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OSDOCS-294: Included CSI details.
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‎_topic_map.yml

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@@ -343,6 +343,8 @@ Topics:
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File: persistent-storage-aws
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- Name: Persistent Storage using iSCSI
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File: persistent-storage-iscsi
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- Name: Persistent storage using Container Storage Interface (CSI)
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File: persistent-storage-csi
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- Name: Dynamic provisioning
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File: dynamic-provisioning
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---

‎images/csi-arch.png

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‎modules/persistent-storage-csi-architecture.adoc

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// Module included in the following assemblies:
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//
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// * storage/persistent_storage/persistent-storage-csi.adoc
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[id="persistent-storage-csi-architecture-{context}"]
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= CSI Architecture
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CSI drivers are typically shipped as container images. These containers
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are not aware of {product-title} where they run. To use CSI-compatible
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storage backend in {product-title}, the cluster administrator must deploy
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several components that serve as a bridge between {product-title} and the
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storage driver.
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The following diagram provides a high-level overview about the components
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running in pods in the {product-title} cluster.
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image::../../images/csi-arch.png["Architecture of CSI components"]
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It is possible to run multiple CSI drivers for different storage backends.
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Each driver needs its own external controllers' deployment and DaemonSet
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with the driver and CSI registrar.
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‎modules/persistent-storage-csi-driver-daemonset.adoc

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// Module included in the following assemblies:
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//
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// * storage/persistent-storage/persistent-storage-csi.adoc
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[id="csi-driver-daemonset-{context}"]
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= CSI Driver DaemonSet
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The CSI driver DaemonSet runs a pod on every node that allows
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{product-title} to mount storage provided by the CSI driver to the node
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and use it in user workloads (pods) as persistent volumes (PVs). The pod
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with the CSI driver installed contains the following containers:
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* A CSI driver registrar, which registers the CSI driver into the
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`openshift-node` service running on the node. The `openshift-node` process
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running on the node then directly connects with the CSI driver using the
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UNIX Domain Socket available on the node.
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* A CSI driver.
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The CSI driver deployed on the node should have as few credentials to the
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storage backend as possible. {product-title} will only use the node plug-in
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set of CSI calls such as `NodePublish`/`NodeUnpublish` and
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`NodeStage`/`NodeUnstage`, if these calls are implemented.

‎modules/persistent-storage-csi-dynamic-provisioning.adoc

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// Module included in the following assemblies:
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//
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// * storage/persistent-storage/persistent-storage-csi.adoc
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[id="csi-dynamic-provisioning-{context}"]
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= Dynamic Provisioning
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Dynamic provisioning of persistent storage depends on the capabilities of
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the CSI driver and underlying storage backend. The provider of the CSI
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driver should document how to create a StorageClass in {product-title} and
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the parameters available for configuration.
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As seen in the OpenStack Cinder example, you can deploy this StorageClass
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to enable dynamic provisioning.
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.Procedure
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* Create a default storage class that ensures all PVCs that do not require
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any special storage class are provisioned by the installed CSI driver.
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+
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[source,shell]
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----
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# oc create -f - << EOF
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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: cinder
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annotations:
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storageclass.kubernetes.io/is-default-class: "true"
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provisioner: csi-cinderplugin
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parameters:
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EOF
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----
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‎modules/persistent-storage-csi-example-deployment.adoc

