1477 lines
53 KiB
Markdown
1477 lines
53 KiB
Markdown
---
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reviewers:
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- jsafrane
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- saad-ali
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- thockin
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- msau42
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title: Volumes
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content_template: templates/concept
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weight: 10
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---
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{{% capture overview %}}
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On-disk files in a Container are ephemeral, which presents some problems for
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non-trivial applications when running in Containers. First, when a Container
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crashes, kubelet will restart it, but the files will be lost - the
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Container starts with a clean state. Second, when running Containers together
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in a `Pod` it is often necessary to share files between those Containers. The
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Kubernetes `Volume` abstraction solves both of these problems.
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Familiarity with [Pods](/docs/user-guide/pods) is suggested.
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{{% /capture %}}
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{{% capture body %}}
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## Background
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Docker also has a concept of
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[volumes](https://docs.docker.com/engine/admin/volumes/), though it is
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somewhat looser and less managed. In Docker, a volume is simply a directory on
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disk or in another Container. Lifetimes are not managed and until very
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recently there were only local-disk-backed volumes. Docker now provides volume
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drivers, but the functionality is very limited for now (e.g. as of Docker 1.7
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only one volume driver is allowed per Container and there is no way to pass
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parameters to volumes).
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A Kubernetes volume, on the other hand, has an explicit lifetime - the same as
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the Pod that encloses it. Consequently, a volume outlives any Containers that run
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within the Pod, and data is preserved across Container restarts. Of course, when a
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Pod ceases to exist, the volume will cease to exist, too. Perhaps more
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importantly than this, Kubernetes supports many types of volumes, and a Pod can
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use any number of them simultaneously.
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At its core, a volume is just a directory, possibly with some data in it, which
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is accessible to the Containers in a Pod. How that directory comes to be, the
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medium that backs it, and the contents of it are determined by the particular
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volume type used.
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To use a volume, a Pod specifies what volumes to provide for the Pod (the
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`.spec.volumes`
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field) and where to mount those into Containers (the
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`.spec.containers[*].volumeMounts`
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field).
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A process in a container sees a filesystem view composed from their Docker
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image and volumes. The [Docker
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image](https://docs.docker.com/userguide/dockerimages/) is at the root of the
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filesystem hierarchy, and any volumes are mounted at the specified paths within
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the image. Volumes can not mount onto other volumes or have hard links to
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other volumes. Each Container in the Pod must independently specify where to
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mount each volume.
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## Types of Volumes
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Kubernetes supports several types of Volumes:
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* [awsElasticBlockStore](#awselasticblockstore)
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* [azureDisk](#azuredisk)
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* [azureFile](#azurefile)
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* [cephfs](#cephfs)
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* [cinder](#cinder)
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* [configMap](#configmap)
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* [csi](#csi)
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* [downwardAPI](#downwardapi)
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* [emptyDir](#emptydir)
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* [fc (fibre channel)](#fc)
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* [flexVolume](#flexVolume)
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* [flocker](#flocker)
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* [gcePersistentDisk](#gcepersistentdisk)
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* [gitRepo (deprecated)](#gitrepo)
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* [glusterfs](#glusterfs)
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* [hostPath](#hostpath)
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* [iscsi](#iscsi)
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* [local](#local)
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* [nfs](#nfs)
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* [persistentVolumeClaim](#persistentvolumeclaim)
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* [projected](#projected)
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* [portworxVolume](#portworxvolume)
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* [quobyte](#quobyte)
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* [rbd](#rbd)
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* [scaleIO](#scaleio)
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* [secret](#secret)
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* [storageos](#storageos)
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* [vsphereVolume](#vspherevolume)
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We welcome additional contributions.
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### awsElasticBlockStore {#awselasticblockstore}
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An `awsElasticBlockStore` volume mounts an Amazon Web Services (AWS) [EBS
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Volume](http://aws.amazon.com/ebs/) into your Pod. Unlike
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`emptyDir`, which is erased when a Pod is removed, the contents of an EBS
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volume are preserved and the volume is merely unmounted. This means that an
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EBS volume can be pre-populated with data, and that data can be "handed off"
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between Pods.
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{{< caution >}}
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You must create an EBS volume using `aws ec2 create-volume` or the AWS API before you can use it.
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{{< /caution >}}
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There are some restrictions when using an `awsElasticBlockStore` volume:
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* the nodes on which Pods are running must be AWS EC2 instances
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* those instances need to be in the same region and availability-zone as the EBS volume
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* EBS only supports a single EC2 instance mounting a volume
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#### Creating an EBS volume
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Before you can use an EBS volume with a Pod, you need to create it.
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```shell
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aws ec2 create-volume --availability-zone=eu-west-1a --size=10 --volume-type=gp2
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```
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Make sure the zone matches the zone you brought up your cluster in. (And also check that the size and EBS volume
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type are suitable for your use!)
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#### AWS EBS Example configuration
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: test-ebs
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spec:
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containers:
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- image: k8s.gcr.io/test-webserver
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name: test-container
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volumeMounts:
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- mountPath: /test-ebs
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name: test-volume
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volumes:
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- name: test-volume
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# This AWS EBS volume must already exist.
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awsElasticBlockStore:
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volumeID: <volume-id>
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fsType: ext4
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```
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#### CSI Migration
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{{< feature-state for_k8s_version="v1.17" state="beta" >}}
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The CSI Migration feature for awsElasticBlockStore, when enabled, shims all plugin operations
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from the existing in-tree plugin to the `ebs.csi.aws.com` Container
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Storage Interface (CSI) Driver. In order to use this feature, the [AWS EBS CSI
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Driver](https://github.com/kubernetes-sigs/aws-ebs-csi-driver)
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must be installed on the cluster and the `CSIMigration` and `CSIMigrationAWS`
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Beta features must be enabled.
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#### CSI Migration Complete
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{{< feature-state for_k8s_version="v1.17" state="alpha" >}}
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To turn off the awsElasticBlockStore storage plugin from being loaded by controller manager and kubelet, you need to set this feature flag to true. This requires `ebs.csi.aws.com` Container Storage Interface (CSI) driver being installed on all worker nodes.
