Chapter 4. Configuring persistent storage

4.1. Persistent storage using AWS Elastic Block Store

OpenShift Container Platform supports AWS Elastic Block Store volumes (EBS). You can provision your OpenShift Container Platform cluster with persistent storage by using Amazon EC2. Some familiarity with Kubernetes and AWS is assumed.

The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure. AWS Elastic Block Store volumes can be provisioned dynamically. Persistent volumes are not bound to a single project or namespace; they can be shared across the OpenShift Container Platform cluster. Persistent volume claims are specific to a project or namespace and can be requested by users. You can define a KMS key to encrypt container-persistent volumes on AWS.

Important

OpenShift Container Platform defaults to using an in-tree (non-CSI) plugin to provision AWS EBS storage.

In future OpenShift Container Platform versions, volumes provisioned using existing in-tree plugins are planned for migration to their equivalent CSI driver. CSI automatic migration should be seamless. Migration does not change how you use all existing API objects, such as persistent volumes, persistent volume claims, and storage classes. For more information about migration, see CSI automatic migration.

After full migration, in-tree plugins will eventually be removed in future versions of OpenShift Container Platform.

Important

High-availability of storage in the infrastructure is left to the underlying storage provider.

For OpenShift Container Platform, automatic migration from AWS EBS in-tree to the Container Storage Interface (CSI) driver is available as a Technology Preview (TP) feature. With migration enabled, volumes provisioned using the existing in-tree driver are automatically migrated to use the AWS EBS CSI driver. For more information, see CSI automatic migration feature.

4.1.1. Creating the EBS storage class

Storage classes are used to differentiate and delineate storage levels and usages. By defining a storage class, users can obtain dynamically provisioned persistent volumes.

4.1.2. Creating the persistent volume claim

Prerequisites

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform.

Procedure

In the OpenShift Container Platform console, click Storage Persistent Volume Claims.
In the persistent volume claims overview, click Create Persistent Volume Claim.
Define the desired options on the page that appears.
1. Select the storage class created previously from the drop-down menu.
2. Enter a unique name for the storage claim.
3. Select the access mode. This determines the read and write access for the created storage claim.
4. Define the size of the storage claim.
Click Create to create the persistent volume claim and generate a persistent volume.

4.1.3. Volume format

Before OpenShift Container Platform mounts the volume and passes it to a container, it checks that it contains a file system as specified by the fsType parameter in the persistent volume definition. If the device is not formatted with the file system, all data from the device is erased and the device is automatically formatted with the given file system.

This allows using unformatted AWS volumes as persistent volumes, because OpenShift Container Platform formats them before the first use.

4.1.4. Maximum number of EBS volumes on a node

By default, OpenShift Container Platform supports a maximum of 39 EBS volumes attached to one node. This limit is consistent with the AWS volume limits. The volume limit depends on the instance type.

Important

As a cluster administrator, you must use either in-tree or Container Storage Interface (CSI) volumes and their respective storage classes, but never both volume types at the same time. The maximum attached EBS volume number is counted separately for in-tree and CSI volumes.

4.1.5. Encrypting container persistent volumes on AWS with a KMS key

Defining a KMS key to encrypt container-persistent volumes on AWS is useful when you have explicit compliance and security guidelines when deploying to AWS.

Prerequisites

Underlying infrastructure must contain storage.
You must create a customer KMS key on AWS.

Procedure

Create a storage class:
```
$ cat << EOF | oc create -f -
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: <storage-class-name> 1
parameters:
  fsType: ext4 2
  encrypted: "true"
  kmsKeyId: keyvalue 3
provisioner: ebs.csi.aws.com
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
EOF
```
1
Specifies the name of the storage class.
2
File system that is created on provisioned volumes.
3
Specifies the full Amazon Resource Name (ARN) of the key to use when encrypting the container-persistent volume. If you do not provide any key, but the encrypted field is set to true, then the default KMS key is used. See Finding the key ID and key ARN on AWS in the AWS documentation.

Create a persistent volume claim (PVC) with the storage class specifying the KMS key:

$ cat << EOF | oc create -f -
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mypvc
spec:
  accessModes:
    - ReadWriteOnce
  volumeMode: Filesystem
  storageClassName: <storage-class-name>
  resources:
    requests:
      storage: 1Gi
EOF

Create workload containers to consume the PVC:

$ cat << EOF | oc create -f -
kind: Pod
metadata:
  name: mypod
spec:
  containers:
    - name: httpd
      image: quay.io/centos7/httpd-24-centos7
      ports:
        - containerPort: 80
      volumeMounts:
        - mountPath: /mnt/storage
          name: data
  volumes:
    - name: data
      persistentVolumeClaim:
        claimName: mypvc
EOF

4.1.6. Additional resources

See AWS Elastic Block Store CSI Driver Operator for information about accessing additional storage options, such as volume snapshots, that are not possible with in-tree volume plugins.

4.2. Persistent storage using Azure

OpenShift Container Platform supports Microsoft Azure Disk volumes. You can provision your OpenShift Container Platform cluster with persistent storage using Azure. Some familiarity with Kubernetes and Azure is assumed. The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure. Azure Disk volumes can be provisioned dynamically. Persistent volumes are not bound to a single project or namespace; they can be shared across the OpenShift Container Platform cluster. Persistent volume claims are specific to a project or namespace and can be requested by users.

Important

OpenShift Container Platform defaults to using an in-tree (non-CSI) plugin to provision Azure Disk storage.

In future OpenShift Container Platform versions, volumes provisioned using existing in-tree plugins are planned for migration to their equivalent CSI driver. CSI automatic migration should be seamless. Migration does not change how you use all existing API objects, such as persistent volumes, persistent volume claims, and storage classes. For more information about migration, see CSI automatic migration.

After full migration, in-tree plugins will eventually be removed in future versions of OpenShift Container Platform.

Important

High availability of storage in the infrastructure is left to the underlying storage provider.

Additional resources

Microsoft Azure Disk

4.2.1. Creating the Azure storage class

Storage classes are used to differentiate and delineate storage levels and usages. By defining a storage class, users can obtain dynamically provisioned persistent volumes.

Procedure

In the OpenShift Container Platform console, click Storage Storage Classes.
In the storage class overview, click Create Storage Class.
Define the desired options on the page that appears.
1. Enter a name to reference the storage class.
2. Enter an optional description.
3. Select the reclaim policy.
4. Select kubernetes.io/azure-disk from the drop down list.
  1. Enter the storage account type. This corresponds to your Azure storage account SKU tier. Valid options are Premium_LRS, Standard_LRS, StandardSSD_LRS, and UltraSSD_LRS.
  2. Enter the kind of account. Valid options are shared, dedicated, and managed.
    Important
    Red Hat only supports the use of kind: Managed in the storage class.
    With Shared and Dedicated, Azure creates unmanaged disks, while OpenShift Container Platform creates a managed disk for machine OS (root) disks. But because Azure Disk does not allow the use of both managed and unmanaged disks on a node, unmanaged disks created with Shared or Dedicated cannot be attached to OpenShift Container Platform nodes.
5. Enter additional parameters for the storage class as desired.
Click Create to create the storage class.

Additional resources

Azure Disk Storage Class

4.2.2. Creating the persistent volume claim

Prerequisites

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform.

Procedure

In the OpenShift Container Platform console, click Storage Persistent Volume Claims.
In the persistent volume claims overview, click Create Persistent Volume Claim.
Define the desired options on the page that appears.
1. Select the storage class created previously from the drop-down menu.
2. Enter a unique name for the storage claim.
3. Select the access mode. This determines the read and write access for the created storage claim.
4. Define the size of the storage claim.
Click Create to create the persistent volume claim and generate a persistent volume.

4.2.3. Volume format

Before OpenShift Container Platform mounts the volume and passes it to a container, it checks that it contains a file system as specified by the fsType parameter in the persistent volume definition. If the device is not formatted with the file system, all data from the device is erased and the device is automatically formatted with the given file system.

This allows using unformatted Azure volumes as persistent volumes, because OpenShift Container Platform formats them before the first use.

4.2.4. Machine sets that deploy machines with ultra disks using PVCs

You can create a machine set running on Azure that deploys machines with ultra disks. Ultra disks are high-performance storage that are intended for use with the most demanding data workloads.

Both the in-tree plugin and CSI driver support using PVCs to enable ultra disks. You can also deploy machines with ultra disks as data disks without creating a PVC.

Additional resources

4.2.4.1. Creating machines with ultra disks by using machine sets

You can deploy machines with ultra disks on Azure by editing your machine set YAML file.

Prerequisites

Have an existing Microsoft Azure cluster.

Procedure

Copy an existing Azure MachineSet custom resource (CR) and edit it by running the following command:
```
$ oc edit machineset <machine-set-name>
```
where <machine-set-name> is the machine set that you want to provision machines with ultra disks.

Add the following lines in the positions indicated:

apiVersion: machine.openshift.io/v1beta1
kind: MachineSet
  ...
spec:
  ...
  template:
    ...
    spec:
      metadata:
        ...
        labels:
          ...
          disk: ultrassd 1
          ...
      providerSpec:
        value:
          ...
          ultraSSDCapability: Enabled 2
             ...

1: Specify a label to use to select a node that is created by this machine set. This procedure uses disk.ultrassd for this value.
2: These lines enable the use of ultra disks.

Create a machine set using the updated configuration by running the following command:
```
$ oc create -f <machine-set-name>.yaml
```
Create a storage class that contains the following YAML definition:
```
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: ultra-disk-sc 1
parameters:
  cachingMode: None
  diskIopsReadWrite: "2000" 2
  diskMbpsReadWrite: "320" 3
  kind: managed
  skuname: UltraSSD_LRS
provisioner: disk.csi.azure.com 4
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer 5
```
1
Specify the name of the storage class. This procedure uses ultra-disk-sc for this value.
2
Specify the number of IOPS for the storage class.
3
Specify the throughput in MBps for the storage class.
4
For Azure Kubernetes Service (AKS) version 1.21 or later, use disk.csi.azure.com. For earlier versions of AKS, use kubernetes.io/azure-disk.
5
Optional: Specify this parameter to wait for the creation of the pod that will use the disk.
Create a persistent volume claim (PVC) to reference the ultra-disk-sc storage class that contains the following YAML definition:
```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: ultra-disk 1
spec:
  accessModes:
  - ReadWriteOnce
  storageClassName: ultra-disk-sc 2
  resources:
    requests:
      storage: 4Gi 3
```
1
Specify the name of the PVC. This procedure uses ultra-disk for this value.
2
This PVC references the ultra-disk-sc storage class.
3
Specify the size for the storage class. The minimum value is 4Gi.

