# yum install -y ceph-common
This topic provides an end-to-end example of using an existing Ceph cluster as an OpenShift Container Platform dynamic persistent store. It is assumed that a working Ceph cluster is already set up. If not, consult the Overview of Red Hat Ceph Storage.
Persistent Storage Using Ceph Rados Block Device provides an explanation of persistent volumes (PVs), persistent volume claims (PVCs), and how to use Ceph Rados Block Device (RBD) as persistent storage.
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All |
The ceph-common library must be installed on all schedulable OpenShift Container Platform nodes:
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The OpenShift Container Platform all-in-one host is not often used to run pod workloads and, thus, is not included as a schedulable node. |
# yum install -y ceph-common
It is recommended that you create a pool for your dynamic volumes to live in.
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Using the default pool of RBD is an option, but not recommended. |
From a Ceph administrator or MON node, create a new pool for dynamic volumes:
$ ceph osd pool create kube 1024 $ ceph auth get-or-create client.kube mon 'allow r' osd 'allow class-read object_prefix rbd_children, allow rwx pool=kube' -o ceph.client.kube.keyring
Run the ceph auth get-key command on a Ceph MON node to display the key
value for the client.admin user:
apiVersion: v1
kind: Secret
metadata:
name: ceph-secret
namespace: kube-system
data:
key: QVFBOFF2SlZheUJQRVJBQWgvS2cwT1laQUhPQno3akZwekxxdGc9PQ== (1)
type:
kubernetes.io/rbd (2)| 1 | This base64 key is generated on one of the Ceph MON nodes using the ceph auth
get-key client.admin | base64 command, then copying the output and pasting it
as the secret key’s value. |
| 2 | This is required for Ceph RBD to work with dynamic provisioning. |
Save the secret definition to a file, for example ceph-secret.yaml, then create the secret:
$ oc create -f ceph-secret.yaml secret "ceph-secret" created
Verify that the secret was created:
# oc get secret ceph-secret NAME TYPE DATA AGE ceph-secret kubernetes.io/rbd 1 5d
Run the ceph auth get-key command on a Ceph MON node to display the key
value for the client.kube user:
apiVersion: v1
kind: Secret
metadata:
name: ceph-user-secret
namespace: default
data:
key: QVFCbEV4OVpmaGJtQ0JBQW55d2Z0NHZtcS96cE42SW1JVUQvekE9PQ== (1)
type:
kubernetes.io/rbd (2)| 1 | This base64 key is generated on one of the Ceph MON nodes using the ceph auth
get-key client.kube | base64 command, then copying the output and pasting it as
the secret key’s value. |
| 2 | This is required for Ceph RBD to work with dynamic provisioning. |
Save the secret definition to a file, for example ceph-user-secret.yaml, then create the secret:
$ oc create -f ceph-user-secret.yaml secret "ceph-user-secret" created
Verify that the secret was created:
# oc get secret ceph-user-secret NAME TYPE DATA AGE ceph-user-secret kubernetes.io/rbd 1 5d
Create a storage class to for your dynamic volumes.
apiVersion: storage.k8s.io/v1beta1
kind: StorageClass
metadata:
name: dynamic
annotations:
storageclass.beta.kubernetes.io/is-default-class: "true"
provisioner: kubernetes.io/rbd
parameters:
monitors: 192.168.1.11:6789,192.168.1.12:6789,192.168.1.13:6789 (1)
adminId: admin (2)
adminSecretName: ceph-secret (3)
adminSecretNamespace: kube-system (4)
pool: kube (5)
userId: kube (6)
userSecretName: ceph-secret-user (7)| 1 | Ceph monitors, comma delimited. It is required. |
| 2 | Ceph client ID that is capable of creating images in the pool. Default is admin. |
| 3 | Secret Name for adminId. It is required. The provided secret must have type kubernetes.io/rbd. |
| 4 | The namespace for adminSecret. Default is default. |
| 5 | Ceph RBD pool. Default is rbd, but that value is not recommended. |
| 6 | Ceph client ID that is used to map the Ceph RBD image. Default is the same as adminId. |
| 7 | The name of Ceph Secret for userId to map Ceph RBD image. It must exist in the
same namespace as PVCs. It is required unless its set as the default in new
projects. |
A persistent volume claim (PVC) specifies the desired access mode and storage capacity. Currently, based on only these two attributes, a PVC is bound to a single PV. Once a PV is bound to a PVC, that PV is essentially tied to the PVC’s project and cannot be bound to by another PVC. There is a one-to-one mapping of PVs and PVCs. However, multiple pods in the same project can use the same PVC.
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: ceph-claim
spec:
accessModes: (1)
- ReadWriteOnce
resources:
requests:
storage: 2Gi (2)| 1 | As mentioned above for PVs, the accessModes do not enforce access right, but
rather act as labels to match a PV to a PVC. |
| 2 | This claim will look for PVs offering 2Gi or greater capacity.
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| 3 | the claim dynamically created a Ceph RBD PV. |
A pod definition file or a template file can be used to define a pod. Below is a pod specification that creates a single container and mounts the Ceph RBD volume for read-write access:
apiVersion: v1
kind: Pod
metadata:
name: ceph-pod1 (1)
spec:
containers:
- name: ceph-busybox
image: busybox (2)
command: ["sleep", "60000"]
volumeMounts:
- name: ceph-vol1 (3)
mountPath: /usr/share/busybox (4)
readOnly: false
volumes:
- name: ceph-vol1 (3)
persistentVolumeClaim:
claimName: ceph-claim (5)| 1 | The name of this pod as displayed by oc get pod. |
| 2 | The image run by this pod. In this case, we are telling busybox to sleep. |
| 3 | The name of the volume. This name must be the same in both the containers and
volumes sections. |
| 4 | The mount path as seen in the container. |
| 5 | The PVC that is bound to the Ceph RBD cluster.
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| 6 | After approximately a minute, the pod will be in the Running state. |
If you want to make the persistent storage available to every project, you must modify the default project template. Read more on modifying the default project template. Adding this to your default project template allows every user who has access to create a project access to the Ceph cluster.
...
apiVersion: v1
kind: Template
metadata:
creationTimestamp: null
name: project-request
objects:
- apiVersion: v1
kind: Project
metadata:
annotations:
openshift.io/description: ${PROJECT_DESCRIPTION}
openshift.io/display-name: ${PROJECT_DISPLAYNAME}
openshift.io/requester: ${PROJECT_REQUESTING_USER}
creationTimestamp: null
name: ${PROJECT_NAME}
spec: {}
status: {}
- apiVersion: v1
kind: Secret
metadata:
name: ceph-user-secret
data:
key: QVFCbEV4OVpmaGJtQ0JBQW55d2Z0NHZtcS96cE42SW1JVUQvekE9PQ== (1)
type:
kubernetes.io/rbd
...| 1 | Place the key from ceph-user-secret here in base64 format. See
Creating
the Ceph Secret. |