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// Module included in the following assemblies:
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//
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// * storage/persistent-storage/persistent-storage-csi.adoc
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[id="csi-example-deployment-{context}"]
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= Example CSI deployment
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Since {product-title} does not ship with any CSI driver installed, this
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example shows how to deploy a community driver for OpenStack Cinder in
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{product-title}.
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.Procedure
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. Create a new project where the CSI components will run, and then create
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a new service account to run the components. An explicit node selector is
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used to run the Daemonset with the CSI driver also on master nodes.
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+
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----
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# oc adm new-project csi --node-selector=""
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Now using project "csi" on server "https://example.com:8443".
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# oc create serviceaccount cinder-csi
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serviceaccount "cinder-csi" created
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# oc adm policy add-scc-to-user privileged system:serviceaccount:csi:cinder-csi
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scc "privileged" added to: ["system:serviceaccount:csi:cinder-csi"]
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----
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. Apply this YAML file to create the deployment with the external CSI
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attacher and provisioner and DaemonSet with the CSI driver.
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+
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[source,yaml]
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----
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# This YAML file contains all API objects that are necessary to run Cinder CSI
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# driver.
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#
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# In production, this needs to be in separate files, e.g. service account and
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# role and role binding needs to be created once.
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#
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# It server as an example how to use external attacher and external provisioner
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# images shipped with {product-title} with a community CSI driver.
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: cinder-csi-role
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rules:
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- apiGroups: [""]
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resources: ["persistentvolumes"]
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verbs: ["create", "delete", "get", "list", "watch", "update", "patch"]
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- apiGroups: [""]
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resources: ["events"]
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verbs: ["create", "get", "list", "watch", "update", "patch"]
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- apiGroups: [""]
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resources: ["persistentvolumeclaims"]
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verbs: ["get", "list", "watch", "update", "patch"]
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- apiGroups: [""]
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resources: ["nodes"]
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verbs: ["get", "list", "watch", "update", "patch"]
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- apiGroups: ["storage.k8s.io"]
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resources: ["storageclasses"]
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verbs: ["get", "list", "watch"]
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- apiGroups: ["storage.k8s.io"]
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resources: ["volumeattachments"]
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verbs: ["get", "list", "watch", "update", "patch"]
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- apiGroups: [""]
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resources: ["configmaps"]
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verbs: ["get", "list", "watch", "create", "update", "patch"]
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---
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kind: ClusterRoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: cinder-csi-role
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subjects:
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- kind: ServiceAccount
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name: cinder-csi
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namespace: csi
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roleRef:
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kind: ClusterRole
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name: cinder-csi-role
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apiGroup: rbac.authorization.k8s.io
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---
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apiVersion: v1
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data:
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cloud.conf: W0dsb2JhbF0KYXV0aC11cmwgPSBodHRwczovL2V4YW1wbGUuY29tOjEzMDAwL3YyLjAvCnVzZXJuYW1lID0gYWxhZGRpbgpwYXNzd29yZCA9IG9wZW5zZXNhbWUKdGVuYW50LWlkID0gZTBmYTg1YjZhMDY0NDM5NTlkMmQzYjQ5NzE3NGJlZDYKcmVnaW9uID0gcmVnaW9uT25lCg== <1>
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kind: Secret
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metadata:
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creationTimestamp: null
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name: cloudconfig
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---
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kind: Deployment
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apiVersion: apps/v1
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metadata:
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name: cinder-csi-controller
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spec:
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replicas: 2
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selector:
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matchLabels:
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app: cinder-csi-controllers
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template:
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metadata:
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labels:
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app: cinder-csi-controllers
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spec:
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serviceAccount: cinder-csi
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containers:
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- name: csi-attacher
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image: registry.redhat.io/openshift/csi-attacher:v4.0
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args:
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- "--v=5"
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- "--csi-address=$(ADDRESS)"
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- "--leader-election"
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- "--leader-election-namespace=$(MY_NAMESPACE)"
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- "--leader-election-identity=$(MY_NAME)"
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env:
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- name: MY_NAME
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valueFrom:
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fieldRef:
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fieldPath: metadata.name
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- name: MY_NAMESPACE
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valueFrom:
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fieldRef:
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fieldPath: metadata.namespace
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- name: ADDRESS
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value: /csi/csi.sock
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volumeMounts:
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- name: socket-dir
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mountPath: /csi
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- name: csi-provisioner
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image: registry.redhat.io/openshift/csi-provisioner:v4.0
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args:
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- "--v=5"
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- "--provisioner=csi-cinderplugin"
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- "--csi-address=$(ADDRESS)"
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env:
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- name: ADDRESS
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value: /csi/csi.sock
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volumeMounts:
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- name: socket-dir
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mountPath: /csi
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- name: cinder-driver
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image: k8scloudprovider/cinder-csi-plugin:v0.3.0
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command: [ "/bin/cinder-csi-plugin" ]
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args:
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- "--nodeid=$(NODEID)"
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- "--endpoint=unix://$(ADDRESS)"
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- "--cloud-config=/etc/cloudconfig/cloud.conf"
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env:
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- name: NODEID
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valueFrom:
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fieldRef:
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fieldPath: spec.nodeName
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- name: ADDRESS
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value: /csi/csi.sock
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volumeMounts:
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- name: socket-dir
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mountPath: /csi
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- name: cloudconfig
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mountPath: /etc/cloudconfig
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volumes:
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- name: socket-dir
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emptyDir:
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- name: cloudconfig
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secret:
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secretName: cloudconfig
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---
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kind: DaemonSet
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apiVersion: apps/v1
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metadata:
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name: cinder-csi-ds
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spec:
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selector:
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matchLabels:
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app: cinder-csi-driver
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template:
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metadata:
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labels:
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app: cinder-csi-driver
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spec:
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<2>
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serviceAccount: cinder-csi
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containers:
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- name: csi-driver-registrar
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image: registry.redhat.io/openshift/csi-driver-registrar:v4.0
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securityContext:
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privileged: true
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args:
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- "--v=5"
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- "--csi-address=$(ADDRESS)"
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env:
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- name: ADDRESS
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value: /csi/csi.sock
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- name: KUBE_NODE_NAME
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valueFrom:
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fieldRef:
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fieldPath: spec.nodeName
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volumeMounts:
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- name: socket-dir
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mountPath: /csi
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- name: cinder-driver
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securityContext:
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privileged: true
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capabilities:
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add: ["SYS_ADMIN"]
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allowPrivilegeEscalation: true
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image: k8scloudprovider/cinder-csi-plugin:v0.3.0
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command: [ "/bin/cinder-csi-plugin" ]
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args:
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- "--nodeid=$(NODEID)"
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- "--endpoint=unix://$(ADDRESS)"
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- "--cloud-config=/etc/cloudconfig/cloud.conf"
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env:
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- name: NODEID
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valueFrom:
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fieldRef:
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fieldPath: spec.nodeName
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- name: ADDRESS
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value: /csi/csi.sock
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volumeMounts:
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- name: socket-dir
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mountPath: /csi
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- name: cloudconfig
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mountPath: /etc/cloudconfig
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- name: mountpoint-dir
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mountPath: /var/lib/origin/openshift.local.volumes/pods/
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mountPropagation: "Bidirectional"
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- name: cloud-metadata
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mountPath: /var/lib/cloud/data/
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- name: dev
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mountPath: /dev
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volumes:
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- name: cloud-metadata
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hostPath:
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path: /var/lib/cloud/data/
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- name: socket-dir
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hostPath:
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path: /var/lib/kubelet/plugins/csi-cinderplugin
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type: DirectoryOrCreate
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- name: mountpoint-dir
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hostPath:
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path: /var/lib/origin/openshift.local.volumes/pods/
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type: Directory
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- name: cloudconfig
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secret:
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secretName: cloudconfig
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- name: dev
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hostPath:
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path: /dev
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----
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<1> Replace with `cloud.conf` for your OpenStack deployment.
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For example, the Secret can be generated using the `oc create secret
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generic cloudconfig --from-file cloud.conf --dry-run -o yaml`.
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<2> Optionally, add `nodeSelector` to the CSI driver pod template to
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configure the nodes on which the CSI driver starts. Only nodes matching
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the selector run pods that use volumes that are served by the CSI driver.
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Without `nodeSelector`, the driver runs on all nodes in the cluster.

