker Registry provides more information on using the Docker registry.

22.7.5. Known Issues
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22.7.5.1. Pod Cannot Resolve the Volume Host
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In non-production cases where the dnsmasq server is located on the same node as the OpenShift Container Platform master service, pods might not resolve to the host machines when mounting the volume, causing errors in the docker-registry-1-deploy pod. This can happen when dnsmasq.service fails to start because of a collision with OpenShift Container Platform DNS on port 53. To run the DNS server on the master host, some configurations needs to be changed.

In /etc/dnsmasq.conf, add: 

# Reverse DNS record for master
host-record=master.example.com,<master-IP>
# Wildcard DNS for OpenShift Applications - Points to Router
address=/apps.example.com/<master-IP>
# Forward .local queries to SkyDNS
server=/local/127.0.0.1#8053
# Forward reverse queries for service network to SkyDNS.
# This is for default OpenShift SDN - change as needed.
server=/17.30.172.in-addr.arpa/127.0.0.1#8053
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With these settings, dnsmasq will pull from the /etc/hosts file on the master node.

Add the appropriate host names and IPs for all necessary hosts.

In master-config.yaml, change bindAddress to: 

dnsConfig:
 bindAddress: 127.0.0.1:8053
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When pods are created, they receive a copy of /etc/resolv.conf, which typically contains only the master DNS server so they can resolve external DNS requests. To enable internal DNS resolution, insert the dnsmasq server at the top of the server list. This way, dnsmasq will attempt to resolve requests internally first.

In /etc/resolv.conf all scheduled nodes: 

nameserver 192.168.1.100
1 

nameserver 192.168.1.1
2
Copy to Clipboard Toggle word wrap
1
Add the internal DNS server.
2
Pre-existing external DNS server.

Once the configurations are changed, restart the OpenShift Container Platform master and dnsmasq services. 

$ systemctl restart atomic-openshift-master
$ systemctl restart dnsmasq
Copy to Clipboard Toggle word wrap

22.8. Binding Persistent Volumes by Labels
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22.8.1. Overview
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This topic provides an end-to-end example for binding persistent volume claims (PVCs) to persistent volumes (PVs), by defining labels in the PV and matching selectors in the PVC. This feature is available for all storage options. It is assumed that a OpenShift Container Platform cluster contains persistent storage resources which are available for binding by PVCs.

A Note on Labels and Selectors

Labels are an OpenShift Container Platform feature that support user-defined tags (key-value pairs) as part of an object’s specification. Their primary purpose is to enable the arbitrary grouping of objects by defining identical labels among them. These labels can then be targeted by selectors to match all objects with specified label values. It is this functionality we will take advantage of to enable our PVC to bind to our PV. For a more in-depth look at labels, see Pods and Services.

Note

For this example, we will be using modified GlusterFS PV and PVC specifications. However, implementation of selectors and labels is generic across for all storage options. See the relevant storage option for your volume provider to learn more about its unique configuration.

22.8.1.1. Assumptions
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It is assumed that you have:

  • An existing OpenShift Container Platform cluster with at least one master and one node
  • At least one supported storage volume
  • A user with cluster-admin privileges

22.8.2. Defining Specifications
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Note

These specifications are tailored to GlusterFS. Consult the relevant storage option for your volume provider to learn more about its unique configuration.

22.8.2.1. Persistent Volume with Labels
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Example 22.17. glusterfs-pv.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: gluster-volume
  labels:
1 

    storage-tier: gold
    aws-availability-zone: us-east-1
spec:
  capacity:
    storage: 2Gi
  accessModes:
    - ReadWriteMany
  glusterfs:
    endpoints: glusterfs-cluster
2 

    path: myVol1
    readOnly: false
  persistentVolumeReclaimPolicy: Retain
Copy to Clipboard Toggle word wrap
1
Use labels to identify common attributes or characteristics shared among volumes. In this case, we defined the Gluster volume to have a custom attribute (key) named storage-tier with a value of gold assigned. A claim will be able to select a PV with storage-tier=gold to match this PV.
2
Endpoints define the Gluster trusted pool and are discussed below.

22.8.2.2. Persistent Volume Claim with Selectors
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A claim with a selector stanza (see example below) attempts to match existing, unclaimed, and non-prebound PVs. The existence of a PVC selector ignores a PV’s capacity. However, accessModes are still considered in the matching criteria.

It is important to note that a claim must match all of the key-value pairs included in its selector stanza. If no PV matches the claim, then the PVC will remain unbound (Pending). A PV can subsequently be created and the claim will automatically check for a label match.

