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https://github.com/ceph/ceph
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365 lines
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365 lines
13 KiB
ReStructuredText
==============================
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Block Devices and Kubernetes
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==============================
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You may use Ceph Block Device images with Kubernetes v1.13 and later through
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`ceph-csi`_, which dynamically provisions RBD images to back Kubernetes
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`volumes`_ and maps these RBD images as block devices (optionally mounting
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a file system contained within the image) on worker nodes running
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`pods`_ that reference an RBD-backed volume. Ceph stripes block device images as
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objects across the cluster, which means that large Ceph Block Device images have
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better performance than a standalone server!
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To use Ceph Block Devices with Kubernetes v1.13 and higher, you must install
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and configure ``ceph-csi`` within your Kubernetes environment. The following
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diagram depicts the Kubernetes/Ceph technology stack.
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.. ditaa::
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+---------------------------------------------------+
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| Kubernetes |
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+---------------------------------------------------+
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| ceph--csi |
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+------------------------+--------------------------+
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| configures
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v
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+------------------------+ +------------------------+
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| | | rbd--nbd |
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| Kernel Modules | +------------------------+
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| | | librbd |
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+------------------------+-+------------------------+
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| RADOS Protocol |
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+------------------------+-+------------------------+
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| OSDs | | Monitors |
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+------------------------+ +------------------------+
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.. important::
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``ceph-csi`` uses the RBD kernel modules by default which may not support all
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Ceph `CRUSH tunables`_ or `RBD image features`_.
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Create a Pool
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=============
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By default, Ceph block devices use the ``rbd`` pool. Create a pool for
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Kubernetes volume storage. Ensure your Ceph cluster is running, then create
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the pool. ::
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$ ceph osd pool create kubernetes
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See `Create a Pool`_ for details on specifying the number of placement groups
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for your pools, and `Placement Groups`_ for details on the number of placement
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groups you should set for your pools.
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A newly created pool must be initialized prior to use. Use the ``rbd`` tool
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to initialize the pool::
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$ rbd pool init kubernetes
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Configure ceph-csi
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==================
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Setup Ceph Client Authentication
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--------------------------------
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Create a new user for Kubernetes and `ceph-csi`. Execute the following and
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record the generated key::
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$ ceph auth get-or-create client.kubernetes mon 'profile rbd' osd 'profile rbd pool=kubernetes' mgr 'profile rbd pool=kubernetes'
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[client.kubernetes]
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key = AQD9o0Fd6hQRChAAt7fMaSZXduT3NWEqylNpmg==
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Generate `ceph-csi` `ConfigMap`
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-------------------------------
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The `ceph-csi` requires a `ConfigMap` object stored in Kubernetes to define the
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the Ceph monitor addresses for the Ceph cluster. Collect both the Ceph cluster
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unique `fsid` and the monitor addresses::
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$ ceph mon dump
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<...>
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fsid b9127830-b0cc-4e34-aa47-9d1a2e9949a8
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<...>
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0: [v2:192.168.1.1:3300/0,v1:192.168.1.1:6789/0] mon.a
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1: [v2:192.168.1.2:3300/0,v1:192.168.1.2:6789/0] mon.b
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2: [v2:192.168.1.3:3300/0,v1:192.168.1.3:6789/0] mon.c
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.. note::
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``ceph-csi`` currently only supports the `legacy V1 protocol`_.
