Deploy Ceph RBD Storage in Kubernetes: Step‑by‑Step Guide

Using RBD as Storage in Kubernetes

To use RBD as a backend storage for Kubernetes, first install

ceph-common

on the nodes.

1. Create RBD in Ceph Cluster

Prepare a pool and an image in the Ceph cluster before using it in Kubernetes.

<code># ceph osd pool create pool01
# ceph osd pool application enable pool01 rbd
# rbd pool init pool01
# rbd create pool01/test --size 10G --image-format 2 --image-feature layering
# rbd info pool01/test
</code>

2. Write Kubernetes YAML Files

Define a Deployment that mounts the RBD image.

<code>apiVersion: apps/v1
kind: Deployment
metadata:
  name: rbd
spec:
  replicas: 1
  selector:
    matchLabels:
      app: rbd
  template:
    metadata:
      labels:
        app: rbd
    spec:
      volumes:
      - name: test
        rbd:
          fsType: xfs
          image: test
          pool: pool01
          user: admin
          keyring: /root/admin.keyring
          monitors:
          - 192.168.200.230:6789
          readOnly: false
      containers:
      - name: nginx
        image: nginx
        imagePullPolicy: IfNotPresent
        volumeMounts:
        - name: test
          mountPath: /usr/share/nginx/html
</code>

Apply the manifest and verify the pod is running:

<code># kubectl get pods
NAME                     READY   STATUS    RESTARTS   AGE
rbd-888b8b747-n56wr      1/1     Running   0         26m
</code>

If the pod stays in

ContainerCreating

, ensure

ceph-common

is installed and the

keyring

and

ceph.conf

are available on the node.

2.1 Enter the Container to Check Mount

<code># kubectl exec -it rbd-5db4759c-nj2b4 -- bash
root@rbd-5db4759c-nj2b4:/# df -hT | grep /dev/rbd0
/dev/rbd0  xfs  10G  105M  9.9G  2% /usr/share/nginx/html
</code>

The RBD device is formatted as XFS and mounted at

/usr/share/nginx/html

.

2.2 Modify Content Inside the Container

<code># cd /usr/share/nginx/html
# echo 123 > index.html
# chmod 644 index.html
# exit
</code>

Access the service to confirm the content:

<code># curl 192.168.166.131
123
</code>

Delete the pod and let Kubernetes recreate it to verify persistence:

<code># kubectl delete pod rbd-5db4759c-nj2b4
pod "rbd-5db4759c-nj2b4" deleted
# kubectl get pods -o wide
NAME                     READY   STATUS    RESTARTS   AGE   IP               NODE   
rbd-5db4759c-v9cgm       1/1     Running   0         40s   192.168.166.132   node1
# curl 192.168.166.132
123
</code>

3. Use PersistentVolume (PV) with RBD

Developers often prefer to request storage via a PVC rather than writing low‑level YAML for each volume.

3.1 Create a PersistentVolumeClaim (PVC)

<code>apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: myclaim
spec:
  accessModes:
  - ReadWriteOnce
  volumeMode: Block
  resources:
    requests:
      storage: 8Gi
</code>

The PVC is pending until a matching PV is created.

3.2 Create a PersistentVolume (PV)

<code>apiVersion: v1
kind: PersistentVolume
metadata:
  name: rbdpv
spec:
  capacity:
    storage: 8Gi
  volumeMode: Block
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Recycle
  mountOptions:
  - hard
  - nfsvers=4.1
  rbd:
    fsType: xfs
    image: test
    pool: rbd
    user: admin
    keyring: /etc/ceph/ceph.client.admin.keyring
    monitors:
    - 172.16.1.33
    readOnly: false
</code>

Bind the PV to the PVC:

<code># kubectl get pvc
NAME      STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
myclaim   Bound    rbdpv    8Gi        RWO           11s
</code>

3.3 Use the PVC in a Pod

<code>apiVersion: v1
kind: Pod
metadata:
  name: pvc-pod
spec:
  volumes:
  - name: rbd
    persistentVolumeClaim:
      claimName: myclaim
      readOnly: false
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    volumeDevices:
    - devicePath: /dev/rbd0
      name: rbd
</code>

Verify the block device appears inside the container:

<code># kubectl exec -it pvc-pod -- bash
root@pvc-pod:/# ls /dev/rbd0
/dev/rbd0
</code>

4. Dynamic Provisioning

Use a StorageClass to let Kubernetes automatically create PVs for PVCs.

4.1 Install Ceph CSI Driver

<code># git clone https://gitee.com/yftyxa/ceph-csi.git
# cd ceph-csi/deploy/
# kubectl create ns csi
# kubectl apply -f . -n csi
</code>

Adjust

csi-rbdplugin-provisioner.yaml

(set

--extra-create-metadata=false

) and the ConfigMap

csi-config-map.yaml

to match your Ceph monitors and cluster ID.

4.2 Create a Secret with Ceph Credentials

<code>apiVersion: v1
kind: Secret
metadata:
  name: csi-secret
  namespace: csi
stringData:
  userID: admin
  userKey: AQC4QnJmng4HIhAA42s27yOflqOBNtEWDgEmkg==
  adminID: admin
  adminKey: AQC4QnJmng4HIhAA42s27yOflqOBNtEWDgEmkg==
</code>

4.3 Define the StorageClass

<code>apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: csi-rbd-sc
provisioner: rbd.csi.ceph.com
parameters:
  clusterID: c1f213ae-2de3-11ef-ae15-00163e179ce3
  pool: rbd
  imageFeatures: "layering"
  csi.storage.k8s.io/provisioner-secret-name: csi-secret
  csi.storage.k8s.io/provisioner-secret-namespace: csi
  csi.storage.k8s.io/controller-expand-secret-name: csi-secret
  csi.storage.k8s.io/controller-expand-secret-namespace: csi
  csi.storage.k8s.io/node-stage-secret-name: csi-secret
  csi.storage.k8s.io/node-stage-secret-namespace: csi
  csi.storage.k8s.io/fstype: ext4
reclaimPolicy: Retain
allowVolumeExpansion: true
mountOptions:
- discard
</code>

4.4 Set the StorageClass as Default (optional)

<code># kubectl edit sc csi-rbd-sc
# add annotation:
#   storageclass.kubernetes.io/is-default-class: "true"
</code>

5. Test Dynamic Provisioning

5.1 Create a PVC without specifying a StorageClass

<code>apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: sc-pvc1
spec:
  accessModes:
  - ReadWriteOnce
  volumeMode: Block
  resources:
    requests:
      storage: 20Gi
</code>

Because the

csi-rbd-sc

StorageClass is default, the PVC is bound automatically:

<code># kubectl get pvc
NAME      STATUS   VOLUME                                    CAPACITY   ACCESS MODES   STORAGECLASS   AGE
sc-pvc1   Bound    pvc-167cf73b-4983-4c28-aa98-bb65bb966649 20Gi       RWO            csi-rbd-sc      6s
</code>

The corresponding RBD image can be seen in the Ceph cluster:

<code># rbd ls
csi-vol-56e37046-b9d7-4ef1-a534-970a766744f3
# rbd info csi-vol-56e37046-b9d7-4ef1-a534-970a766744f3
size 20 GiB in 3840 objects
features: layering
...</code>

This completes the end‑to‑end setup of Ceph RBD storage for Kubernetes, covering manual PV/PVC usage and fully automated dynamic provisioning.