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### azureDisk {#azuredisk}
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A `azureDisk` is used to mount a Microsoft Azure [Data Disk](https://azure.microsoft.com/en-us/documentation/articles/virtual-machines-linux-about-disks-vhds/) into a Pod.
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More details can be found [here](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/volumes/azure_disk/README.md).
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#### CSI Migration
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{{< feature-state for_k8s_version="v1.15" state="alpha" >}}
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The CSI Migration feature for azureDisk, when enabled, shims all plugin operations
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from the existing in-tree plugin to the `disk.csi.azure.com` Container
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Storage Interface (CSI) Driver. In order to use this feature, the [Azure Disk CSI
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Driver](https://github.com/kubernetes-sigs/azuredisk-csi-driver)
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must be installed on the cluster and the `CSIMigration` and `CSIMigrationAzureDisk`
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Alpha features must be enabled.
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### azureFile {#azurefile}
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A `azureFile` is used to mount a Microsoft Azure File Volume (SMB 2.1 and 3.0)
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into a Pod.
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More details can be found [here](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/volumes/azure_file/README.md).
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#### CSI Migration
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{{< feature-state for_k8s_version="v1.15" state="alpha" >}}
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The CSI Migration feature for azureFile, when enabled, shims all plugin operations
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from the existing in-tree plugin to the `file.csi.azure.com` Container
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Storage Interface (CSI) Driver. In order to use this feature, the [Azure File CSI
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Driver](https://github.com/kubernetes-sigs/azurefile-csi-driver)
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must be installed on the cluster and the `CSIMigration` and `CSIMigrationAzureFile`
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Alpha features must be enabled.
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### cephfs {#cephfs}
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A `cephfs` volume allows an existing CephFS volume to be
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mounted into your Pod. Unlike `emptyDir`, which is erased when a Pod is
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removed, the contents of a `cephfs` volume are preserved and the volume is merely
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unmounted. This means that a CephFS volume can be pre-populated with data, and
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that data can be "handed off" between Pods. CephFS can be mounted by multiple
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writers simultaneously.
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{{< caution >}}
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You must have your own Ceph server running with the share exported before you can use it.
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{{< /caution >}}
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See the [CephFS example](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/volumes/cephfs/) for more details.
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### cinder {#cinder}
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{{< note >}}
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Prerequisite: Kubernetes with OpenStack Cloud Provider configured. For cloudprovider
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configuration please refer [cloud provider openstack](/docs/concepts/cluster-administration/cloud-providers/#openstack).
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{{< /note >}}
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`cinder` is used to mount OpenStack Cinder Volume into your Pod.
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#### Cinder Volume Example configuration
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: test-cinder
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spec:
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containers:
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- image: k8s.gcr.io/test-webserver
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name: test-cinder-container
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volumeMounts:
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- mountPath: /test-cinder
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name: test-volume
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volumes:
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- name: test-volume
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# This OpenStack volume must already exist.
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cinder:
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volumeID: <volume-id>
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fsType: ext4
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```
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#### CSI Migration
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{{< feature-state for_k8s_version="v1.14" state="alpha" >}}
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The CSI Migration feature for Cinder, when enabled, shims all plugin operations
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from the existing in-tree plugin to the `cinder.csi.openstack.org` Container
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Storage Interface (CSI) Driver. In order to use this feature, the [Openstack Cinder CSI
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Driver](https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/using-cinder-csi-plugin.md)
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must be installed on the cluster and the `CSIMigration` and `CSIMigrationOpenStack`
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Alpha features must be enabled.
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### configMap {#configmap}
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The [`configMap`](/docs/tasks/configure-pod-container/configure-pod-configmap/) resource
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provides a way to inject configuration data into Pods.
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The data stored in a `ConfigMap` object can be referenced in a volume of type
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`configMap` and then consumed by containerized applications running in a Pod.
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When referencing a `configMap` object, you can simply provide its name in the
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volume to reference it. You can also customize the path to use for a specific
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entry in the ConfigMap.
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For example, to mount the `log-config` ConfigMap onto a Pod called `configmap-pod`,
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you might use the YAML below:
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: configmap-pod
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spec:
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containers:
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- name: test
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image: busybox
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volumeMounts:
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- name: config-vol
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mountPath: /etc/config
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volumes:
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- name: config-vol
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configMap:
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name: log-config
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items:
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- key: log_level
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path: log_level
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```
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The `log-config` ConfigMap is mounted as a volume, and all contents stored in
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its `log_level` entry are mounted into the Pod at path "`/etc/config/log_level`".
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Note that this path is derived from the volume's `mountPath` and the `path`
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keyed with `log_level`.
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{{< caution >}}
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You must create a [ConfigMap](/docs/tasks/configure-pod-container/configure-pod-configmap/) before you can use it.
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{{< /caution >}}
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{{< note >}}
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A Container using a ConfigMap as a [subPath](#using-subpath) volume mount will not
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receive ConfigMap updates.
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{{< /note >}}
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### downwardAPI {#downwardapi}
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A `downwardAPI` volume is used to make downward API data available to applications.
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It mounts a directory and writes the requested data in plain text files.
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{{< note >}}
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A Container using Downward API as a [subPath](#using-subpath) volume mount will not
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receive Downward API updates.
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{{< /note >}}
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See the [`downwardAPI` volume example](/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/) for more details.
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### emptyDir {#emptydir}
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An `emptyDir` volume is first created when a Pod is assigned to a Node, and
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exists as long as that Pod is running on that node. As the name says, it is
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initially empty. Containers in the Pod can all read and write the same
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files in the `emptyDir` volume, though that volume can be mounted at the same
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or different paths in each Container. When a Pod is removed from a node for
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any reason, the data in the `emptyDir` is deleted forever.
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{{< note >}}
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A Container crashing does *NOT* remove a Pod from a node, so the data in an `emptyDir` volume is safe across Container crashes.