Example 22.18. glusterfs-pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: gluster-claim
spec:
  accessModes:
  - ReadWriteMany
  resources:
     requests:
       storage: 1Gi
  selector:
1 

    matchLabels:
      storage-tier: gold
      aws-availability-zone: us-east-1
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1
The selector stanza defines all labels necessary in a PV in order to match this claim.

22.8.2.3. Volume Endpoints
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To attach the PV to the Gluster volume, endpoints should be configured before creating our objects.

Example 22.19. glusterfs-ep.yaml

  apiVersion: v1
  kind: Endpoints
  metadata:
    name: glusterfs-cluster
  subsets:
    - addresses:
        - ip: 192.168.122.221
      ports:
        - port: 1
    - addresses:
        - ip: 192.168.122.222
      ports:
        - port: 1
Copy to Clipboard Toggle word wrap

22.8.2.4. Deploy the PV, PVC, and Endpoints
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For this example, run the oc commands as a cluster-admin privileged user. In a production environment, cluster clients might be expected to define and create the PVC. 

# oc create -f glusterfs-ep.yaml
endpoints "glusterfs-cluster" created
# oc create -f glusterfs-pv.yaml
persistentvolume "gluster-volume" created
# oc create -f glusterfs-pvc.yaml
persistentvolumeclaim "gluster-claim" created
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Lastly, confirm that the PV and PVC bound successfully. 

# oc get pv,pvc
NAME              CAPACITY   ACCESSMODES      STATUS     CLAIM                     REASON    AGE
gluster-volume    2Gi        RWX              Bound      gfs-trial/gluster-claim             7s
NAME              STATUS     VOLUME           CAPACITY   ACCESSMODES               AGE
gluster-claim     Bound      gluster-volume   2Gi        RWX                       7s
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Note

PVCs are local to a project, whereas PVs are a cluster-wide, global resource. Developers and non-administrator users may not have access to see all (or any) of the available PVs.

22.9.1. Overview
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In these examples we will walk through a few scenarios of various configuratons of StorageClasses and Dynamic Provisioning using Google Cloud Platform Compute Engine (GCE). These examples assume some familiarity with Kubernetes, GCE and Persistent Disks and OpenShift Container Platform is installed and properly configured to use GCE.

StorageClasses can be used to differentiate and delineate storage levels and usages. In this case, the cluster-admin or storage-admin sets up two distinct classes of storage in GCE.

  • slow: Cheap, efficient, and optimized for sequential data operations (slower reading and writing)
  • fast: Optimized for higher rates of random IOPS and sustained throughput (faster reading and writing)

By creating these StorageClasses, the cluster-admin or storage-admin allows users to create claims requesting a particular level or service of StorageClass.

Example 22.20. StorageClass Slow Object Definitions

kind: StorageClass
apiVersion: storage.k8s.io/v1beta1
metadata:
  name: slow
1 

provisioner: kubernetes.io/gce-pd
2 

parameters:
  type: pd-standard
3 

  zone: us-east1-d
4
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1
Name of the StorageClass.
2
The provisioner plug-in to be used. This is a required field for StorageClasses.
3
PD type. This example uses pd-standard, which has a slightly lower cost, rate of sustained IOPS, and throughput versus pd-ssd, which carries more sustained IOPS and throughput.
4
The zone is required.

Example 22.21. StorageClass Fast Object Definition

kind: StorageClass
apiVersion: storage.k8s.io/v1beta1
metadata:
  name: fast
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-ssd
  zone: us-east1-d
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As a cluster-admin or storage-admin, save both definitions as YAML files. For example, slow-gce.yaml and fast-gce.yaml. Then create the StorageClasses. 

# oc create -f slow-gce.yaml
storageclass "slow" created

# oc create -f fast-gce.yaml
storageclass "fast" created

# oc get storageclass
NAME       TYPE
fast       kubernetes.io/gce-pd
slow       kubernetes.io/gce-pd
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Important

cluster-admin or storage-admin users are responsible for relaying the correct StorageClass name to the correct users, groups, and projects.