Create a pod that contains the following YAML definition:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-ultra
spec:
  nodeSelector:
    disk: ultrassd 1
  containers:
  - name: nginx-ultra
    image: alpine:latest
    command:
      - "sleep"
      - "infinity"
    volumeMounts:
    - mountPath: "/mnt/azure"
      name: volume
  volumes:
    - name: volume
      persistentVolumeClaim:
        claimName: ultra-disk 2

1: Specify the label of the machine set that enables the use of ultra disks. This procedure uses disk.ultrassd for this value.
2: This pod references the ultra-disk PVC.

Verification

Validate that the machines are created by running the following command:
```
$ oc get machines
```
The machines should be in the Running state.
For a machine that is running and has a node attached, validate the partition by running the following command:
```
$ oc debug node/<node-name> -- chroot /host lsblk
```
In this command, oc debug node/<node-name> starts a debugging shell on the node <node-name> and passes a command with --. The passed command chroot /host provides access to the underlying host OS binaries, and lsblk shows the block devices that are attached to the host OS machine.

Next steps

To use an ultra disk from within a pod, create workload that uses the mount point. Create a YAML file similar to the following example:

apiVersion: v1
kind: Pod
metadata:
  name: ssd-benchmark1
spec:
  containers:
  - name: ssd-benchmark1
    image: nginx
    ports:
      - containerPort: 80
        name: "http-server"
    volumeMounts:
    - name: lun0p1
      mountPath: "/tmp"
  volumes:
    - name: lun0p1
      hostPath:
        path: /var/lib/lun0p1
        type: DirectoryOrCreate
  nodeSelector:
    disktype: ultrassd

4.2.4.2. Troubleshooting resources for machine sets that enable ultra disks

Use the information in this section to understand and recover from issues you might encounter.

4.2.4.2.1. Unable to mount a persistent volume claim backed by an ultra disk

If there is an issue mounting a persistent volume claim backed by an ultra disk, the pod becomes stuck in the ContainerCreating state and an alert is triggered.

For example, if the additionalCapabilities.ultraSSDEnabled parameter is not set on the machine that backs the node that hosts the pod, the following error message appears:

StorageAccountType UltraSSD_LRS can be used only when additionalCapabilities.ultraSSDEnabled is set.

To resolve this issue, describe the pod by running the following command:
```
$ oc -n <stuck_pod_namespace> describe pod <stuck_pod_name>
```

4.3. Persistent storage using Azure File

OpenShift Container Platform supports Microsoft Azure File volumes. You can provision your OpenShift Container Platform cluster with persistent storage using Azure. Some familiarity with Kubernetes and Azure is assumed.

The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure. You can provision Azure File volumes dynamically.

Persistent volumes are not bound to a single project or namespace, and you can share them across the OpenShift Container Platform cluster. Persistent volume claims are specific to a project or namespace, and can be requested by users for use in applications.

Important

High availability of storage in the infrastructure is left to the underlying storage provider.

Important

Azure File volumes use Server Message Block.

Important

In future OpenShift Container Platform versions, volumes provisioned using existing in-tree plugins are planned for migration to their equivalent CSI driver. CSI automatic migration should be seamless. Migration does not change how you use all existing API objects, such as persistent volumes, persistent volume claims, and storage classes. For more information about migration, see CSI automatic migration.

After full migration, in-tree plugins will eventually be removed in future versions of OpenShift Container Platform.

Additional resources

Azure Files

4.3.1. Create the Azure File share persistent volume claim

To create the persistent volume claim, you must first define a Secret object that contains the Azure account and key. This secret is used in the PersistentVolume definition, and will be referenced by the persistent volume claim for use in applications.

Prerequisites

An Azure File share exists.
The credentials to access this share, specifically the storage account and key, are available.

Procedure

Create a Secret object that contains the Azure File credentials:

$ oc create secret generic <secret-name> --from-literal=azurestorageaccountname=<storage-account> \ 1
  --from-literal=azurestorageaccountkey=<storage-account-key> 2

1: The Azure File storage account name.
2: The Azure File storage account key.

Create a PersistentVolume object that references the Secret object you created:

apiVersion: "v1"
kind: "PersistentVolume"
metadata:
  name: "pv0001" 1
spec:
  capacity:
    storage: "5Gi" 2
  accessModes:
    - "ReadWriteOnce"
  storageClassName: azure-file-sc
  azureFile:
    secretName: <secret-name> 3
    shareName: share-1 4
    readOnly: false

1: The name of the persistent volume.
2: The size of this persistent volume.
3: The name of the secret that contains the Azure File share credentials.
4: The name of the Azure File share.

Create a PersistentVolumeClaim object that maps to the persistent volume you created:
```
apiVersion: "v1"
kind: "PersistentVolumeClaim"
metadata:
  name: "claim1" 1
spec:
  accessModes:
    - "ReadWriteOnce"
  resources:
    requests:
      storage: "5Gi" 2
  storageClassName: azure-file-sc 3
  volumeName: "pv0001" 4
```
1
The name of the persistent volume claim.
2
The size of this persistent volume claim.
3
The name of the storage class that is used to provision the persistent volume. Specify the storage class used in the PersistentVolume definition.
4
The name of the existing PersistentVolume object that references the Azure File share.

4.3.2. Mount the Azure File share in a pod

After the persistent volume claim has been created, it can be used inside by an application. The following example demonstrates mounting this share inside of a pod.

Prerequisites

A persistent volume claim exists that is mapped to the underlying Azure File share.

Procedure

Create a pod that mounts the existing persistent volume claim:
```
apiVersion: v1
kind: Pod
metadata:
  name: pod-name 1
spec:
  containers:
    ...
    volumeMounts:
    - mountPath: "/data" 2
      name: azure-file-share
  volumes:
    - name: azure-file-share
      persistentVolumeClaim:
        claimName: claim1 3
```
1
The name of the pod.
2
The path to mount the Azure File share inside the pod. Do not mount to the container root, /, or any path that is the same in the host and the container. This can corrupt your host system if the container is sufficiently privileged, such as the host /dev/pts files. It is safe to mount the host by using /host.
3
The name of the PersistentVolumeClaim object that has been previously created.

4.4. Persistent storage using Cinder

OpenShift Container Platform supports OpenStack Cinder. Some familiarity with Kubernetes and OpenStack is assumed.

Cinder volumes can be provisioned dynamically. Persistent volumes are not bound to a single project or namespace; they can be shared across the OpenShift Container Platform cluster. Persistent volume claims are specific to a project or namespace and can be requested by users.

Important

OpenShift Container Platform defaults to using an in-tree (non-CSI) plugin to provision Cinder storage.

In future OpenShift Container Platform versions, volumes provisioned using existing in-tree plugins are planned for migration to their equivalent CSI driver. CSI automatic migration should be seamless. Migration does not change how you use all existing API objects, such as persistent volumes, persistent volume claims, and storage classes. For more information about migration, see CSI automatic migration.

After full migration, in-tree plugins will eventually be removed in future versions of OpenShift Container Platform.

Additional resources

For more information about how OpenStack Block Storage provides persistent block storage management for virtual hard drives, see OpenStack Cinder.

4.4.1. Manual provisioning with Cinder

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform.

Prerequisites

OpenShift Container Platform configured for Red Hat OpenStack Platform (RHOSP)
Cinder volume ID

4.4.1.1. Creating the persistent volume

You must define your persistent volume (PV) in an object definition before creating it in OpenShift Container Platform:

Procedure

Save your object definition to a file.
cinder-persistentvolume.yaml
```
apiVersion: "v1"
kind: "PersistentVolume"
metadata:
  name: "pv0001" 1
spec:
  capacity:
    storage: "5Gi" 2
  accessModes:
    - "ReadWriteOnce"
  cinder: 3
    fsType: "ext3" 4
    volumeID: "f37a03aa-6212-4c62-a805-9ce139fab180" 5
```
1
The name of the volume that is used by persistent volume claims or pods.
2
The amount of storage allocated to this volume.
3
Indicates cinder for Red Hat OpenStack Platform (RHOSP) Cinder volumes.
4
The file system that is created when the volume is mounted for the first time.
5
The Cinder volume to use.
Important
Do not change the fstype parameter value after the volume is formatted and provisioned. Changing this value can result in data loss and pod failure.
Create the object definition file you saved in the previous step.
```
$ oc create -f cinder-persistentvolume.yaml
```

4.4.1.2. Persistent volume formatting

You can use unformatted Cinder volumes as PVs because OpenShift Container Platform formats them before the first use.

Before OpenShift Container Platform mounts the volume and passes it to a container, the system checks that it contains a file system as specified by the fsType parameter in the PV definition. If the device is not formatted with the file system, all data from the device is erased and the device is automatically formatted with the given file system.

4.4.1.3. Cinder volume security

If you use Cinder PVs in your application, configure security for their deployment configurations.

Prerequisites

An SCC must be created that uses the appropriate fsGroup strategy.

Procedure

Create a service account and add it to the SCC:

$ oc create serviceaccount <service_account>

$ oc adm policy add-scc-to-user <new_scc> -z <service_account> -n <project>

In your application’s deployment configuration, provide the service account name and securityContext:

apiVersion: v1
kind: ReplicationController
metadata:
  name: frontend-1
spec:
  replicas: 1  1
  selector:    2
    name: frontend
  template:    3
    metadata:
      labels:  4
        name: frontend 5
    spec:
      containers:
      - image: openshift/hello-openshift
        name: helloworld
        ports:
        - containerPort: 8080
          protocol: TCP
      restartPolicy: Always
      serviceAccountName: <service_account> 6
      securityContext:
        fsGroup: 7777 7

1: The number of copies of the pod to run.
2: The label selector of the pod to run.
3: A template for the pod that the controller creates.
4: The labels on the pod. They must include labels from the label selector.
5: The maximum name length after expanding any parameters is 63 characters.
6: Specifies the service account you created.
7: Specifies an fsGroup for the pods.

4.5. Persistent storage using Fibre Channel

OpenShift Container Platform supports Fibre Channel, allowing you to provision your OpenShift Container Platform cluster with persistent storage using Fibre channel volumes. Some familiarity with Kubernetes and Fibre Channel is assumed.

Important

Persistent storage using Fibre Channel is not supported on ARM architecture based infrastructures.