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Generate a `csi-config-map.yaml` file similar to the example below, substituting
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the `fsid` for "clusterID", and the monitor addresses for "monitors"::
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$ cat <<EOF > csi-config-map.yaml
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---
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apiVersion: v1
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kind: ConfigMap
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data:
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config.json: |-
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[
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{
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"clusterID": "b9127830-b0cc-4e34-aa47-9d1a2e9949a8",
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"monitors": [
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"192.168.1.1:6789",
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"192.168.1.2:6789",
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"192.168.1.3:6789"
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]
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}
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]
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metadata:
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name: ceph-csi-config
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EOF
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Once generated, store the new `ConfigMap` object in Kubernetes::
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$ kubectl apply -f csi-config-map.yaml
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Recent versions of `ceph-csi` also require an additional `ConfigMap` object to
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define Key Management Service (KMS) provider details. If KMS isn't set up, put
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an empty configuration in a `csi-kms-config-map.yaml` file or refer to examples
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at https://github.com/ceph/ceph-csi/tree/master/examples/kms::
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$ cat <<EOF > csi-kms-config-map.yaml
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---
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apiVersion: v1
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kind: ConfigMap
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data:
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config.json: |-
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{}
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metadata:
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name: ceph-csi-encryption-kms-config
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EOF
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Once generated, store the new `ConfigMap` object in Kubernetes::
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$ kubectl apply -f csi-kms-config-map.yaml
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Recent versions of `ceph-csi` also require yet another `ConfigMap` object
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to define Ceph configuration to add to ceph.conf file inside CSI containers::
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$ cat <<EOF > ceph-config-map.yaml
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---
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apiVersion: v1
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kind: ConfigMap
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data:
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ceph.conf: |
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[global]
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auth_cluster_required = cephx
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auth_service_required = cephx
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auth_client_required = cephx
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# keyring is a required key and its value should be empty
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keyring: |
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metadata:
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name: ceph-config
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EOF
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Once generated, store the new `ConfigMap` object in Kubernetes::
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$ kubectl apply -f ceph-config-map.yaml
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Generate `ceph-csi` cephx `Secret`
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----------------------------------
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`ceph-csi` requires the cephx credentials for communicating with the Ceph
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cluster. Generate a `csi-rbd-secret.yaml` file similar to the example below,
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using the newly created Kubernetes user id and cephx key::
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$ cat <<EOF > csi-rbd-secret.yaml
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---
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apiVersion: v1
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kind: Secret
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metadata:
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name: csi-rbd-secret
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namespace: default
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stringData:
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userID: kubernetes
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userKey: AQD9o0Fd6hQRChAAt7fMaSZXduT3NWEqylNpmg==
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EOF
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Once generated, store the new `Secret` object in Kubernetes::
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$ kubectl apply -f csi-rbd-secret.yaml
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Configure `ceph-csi` Plugins
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----------------------------
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Create the required `ServiceAccount` and RBAC `ClusterRole`/`ClusterRoleBinding`
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Kubernetes objects. These objects do not necessarily need to be customized for
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your Kubernetes environment and therefore can be used as-is from the `ceph-csi`
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deployment YAMLs::
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$ kubectl apply -f https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-provisioner-rbac.yaml
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$ kubectl apply -f https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-nodeplugin-rbac.yaml
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Finally, create the `ceph-csi` provisioner and node plugins. With the
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possible exception of the `ceph-csi` container release version, these objects do
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not necessarily need to be customized for your Kubernetes environment and
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therefore can be used as-is from the `ceph-csi` deployment YAMLs::
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$ wget https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-rbdplugin-provisioner.yaml
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$ kubectl apply -f csi-rbdplugin-provisioner.yaml
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$ wget https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-rbdplugin.yaml
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$ kubectl apply -f csi-rbdplugin.yaml
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.. important::
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The provisioner and node plugin YAMLs will, by default, pull the development
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release of the `ceph-csi` container (quay.io/cephcsi/cephcsi:canary).
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The YAMLs should be updated to use a release version container for
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production workloads.
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Using Ceph Block Devices
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========================
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Create a `StorageClass`
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-----------------------
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The Kubernetes `StorageClass` defines a class of storage. Multiple `StorageClass`
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objects can be created to map to different quality-of-service levels (i.e. NVMe
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vs HDD-based pools) and features.
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For example, to create a `ceph-csi` `StorageClass` that maps to the `kubernetes`
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pool created above, the following YAML file can be used after ensuring that the
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"clusterID" property matches your Ceph cluster's `fsid`::
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$ cat <<EOF > csi-rbd-sc.yaml
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---
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apiVersion: storage.k8s.io/v1
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kind: StorageClass
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metadata:
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name: csi-rbd-sc
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provisioner: rbd.csi.ceph.com
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parameters:
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clusterID: b9127830-b0cc-4e34-aa47-9d1a2e9949a8
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pool: kubernetes
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imageFeatures: layering
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csi.storage.k8s.io/provisioner-secret-name: csi-rbd-secret
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csi.storage.k8s.io/provisioner-secret-namespace: default
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csi.storage.k8s.io/controller-expand-secret-name: csi-rbd-secret
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csi.storage.k8s.io/controller-expand-secret-namespace: default
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csi.storage.k8s.io/node-stage-secret-name: csi-rbd-secret
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csi.storage.k8s.io/node-stage-secret-namespace: default
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reclaimPolicy: Delete
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allowVolumeExpansion: true
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mountOptions:
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- discard
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EOF
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$ kubectl apply -f csi-rbd-sc.yaml
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Note that in Kubernetes v1.14 and v1.15 volume expansion feature was in alpha
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status and required enabling `ExpandCSIVolumes` feature gate.