As a regular user, create a new project: 

# oc new-project rh-eng
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Create the claim YAML definition, save it to a file (pvc-fast.yaml): 

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: pvc-engineering
 annotations:
   volume.beta.kubernetes.io/storage-class: fast
spec:
 accessModes:
  - ReadWriteMany
 resources:
   requests:
     storage: 10Gi
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Add the claim with the oc create command: 

# oc create -f pvc-fast.yaml
persistentvolumeclaim "pvc-engineering" created
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Check to see if your claim is bound: 

# oc get pvc
NAME              STATUS    VOLUME                                     CAPACITY   ACCESSMODES   AGE
pvc-engineering   Bound     pvc-e9b4fef7-8bf7-11e6-9962-42010af00004   10Gi       RWX           2m
Copy to Clipboard Toggle word wrap
Important

Since this claim was created and bound in the rh-eng project, it can be shared by any user in the same project.

As a cluster-admin or storage-admin user, view the recent dynamically provisioned Persistent Volume (PV). 

# oc get pv
NAME                                       CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                     REASON    AGE
pvc-e9b4fef7-8bf7-11e6-9962-42010af00004   10Gi       RWX           Delete          Bound     rh-eng/pvc-engineering              5m
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Important

Notice the RECLAIMPOLICY is Delete by default for all dynamically provisioned volumes. This means the volume only lasts as long as the claim still exists in the system. If you delete the claim, the volume is also deleted and all data on the volume is lost.

Finally, check the GCE console. The new disk has been created and is ready for use. 

kubernetes-dynamic-pvc-e9b4fef7-8bf7-11e6-9962-42010af00004 	SSD persistent disk 	10 GB 	us-east1-d
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Pods can now reference the persistent volume claim and start using the volume.

In this example, a cluster-admin or storage-admin enables a default storage class for all other users and projects that do not implicitly specify a StorageClass annotation in their claim. This is useful for a cluster-admin or storage-admin to provide easy management of a storage volume without having to set up or communicate specialized StorageClasses across the cluster.

This example builds upon Section 22.9.2, “Scenario 1: Basic Dynamic Provisioning with Two Types of StorageClasses”. The cluster-admin or storage-admin will create another StorageClass for designation as the defaultStorageClass.

Example 22.22. Default StorageClass Object Definition

kind: StorageClass
apiVersion: storage.k8s.io/v1beta1
metadata:
  name: generic
1 

  annotations:
    storageclass.beta.kubernetes.io/is-default-class: "true"
2 

provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-standard
  zone: us-east1-d
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1
Name of the StorageClass, which needs to be unique in the cluster.
2
Annotation that marks this StorageClass as the default class. You must use "true" quoted in this version of the API. Without this annotation, OpenShift Container Platform considers this not the default StorageClass.

As a cluster-admin or storage-admin save the definition to a YAML file (generic-gce.yaml), then create the StorageClasses: 

# oc create -f generic-gce.yaml
storageclass "generic" created

# oc get storageclass
NAME       TYPE
generic    kubernetes.io/gce-pd
fast       kubernetes.io/gce-pd
slow       kubernetes.io/gce-pd
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As a regular user, create a new claim definition without any StorageClass annotation and save it to a file (generic-pvc.yaml).

Example 22.23. default Storage Claim Object Definition

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: pvc-engineering2
spec:
 accessModes:
  - ReadWriteMany
 resources:
   requests:
     storage: 5Gi
Copy to Clipboard Toggle word wrap

Execute it and check the claim is bound: 

# oc create -f generic-pvc.yaml
persistentvolumeclaim "pvc-engineering2" created
                                                                   3s
# oc get pvc
NAME               STATUS    VOLUME                                     CAPACITY   ACCESSMODES   AGE
pvc-engineering    Bound     pvc-e9b4fef7-8bf7-11e6-9962-42010af00004   10Gi       RWX           41m
pvc-engineering2   Bound     pvc-a9f70544-8bfd-11e6-9962-42010af00004   5Gi        RWX           7s
1
Copy to Clipboard Toggle word wrap
1
pvc-engineering2 is bound to a dynamically provisioned Volume by default.

As a cluster-admin or storage-admin, view the Persistent Volumes defined so far: 

# oc get pv
NAME                                       CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                     REASON    AGE
pvc-a9f70544-8bfd-11e6-9962-42010af00004   5Gi        RWX           Delete          Bound     rh-eng/pvc-engineering2             5m
1 

pvc-ba4612ce-8b4d-11e6-9962-42010af00004   5Gi        RWO           Delete          Bound     mytest/gce-dyn-claim1               21h
pvc-e9b4fef7-8bf7-11e6-9962-42010af00004   10Gi       RWX           Delete          Bound     rh-eng/pvc-engineering              46m
2
Copy to Clipboard Toggle word wrap
1
This PV was bound to our default dynamic volume from the default StorageClass.
2
This PV was bound to our first PVC from Section 22.9.2, “Scenario 1: Basic Dynamic Provisioning with Two Types of StorageClasses” with our fast StorageClass.