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{{< /note >}}
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Some uses for an `emptyDir` are:
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* scratch space, such as for a disk-based merge sort
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* checkpointing a long computation for recovery from crashes
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* holding files that a content-manager Container fetches while a webserver
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Container serves the data
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By default, `emptyDir` volumes are stored on whatever medium is backing the
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node - that might be disk or SSD or network storage, depending on your
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environment. However, you can set the `emptyDir.medium` field to `"Memory"`
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to tell Kubernetes to mount a tmpfs (RAM-backed filesystem) for you instead.
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While tmpfs is very fast, be aware that unlike disks, tmpfs is cleared on
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node reboot and any files you write will count against your Container's
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memory limit.
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#### Example Pod
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: test-pd
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spec:
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containers:
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- image: k8s.gcr.io/test-webserver
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name: test-container
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volumeMounts:
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- mountPath: /cache
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name: cache-volume
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volumes:
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- name: cache-volume
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emptyDir: {}
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```
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### fc (fibre channel) {#fc}
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An `fc` volume allows an existing fibre channel volume to be mounted in a Pod.
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You can specify single or multiple target World Wide Names using the parameter
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`targetWWNs` in your volume configuration. If multiple WWNs are specified,
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targetWWNs expect that those WWNs are from multi-path connections.
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{{< caution >}}
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You must configure FC SAN Zoning to allocate and mask those LUNs (volumes) to the target WWNs beforehand so that Kubernetes hosts can access them.
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{{< /caution >}}
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See the [FC example](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/volumes/fibre_channel) for more details.
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### flocker {#flocker}
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[Flocker](https://github.com/ClusterHQ/flocker) is an open-source clustered Container data volume manager. It provides management
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and orchestration of data volumes backed by a variety of storage backends.
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A `flocker` volume allows a Flocker dataset to be mounted into a Pod. If the
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dataset does not already exist in Flocker, it needs to be first created with the Flocker
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CLI or by using the Flocker API. If the dataset already exists it will be
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reattached by Flocker to the node that the Pod is scheduled. This means data
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can be "handed off" between Pods as required.
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{{< caution >}}
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You must have your own Flocker installation running before you can use it.
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{{< /caution >}}
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See the [Flocker example](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/volumes/flocker) for more details.
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### gcePersistentDisk {#gcepersistentdisk}
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A `gcePersistentDisk` volume mounts a Google Compute Engine (GCE) [Persistent
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Disk](http://cloud.google.com/compute/docs/disks) into your Pod. Unlike
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`emptyDir`, which is erased when a Pod is removed, the contents of a PD are
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preserved and the volume is merely unmounted. This means that a PD can be
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pre-populated with data, and that data can be "handed off" between Pods.
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{{< caution >}}
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You must create a PD using `gcloud` or the GCE API or UI before you can use it.
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{{< /caution >}}
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There are some restrictions when using a `gcePersistentDisk`:
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* the nodes on which Pods are running must be GCE VMs
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* those VMs need to be in the same GCE project and zone as the PD
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A feature of PD is that they can be mounted as read-only by multiple consumers
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simultaneously. This means that you can pre-populate a PD with your dataset
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and then serve it in parallel from as many Pods as you need. Unfortunately,
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PDs can only be mounted by a single consumer in read-write mode - no
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simultaneous writers allowed.
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Using a PD on a Pod controlled by a ReplicationController will fail unless
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the PD is read-only or the replica count is 0 or 1.
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#### Creating a PD
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Before you can use a GCE PD with a Pod, you need to create it.
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```shell
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gcloud compute disks create --size=500GB --zone=us-central1-a my-data-disk
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```
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#### Example Pod
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: test-pd
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spec:
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containers:
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- image: k8s.gcr.io/test-webserver
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name: test-container
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volumeMounts:
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- mountPath: /test-pd
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name: test-volume
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volumes:
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- name: test-volume
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# This GCE PD must already exist.
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gcePersistentDisk:
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pdName: my-data-disk
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fsType: ext4
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```
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#### Regional Persistent Disks
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{{< feature-state for_k8s_version="v1.10" state="beta" >}}
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The [Regional Persistent Disks](https://cloud.google.com/compute/docs/disks/#repds) feature allows the creation of Persistent Disks that are available in two zones within the same region. In order to use this feature, the volume must be provisioned as a PersistentVolume; referencing the volume directly from a pod is not supported.
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#### Manually provisioning a Regional PD PersistentVolume
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Dynamic provisioning is possible using a [StorageClass for GCE PD](/docs/concepts/storage/storage-classes/#gce).
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Before creating a PersistentVolume, you must create the PD:
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```shell
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gcloud beta compute disks create --size=500GB my-data-disk
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--region us-central1
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--replica-zones us-central1-a,us-central1-b
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```
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Example PersistentVolume spec:
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```yaml
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apiVersion: v1
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kind: PersistentVolume
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metadata:
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name: test-volume
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labels:
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failure-domain.beta.kubernetes.io/zone: us-central1-a__us-central1-b
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spec:
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capacity:
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storage: 400Gi
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accessModes:
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- ReadWriteOnce
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gcePersistentDisk:
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pdName: my-data-disk
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fsType: ext4
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```
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#### CSI Migration
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|
|
{{< feature-state for_k8s_version="v1.17" state="beta" >}}
|
|
|
|
The CSI Migration feature for GCE PD, when enabled, shims all plugin operations
|
|
from the existing in-tree plugin to the `pd.csi.storage.gke.io` Container
|
|
Storage Interface (CSI) Driver. In order to use this feature, the [GCE PD CSI
|
|
Driver](https://github.com/kubernetes-sigs/gcp-compute-persistent-disk-csi-driver)
|
|
must be installed on the cluster and the `CSIMigration` and `CSIMigrationGCE`
|
|
Beta features must be enabled.
|
|
|
|
### gitRepo (deprecated) {#gitrepo}
|
|
|
|
{{< warning >}}
|
|
The gitRepo volume type is deprecated. To provision a container with a git repo, mount an [EmptyDir](#emptydir) into an InitContainer that clones the repo using git, then mount the [EmptyDir](#emptydir) into the Pod's container.