The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure. Persistent volumes are not bound to a single project or namespace; they can be shared across the OpenShift Container Platform cluster. Persistent volume claims are specific to a project or namespace and can be requested by users.

Important

High availability of storage in the infrastructure is left to the underlying storage provider.

Additional resources

Using Fibre Channel devices

4.5.1. Provisioning

To provision Fibre Channel volumes using the PersistentVolume API the following must be available:

The targetWWNs (array of Fibre Channel target’s World Wide Names).
A valid LUN number.
The filesystem type.

A persistent volume and a LUN have a one-to-one mapping between them.

Prerequisites

Fibre Channel LUNs must exist in the underlying infrastructure.

PersistentVolume object definition

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv0001
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  fc:
    wwids: [scsi-3600508b400105e210000900000490000] 1
    targetWWNs: ['500a0981891b8dc5', '500a0981991b8dc5'] 2
    lun: 2 3
    fsType: ext4

1: World wide identifiers (WWIDs). Either FC wwids or a combination of FC targetWWNs and lun must be set, but not both simultaneously. The FC WWID identifier is recommended over the WWNs target because it is guaranteed to be unique for every storage device, and independent of the path that is used to access the device. The WWID identifier can be obtained by issuing a SCSI Inquiry to retrieve the Device Identification Vital Product Data (page 0x83) or Unit Serial Number (page 0x80). FC WWIDs are identified as /dev/disk/by-id/ to reference the data on the disk, even if the path to the device changes and even when accessing the device from different systems.
2 3: Fibre Channel WWNs are identified as /dev/disk/by-path/pci-<IDENTIFIER>-fc-0x<WWN>-lun-<LUN#>, but you do not need to provide any part of the path leading up to the WWN, including the 0x, and anything after, including the - (hyphen).

Important

Changing the value of the fstype parameter after the volume has been formatted and provisioned can result in data loss and pod failure.

4.5.1.1. Enforcing disk quotas

Use LUN partitions to enforce disk quotas and size constraints. Each LUN is mapped to a single persistent volume, and unique names must be used for persistent volumes.

Enforcing quotas in this way allows the end user to request persistent storage by a specific amount, such as 10Gi, and be matched with a corresponding volume of equal or greater capacity.

4.5.1.2. Fibre Channel volume security

Users request storage with a persistent volume claim. This claim only lives in the user’s namespace, and can only be referenced by a pod within that same namespace. Any attempt to access a persistent volume across a namespace causes the pod to fail.

Each Fibre Channel LUN must be accessible by all nodes in the cluster.

4.6. Persistent storage using FlexVolume

Important

FlexVolume is a deprecated feature. Deprecated functionality is still included in OpenShift Container Platform and continues to be supported; however, it will be removed in a future release of this product and is not recommended for new deployments.

Out-of-tree Container Storage Interface (CSI) driver is the recommended way to write volume drivers in OpenShift Container Platform. Maintainers of FlexVolume drivers should implement a CSI driver and move users of FlexVolume to CSI. Users of FlexVolume should move their workloads to CSI driver.

For the most recent list of major functionality that has been deprecated or removed within OpenShift Container Platform, refer to the Deprecated and removed features section of the OpenShift Container Platform release notes.

OpenShift Container Platform supports FlexVolume, an out-of-tree plugin that uses an executable model to interface with drivers.

To use storage from a back-end that does not have a built-in plugin, you can extend OpenShift Container Platform through FlexVolume drivers and provide persistent storage to applications.

Pods interact with FlexVolume drivers through the flexvolume in-tree plugin.

Additional resources

Expanding persistent volumes

4.6.1. About FlexVolume drivers

A FlexVolume driver is an executable file that resides in a well-defined directory on all nodes in the cluster. OpenShift Container Platform calls the FlexVolume driver whenever it needs to mount or unmount a volume represented by a PersistentVolume object with flexVolume as the source.

Important

Attach and detach operations are not supported in OpenShift Container Platform for FlexVolume.

4.6.2. FlexVolume driver example

The first command-line argument of the FlexVolume driver is always an operation name. Other parameters are specific to each operation. Most of the operations take a JavaScript Object Notation (JSON) string as a parameter. This parameter is a complete JSON string, and not the name of a file with the JSON data.

The FlexVolume driver contains:

All flexVolume.options.
Some options from flexVolume prefixed by kubernetes.io/, such as fsType and readwrite.
The content of the referenced secret, if specified, prefixed by kubernetes.io/secret/.

FlexVolume driver JSON input example

{
	"fooServer": "192.168.0.1:1234", 1
        "fooVolumeName": "bar",
	"kubernetes.io/fsType": "ext4", 2
	"kubernetes.io/readwrite": "ro", 3
	"kubernetes.io/secret/<key name>": "<key value>", 4
	"kubernetes.io/secret/<another key name>": "<another key value>",
}

1: All options from flexVolume.options.
2: The value of flexVolume.fsType.
3: ro/rw based on flexVolume.readOnly.
4: All keys and their values from the secret referenced by flexVolume.secretRef.

OpenShift Container Platform expects JSON data on standard output of the driver. When not specified, the output describes the result of the operation.

FlexVolume driver default output example

{
	"status": "<Success/Failure/Not supported>",
	"message": "<Reason for success/failure>"
}

Exit code of the driver should be 0 for success and 1 for error.

Operations should be idempotent, which means that the mounting of an already mounted volume should result in a successful operation.

4.6.3. Installing FlexVolume drivers

FlexVolume drivers that are used to extend OpenShift Container Platform are executed only on the node. To implement FlexVolumes, a list of operations to call and the installation path are all that is required.

Prerequisites

FlexVolume drivers must implement these operations:
init
Initializes the driver. It is called during initialization of all nodes.
Arguments: none
Executed on: node
Expected output: default JSON
mount
Mounts a volume to directory. This can include anything that is necessary to mount the volume, including finding the device and then mounting the device.
Arguments: <mount-dir> <json>
Executed on: node
Expected output: default JSON
unmount
Unmounts a volume from a directory. This can include anything that is necessary to clean up the volume after unmounting.
Arguments: <mount-dir>
Executed on: node
Expected output: default JSON
mountdevice
Mounts a volume’s device to a directory where individual pods can then bind mount.

This call-out does not pass "secrets" specified in the FlexVolume spec. If your driver requires secrets, do not implement this call-out.

Arguments: <mount-dir> <json>
Executed on: node
Expected output: default JSON
unmountdevice
Unmounts a volume’s device from a directory.
Arguments: <mount-dir>
Executed on: node
Expected output: default JSON
- All other operations should return JSON with {"status": "Not supported"} and exit code 1.

Procedure

To install the FlexVolume driver:

Ensure that the executable file exists on all nodes in the cluster.
Place the executable file at the volume plugin path: /etc/kubernetes/kubelet-plugins/volume/exec/<vendor>~<driver>/<driver>.

For example, to install the FlexVolume driver for the storage foo, place the executable file at: /etc/kubernetes/kubelet-plugins/volume/exec/openshift.com~foo/foo.

4.6.4. Consuming storage using FlexVolume drivers

Each PersistentVolume object in OpenShift Container Platform represents one storage asset in the storage back-end, such as a volume.

Procedure

Use the PersistentVolume object to reference the installed storage.

Persistent volume object definition using FlexVolume drivers example

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv0001 1
spec:
  capacity:
    storage: 1Gi 2
  accessModes:
    - ReadWriteOnce
  flexVolume:
    driver: openshift.com/foo 3
    fsType: "ext4" 4
    secretRef: foo-secret 5
    readOnly: true 6
    options: 7
      fooServer: 192.168.0.1:1234
      fooVolumeName: bar

1

The name of the volume. This is how it is identified through persistent volume claims or from pods. This name can be different from the name of the volume on back-end storage.

2

The amount of storage allocated to this volume.

3

The name of the driver. This field is mandatory.

4

The file system that is present on the volume. This field is optional.

5

The reference to a secret. Keys and values from this secret are provided to the FlexVolume driver on invocation. This field is optional.

6

The read-only flag. This field is optional.

7

The additional options for the FlexVolume driver. In addition to the flags specified by the user in the options field, the following flags are also passed to the executable:

"fsType":"<FS type>",
"readwrite":"<rw>",
"secret/key1":"<secret1>"
...
"secret/keyN":"<secretN>"

Note

Secrets are passed only to mount or unmount call-outs.

4.7. Persistent storage using GCE Persistent Disk

OpenShift Container Platform supports GCE Persistent Disk volumes (gcePD). You can provision your OpenShift Container Platform cluster with persistent storage using GCE. Some familiarity with Kubernetes and GCE is assumed.

The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure.

GCE Persistent Disk volumes can be provisioned dynamically.

Persistent volumes are not bound to a single project or namespace; they can be shared across the OpenShift Container Platform cluster. Persistent volume claims are specific to a project or namespace and can be requested by users.

Important

OpenShift Container Platform defaults to using an in-tree (non-CSI) plugin to provision gcePD storage.

In future OpenShift Container Platform versions, volumes provisioned using existing in-tree plugins are planned for migration to their equivalent CSI driver. CSI automatic migration should be seamless. Migration does not change how you use all existing API objects, such as persistent volumes, persistent volume claims, and storage classes. For more information about migration, see CSI automatic migration.

After full migration, in-tree plugins will eventually be removed in future versions of OpenShift Container Platform.

Important

High availability of storage in the infrastructure is left to the underlying storage provider.

Additional resources

GCE Persistent Disk

4.7.1. Creating the GCE storage class

Storage classes are used to differentiate and delineate storage levels and usages. By defining a storage class, users can obtain dynamically provisioned persistent volumes.

4.7.2. Creating the persistent volume claim

Prerequisites

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform.

Procedure

In the OpenShift Container Platform console, click Storage Persistent Volume Claims.
In the persistent volume claims overview, click Create Persistent Volume Claim.
Define the desired options on the page that appears.
1. Select the storage class created previously from the drop-down menu.
2. Enter a unique name for the storage claim.
3. Select the access mode. This determines the read and write access for the created storage claim.
4. Define the size of the storage claim.
Click Create to create the persistent volume claim and generate a persistent volume.

4.7.3. Volume format

Before OpenShift Container Platform mounts the volume and passes it to a container, it checks that it contains a file system as specified by the fsType parameter in the persistent volume definition. If the device is not formatted with the file system, all data from the device is erased and the device is automatically formatted with the given file system.

This allows using unformatted GCE volumes as persistent volumes, because OpenShift Container Platform formats them before the first use.

