PLEASE NOTE: This document applies to an unreleased version of Rook. It is strongly recommended that you only use official releases of Rook, as unreleased versions are subject to changes and incompatibilities that will not be supported in the official releases.

    If you are using an official release version of Rook, you should refer to the documentation for your specific version.

    Documentation for other releases can be found by using the version selector in the bottom left of any doc page.

    Shared Filesystem

    A shared filesystem can be mounted with read/write permission from multiple pods. This may be useful for applications which can be clustered using a shared filesystem.

    This example runs a shared filesystem for the kube-registry.


    This guide assumes you have created a Rook cluster as explained in the main Kubernetes guide

    Multiple Filesystems Support

    Multiple filesystems are supported as of the Ceph Pacific release.

    Create the Filesystem

    Create the filesystem by specifying the desired settings for the metadata pool, data pools, and metadata server in the CephFilesystem CRD. In this example we create the metadata pool with replication of three and a single data pool with replication of three. For more options, see the documentation on creating shared filesystems.

    Save this shared filesystem definition as filesystem.yaml:

    kind: CephFilesystem
      name: myfs
      namespace: rook-ceph
          size: 3
        - replicated:
            size: 3
      preserveFilesystemOnDelete: true
        activeCount: 1
        activeStandby: true

    The Rook operator will create all the pools and other resources necessary to start the service. This may take a minute to complete.

    # Create the filesystem
    kubectl create -f filesystem.yaml
    # To confirm the filesystem is configured, wait for the mds pods to start
    kubectl -n rook-ceph get pod -l app=rook-ceph-mds
    NAME                                      READY     STATUS    RESTARTS   AGE
    rook-ceph-mds-myfs-7d59fdfcf4-h8kw9       1/1       Running   0          12s
    rook-ceph-mds-myfs-7d59fdfcf4-kgkjp       1/1       Running   0          12s

    To see detailed status of the filesystem, start and connect to the Rook toolbox. A new line will be shown with ceph status for the mds service. In this example, there is one active instance of MDS which is up, with one MDS instance in standby-replay mode in case of failover.

    ceph status
       mds: myfs-1/1/1 up {[myfs:0]=mzw58b=up:active}, 1 up:standby-replay

    Provision Storage

    Before Rook can start provisioning storage, a StorageClass needs to be created based on the filesystem. This is needed for Kubernetes to interoperate with the CSI driver to create persistent volumes.

    NOTE: This example uses the CSI driver, which is the preferred driver going forward for K8s 1.13 and newer. Examples are found in the CSI CephFS directory. For an example of a volume using the flex driver (required for K8s 1.12 and earlier), see the Flex Driver section below.

    Save this storage class definition as storageclass.yaml:

    kind: StorageClass
      name: rook-cephfs
    # Change "rook-ceph" provisioner prefix to match the operator namespace if needed
      # clusterID is the namespace where operator is deployed.
      clusterID: rook-ceph
      # CephFS filesystem name into which the volume shall be created
      fsName: myfs
      # Ceph pool into which the volume shall be created
      # Required for provisionVolume: "true"
      pool: myfs-data0
      # The secrets contain Ceph admin credentials. These are generated automatically by the operator
      # in the same namespace as the cluster. rook-csi-cephfs-provisioner rook-ceph rook-csi-cephfs-provisioner rook-ceph rook-csi-cephfs-node rook-ceph
    reclaimPolicy: Delete

    If you’ve deployed the Rook operator in a namespace other than “rook-ceph” as is common change the prefix in the provisioner to match the namespace you used. For example, if the Rook operator is running in “rook-op” the provisioner value should be “”.

    Create the storage class.

    kubectl create -f cluster/examples/kubernetes/ceph/csi/cephfs/storageclass.yaml


    Since Ceph Pacific, CephFS supports asynchronous replication of snapshots to a remote CephFS file system via cephfs-mirror tool. Snapshots are synchronized by mirroring snapshot data followed by creating a snapshot with the same name (for a given directory on the remote file system) as the snapshot being synchronized. It is generally useful when planning for Disaster Recovery. For clusters that are geographically distributed and stretching is not possible due to high latencies.

    kind: CephFilesystem
      name: myfs
      namespace: rook-ceph
        enabled: true


    IMPORTANT: The CephFS CSI driver uses quotas to enforce the PVC size requested. Only newer kernels support CephFS quotas (kernel version of at least 4.17). If you require quotas to be enforced and the kernel driver does not support it, you can disable the kernel driver and use the FUSE client. This can be done by setting CSI_FORCE_CEPHFS_KERNEL_CLIENT: false in the operator deployment (operator.yaml). However, it is important to know that when the FUSE client is enabled, there is an issue that during upgrade the application pods will be disconnected from the mount and will need to be restarted. See the upgrade guide for more details.

    Consume the Shared Filesystem: K8s Registry Sample

    As an example, we will start the kube-registry pod with the shared filesystem as the backing store. Save the following spec as kube-registry.yaml:

    apiVersion: v1
    kind: PersistentVolumeClaim
      name: cephfs-pvc
      namespace: kube-system
      - ReadWriteMany
          storage: 1Gi
      storageClassName: rook-cephfs
    apiVersion: apps/v1
    kind: Deployment
      name: kube-registry
      namespace: kube-system
        k8s-app: kube-registry "true"
      replicas: 3
          k8s-app: kube-registry
            k8s-app: kube-registry
          - name: registry
            image: registry:2
            imagePullPolicy: Always
                cpu: 100m
                memory: 100Mi
            # Configuration reference:
            - name: REGISTRY_HTTP_ADDR
              value: :5000
            - name: REGISTRY_HTTP_SECRET
              value: "Ple4seCh4ngeThisN0tAVerySecretV4lue"
              value: /var/lib/registry
            - name: image-store
              mountPath: /var/lib/registry
            - containerPort: 5000
              name: registry
              protocol: TCP
                path: /
                port: registry
                path: /
                port: registry
          - name: image-store
              claimName: cephfs-pvc
              readOnly: false

    Create the Kube registry deployment:

    kubectl create -f cluster/examples/kubernetes/ceph/csi/cephfs/kube-registry.yaml

    You now have a docker registry which is HA with persistent storage.

    Kernel Version Requirement

    If the Rook cluster has more than one filesystem and the application pod is scheduled to a node with kernel version older than 4.7, inconsistent results may arise since kernels older than 4.7 do not support specifying filesystem namespaces.

    Consume the Shared Filesystem: Toolbox

    Once you have pushed an image to the registry (see the instructions to expose and use the kube-registry), verify that kube-registry is using the filesystem that was configured above by mounting the shared filesystem in the toolbox pod. See the Direct Filesystem topic for more details.


    To clean up all the artifacts created by the filesystem demo:

    kubectl delete -f kube-registry.yaml

    To delete the filesystem components and backing data, delete the Filesystem CRD.

    WARNING: Data will be deleted if preserveFilesystemOnDelete=false.

    kubectl -n rook-ceph delete cephfilesystem myfs

    Note: If the “preserveFilesystemOnDelete” filesystem attribute is set to true, the above command won’t delete the filesystem. Recreating the same CRD will reuse the existing filesystem.

    Flex Driver

    To create a volume based on the flex driver instead of the CSI driver, see the kube-registry.yaml example manifest or refer to the complete flow in the Rook v1.0 Shared Filesystem documentation.

    Advanced Example: Erasure Coded Filesystem

    The Ceph filesystem example can be found here: Ceph Shared Filesystem - Samples - Erasure Coded.