|
|
{{< /warning >}}
|
|
|
|
A `gitRepo` volume is an example of what can be done as a volume plugin. It
|
|
mounts an empty directory and clones a git repository into it for your Pod to
|
|
use. In the future, such volumes may be moved to an even more decoupled model,
|
|
rather than extending the Kubernetes API for every such use case.
|
|
|
|
Here is an example of gitRepo volume:
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: server
|
|
spec:
|
|
containers:
|
|
- image: nginx
|
|
name: nginx
|
|
volumeMounts:
|
|
- mountPath: /mypath
|
|
name: git-volume
|
|
volumes:
|
|
- name: git-volume
|
|
gitRepo:
|
|
repository: "git@somewhere:me/my-git-repository.git"
|
|
revision: "22f1d8406d464b0c0874075539c1f2e96c253775"
|
|
```
|
|
|
|
### glusterfs {#glusterfs}
|
|
|
|
A `glusterfs` volume allows a [Glusterfs](http://www.gluster.org) (an open
|
|
source networked filesystem) volume to be mounted into your Pod. Unlike
|
|
`emptyDir`, which is erased when a Pod is removed, the contents of a
|
|
`glusterfs` volume are preserved and the volume is merely unmounted. This
|
|
means that a glusterfs volume can be pre-populated with data, and that data can
|
|
be "handed off" between Pods. GlusterFS can be mounted by multiple writers
|
|
simultaneously.
|
|
|
|
{{< caution >}}
|
|
You must have your own GlusterFS installation running before you can use it.
|
|
{{< /caution >}}
|
|
|
|
See the [GlusterFS example](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/volumes/glusterfs) for more details.
|
|
|
|
### hostPath {#hostpath}
|
|
|
|
A `hostPath` volume mounts a file or directory from the host node's filesystem
|
|
into your Pod. This is not something that most Pods will need, but it offers a
|
|
powerful escape hatch for some applications.
|
|
|
|
For example, some uses for a `hostPath` are:
|
|
|
|
* running a Container that needs access to Docker internals; use a `hostPath`
|
|
of `/var/lib/docker`
|
|
* running cAdvisor in a Container; use a `hostPath` of `/sys`
|
|
* allowing a Pod to specify whether a given `hostPath` should exist prior to the
|
|
Pod running, whether it should be created, and what it should exist as
|
|
|
|
In addition to the required `path` property, user can optionally specify a `type` for a `hostPath` volume.
|
|
|
|
The supported values for field `type` are:
|
|
|
|
|
|
| Value | Behavior |
|
|
|:------|:---------|
|
|
| | Empty string (default) is for backward compatibility, which means that no checks will be performed before mounting the hostPath volume. |
|
|
| `DirectoryOrCreate` | If nothing exists at the given path, an empty directory will be created there as needed with permission set to 0755, having the same group and ownership with Kubelet. |
|
|
| `Directory` | A directory must exist at the given path |
|
|
| `FileOrCreate` | If nothing exists at the given path, an empty file will be created there as needed with permission set to 0644, having the same group and ownership with Kubelet. |
|
|
| `File` | A file must exist at the given path |
|
|
| `Socket` | A UNIX socket must exist at the given path |
|
|
| `CharDevice` | A character device must exist at the given path |
|
|
| `BlockDevice` | A block device must exist at the given path |
|
|
|
|
Watch out when using this type of volume, because:
|
|
|
|
* Pods with identical configuration (such as created from a podTemplate) may
|
|
behave differently on different nodes due to different files on the nodes
|
|
* when Kubernetes adds resource-aware scheduling, as is planned, it will not be
|
|
able to account for resources used by a `hostPath`
|
|
* the files or directories created on the underlying hosts are only writable by root. You
|
|
either need to run your process as root in a
|
|
[privileged Container](/docs/user-guide/security-context) or modify the file
|
|
permissions on the host to be able to write to a `hostPath` volume
|
|
|
|
#### Example Pod
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: test-pd
|
|
spec:
|
|
containers:
|
|
- image: k8s.gcr.io/test-webserver
|
|
name: test-container
|
|
volumeMounts:
|
|
- mountPath: /test-pd
|
|
name: test-volume
|
|
volumes:
|
|
- name: test-volume
|
|
hostPath:
|
|
# directory location on host
|
|
path: /data
|
|
# this field is optional
|
|
type: Directory
|
|
```
|
|
|
|
{{< caution >}}
|
|
It should be noted that the `FileOrCreate` mode does not create the parent directory of the file. If the parent directory of the mounted file does not exist, the pod fails to start. To ensure that this mode works, you can try to mount directories and files separately, as shown below.
|
|
{{< /caution >}}
|
|
|
|
#### Example Pod FileOrCreate
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: test-webserver
|
|
spec:
|
|
containers:
|
|
- name: test-webserver
|
|
image: k8s.gcr.io/test-webserver:latest
|
|
volumeMounts:
|
|
- mountPath: /var/local/aaa
|
|
name: mydir
|
|
- mountPath: /var/local/aaa/1.txt
|
|
name: myfile
|
|
volumes:
|
|
- name: mydir
|
|
hostPath:
|
|
# Ensure the file directory is created.
|
|
path: /var/local/aaa
|
|
type: DirectoryOrCreate
|
|
- name: myfile
|
|
hostPath:
|
|
path: /var/local/aaa/1.txt
|
|
type: FileOrCreate
|
|
```
|
|
|
|
### iscsi {#iscsi}
|
|
|
|
An `iscsi` volume allows an existing iSCSI (SCSI over IP) volume to be mounted
|
|
into your Pod. Unlike `emptyDir`, which is erased when a Pod is removed, the
|
|
contents of an `iscsi` volume are preserved and the volume is merely
|
|
unmounted. This means that an iscsi volume can be pre-populated with data, and
|
|
that data can be "handed off" between Pods.
|
|
|
|
{{< caution >}}
|
|
You must have your own iSCSI server running with the volume created before you can use it.