4.8. Persistent storage using hostPath

A hostPath volume in an OpenShift Container Platform cluster mounts a file or directory from the host node’s filesystem into your pod. Most pods will not need a hostPath volume, but it does offer a quick option for testing should an application require it.

Important

The cluster administrator must configure pods to run as privileged. This grants access to pods in the same node.

4.8.1. Overview

OpenShift Container Platform supports hostPath mounting for development and testing on a single-node cluster.

In a production cluster, you would not use hostPath. Instead, a cluster administrator would provision a network resource, such as a GCE Persistent Disk volume, an NFS share, or an Amazon EBS volume. Network resources support the use of storage classes to set up dynamic provisioning.

A hostPath volume must be provisioned statically.

Important

Do not mount to the container root, /, or any path that is the same in the host and the container. This can corrupt your host system if the container is sufficiently privileged. It is safe to mount the host by using /host. The following example shows the / directory from the host being mounted into the container at /host.

apiVersion: v1
kind: Pod
metadata:
  name: test-host-mount
spec:
  containers:
  - image: registry.access.redhat.com/ubi8/ubi
    name: test-container
    command: ['sh', '-c', 'sleep 3600']
    volumeMounts:
    - mountPath: /host
      name: host-slash
  volumes:
   - name: host-slash
     hostPath:
       path: /
       type: ''

4.8.2. Statically provisioning hostPath volumes

A pod that uses a hostPath volume must be referenced by manual (static) provisioning.

Procedure

Define the persistent volume (PV). Create a file, pv.yaml, with the PersistentVolume object definition:
```
  apiVersion: v1
  kind: PersistentVolume
  metadata:
    name: task-pv-volume 1
    labels:
      type: local
  spec:
    storageClassName: manual 2
    capacity:
      storage: 5Gi
    accessModes:
      - ReadWriteOnce 3
    persistentVolumeReclaimPolicy: Retain
    hostPath:
      path: "/mnt/data" 4
```
1
The name of the volume. This name is how it is identified by persistent volume claims or pods.
2
Used to bind persistent volume claim requests to this persistent volume.
3
The volume can be mounted as read-write by a single node.
4
The configuration file specifies that the volume is at /mnt/data on the cluster’s node. Do not mount to the container root, /, or any path that is the same in the host and the container. This can corrupt your host system. It is safe to mount the host by using /host.
Create the PV from the file:
```
$ oc create -f pv.yaml
```

Define the persistent volume claim (PVC). Create a file, pvc.yaml, with the PersistentVolumeClaim object definition:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: task-pvc-volume
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
  storageClassName: manual

Create the PVC from the file:
```
$ oc create -f pvc.yaml
```

4.8.3. Mounting the hostPath share in a privileged pod

After the persistent volume claim has been created, it can be used inside by an application. The following example demonstrates mounting this share inside of a pod.

Prerequisites

A persistent volume claim exists that is mapped to the underlying hostPath share.

Procedure

Create a privileged pod that mounts the existing persistent volume claim:
```
apiVersion: v1
kind: Pod
metadata:
  name: pod-name 1
spec:
  containers:
    ...
    securityContext:
      privileged: true 2
    volumeMounts:
    - mountPath: /data 3
      name: hostpath-privileged
  ...
  securityContext: {}
  volumes:
    - name: hostpath-privileged
      persistentVolumeClaim:
        claimName: task-pvc-volume 4
```
1
The name of the pod.
2
The pod must run as privileged to access the node’s storage.
3
The path to mount the host path share inside the privileged pod. Do not mount to the container root, /, or any path that is the same in the host and the container. This can corrupt your host system if the container is sufficiently privileged, such as the host /dev/pts files. It is safe to mount the host by using /host.
4
The name of the PersistentVolumeClaim object that has been previously created.

4.9. Persistent storage using iSCSI

You can provision your OpenShift Container Platform cluster with persistent storage using iSCSI. Some familiarity with Kubernetes and iSCSI is assumed.

The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure.

Important

High-availability of storage in the infrastructure is left to the underlying storage provider.

Important

When you use iSCSI on Amazon Web Services, you must update the default security policy to include TCP traffic between nodes on the iSCSI ports. By default, they are ports 860 and 3260.

Important

Users must ensure that the iSCSI initiator is already configured on all OpenShift Container Platform nodes by installing the iscsi-initiator-utils package and configuring their initiator name in /etc/iscsi/initiatorname.iscsi. The iscsi-initiator-utils package is already installed on deployments that use Red Hat Enterprise Linux CoreOS (RHCOS).

For more information, see Managing Storage Devices.

4.9.1. Provisioning

Verify that the storage exists in the underlying infrastructure before mounting it as a volume in OpenShift Container Platform. All that is required for the iSCSI is the iSCSI target portal, a valid iSCSI Qualified Name (IQN), a valid LUN number, the filesystem type, and the PersistentVolume API.

PersistentVolume object definition

apiVersion: v1
kind: PersistentVolume
metadata:
  name: iscsi-pv
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  iscsi:
     targetPortal: 10.16.154.81:3260
     iqn: iqn.2014-12.example.server:storage.target00
     lun: 0
     fsType: 'ext4'

4.9.2. Enforcing disk quotas

Use LUN partitions to enforce disk quotas and size constraints. Each LUN is one persistent volume. Kubernetes enforces unique names for persistent volumes.

Enforcing quotas in this way allows the end user to request persistent storage by a specific amount (for example, 10Gi) and be matched with a corresponding volume of equal or greater capacity.

4.9.3. iSCSI volume security

Users request storage with a PersistentVolumeClaim object. This claim only lives in the user’s namespace and can only be referenced by a pod within that same namespace. Any attempt to access a persistent volume claim across a namespace causes the pod to fail.

Each iSCSI LUN must be accessible by all nodes in the cluster.

4.9.3.1. Challenge Handshake Authentication Protocol (CHAP) configuration

Optionally, OpenShift Container Platform can use CHAP to authenticate itself to iSCSI targets:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: iscsi-pv
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  iscsi:
    targetPortal: 10.0.0.1:3260
    iqn: iqn.2016-04.test.com:storage.target00
    lun: 0
    fsType: ext4
    chapAuthDiscovery: true 1
    chapAuthSession: true 2
    secretRef:
      name: chap-secret 3

1: Enable CHAP authentication of iSCSI discovery.
2: Enable CHAP authentication of iSCSI session.
3: Specify name of Secrets object with user name + password. This Secret object must be available in all namespaces that can use the referenced volume.

4.9.4. iSCSI multipathing

For iSCSI-based storage, you can configure multiple paths by using the same IQN for more than one target portal IP address. Multipathing ensures access to the persistent volume when one or more of the components in a path fail.

To specify multi-paths in the pod specification, use the portals field. For example:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: iscsi-pv
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  iscsi:
    targetPortal: 10.0.0.1:3260
    portals: ['10.0.2.16:3260', '10.0.2.17:3260', '10.0.2.18:3260'] 1
    iqn: iqn.2016-04.test.com:storage.target00
    lun: 0
    fsType: ext4
    readOnly: false

1: Add additional target portals using the portals field.

4.9.5. iSCSI custom initiator IQN

Configure the custom initiator iSCSI Qualified Name (IQN) if the iSCSI targets are restricted to certain IQNs, but the nodes that the iSCSI PVs are attached to are not guaranteed to have these IQNs.

To specify a custom initiator IQN, use initiatorName field.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: iscsi-pv
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  iscsi:
    targetPortal: 10.0.0.1:3260
    portals: ['10.0.2.16:3260', '10.0.2.17:3260', '10.0.2.18:3260']
    iqn: iqn.2016-04.test.com:storage.target00
    lun: 0
    initiatorName: iqn.2016-04.test.com:custom.iqn 1
    fsType: ext4
    readOnly: false

1: Specify the name of the initiator.

4.10. Persistent storage using local volumes

OpenShift Container Platform can be provisioned with persistent storage by using local volumes. Local persistent volumes allow you to access local storage devices, such as a disk or partition, by using the standard persistent volume claim interface.

Local volumes can be used without manually scheduling pods to nodes because the system is aware of the volume node constraints. However, local volumes are still subject to the availability of the underlying node and are not suitable for all applications.

Note

Local volumes can only be used as a statically created persistent volume.

4.10.1. Installing the Local Storage Operator

The Local Storage Operator is not installed in OpenShift Container Platform by default. Use the following procedure to install and configure this Operator to enable local volumes in your cluster.

Prerequisites

Access to the OpenShift Container Platform web console or command-line interface (CLI).

Procedure

Create the openshift-local-storage project:

$ oc adm new-project openshift-local-storage

Optional: Allow local storage creation on infrastructure nodes.
You might want to use the Local Storage Operator to create volumes on infrastructure nodes in support of components such as logging and monitoring.
You must adjust the default node selector so that the Local Storage Operator includes the infrastructure nodes, and not just worker nodes.
To block the Local Storage Operator from inheriting the cluster-wide default selector, enter the following command:
```
$ oc annotate namespace openshift-local-storage openshift.io/node-selector=''
```
Optional: Allow local storage to run on the management pool of CPUs in single-node deployment.
Use the Local Storage Operator in single-node deployments and allow the use of CPUs that belong to the management pool. Perform this step on single-node installations that use management workload partitioning.
To allow Local Storage Operator to run on the management CPU pool, run following commands:
```
$ oc annotate namespace openshift-local-storage workload.openshift.io/allowed='management'
```

From the UI

To install the Local Storage Operator from the web console, follow these steps:

Log in to the OpenShift Container Platform web console.
Navigate to Operators OperatorHub.
Type Local Storage into the filter box to locate the Local Storage Operator.
Click Install.
On the Install Operator page, select A specific namespace on the cluster. Select openshift-local-storage from the drop-down menu.
Adjust the values for Update Channel and Approval Strategy to the values that you want.
Click Install.

Once finished, the Local Storage Operator will be listed in the Installed Operators section of the web console.

From the CLI

Install the Local Storage Operator from the CLI.

Create an object YAML file to define an Operator group and subscription for the Local Storage Operator, such as openshift-local-storage.yaml:

Example openshift-local-storage.yaml

apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: local-operator-group
  namespace: openshift-local-storage
spec:
  targetNamespaces:
    - openshift-local-storage
---
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: local-storage-operator
  namespace: openshift-local-storage
spec:
  channel: stable
  installPlanApproval: Automatic 1
  name: local-storage-operator
  source: redhat-operators
  sourceNamespace: openshift-marketplace

1: The user approval policy for an install plan.