‎modules/persistent-storage-csi-external-controllers.adoc

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// Module included in the following assemblies:
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//
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// * storage/persistent-storage/persistent-storage-csi.adoc
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[id="external-csi-contollers-{context}"]
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= External CSI controllers
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External CSI Controllers is a deployment that deploys one or more pods
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with three containers:
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* An external CSI attacher container translates `attach` and `detach`
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calls from {product-title} to respective `ControllerPublish` and
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`ControllerUnpublish` calls to the CSI driver.
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* An external CSI provisioner container that translates `provision` and
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`delete` calls from {product-title} to respective `CreateVolume` and
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`DeleteVolume` calls to the CSI driver.
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* A CSI driver container
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The CSI attacher and CSI provisioner containers communicate with the CSI
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driver container using UNIX Domain Sockets, ensuring that no CSI
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communication leaves the pod. The CSI driver is not accessible from
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outside of the pod.
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[NOTE]
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====
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`attach`, `detach`, `provision`, and `delete` operations typically require
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the CSI driver to use credentials to the storage backend. Run the CSI
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controller pods on infrastructure nodes so the credentials are never leaked
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to user processes, even in the event of a catastrophic security breach
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on a compute node.
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====
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[NOTE]
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====
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The external attacher must also run for CSI drivers that do not support
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third-party `attach` or `detach` operations. The external attacher will
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not issue any `ControllerPublish` or `ControllerUnpublish` operations to
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the CSI driver. However, it still must run to implement the necessary
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{product-title} attachment API.
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====
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