|
|
{{< /caution >}}
|
|
|
|
A feature of iSCSI is that it can be mounted as read-only by multiple consumers
|
|
simultaneously. This means that you can pre-populate a volume with your dataset
|
|
and then serve it in parallel from as many Pods as you need. Unfortunately,
|
|
iSCSI volumes can only be mounted by a single consumer in read-write mode - no
|
|
simultaneous writers allowed.
|
|
|
|
See the [iSCSI example](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/volumes/iscsi) for more details.
|
|
|
|
### local {#local}
|
|
|
|
{{< feature-state for_k8s_version="v1.14" state="stable" >}}
|
|
|
|
A `local` volume represents a mounted local storage device such as a disk,
|
|
partition or directory.
|
|
|
|
Local volumes can only be used as a statically created PersistentVolume. Dynamic
|
|
provisioning is not supported yet.
|
|
|
|
Compared to `hostPath` volumes, local volumes can be used in a durable and
|
|
portable manner without manually scheduling Pods to nodes, as the system is aware
|
|
of the volume's node constraints by looking at the node affinity on the PersistentVolume.
|
|
|
|
However, local volumes are still subject to the availability of the underlying
|
|
node and are not suitable for all applications. If a node becomes unhealthy,
|
|
then the local volume will also become inaccessible, and a Pod using it will not
|
|
be able to run. Applications using local volumes must be able to tolerate this
|
|
reduced availability, as well as potential data loss, depending on the
|
|
durability characteristics of the underlying disk.
|
|
|
|
The following is an example of PersistentVolume spec using a `local` volume and
|
|
`nodeAffinity`:
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: PersistentVolume
|
|
metadata:
|
|
name: example-pv
|
|
spec:
|
|
capacity:
|
|
storage: 100Gi
|
|
volumeMode: Filesystem
|
|
accessModes:
|
|
- ReadWriteOnce
|
|
persistentVolumeReclaimPolicy: Delete
|
|
storageClassName: local-storage
|
|
local:
|
|
path: /mnt/disks/ssd1
|
|
nodeAffinity:
|
|
required:
|
|
nodeSelectorTerms:
|
|
- matchExpressions:
|
|
- key: kubernetes.io/hostname
|
|
operator: In
|
|
values:
|
|
- example-node
|
|
```
|
|
|
|
PersistentVolume `nodeAffinity` is required when using local volumes. It enables
|
|
the Kubernetes scheduler to correctly schedule Pods using local volumes to the
|
|
correct node.
|
|
|
|
PersistentVolume `volumeMode` can be set to "Block" (instead of the default
|
|
value "Filesystem") to expose the local volume as a raw block device.
|
|
|
|
When using local volumes, it is recommended to create a StorageClass with
|
|
`volumeBindingMode` set to `WaitForFirstConsumer`. See the
|
|
[example](/docs/concepts/storage/storage-classes/#local). Delaying volume binding ensures
|
|
that the PersistentVolumeClaim binding decision will also be evaluated with any
|
|
other node constraints the Pod may have, such as node resource requirements, node
|
|
selectors, Pod affinity, and Pod anti-affinity.
|
|
|
|
An external static provisioner can be run separately for improved management of
|
|
the local volume lifecycle. Note that this provisioner does not support dynamic
|
|
provisioning yet. For an example on how to run an external local provisioner,
|
|
see the [local volume provisioner user
|
|
guide](https://github.com/kubernetes-sigs/sig-storage-local-static-provisioner).
|
|
|
|
{{< note >}}
|
|
The local PersistentVolume requires manual cleanup and deletion by the
|
|
user if the external static provisioner is not used to manage the volume
|
|
lifecycle.
|
|
{{< /note >}}
|
|
|
|
### nfs {#nfs}
|
|
|
|
An `nfs` volume allows an existing NFS (Network File System) share to be
|
|
mounted into your Pod. Unlike `emptyDir`, which is erased when a Pod is
|
|
removed, the contents of an `nfs` volume are preserved and the volume is merely
|
|
unmounted. This means that an NFS volume can be pre-populated with data, and
|
|
that data can be "handed off" between Pods. NFS can be mounted by multiple
|
|
writers simultaneously.
|
|
|
|
{{< caution >}}
|
|
You must have your own NFS server running with the share exported before you can use it.
|
|
{{< /caution >}}
|
|
|
|
See the [NFS example](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/volumes/nfs) for more details.
|
|
|
|
### persistentVolumeClaim {#persistentvolumeclaim}
|
|
|
|
A `persistentVolumeClaim` volume is used to mount a
|
|
[PersistentVolume](/docs/concepts/storage/persistent-volumes/) into a Pod. PersistentVolumes are a
|
|
way for users to "claim" durable storage (such as a GCE PersistentDisk or an
|
|
iSCSI volume) without knowing the details of the particular cloud environment.
|
|
|
|
See the [PersistentVolumes example](/docs/concepts/storage/persistent-volumes/) for more
|
|
details.
|
|
|
|
### projected {#projected}
|
|
|
|
A `projected` volume maps several existing volume sources into the same directory.
|
|
|
|
Currently, the following types of volume sources can be projected:
|
|
|
|
- [`secret`](#secret)
|
|
- [`downwardAPI`](#downwardapi)
|
|
- [`configMap`](#configmap)
|
|
- `serviceAccountToken`
|
|
|
|
All sources are required to be in the same namespace as the Pod. For more details,
|
|
see the [all-in-one volume design document](https://github.com/kubernetes/community/blob/{{< param "githubbranch" >}}/contributors/design-proposals/node/all-in-one-volume.md).
|
|
|
|
The projection of service account tokens is a feature introduced in Kubernetes
|
|
1.11 and promoted to Beta in 1.12.
|
|
To enable this feature on 1.11, you need to explicitly set the `TokenRequestProjection`
|
|
[feature gate](/docs/reference/command-line-tools-reference/feature-gates/) to
|
|
True.