Create the Local Storage Operator object by entering the following command:
```
$ oc apply -f openshift-local-storage.yaml
```
At this point, the Operator Lifecycle Manager (OLM) is now aware of the Local Storage Operator. A ClusterServiceVersion (CSV) for the Operator should appear in the target namespace, and APIs provided by the Operator should be available for creation.

Verify local storage installation by checking that all pods and the Local Storage Operator have been created:

Check that all the required pods have been created:

$ oc -n openshift-local-storage get pods

Example output

NAME                                      READY   STATUS    RESTARTS   AGE
local-storage-operator-746bf599c9-vlt5t   1/1     Running   0          19m

Check the ClusterServiceVersion (CSV) YAML manifest to see that the Local Storage Operator is available in the openshift-local-storage project:

$ oc get csvs -n openshift-local-storage

Example output

NAME                                         DISPLAY         VERSION               REPLACES   PHASE
local-storage-operator.4.2.26-202003230335   Local Storage   4.2.26-202003230335              Succeeded

After all checks have passed, the Local Storage Operator is installed successfully.

4.10.2. Provisioning local volumes by using the Local Storage Operator

Local volumes cannot be created by dynamic provisioning. Instead, persistent volumes can be created by the Local Storage Operator. The local volume provisioner looks for any file system or block volume devices at the paths specified in the defined resource.

Prerequisites

The Local Storage Operator is installed.
You have a local disk that meets the following conditions:
- It is attached to a node.
- It is not mounted.
- It does not contain partitions.

Procedure

Create the local volume resource. This resource must define the nodes and paths to the local volumes.
Note
Do not use different storage class names for the same device. Doing so will create multiple persistent volumes (PVs).
Example: Filesystem
```
apiVersion: "local.storage.openshift.io/v1"
kind: "LocalVolume"
metadata:
  name: "local-disks"
  namespace: "openshift-local-storage" 1
spec:
  nodeSelector: 2
    nodeSelectorTerms:
    - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - ip-10-0-140-183
          - ip-10-0-158-139
          - ip-10-0-164-33
  storageClassDevices:
    - storageClassName: "local-sc" 3
      volumeMode: Filesystem 4
      fsType: xfs 5
      devicePaths: 6
        - /path/to/device 7
```
1
The namespace where the Local Storage Operator is installed.
2
Optional: A node selector containing a list of nodes where the local storage volumes are attached. This example uses the node hostnames, obtained from oc get node. If a value is not defined, then the Local Storage Operator will attempt to find matching disks on all available nodes.
3
The name of the storage class to use when creating persistent volume objects. The Local Storage Operator automatically creates the storage class if it does not exist. Be sure to use a storage class that uniquely identifies this set of local volumes.
4
The volume mode, either Filesystem or Block, that defines the type of local volumes.
Note
A raw block volume (volumeMode: Block) is not formatted with a file system. Use this mode only if any application running on the pod can use raw block devices.
5
The file system that is created when the local volume is mounted for the first time.
6
The path containing a list of local storage devices to choose from.
7
Replace this value with your actual local disks filepath to the LocalVolume resource by-id, such as /dev/disk/by-id/wwn. PVs are created for these local disks when the provisioner is deployed successfully.
Note
If you are running OpenShift Container Platform on IBM Z with RHEL KVM, you must assign a serial number to your VM disk. Otherwise, the VM disk can not be identified after reboot. You can use the virsh edit <VM> command to add the <serial>mydisk</serial> definition.
Example: Block
```
apiVersion: "local.storage.openshift.io/v1"
kind: "LocalVolume"
metadata:
  name: "local-disks"
  namespace: "openshift-local-storage" 1
spec:
  nodeSelector: 2
    nodeSelectorTerms:
    - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - ip-10-0-136-143
          - ip-10-0-140-255
          - ip-10-0-144-180
  storageClassDevices:
    - storageClassName: "localblock-sc" 3
      volumeMode: Block 4
      devicePaths: 5
        - /path/to/device 6
```
1
The namespace where the Local Storage Operator is installed.
2
Optional: A node selector containing a list of nodes where the local storage volumes are attached. This example uses the node hostnames, obtained from oc get node. If a value is not defined, then the Local Storage Operator will attempt to find matching disks on all available nodes.
3
The name of the storage class to use when creating persistent volume objects.
4
The volume mode, either Filesystem or Block, that defines the type of local volumes.
5
The path containing a list of local storage devices to choose from.
6
Replace this value with your actual local disks filepath to the LocalVolume resource by-id, such as dev/disk/by-id/wwn. PVs are created for these local disks when the provisioner is deployed successfully.
Note
If you are running OpenShift Container Platform on IBM Z with RHEL KVM, you must assign a serial number to your VM disk. Otherwise, the VM disk can not be identified after reboot. You can use the virsh edit <VM> command to add the <serial>mydisk</serial> definition.
Create the local volume resource in your OpenShift Container Platform cluster. Specify the file you just created:
```
$ oc create -f <local-volume>.yaml
```

Verify that the provisioner was created and that the corresponding daemon sets were created:

$ oc get all -n openshift-local-storage

Example output

NAME                                          READY   STATUS    RESTARTS   AGE
pod/diskmaker-manager-9wzms                   1/1     Running   0          5m43s
pod/diskmaker-manager-jgvjp                   1/1     Running   0          5m43s
pod/diskmaker-manager-tbdsj                   1/1     Running   0          5m43s
pod/local-storage-operator-7db4bd9f79-t6k87   1/1     Running   0          14m

NAME                                     TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)             AGE
service/local-storage-operator-metrics   ClusterIP   172.30.135.36   <none>        8383/TCP,8686/TCP   14m

NAME                               DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
daemonset.apps/diskmaker-manager   3         3         3       3            3           <none>          5m43s

NAME                                     READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/local-storage-operator   1/1     1            1           14m

NAME                                                DESIRED   CURRENT   READY   AGE
replicaset.apps/local-storage-operator-7db4bd9f79   1         1         1       14m

Note the desired and current number of daemon set processes. A desired count of 0 indicates that the label selectors were invalid.

Verify that the persistent volumes were created:

$ oc get pv

Example output

NAME                CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
local-pv-1cec77cf   100Gi      RWO            Delete           Available           local-sc                88m
local-pv-2ef7cd2a   100Gi      RWO            Delete           Available           local-sc                82m
local-pv-3fa1c73    100Gi      RWO            Delete           Available           local-sc                48m

Important

Editing the LocalVolume object does not change the fsType or volumeMode of existing persistent volumes because doing so might result in a destructive operation.

4.10.3. Provisioning local volumes without the Local Storage Operator

Local volumes cannot be created by dynamic provisioning. Instead, persistent volumes can be created by defining the persistent volume (PV) in an object definition. The local volume provisioner looks for any file system or block volume devices at the paths specified in the defined resource.

Important

Manual provisioning of PVs includes the risk of potential data leaks across PV reuse when PVCs are deleted. The Local Storage Operator is recommended for automating the life cycle of devices when provisioning local PVs.

Prerequisites

Local disks are attached to the OpenShift Container Platform nodes.

Procedure

Define the PV. Create a file, such as example-pv-filesystem.yaml or example-pv-block.yaml, with the PersistentVolume object definition. This resource must define the nodes and paths to the local volumes.
Note
Do not use different storage class names for the same device. Doing so will create multiple PVs.
example-pv-filesystem.yaml
```
apiVersion: v1
kind: PersistentVolume
metadata:
  name: example-pv-filesystem
spec:
  capacity:
    storage: 100Gi
  volumeMode: Filesystem 1
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Delete
  storageClassName: local-storage 2
  local:
    path: /dev/xvdf 3
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - example-node
```
1
The volume mode, either Filesystem or Block, that defines the type of PVs.
2
The name of the storage class to use when creating PV resources. Use a storage class that uniquely identifies this set of PVs.
3
The path containing a list of local storage devices to choose from, or a directory. You can only specify a directory with Filesystem volumeMode.
Note
A raw block volume (volumeMode: block) is not formatted with a file system. Use this mode only if any application running on the pod can use raw block devices.
example-pv-block.yaml
```
apiVersion: v1
kind: PersistentVolume
metadata:
  name: example-pv-block
spec:
  capacity:
    storage: 100Gi
  volumeMode: Block 1
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Delete
  storageClassName: local-storage 2
  local:
    path: /dev/xvdf 3
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - example-node
```
1
The volume mode, either Filesystem or Block, that defines the type of PVs.
2
The name of the storage class to use when creating PV resources. Be sure to use a storage class that uniquely identifies this set of PVs.
3
The path containing a list of local storage devices to choose from.
Create the PV resource in your OpenShift Container Platform cluster. Specify the file you just created:
```
$ oc create -f <example-pv>.yaml
```

Verify that the local PV was created:

$ oc get pv

Example output

NAME                    CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM                STORAGECLASS    REASON   AGE
example-pv-filesystem   100Gi      RWO            Delete           Available                        local-storage            3m47s
example-pv1             1Gi        RWO            Delete           Bound       local-storage/pvc1   local-storage            12h
example-pv2             1Gi        RWO            Delete           Bound       local-storage/pvc2   local-storage            12h
example-pv3             1Gi        RWO            Delete           Bound       local-storage/pvc3   local-storage            12h

4.10.4. Creating the local volume persistent volume claim

Local volumes must be statically created as a persistent volume claim (PVC) to be accessed by the pod.

Prerequisites

Persistent volumes have been created using the local volume provisioner.

Procedure

Create the PVC using the corresponding storage class:

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: local-pvc-name 1
spec:
  accessModes:
  - ReadWriteOnce
  volumeMode: Filesystem 2
  resources:
    requests:
      storage: 100Gi 3
  storageClassName: local-sc 4

1: Name of the PVC.
2: The type of the PVC. Defaults to Filesystem.
3: The amount of storage available to the PVC.
4: Name of the storage class required by the claim.

Create the PVC in the OpenShift Container Platform cluster, specifying the file you just created:
```
$ oc create -f <local-pvc>.yaml
```

4.10.5. Attach the local claim

After a local volume has been mapped to a persistent volume claim it can be specified inside of a resource.

Prerequisites

A persistent volume claim exists in the same namespace.