Create a manually provisioned disk using GCE (not dynamically provisioned). Then create a Persistent Volume that connects to the new GCE disk (pv-manual-gce.yaml).

Example 22.24. Manual PV Object Defition

apiVersion: v1
kind: PersistentVolume
metadata:
 name: pv-manual-gce
spec:
 capacity:
   storage: 35Gi
 accessModes:
   - ReadWriteMany
 gcePersistentDisk:
   readOnly: false
   pdName: the-newly-created-gce-PD
   fsType: ext4
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Execute the object definition file: 

# oc create -f pv-manual-gce.yaml
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Now view the PVs again. Notice that a pv-manual-gce volume is Available. 

# oc get pv
NAME                                       CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS      CLAIM                     REASON    AGE
pv-manual-gce                              35Gi       RWX           Retain          Available                                       4s
pvc-a9f70544-8bfd-11e6-9962-42010af00004   5Gi        RWX           Delete          Bound       rh-eng/pvc-engineering2             12m
pvc-ba4612ce-8b4d-11e6-9962-42010af00004   5Gi        RWO           Delete          Bound       mytest/gce-dyn-claim1               21h
pvc-e9b4fef7-8bf7-11e6-9962-42010af00004   10Gi       RWX           Delete          Bound       rh-eng/pvc-engineering              53m
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Now create another claim identical to the generic-pvc.yaml PVC definition but change the name and do not set an annotation.

Example 22.25. Claim Object Definition

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: pvc-engineering3
spec:
 accessModes:
  - ReadWriteMany
 resources:
   requests:
     storage: 15Gi
Copy to Clipboard Toggle word wrap

Because default StorageClass is enabled in this instance, the manually created PV does not satisfy the claim request. The user receives a new dynamically provisioned Persistent Volume. 

# oc get pvc
NAME               STATUS    VOLUME                                     CAPACITY   ACCESSMODES   AGE
pvc-engineering    Bound     pvc-e9b4fef7-8bf7-11e6-9962-42010af00004   10Gi       RWX           1h
pvc-engineering2   Bound     pvc-a9f70544-8bfd-11e6-9962-42010af00004   5Gi        RWX           19m
pvc-engineering3   Bound     pvc-6fa8e73b-8c00-11e6-9962-42010af00004   15Gi       RWX           6s
Copy to Clipboard Toggle word wrap
Important

Since the default StorageClass is enabled on this system, for the manually created Persistent Volume to get bound by the above claim and not have a new dynamic provisioned volume be bound, the PV would need to have been created in the default StorageClass.

Since the default StorageClass is enabled on this system, you would need to create the PV in the default StorageClass for the manually created Persistent Volume to get bound to the above claim and not have a new dynamic provisioned volume bound to the claim.

To fix this, the cluster-admin or storage-admin user simply needs to create another GCE disk or delete the first manual PV and use a PV object definition that assigns a StorageClass annotation (pv-manual-gce2.yaml) if necessary:

Example 22.26. Manual PV Spec with default StorageClass annotation

apiVersion: v1
kind: PersistentVolume
metadata:
 name: pv-manual-gce2
 annotations:
   volume.beta.kubernetes.io/storage-class: generic
1 

spec:
 capacity:
   storage: 35Gi
 accessModes:
   - ReadWriteMany
 gcePersistentDisk:
   readOnly: false
   pdName: the-newly-created-gce-PD
   fsType: ext4
Copy to Clipboard Toggle word wrap
1
The annotation for previously created generic StorageClass.

Execute the object definition file: 

# oc create -f pv-manual-gce2.yaml
Copy to Clipboard Toggle word wrap

List the PVs: 

# oc get pv
NAME                                       CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS      CLAIM                     REASON    AGE
pv-manual-gce                              35Gi       RWX           Retain          Available                                       4s
1 

pv-manual-gce2                             35Gi       RWX           Retain          Bound       rh-eng/pvc-engineering3             4s
2 

pvc-a9f70544-8bfd-11e6-9962-42010af00004   5Gi        RWX           Delete          Bound       rh-eng/pvc-engineering2             12m
pvc-ba4612ce-8b4d-11e6-9962-42010af00004   5Gi        RWO           Delete          Bound       mytest/gce-dyn-claim1               21h
pvc-e9b4fef7-8bf7-11e6-9962-42010af00004   10Gi       RWX           Delete          Bound       rh-eng/pvc-engineering              53m
Copy to Clipboard Toggle word wrap
1
The original manual PV, still unbound and Available. This is because it was not created in the default StorageClass.
2
The second PVC (other than the name) is bound to the Available manually created PV pv-manual-gce2.
Important

Notice that all dynamically provisioned volumes by default have a RECLAIMPOLICY of Delete. Once the PVC dynamically bound to the PV is deleted, the GCE volume is deleted and all data is lost. However, the manually created PV has a default RECLAIMPOLICY of Retain.