|
|
|
|
#### Example Pod with a secret, a downward API, and a configmap.
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: volume-test
|
|
spec:
|
|
containers:
|
|
- name: container-test
|
|
image: busybox
|
|
volumeMounts:
|
|
- name: all-in-one
|
|
mountPath: "/projected-volume"
|
|
readOnly: true
|
|
volumes:
|
|
- name: all-in-one
|
|
projected:
|
|
sources:
|
|
- secret:
|
|
name: mysecret
|
|
items:
|
|
- key: username
|
|
path: my-group/my-username
|
|
- downwardAPI:
|
|
items:
|
|
- path: "labels"
|
|
fieldRef:
|
|
fieldPath: metadata.labels
|
|
- path: "cpu_limit"
|
|
resourceFieldRef:
|
|
containerName: container-test
|
|
resource: limits.cpu
|
|
- configMap:
|
|
name: myconfigmap
|
|
items:
|
|
- key: config
|
|
path: my-group/my-config
|
|
```
|
|
|
|
#### Example Pod with multiple secrets with a non-default permission mode set.
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: volume-test
|
|
spec:
|
|
containers:
|
|
- name: container-test
|
|
image: busybox
|
|
volumeMounts:
|
|
- name: all-in-one
|
|
mountPath: "/projected-volume"
|
|
readOnly: true
|
|
volumes:
|
|
- name: all-in-one
|
|
projected:
|
|
sources:
|
|
- secret:
|
|
name: mysecret
|
|
items:
|
|
- key: username
|
|
path: my-group/my-username
|
|
- secret:
|
|
name: mysecret2
|
|
items:
|
|
- key: password
|
|
path: my-group/my-password
|
|
mode: 511
|
|
```
|
|
|
|
Each projected volume source is listed in the spec under `sources`. The
|
|
parameters are nearly the same with two exceptions:
|
|
|
|
* For secrets, the `secretName` field has been changed to `name` to be consistent
|
|
with ConfigMap naming.
|
|
* The `defaultMode` can only be specified at the projected level and not for each
|
|
volume source. However, as illustrated above, you can explicitly set the `mode`
|
|
for each individual projection.
|
|
|
|
When the `TokenRequestProjection` feature is enabled, you can inject the token
|
|
for the current [service account](/docs/reference/access-authn-authz/authentication/#service-account-tokens)
|
|
into a Pod at a specified path. Below is an example:
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: sa-token-test
|
|
spec:
|
|
containers:
|
|
- name: container-test
|
|
image: busybox
|
|
volumeMounts:
|
|
- name: token-vol
|
|
mountPath: "/service-account"
|
|
readOnly: true
|
|
volumes:
|
|
- name: token-vol
|
|
projected:
|
|
sources:
|
|
- serviceAccountToken:
|
|
audience: api
|
|
expirationSeconds: 3600
|
|
path: token
|
|
```
|
|
|
|
The example Pod has a projected volume containing the injected service account
|
|
token. This token can be used by Pod containers to access the Kubernetes API
|
|
server, for example. The `audience` field contains the intended audience of the
|
|
token. A recipient of the token must identify itself with an identifier specified
|
|
in the audience of the token, and otherwise should reject the token. This field
|
|
is optional and it defaults to the identifier of the API server.
|
|
|
|
The `expirationSeconds` is the expected duration of validity of the service account
|
|
token. It defaults to 1 hour and must be at least 10 minutes (600 seconds). An administrator
|
|
can also limit its maximum value by specifying the `--service-account-max-token-expiration`
|
|
option for the API server. The `path` field specifies a relative path to the mount point
|
|
of the projected volume.
|
|
|
|
{{< note >}}
|
|
A Container using a projected volume source as a [subPath](#using-subpath) volume mount will not
|
|
receive updates for those volume sources.
|
|
{{< /note >}}
|
|
|
|
### portworxVolume {#portworxvolume}
|
|
|
|
A `portworxVolume` is an elastic block storage layer that runs hyperconverged with
|
|
Kubernetes. [Portworx](https://portworx.com/use-case/kubernetes-storage/) fingerprints storage in a server, tiers based on capabilities,
|
|
and aggregates capacity across multiple servers. Portworx runs in-guest in virtual machines or on bare metal Linux nodes.
|
|
|
|
A `portworxVolume` can be dynamically created through Kubernetes or it can also
|
|
be pre-provisioned and referenced inside a Kubernetes Pod.
|
|
Here is an example Pod referencing a pre-provisioned PortworxVolume:
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: test-portworx-volume-pod
|
|
spec:
|
|
containers:
|
|
- image: k8s.gcr.io/test-webserver
|
|
name: test-container
|
|
volumeMounts:
|
|
- mountPath: /mnt
|
|
name: pxvol
|
|
volumes:
|
|
- name: pxvol
|
|
# This Portworx volume must already exist.
|
|
portworxVolume:
|
|
volumeID: "pxvol"
|
|
fsType: "<fs-type>"
|
|
```
|
|
|
|
{{< caution >}}
|
|
Make sure you have an existing PortworxVolume with name `pxvol`
|
|
before using it in the Pod.
|
|
{{< /caution >}}
|
|
|
|
More details and examples can be found [here](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/volumes/portworx/README.md).
|
|
|
|
### quobyte {#quobyte}
|
|
|
|
A `quobyte` volume allows an existing [Quobyte](http://www.quobyte.com) volume to
|
|
be mounted into your Pod.
|
|
|
|
{{< caution >}}
|
|
You must have your own Quobyte setup running with the volumes
|
|
created before you can use it.
|
|
{{< /caution >}}
|
|
|
|
Quobyte supports the {{< glossary_tooltip text="Container Storage Interface" term_id="csi" >}}.
|
|
CSI is the recommended plugin to use Quobyte volumes inside Kubernetes. Quobyte's
|
|
GitHub project has [instructions](https://github.com/quobyte/quobyte-csi#quobyte-csi) for deploying Quobyte using CSI, along with examples.
|
|
|
|
### rbd {#rbd}
|
|
|
|
An `rbd` volume allows a [Rados Block
|
|
Device](http://ceph.com/docs/master/rbd/rbd/) volume to be mounted into your
|
|
Pod. Unlike `emptyDir`, which is erased when a Pod is removed, the contents of
|
|
a `rbd` volume are preserved and the volume is merely unmounted. This
|
|
means that a RBD volume can be pre-populated with data, and that data can
|
|
be "handed off" between Pods.