Procedure

Include the defined claim in the resource spec. The following example declares the persistent volume claim inside a pod:
```
apiVersion: v1
kind: Pod
spec:
# ...
  containers:
    volumeMounts:
    - name: local-disks 1
      mountPath: /data 2
  volumes:
  - name: local-disks
    persistentVolumeClaim:
      claimName: local-pvc-name 3
# ...
```
1
The name of the volume to mount.
2
The path inside the pod where the volume is mounted. Do not mount to the container root, /, or any path that is the same in the host and the container. This can corrupt your host system if the container is sufficiently privileged, such as the host /dev/pts files. It is safe to mount the host by using /host.
3
The name of the existing persistent volume claim to use.
Create the resource in the OpenShift Container Platform cluster, specifying the file you just created:
```
$ oc create -f <local-pod>.yaml
```

4.10.6. Automating discovery and provisioning for local storage devices

The Local Storage Operator automates local storage discovery and provisioning. With this feature, you can simplify installation when dynamic provisioning is not available during deployment, such as with bare metal, VMware, or AWS store instances with attached devices.

Important

Automatic discovery and provisioning is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Important

Automatic discovery and provisioning is fully supported when used to deploy Red Hat OpenShift Data Foundation on-premise or with platform-agnostic deployment.

Use the following procedure to automatically discover local devices, and to automatically provision local volumes for selected devices.

Warning

Use the LocalVolumeSet object with caution. When you automatically provision persistent volumes (PVs) from local disks, the local PVs might claim all devices that match. If you are using a LocalVolumeSet object, make sure the Local Storage Operator is the only entity managing local devices on the node. Creating multiple instances of a LocalVolumeSet that target a node more than once is not supported.

Prerequisites

You have cluster administrator permissions.
You have installed the Local Storage Operator.
You have attached local disks to OpenShift Container Platform nodes.
You have access to the OpenShift Container Platform web console and the oc command-line interface (CLI).

Procedure

To enable automatic discovery of local devices from the web console:
1. In the Administrator perspective, navigate to Operators Installed Operators and click on the Local Volume Discovery tab.
2. Click Create Local Volume Discovery.
3. Select either All nodes or Select nodes, depending on whether you want to discover available disks on all or specific nodes.
  Note
  Only worker nodes are available, regardless of whether you filter using All nodes or Select nodes.
4. Click Create.

A local volume discovery instance named auto-discover-devices is displayed.

To display a continuous list of available devices on a node:
1. Log in to the OpenShift Container Platform web console.
2. Navigate to Compute Nodes.
3. Click the node name that you want to open. The "Node Details" page is displayed.
4. Select the Disks tab to display the list of the selected devices.
  The device list updates continuously as local disks are added or removed. You can filter the devices by name, status, type, model, capacity, and mode.
To automatically provision local volumes for the discovered devices from the web console:
1. Navigate to Operators Installed Operators and select Local Storage from the list of Operators.
2. Select Local Volume Set Create Local Volume Set.
3. Enter a volume set name and a storage class name.
4. Choose All nodes or Select nodes to apply filters accordingly.
  Note
  Only worker nodes are available, regardless of whether you filter using All nodes or Select nodes.
5. Select the disk type, mode, size, and limit you want to apply to the local volume set, and click Create.
  A message displays after several minutes, indicating that the "Operator reconciled successfully."

Alternatively, to provision local volumes for the discovered devices from the CLI:

Create an object YAML file to define the local volume set, such as local-volume-set.yaml, as shown in the following example:

apiVersion: local.storage.openshift.io/v1alpha1
kind: LocalVolumeSet
metadata:
  name: example-autodetect
spec:
  nodeSelector:
    nodeSelectorTerms:
      - matchExpressions:
          - key: kubernetes.io/hostname
            operator: In
            values:
              - worker-0
              - worker-1
  storageClassName: example-storageclass 1
  volumeMode: Filesystem
  fsType: ext4
  maxDeviceCount: 10
  deviceInclusionSpec:
    deviceTypes: 2
      - disk
      - part
    deviceMechanicalProperties:
      - NonRotational
    minSize: 10G
    maxSize: 100G
    models:
      - SAMSUNG
      - Crucial_CT525MX3
    vendors:
      - ATA
      - ST2000LM

1: Determines the storage class that is created for persistent volumes that are provisioned from discovered devices. The Local Storage Operator automatically creates the storage class if it does not exist. Be sure to use a storage class that uniquely identifies this set of local volumes.
2: When using the local volume set feature, the Local Storage Operator does not support the use of logical volume management (LVM) devices.

Create the local volume set object:
```
$ oc apply -f local-volume-set.yaml
```

Verify that the local persistent volumes were dynamically provisioned based on the storage class:

$ oc get pv

Example output

NAME                CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS           REASON   AGE
local-pv-1cec77cf   100Gi      RWO            Delete           Available           example-storageclass            88m
local-pv-2ef7cd2a   100Gi      RWO            Delete           Available           example-storageclass            82m
local-pv-3fa1c73    100Gi      RWO            Delete           Available           example-storageclass            48m

Note

Results are deleted after they are removed from the node. Symlinks must be manually removed.

4.10.7. Using tolerations with Local Storage Operator pods

Taints can be applied to nodes to prevent them from running general workloads. To allow the Local Storage Operator to use tainted nodes, you must add tolerations to the Pod or DaemonSet definition. This allows the created resources to run on these tainted nodes.

You apply tolerations to the Local Storage Operator pod through the LocalVolume resource and apply taints to a node through the node specification. A taint on a node instructs the node to repel all pods that do not tolerate the taint. Using a specific taint that is not on other pods ensures that the Local Storage Operator pod can also run on that node.

Important

Taints and tolerations consist of a key, value, and effect. As an argument, it is expressed as key=value:effect. An operator allows you to leave one of these parameters empty.

Prerequisites

The Local Storage Operator is installed.
Local disks are attached to OpenShift Container Platform nodes with a taint.
Tainted nodes are expected to provision local storage.

Procedure

To configure local volumes for scheduling on tainted nodes:

Modify the YAML file that defines the Pod and add the LocalVolume spec, as shown in the following example:
```
  apiVersion: "local.storage.openshift.io/v1"
  kind: "LocalVolume"
  metadata:
    name: "local-disks"
    namespace: "openshift-local-storage"
  spec:
    tolerations:
      - key: localstorage 1
        operator: Equal 2
        value: "localstorage" 3
    storageClassDevices:
        - storageClassName: "localblock-sc"
          volumeMode: Block 4
          devicePaths: 5
            - /dev/xvdg
```
1
Specify the key that you added to the node.
2
Specify the Equal operator to require the key/value parameters to match. If operator is Exists, the system checks that the key exists and ignores the value. If operator is Equal, then the key and value must match.
3
Specify the value local of the tainted node.
4
The volume mode, either Filesystem or Block, defining the type of the local volumes.
5
The path containing a list of local storage devices to choose from.
Optional: To create local persistent volumes on only tainted nodes, modify the YAML file and add the LocalVolume spec, as shown in the following example:
```
spec:
  tolerations:
    - key: node-role.kubernetes.io/master
      operator: Exists
```

The defined tolerations will be passed to the resulting daemon sets, allowing the diskmaker and provisioner pods to be created for nodes that contain the specified taints.

4.10.8. Local Storage Operator Metrics

OpenShift Container Platform provides the following metrics for the Local Storage Operator:

lso_discovery_disk_count: total number of discovered devices on each node
lso_lvset_provisioned_PV_count: total number of PVs created by LocalVolumeSet objects
lso_lvset_unmatched_disk_count: total number of disks that Local Storage Operator did not select for provisioning because of mismatching criteria
lso_lvset_orphaned_symlink_count: number of devices with PVs that no longer match LocalVolumeSet object criteria
lso_lv_orphaned_symlink_count: number of devices with PVs that no longer match LocalVolume object criteria
lso_lv_provisioned_PV_count: total number of provisioned PVs for LocalVolume

To use these metrics, be sure to:

Enable support for monitoring when installing the Local Storage Operator.
When upgrading to OpenShift Container Platform 4.9 or later, enable metric support manually by adding the operator-metering=true label to the namespace.

For more information about metrics, see Managing metrics.

4.10.9. Deleting the Local Storage Operator resources

4.10.9.1. Removing a local volume or local volume set

Occasionally, local volumes and local volume sets must be deleted. While removing the entry in the resource and deleting the persistent volume is typically enough, if you want to reuse the same device path or have it managed by a different storage class, then additional steps are needed.

Note

The following procedure outlines an example for removing a local volume. The same procedure can also be used to remove symlinks for a local volume set custom resource.

Prerequisites

The persistent volume must be in a Released or Available state.
Warning
Deleting a persistent volume that is still in use can result in data loss or corruption.

Procedure

Edit the previously created local volume to remove any unwanted disks.
1. Edit the cluster resource:
```
$ oc edit localvolume <name> -n openshift-local-storage
```
2. Navigate to the lines under devicePaths, and delete any representing unwanted disks.
Delete any persistent volumes created.
```
$ oc delete pv <pv-name>
```
Delete directory and included symlinks on the node.
Warning
The following step involves accessing a node as the root user. Modifying the state of the node beyond the steps in this procedure could result in cluster instability.
```
$ oc debug node/<node-name> -- chroot /host rm -rf /mnt/local-storage/<sc-name> 1
```
1
The name of the storage class used to create the local volumes.

4.10.9.2. Uninstalling the Local Storage Operator

To uninstall the Local Storage Operator, you must remove the Operator and all created resources in the openshift-local-storage project.

Warning

Uninstalling the Local Storage Operator while local storage PVs are still in use is not recommended. While the PVs will remain after the Operator’s removal, there might be indeterminate behavior if the Operator is uninstalled and reinstalled without removing the PVs and local storage resources.

Prerequisites

Access to the OpenShift Container Platform web console.

Procedure

Delete any local volume resources installed in the project, such as localvolume, localvolumeset, and localvolumediscovery:

$ oc delete localvolume --all --all-namespaces
$ oc delete localvolumeset --all --all-namespaces
$ oc delete localvolumediscovery --all --all-namespaces

Uninstall the Local Storage Operator from the web console.
1. Log in to the OpenShift Container Platform web console.
2. Navigate to Operators Installed Operators.
3. Type Local Storage into the filter box to locate the Local Storage Operator.
4. Click the Options menu at the end of the Local Storage Operator.
5. Click Uninstall Operator.
6. Click Remove in the window that appears.
The PVs created by the Local Storage Operator will remain in the cluster until deleted. After these volumes are no longer in use, delete them by running the following command:
```
$ oc delete pv <pv-name>
```

Delete the openshift-local-storage project:

$ oc delete project openshift-local-storage

4.11. Persistent storage using NFS

OpenShift Container Platform clusters can be provisioned with persistent storage using NFS. Persistent volumes (PVs) and persistent volume claims (PVCs) provide a convenient method for sharing a volume across a project. While the NFS-specific information contained in a PV definition could also be defined directly in a Pod definition, doing so does not create the volume as a distinct cluster resource, making the volume more susceptible to conflicts.

