rbd

PLEASE NOTE: This document applies to the HEAD of the source tree

If you are using a released version of Kubernetes, you should refer to the docs that go with that version.

The latest release of this document can be found [here](http://releases.k8s.io/release-1.1/examples/rbd/README.md).

Documentation for other releases can be found at releases.k8s.io.

How to Use it?

Install Ceph on the Kubernetes host. For example, on Fedora 21

# yum -y install ceph-common

If you don't have a Ceph cluster, you can set up a containerized Ceph cluster

Then get the keyring from the Ceph cluster and copy it to /etc/ceph/keyring.

Once you have installed Ceph and new Kubernetes, you can create a pod based on my examples rbd.json rbd-with-secret.json. In the pod JSON, you need to provide the following information.

• monitors: Ceph monitors.
• pool: The name of the RADOS pool, if not provided, default rbd pool is used.
• image: The image name that rbd has created.
• user: The RADOS user name. If not provided, default admin is used.
• keyring: The path to the keyring file. If not provided, default /etc/ceph/keyring is used.
• secretName: The name of the authentication secrets. If provided, secretName overrides keyring. Note, see below about how to create a secret.
• fsType: The filesystem type (ext4, xfs, etc) that formatted on the device.
• readOnly: Whether the filesystem is used as readOnly.

Use Ceph Authentication Secret

If Ceph authentication secret is provided, the secret should be first be base64 encoded, then encoded string is placed in a secret yaml. For example, getting Ceph user kube's base64 encoded secret can use the following command:

  # grep key /etc/ceph/ceph.client.kube.keyring |awk '{printf "%s", $NF}'|base64
QVFBTWdYaFZ3QkNlRGhBQTlubFBhRnlmVVNhdEdENGRyRldEdlE9PQ==

An example yaml is provided here. Then post the secret through kubectl in the following command.

    # kubectl create -f examples/rbd/secret/ceph-secret.yaml

Get started

Here are my commands:

    # kubectl create -f examples/rbd/rbd.json
    # kubectl get pods

On the Kubernetes host, I got these in mount output

    #mount |grep kub
	/dev/rbd0 on /var/lib/kubelet/plugins/kubernetes.io/rbd/rbd/kube-image-foo type ext4 (ro,relatime,stripe=4096,data=ordered)
	/dev/rbd0 on /var/lib/kubelet/pods/ec2166b4-de07-11e4-aaf5-d4bed9b39058/volumes/kubernetes.io~rbd/rbdpd type ext4 (ro,relatime,stripe=4096,data=ordered)

If you ssh to that machine, you can run docker ps to see the actual pod and docker inspect to see the volumes used by the container.