|
|
|
|
{{< caution >}}
|
|
You must have your own Ceph installation running before you can use RBD.
|
|
{{< /caution >}}
|
|
|
|
A feature of RBD is that it can be mounted as read-only by multiple consumers
|
|
simultaneously. This means that you can pre-populate a volume with your dataset
|
|
and then serve it in parallel from as many Pods as you need. Unfortunately,
|
|
RBD volumes can only be mounted by a single consumer in read-write mode - no
|
|
simultaneous writers allowed.
|
|
|
|
See the [RBD example](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/volumes/rbd) for more details.
|
|
|
|
### scaleIO {#scaleio}
|
|
|
|
ScaleIO is a software-based storage platform that can use existing hardware to
|
|
create clusters of scalable shared block networked storage. The `scaleIO` volume
|
|
plugin allows deployed Pods to access existing ScaleIO
|
|
volumes (or it can dynamically provision new volumes for persistent volume claims, see
|
|
[ScaleIO Persistent Volumes](/docs/concepts/storage/persistent-volumes/#scaleio)).
|
|
|
|
{{< caution >}}
|
|
You must have an existing ScaleIO cluster already setup and
|
|
running with the volumes created before you can use them.
|
|
{{< /caution >}}
|
|
|
|
The following is an example of Pod configuration with ScaleIO:
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: pod-0
|
|
spec:
|
|
containers:
|
|
- image: k8s.gcr.io/test-webserver
|
|
name: pod-0
|
|
volumeMounts:
|
|
- mountPath: /test-pd
|
|
name: vol-0
|
|
volumes:
|
|
- name: vol-0
|
|
scaleIO:
|
|
gateway: https://localhost:443/api
|
|
system: scaleio
|
|
protectionDomain: sd0
|
|
storagePool: sp1
|
|
volumeName: vol-0
|
|
secretRef:
|
|
name: sio-secret
|
|
fsType: xfs
|
|
```
|
|
|
|
For further detail, please see the [ScaleIO examples](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/volumes/scaleio).
|
|
|
|
### secret {#secret}
|
|
|
|
A `secret` volume is used to pass sensitive information, such as passwords, to
|
|
Pods. You can store secrets in the Kubernetes API and mount them as files for
|
|
use by Pods without coupling to Kubernetes directly. `secret` volumes are
|
|
backed by tmpfs (a RAM-backed filesystem) so they are never written to
|
|
non-volatile storage.
|
|
|
|
{{< caution >}}
|
|
You must create a secret in the Kubernetes API before you can use it.
|
|
{{< /caution >}}
|
|
|
|
{{< note >}}
|
|
A Container using a Secret as a [subPath](#using-subpath) volume mount will not
|
|
receive Secret updates.
|
|
{{< /note >}}
|
|
|
|
Secrets are described in more detail [here](/docs/user-guide/secrets).
|
|
|
|
### storageOS {#storageos}
|
|
|
|
A `storageos` volume allows an existing [StorageOS](https://www.storageos.com)
|
|
volume to be mounted into your Pod.
|
|
|
|
StorageOS runs as a Container within your Kubernetes environment, making local
|
|
or attached storage accessible from any node within the Kubernetes cluster.
|
|
Data can be replicated to protect against node failure. Thin provisioning and
|
|
compression can improve utilization and reduce cost.
|
|
|
|
At its core, StorageOS provides block storage to Containers, accessible via a file system.
|
|
|
|
The StorageOS Container requires 64-bit Linux and has no additional dependencies.
|
|
A free developer license is available.
|
|
|
|
{{< caution >}}
|
|
You must run the StorageOS Container on each node that wants to
|
|
access StorageOS volumes or that will contribute storage capacity to the pool.
|
|
For installation instructions, consult the
|
|
[StorageOS documentation](https://docs.storageos.com).
|
|
{{< /caution >}}
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
labels:
|
|
name: redis
|
|
role: master
|
|
name: test-storageos-redis
|
|
spec:
|
|
containers:
|
|
- name: master
|
|
image: kubernetes/redis:v1
|
|
env:
|
|
- name: MASTER
|
|
value: "true"
|
|
ports:
|
|
- containerPort: 6379
|
|
volumeMounts:
|
|
- mountPath: /redis-master-data
|
|
name: redis-data
|
|
volumes:
|
|
- name: redis-data
|
|
storageos:
|
|
# The `redis-vol01` volume must already exist within StorageOS in the `default` namespace.
|
|
volumeName: redis-vol01
|
|
fsType: ext4
|
|
```
|
|
|
|
For more information including Dynamic Provisioning and Persistent Volume Claims, please see the
|
|
[StorageOS examples](https://github.com/kubernetes/examples/blob/master/volumes/storageos).
|
|
|
|
### vsphereVolume {#vspherevolume}
|
|
|
|
{{< note >}}
|
|
Prerequisite: Kubernetes with vSphere Cloud Provider configured. For cloudprovider
|
|
configuration please refer [vSphere getting started guide](https://vmware.github.io/vsphere-storage-for-kubernetes/documentation/).
|
|
{{< /note >}}
|
|
|
|
A `vsphereVolume` is used to mount a vSphere VMDK Volume into your Pod. The contents
|
|
of a volume are preserved when it is unmounted. It supports both VMFS and VSAN datastore.
|
|
|
|
{{< caution >}}
|
|
You must create VMDK using one of the following methods before using with Pod.
|
|
{{< /caution >}}
|
|
|
|
#### Creating a VMDK volume
|
|
|
|
Choose one of the following methods to create a VMDK.