Additional resources

Mounting NFS shares

4.11.1. Provisioning

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform. To provision NFS volumes, a list of NFS servers and export paths are all that is required.

Procedure

Create an object definition for the PV:
```
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv0001 1
spec:
  capacity:
    storage: 5Gi 2
  accessModes:
  - ReadWriteOnce 3
  nfs: 4
    path: /tmp 5
    server: 172.17.0.2 6
  persistentVolumeReclaimPolicy: Retain 7
```
1
The name of the volume. This is the PV identity in various oc <command> pod commands.
2
The amount of storage allocated to this volume.
3
Though this appears to be related to controlling access to the volume, it is actually used similarly to labels and used to match a PVC to a PV. Currently, no access rules are enforced based on the accessModes.
4
The volume type being used, in this case the nfs plugin.
5
The path that is exported by the NFS server.
6
The hostname or IP address of the NFS server.
7
The reclaim policy for the PV. This defines what happens to a volume when released.
Note
Each NFS volume must be mountable by all schedulable nodes in the cluster.

Verify that the PV was created:

$ oc get pv

Example output

NAME     LABELS    CAPACITY     ACCESSMODES   STATUS      CLAIM  REASON    AGE
pv0001   <none>    5Gi          RWO           Available                    31s

Create a persistent volume claim that binds to the new PV:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-claim1
spec:
  accessModes:
    - ReadWriteOnce 1
  resources:
    requests:
      storage: 5Gi 2
  volumeName: pv0001
  storageClassName: ""

1: The access modes do not enforce security, but rather act as labels to match a PV to a PVC.
2: This claim looks for PVs offering 5Gi or greater capacity.

Verify that the persistent volume claim was created:

$ oc get pvc

Example output

NAME         STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
nfs-claim1   Bound    pv0001   5Gi        RWO                           2m

4.11.2. Enforcing disk quotas

You can use disk partitions to enforce disk quotas and size constraints. Each partition can be its own export. Each export is one PV. OpenShift Container Platform enforces unique names for PVs, but the uniqueness of the NFS volume’s server and path is up to the administrator.

Enforcing quotas in this way allows the developer to request persistent storage by a specific amount, such as 10Gi, and be matched with a corresponding volume of equal or greater capacity.

4.11.3. NFS volume security

This section covers NFS volume security, including matching permissions and SELinux considerations. The user is expected to understand the basics of POSIX permissions, process UIDs, supplemental groups, and SELinux.

Developers request NFS storage by referencing either a PVC by name or the NFS volume plugin directly in the volumes section of their Pod definition.

The /etc/exports file on the NFS server contains the accessible NFS directories. The target NFS directory has POSIX owner and group IDs. The OpenShift Container Platform NFS plugin mounts the container’s NFS directory with the same POSIX ownership and permissions found on the exported NFS directory. However, the container is not run with its effective UID equal to the owner of the NFS mount, which is the desired behavior.

As an example, if the target NFS directory appears on the NFS server as:

$ ls -lZ /opt/nfs -d

Example output

drwxrws---. nfsnobody 5555 unconfined_u:object_r:usr_t:s0   /opt/nfs

$ id nfsnobody

Example output

uid=65534(nfsnobody) gid=65534(nfsnobody) groups=65534(nfsnobody)

Then the container must match SELinux labels, and either run with a UID of 65534, the nfsnobody owner, or with 5555 in its supplemental groups to access the directory.

Note

The owner ID of 65534 is used as an example. Even though NFS’s root_squash maps root, uid 0, to nfsnobody, uid 65534, NFS exports can have arbitrary owner IDs. Owner 65534 is not required for NFS exports.

4.11.3.1. Group IDs

The recommended way to handle NFS access, assuming it is not an option to change permissions on the NFS export, is to use supplemental groups. Supplemental groups in OpenShift Container Platform are used for shared storage, of which NFS is an example. In contrast, block storage such as iSCSI uses the fsGroup SCC strategy and the fsGroup value in the securityContext of the pod.

Note

To gain access to persistent storage, it is generally preferable to use supplemental group IDs versus user IDs.

Because the group ID on the example target NFS directory is 5555, the pod can define that group ID using supplementalGroups under the securityContext definition of the pod. For example:

spec:
  containers:
    - name:
    ...
  securityContext: 1
    supplementalGroups: [5555] 2

1: securityContext must be defined at the pod level, not under a specific container.
2: An array of GIDs defined for the pod. In this case, there is one element in the array. Additional GIDs would be comma-separated.

Assuming there are no custom SCCs that might satisfy the pod requirements, the pod likely matches the restricted SCC. This SCC has the supplementalGroups strategy set to RunAsAny, meaning that any supplied group ID is accepted without range checking.

As a result, the above pod passes admissions and is launched. However, if group ID range checking is desired, a custom SCC is the preferred solution. A custom SCC can be created such that minimum and maximum group IDs are defined, group ID range checking is enforced, and a group ID of 5555 is allowed.

Note

To use a custom SCC, you must first add it to the appropriate service account. For example, use the default service account in the given project unless another has been specified on the Pod specification.

4.11.3.2. User IDs

User IDs can be defined in the container image or in the Pod definition.

Note

It is generally preferable to use supplemental group IDs to gain access to persistent storage versus using user IDs.

In the example target NFS directory shown above, the container needs its UID set to 65534, ignoring group IDs for the moment, so the following can be added to the Pod definition:

spec:
  containers: 1
  - name:
  ...
    securityContext:
      runAsUser: 65534 2

1: Pods contain a securityContext definition specific to each container and a pod’s securityContext which applies to all containers defined in the pod.
2: 65534 is the nfsnobody user.

Assuming that the project is default and the SCC is restricted, the user ID of 65534 as requested by the pod is not allowed. Therefore, the pod fails for the following reasons:

It requests 65534 as its user ID.
All SCCs available to the pod are examined to see which SCC allows a user ID of 65534. While all policies of the SCCs are checked, the focus here is on user ID.
Because all available SCCs use MustRunAsRange for their runAsUser strategy, UID range checking is required.
65534 is not included in the SCC or project’s user ID range.

It is generally considered a good practice not to modify the predefined SCCs. The preferred way to fix this situation is to create a custom SCC A custom SCC can be created such that minimum and maximum user IDs are defined, UID range checking is still enforced, and the UID of 65534 is allowed.

Note

To use a custom SCC, you must first add it to the appropriate service account. For example, use the default service account in the given project unless another has been specified on the Pod specification.

4.11.3.3. SELinux

Red Hat Enterprise Linux (RHEL) and Red Hat Enterprise Linux CoreOS (RHCOS) systems are configured to use SELinux on remote NFS servers by default.

For non-RHEL and non-RHCOS systems, SELinux does not allow writing from a pod to a remote NFS server. The NFS volume mounts correctly but it is read-only. You will need to enable the correct SELinux permissions by using the following procedure.

Prerequisites

The container-selinux package must be installed. This package provides the virt_use_nfs SELinux boolean.

Procedure

Enable the virt_use_nfs boolean using the following command. The -P option makes this boolean persistent across reboots.
```
# setsebool -P virt_use_nfs 1
```

4.11.3.4. Export settings

To enable arbitrary container users to read and write the volume, each exported volume on the NFS server should conform to the following conditions:

Every export must be exported using the following format:
```
/<example_fs> *(rw,root_squash)
```
The firewall must be configured to allow traffic to the mount point.
- For NFSv4, configure the default port 2049 (nfs).
  NFSv4
```
# iptables -I INPUT 1 -p tcp --dport 2049 -j ACCEPT
```
- For NFSv3, there are three ports to configure: 2049 (nfs), 20048 (mountd), and 111 (portmapper).
  NFSv3
```
# iptables -I INPUT 1 -p tcp --dport 2049 -j ACCEPT
```
```
# iptables -I INPUT 1 -p tcp --dport 20048 -j ACCEPT
```
```
# iptables -I INPUT 1 -p tcp --dport 111 -j ACCEPT
```
The NFS export and directory must be set up so that they are accessible by the target pods. Either set the export to be owned by the container’s primary UID, or supply the pod group access using supplementalGroups, as shown in the group IDs above.

4.11.4. Reclaiming resources

NFS implements the OpenShift Container Platform Recyclable plugin interface. Automatic processes handle reclamation tasks based on policies set on each persistent volume.

By default, PVs are set to Retain.

Once claim to a PVC is deleted, and the PV is released, the PV object should not be reused. Instead, a new PV should be created with the same basic volume details as the original.

For example, the administrator creates a PV named nfs1:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs1
spec:
  capacity:
    storage: 1Mi
  accessModes:
    - ReadWriteMany
  nfs:
    server: 192.168.1.1
    path: "/"

The user creates PVC1, which binds to nfs1. The user then deletes PVC1, releasing claim to nfs1. This results in nfs1 being Released. If the administrator wants to make the same NFS share available, they should create a new PV with the same NFS server details, but a different PV name:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs2
spec:
  capacity:
    storage: 1Mi
  accessModes:
    - ReadWriteMany
  nfs:
    server: 192.168.1.1
    path: "/"

Deleting the original PV and re-creating it with the same name is discouraged. Attempting to manually change the status of a PV from Released to Available causes errors and potential data loss.

4.11.5. Additional configuration and troubleshooting

Depending on what version of NFS is being used and how it is configured, there may be additional configuration steps needed for proper export and security mapping. The following are some that may apply:

NFSv4 mount incorrectly shows all files with ownership of `nobody:nobody`	Could be attributed to the ID mapping settings, found in `/etc/idmapd.conf` on your NFS. See this Red Hat Solution.
Disabling ID mapping on NFSv4	On both the NFS client and server, run: # echo 'Y' > /sys/module/nfsd/parameters/nfs4_disable_idmapping

4.12. Red Hat OpenShift Data Foundation

Red Hat OpenShift Data Foundation is a provider of agnostic persistent storage for OpenShift Container Platform supporting file, block, and object storage, either in-house or in hybrid clouds. As a Red Hat storage solution, Red Hat OpenShift Data Foundation is completely integrated with OpenShift Container Platform for deployment, management, and monitoring.