22.10.1. Overview
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In this example, a legacy data volume exists and a cluster-admin or storage-admin needs to make it available for consumption in a particular project. Using StorageClasses decreases the likelihood of other users and projects gaining access to this volume from a claim because the claim would have to have an exact matching value for the StorageClass annotation. This example also disables dynamic provisioning. This example assumes:

As a cluster-admin or storage-admin, define and create the StorageClass for historical financial data.

Example 22.27. StorageClass finance-history Object Definitions

kind: StorageClass
apiVersion: storage.k8s.io/v1beta1
metadata:
  name: finance-history
1 

provisioner: no-provisioning
2 

parameters:
3
Copy to Clipboard Toggle word wrap
1
Name of the StorageClass.
2
This is a required field, but since there is to be no dynamic provisioning, a value must be put here as long as it is not an actual provisioner plug-in type.
3
Parameters can simply be left blank, since these are only used for the dynamic provisioner.

Save the definitions to a YAML file (finance-history-storageclass.yaml) and create the StorageClass. 

# oc create -f finance-history-storageclass.yaml
storageclass "finance-history" created


# oc get storageclass
NAME              TYPE
finance-history   no-provisioning
Copy to Clipboard Toggle word wrap
Important

cluster-admin or storage-admin users are responsible for relaying the correct StorageClass name to the correct users, groups, and projects.

The StorageClass exists. A cluster-admin or storage-admin can create the Persistent Volume (PV) for use with the StorageClass. Create a manually provisioned disk using GCE (not dynamically provisioned) and a Persistent Volume that connects to the new GCE disk (gce-pv.yaml).

Example 22.28. Finance History PV Object

apiVersion: v1
kind: PersistentVolume
metadata:
 name: pv-finance-history
 annotations:
   volume.beta.kubernetes.io/storage-class: finance-history
1 

spec:
 capacity:
   storage: 35Gi
 accessModes:
   - ReadWriteMany
 gcePersistentDisk:
   readOnly: false
   pdName: the-existing-PD-volume-name-that-contains-the-valuable-data
2 

   fsType: ext4
Copy to Clipboard Toggle word wrap
1
The StorageClass annotation, that must match exactly.
2
The name of the GCE disk that already exists and contains the legacy data.

As a cluster-admin or storage-admin, create and view the PV. 

# oc create -f gce-pv.yaml
persistentvolume "pv-finance-history" created

# oc get pv
NAME                CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS      CLAIM                        REASON    AGE
pv-finance-history   35Gi       RWX           Retain          Available                                          2d
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Notice you have a pv-finance-history Available and ready for consumption.

As a user, create a Persistent Volume Claim (PVC) as a YAML file and specify the correct StorageClass annotation:

Example 22.29. Claim for finance-history Object Definition

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: pvc-finance-history
 annotations:
   volume.beta.kubernetes.io/storage-class: finance-history
1 

spec:
 accessModes:
  - ReadWriteMany
 resources:
   requests:
     storage: 20Gi
Copy to Clipboard Toggle word wrap
1
The StorageClass annotation, that must match exactly or the claim will go unbound until it is deleted or another StorageClass is created that matches the annotation.

Create and view the PVC and PV to see if it is bound. 

# oc create -f pvc-finance-history.yaml
persistentvolumeclaim "pvc-finance-history" created

# oc get pvc
NAME                  STATUS    VOLUME               CAPACITY   ACCESSMODES   AGE
pvc-finance-history   Bound     pv-finance-history   35Gi       RWX           9m


# oc get pv  (cluster/storage-admin)
NAME                 CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS      CLAIM                         REASON    AGE
pv-finance-history   35Gi       RWX           Retain          Bound       default/pvc-finance-history             5m
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Important

You can use StorageClasses in the same cluster for both legacy data (no dynamic provisioning) and with dynamic provisioning.

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