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Create a `PersistentVolumeClaim`
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--------------------------------
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A `PersistentVolumeClaim` is a request for abstract storage resources by a user.
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The `PersistentVolumeClaim` would then be associated to a `Pod` resource to
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provision a `PersistentVolume`, which would be backed by a Ceph block image.
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An optional `volumeMode` can be included to select between a mounted file system
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(default) or raw block device-based volume.
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Using `ceph-csi`, specifying `Filesystem` for `volumeMode` can support both
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`ReadWriteOnce` and `ReadOnlyMany` `accessMode` claims, and specifying `Block`
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for `volumeMode` can support `ReadWriteOnce`, `ReadWriteMany`, and
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`ReadOnlyMany` `accessMode` claims.
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For example, to create a block-based `PersistentVolumeClaim` that utilizes
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the `ceph-csi`-based `StorageClass` created above, the following YAML can be
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used to request raw block storage from the `csi-rbd-sc` `StorageClass`::
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$ cat <<EOF > raw-block-pvc.yaml
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---
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apiVersion: v1
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kind: PersistentVolumeClaim
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metadata:
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name: raw-block-pvc
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spec:
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accessModes:
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- ReadWriteOnce
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volumeMode: Block
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resources:
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requests:
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storage: 1Gi
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storageClassName: csi-rbd-sc
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EOF
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$ kubectl apply -f raw-block-pvc.yaml
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The following demonstrates and example of binding the above
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`PersistentVolumeClaim` to a `Pod` resource as a raw block device::
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$ cat <<EOF > raw-block-pod.yaml
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---
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apiVersion: v1
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kind: Pod
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metadata:
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name: pod-with-raw-block-volume
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spec:
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containers:
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- name: fc-container
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image: fedora:26
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command: ["/bin/sh", "-c"]
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args: ["tail -f /dev/null"]
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volumeDevices:
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- name: data
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devicePath: /dev/xvda
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volumes:
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- name: data
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persistentVolumeClaim:
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claimName: raw-block-pvc
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EOF
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$ kubectl apply -f raw-block-pod.yaml
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To create a file-system-based `PersistentVolumeClaim` that utilizes the
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`ceph-csi`-based `StorageClass` created above, the following YAML can be used to
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request a mounted file system (backed by an RBD image) from the `csi-rbd-sc`
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`StorageClass`::
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$ cat <<EOF > pvc.yaml
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---
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apiVersion: v1
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kind: PersistentVolumeClaim
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metadata:
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name: rbd-pvc
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spec:
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accessModes:
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- ReadWriteOnce
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volumeMode: Filesystem
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resources:
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requests:
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storage: 1Gi
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storageClassName: csi-rbd-sc
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EOF
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$ kubectl apply -f pvc.yaml
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The following demonstrates and example of binding the above
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`PersistentVolumeClaim` to a `Pod` resource as a mounted file system::
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$ cat <<EOF > pod.yaml
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---
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apiVersion: v1
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kind: Pod
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metadata:
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name: csi-rbd-demo-pod
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spec:
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containers:
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- name: web-server
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image: nginx
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volumeMounts:
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- name: mypvc
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mountPath: /var/lib/www/html
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volumes:
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- name: mypvc
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persistentVolumeClaim:
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claimName: rbd-pvc
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readOnly: false
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EOF
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$ kubectl apply -f pod.yaml
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.. _ceph-csi: https://github.com/ceph/ceph-csi/
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.. _volumes: https://kubernetes.io/docs/concepts/storage/volumes/
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.. _pods: https://kubernetes.io/docs/concepts/workloads/pods/pod-overview/
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.. _Create a Pool: ../../rados/operations/pools#createpool
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.. _Placement Groups: ../../rados/operations/placement-groups
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.. _CRUSH tunables: ../../rados/operations/crush-map/#tunables
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.. _RBD image features: ../rbd-config-ref/#image-features
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.. _legacy V1 protocol: ../../rados/configuration/msgr2/#address-formats
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