Red Hat OpenShift Data Foundation provides its own documentation library. The complete set of Red Hat OpenShift Data Foundation documentation is available at https://access.redhat.com/documentation/en-us/red_hat_openshift_data_foundation.

Important

OpenShift Data Foundation on top of Red Hat Hyperconverged Infrastructure (RHHI) for Virtualization, which uses hyperconverged nodes that host virtual machines installed with OpenShift Container Platform, is not a supported configuration. For more information about supported platforms, see the Red Hat OpenShift Data Foundation Supportability and Interoperability Guide.

4.13. Persistent storage using VMware vSphere volumes

OpenShift Container Platform allows use of VMware vSphere’s Virtual Machine Disk (VMDK) volumes. You can provision your OpenShift Container Platform cluster with persistent storage using VMware vSphere. Some familiarity with Kubernetes and VMware vSphere is assumed.

VMware vSphere volumes can be provisioned dynamically. OpenShift Container Platform creates the disk in vSphere and attaches this disk to the correct image.

Note

OpenShift Container Platform provisions new volumes as independent persistent disks that can freely attach and detach the volume on any node in the cluster. Consequently, you cannot back up volumes that use snapshots, or restore volumes from snapshots. See Snapshot Limitations for more information.

The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure.

Persistent volumes are not bound to a single project or namespace; they can be shared across the OpenShift Container Platform cluster. Persistent volume claims are specific to a project or namespace and can be requested by users.

Important

OpenShift Container Platform defaults to using an in-tree (non-CSI) plugin to provision vSphere storage.

In future OpenShift Container Platform versions, volumes provisioned using existing in-tree plugins are planned for migration to their equivalent CSI driver. CSI automatic migration should be seamless. Migration does not change how you use all existing API objects, such as persistent volumes, persistent volume claims, and storage classes. For more information about migration, see CSI automatic migration.

After full migration, in-tree plugins will eventually be removed in future versions of OpenShift Container Platform.

Additional resources

VMware vSphere

4.13.1. Dynamically provisioning VMware vSphere volumes

Dynamically provisioning VMware vSphere volumes is the recommended method.

4.13.2. Prerequisites

An OpenShift Container Platform cluster installed on a VMware vSphere version that meets the requirements for the components that you use. See Installing a cluster on vSphere for information about vSphere version support.

You can use either of the following procedures to dynamically provision these volumes using the default storage class.

4.13.2.1. Dynamically provisioning VMware vSphere volumes using the UI

OpenShift Container Platform installs a default storage class, named thin, that uses the thin disk format for provisioning volumes.

Prerequisites

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform.

Procedure

In the OpenShift Container Platform console, click Storage Persistent Volume Claims.
In the persistent volume claims overview, click Create Persistent Volume Claim.
Define the required options on the resulting page.
1. Select the thin storage class.
2. Enter a unique name for the storage claim.
3. Select the access mode to determine the read and write access for the created storage claim.
4. Define the size of the storage claim.
Click Create to create the persistent volume claim and generate a persistent volume.

4.13.2.2. Dynamically provisioning VMware vSphere volumes using the CLI

OpenShift Container Platform installs a default StorageClass, named thin, that uses the thin disk format for provisioning volumes.

Prerequisites

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform.

Procedure (CLI)

You can define a VMware vSphere PersistentVolumeClaim by creating a file, pvc.yaml, with the following contents:
```
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: pvc 1
spec:
  accessModes:
  - ReadWriteOnce 2
  resources:
    requests:
      storage: 1Gi 3
```
1
A unique name that represents the persistent volume claim.
2
The access mode of the persistent volume claim. With ReadWriteOnce, the volume can be mounted with read and write permissions by a single node.
3
The size of the persistent volume claim.
Enter the following command to create the PersistentVolumeClaim object from the file:
```
$ oc create -f pvc.yaml
```

4.13.3. Statically provisioning VMware vSphere volumes

To statically provision VMware vSphere volumes you must create the virtual machine disks for reference by the persistent volume framework.

Prerequisites

Storage must exist in the underlying infrastructure before it can be mounted as a volume in OpenShift Container Platform.

Procedure

Create the virtual machine disks. Virtual machine disks (VMDKs) must be created manually before statically provisioning VMware vSphere volumes. Use either of the following methods:
- Create using vmkfstools. Access ESX through Secure Shell (SSH) and then use following command to create a VMDK volume:
```
$ vmkfstools -c <size> /vmfs/volumes/<datastore-name>/volumes/<disk-name>.vmdk
```
- Create using vmware-diskmanager:
```
$ shell vmware-vdiskmanager -c -t 0 -s <size> -a lsilogic <disk-name>.vmdk
```
Create a persistent volume that references the VMDKs. Create a file, pv1.yaml, with the PersistentVolume object definition:
```
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv1 1
spec:
  capacity:
    storage: 1Gi 2
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  vsphereVolume: 3
    volumePath: "[datastore1] volumes/myDisk"  4
    fsType: ext4  5
```
1
The name of the volume. This name is how it is identified by persistent volume claims or pods.
2
The amount of storage allocated to this volume.
3
The volume type used, with vsphereVolume for vSphere volumes. The label is used to mount a vSphere VMDK volume into pods. The contents of a volume are preserved when it is unmounted. The volume type supports VMFS and VSAN datastore.
4
The existing VMDK volume to use. If you used vmkfstools, you must enclose the datastore name in square brackets, [], in the volume definition, as shown previously.
5
The file system type to mount. For example, ext4, xfs, or other file systems.
Important
Changing the value of the fsType parameter after the volume is formatted and provisioned can result in data loss and pod failure.
Create the PersistentVolume object from the file:
```
$ oc create -f pv1.yaml
```
Create a persistent volume claim that maps to the persistent volume you created in the previous step. Create a file, pvc1.yaml, with the PersistentVolumeClaim object definition:
```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc1 1
spec:
  accessModes:
    - ReadWriteOnce 2
  resources:
   requests:
     storage: "1Gi" 3
  volumeName: pv1 4
```
1
A unique name that represents the persistent volume claim.
2
The access mode of the persistent volume claim. With ReadWriteOnce, the volume can be mounted with read and write permissions by a single node.
3
The size of the persistent volume claim.
4
The name of the existing persistent volume.
Create the PersistentVolumeClaim object from the file:
```
$ oc create -f pvc1.yaml
```

4.13.3.1. Formatting VMware vSphere volumes

Before OpenShift Container Platform mounts the volume and passes it to a container, it checks that the volume contains a file system that is specified by the fsType parameter value in the PersistentVolume (PV) definition. If the device is not formatted with the file system, all data from the device is erased, and the device is automatically formatted with the specified file system.

Because OpenShift Container Platform formats them before the first use, you can use unformatted vSphere volumes as PVs.

4.1. Persistent storage using AWS Elastic Block Store

4.1.1. Creating the EBS storage class

4.1.2. Creating the persistent volume claim

4.1.3. Volume format

4.1.4. Maximum number of EBS volumes on a node

4.1.5. Encrypting container persistent volumes on AWS with a KMS key

4.1.6. Additional resources

4.2. Persistent storage using Azure

4.2.1. Creating the Azure storage class

4.2.2. Creating the persistent volume claim

4.2.3. Volume format

4.2.4. Machine sets that deploy machines with ultra disks using PVCs

4.2.4.1. Creating machines with ultra disks by using machine sets

4.2.4.2. Troubleshooting resources for machine sets that enable ultra disks

4.2.4.2.1. Unable to mount a persistent volume claim backed by an ultra disk

4.3. Persistent storage using Azure File

4.3.1. Create the Azure File share persistent volume claim

4.3.2. Mount the Azure File share in a pod

4.4. Persistent storage using Cinder

4.4.1. Manual provisioning with Cinder

4.4.1.1. Creating the persistent volume

4.4.1.2. Persistent volume formatting

4.4.1.3. Cinder volume security

4.5. Persistent storage using Fibre Channel

4.5.1. Provisioning

4.5.1.1. Enforcing disk quotas

4.5.1.2. Fibre Channel volume security

4.6. Persistent storage using FlexVolume

4.6.1. About FlexVolume drivers

4.6.2. FlexVolume driver example

4.6.3. Installing FlexVolume drivers

4.6.4. Consuming storage using FlexVolume drivers

4.7. Persistent storage using GCE Persistent Disk

4.7.1. Creating the GCE storage class

4.7.2. Creating the persistent volume claim

4.7.3. Volume format

4.8. Persistent storage using hostPath

4.8.1. Overview

4.8.2. Statically provisioning hostPath volumes

4.8.3. Mounting the hostPath share in a privileged pod

4.9. Persistent storage using iSCSI

4.9.1. Provisioning

4.9.2. Enforcing disk quotas

4.9.3. iSCSI volume security

4.9.3.1. Challenge Handshake Authentication Protocol (CHAP) configuration

4.9.4. iSCSI multipathing

4.9.5. iSCSI custom initiator IQN

4.10. Persistent storage using local volumes

4.10.1. Installing the Local Storage Operator

4.10.2. Provisioning local volumes by using the Local Storage Operator

4.10.3. Provisioning local volumes without the Local Storage Operator

4.10.4. Creating the local volume persistent volume claim

4.10.5. Attach the local claim

4.10.6. Automating discovery and provisioning for local storage devices

4.10.7. Using tolerations with Local Storage Operator pods

4.10.8. Local Storage Operator Metrics

4.10.9. Deleting the Local Storage Operator resources

4.10.9.1. Removing a local volume or local volume set

4.10.9.2. Uninstalling the Local Storage Operator

4.11. Persistent storage using NFS

4.11.1. Provisioning

4.11.2. Enforcing disk quotas

4.11.3. NFS volume security

4.11.3.1. Group IDs

4.11.3.2. User IDs

4.11.3.3. SELinux

4.11.3.4. Export settings

4.11.4. Reclaiming resources

4.11.5. Additional configuration and troubleshooting

4.12. Red Hat OpenShift Data Foundation

4.13. Persistent storage using VMware vSphere volumes

4.13.1. Dynamically provisioning VMware vSphere volumes

4.13.2. Prerequisites

4.13.2.1. Dynamically provisioning VMware vSphere volumes using the UI

4.13.2.2. Dynamically provisioning VMware vSphere volumes using the CLI

4.13.3. Statically provisioning VMware vSphere volumes

4.13.3.1. Formatting VMware vSphere volumes

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