|
|
|
|
{{< tabs name="tabs_volumes" >}}
|
|
{{% tab name="Create using vmkfstools" %}}
|
|
First ssh into ESX, then use the following command to create a VMDK:
|
|
|
|
```shell
|
|
vmkfstools -c 2G /vmfs/volumes/DatastoreName/volumes/myDisk.vmdk
|
|
```
|
|
{{% /tab %}}
|
|
{{% tab name="Create using vmware-vdiskmanager" %}}
|
|
Use the following command to create a VMDK:
|
|
|
|
```shell
|
|
vmware-vdiskmanager -c -t 0 -s 40GB -a lsilogic myDisk.vmdk
|
|
```
|
|
{{% /tab %}}
|
|
|
|
{{< /tabs >}}
|
|
|
|
|
|
#### vSphere VMDK Example configuration
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: test-vmdk
|
|
spec:
|
|
containers:
|
|
- image: k8s.gcr.io/test-webserver
|
|
name: test-container
|
|
volumeMounts:
|
|
- mountPath: /test-vmdk
|
|
name: test-volume
|
|
volumes:
|
|
- name: test-volume
|
|
# This VMDK volume must already exist.
|
|
vsphereVolume:
|
|
volumePath: "[DatastoreName] volumes/myDisk"
|
|
fsType: ext4
|
|
```
|
|
|
|
More examples can be found [here](https://github.com/kubernetes/examples/tree/master/staging/volumes/vsphere).
|
|
|
|
|
|
## Using subPath
|
|
|
|
Sometimes, it is useful to share one volume for multiple uses in a single Pod. The `volumeMounts.subPath`
|
|
property can be used to specify a sub-path inside the referenced volume instead of its root.
|
|
|
|
Here is an example of a Pod with a LAMP stack (Linux Apache Mysql PHP) using a single, shared volume.
|
|
The HTML contents are mapped to its `html` folder, and the databases will be stored in its `mysql` folder:
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: my-lamp-site
|
|
spec:
|
|
containers:
|
|
- name: mysql
|
|
image: mysql
|
|
env:
|
|
- name: MYSQL_ROOT_PASSWORD
|
|
value: "rootpasswd"
|
|
volumeMounts:
|
|
- mountPath: /var/lib/mysql
|
|
name: site-data
|
|
subPath: mysql
|
|
- name: php
|
|
image: php:7.0-apache
|
|
volumeMounts:
|
|
- mountPath: /var/www/html
|
|
name: site-data
|
|
subPath: html
|
|
volumes:
|
|
- name: site-data
|
|
persistentVolumeClaim:
|
|
claimName: my-lamp-site-data
|
|
```
|
|
|
|
### Using subPath with expanded environment variables
|
|
|
|
{{< feature-state for_k8s_version="v1.17" state="stable" >}}
|
|
|
|
|
|
Use the `subPathExpr` field to construct `subPath` directory names from Downward API environment variables.
|
|
This feature requires the `VolumeSubpathEnvExpansion` [feature gate](/docs/reference/command-line-tools-reference/feature-gates/) to be enabled. It is enabled by default starting with Kubernetes 1.15.
|
|
The `subPath` and `subPathExpr` properties are mutually exclusive.
|
|
|
|
In this example, a Pod uses `subPathExpr` to create a directory `pod1` within the hostPath volume `/var/log/pods`, using the pod name from the Downward API. The host directory `/var/log/pods/pod1` is mounted at `/logs` in the container.
|
|
|
|
```yaml
|
|
apiVersion: v1
|
|
kind: Pod
|
|
metadata:
|
|
name: pod1
|
|
spec:
|
|
containers:
|
|
- name: container1
|
|
env:
|
|
- name: POD_NAME
|
|
valueFrom:
|
|
fieldRef:
|
|
apiVersion: v1
|
|
fieldPath: metadata.name
|
|
image: busybox
|
|
command: [ "sh", "-c", "while [ true ]; do echo 'Hello'; sleep 10; done | tee -a /logs/hello.txt" ]
|
|
volumeMounts:
|
|
- name: workdir1
|
|
mountPath: /logs
|
|
subPathExpr: $(POD_NAME)
|
|
restartPolicy: Never
|
|
volumes:
|
|
- name: workdir1
|
|
hostPath:
|
|
path: /var/log/pods
|
|
```
|
|
|
|
## Resources
|
|
|
|
The storage media (Disk, SSD, etc.) of an `emptyDir` volume is determined by the
|
|
medium of the filesystem holding the kubelet root dir (typically
|
|
`/var/lib/kubelet`). There is no limit on how much space an `emptyDir` or
|
|
`hostPath` volume can consume, and no isolation between Containers or between
|
|
Pods.
|
|
|
|
In the future, we expect that `emptyDir` and `hostPath` volumes will be able to
|
|
request a certain amount of space using a [resource](/docs/user-guide/compute-resources)
|
|
specification, and to select the type of media to use, for clusters that have
|
|
several media types.
|
|
|
|
## Out-of-Tree Volume Plugins
|
|
The Out-of-tree volume plugins include the Container Storage Interface (CSI)
|
|
and FlexVolume. They enable storage vendors to create custom storage plugins
|
|
without adding them to the Kubernetes repository.
|
|
|
|
Before the introduction of CSI and FlexVolume, all volume plugins (like
|
|
volume types listed above) were "in-tree" meaning they were built, linked,
|
|
compiled, and shipped with the core Kubernetes binaries and extend the core
|
|
Kubernetes API. This meant that adding a new storage system to Kubernetes (a
|
|
volume plugin) required checking code into the core Kubernetes code repository.
|
|
|
|
Both CSI and FlexVolume allow volume plugins to be developed independent of
|
|
the Kubernetes code base, and deployed (installed) on Kubernetes clusters as
|
|
extensions.
|
|
|
|
For storage vendors looking to create an out-of-tree volume plugin, please refer
|
|
to [this FAQ](https://github.com/kubernetes/community/blob/master/sig-storage/volume-plugin-faq.md).
|
|
|
|
### CSI
|
|
|
|
[Container Storage Interface](https://github.com/container-storage-interface/spec/blob/master/spec.md) (CSI)
|
|
defines a standard interface for container orchestration systems (like
|
|
Kubernetes) to expose arbitrary storage systems to their container workloads.
|
|
|
|
Please read the [CSI design proposal](https://github.com/kubernetes/community/blob/master/contributors/design-proposals/storage/container-storage-interface.md) for more information.
|
|
|
|
CSI support was introduced as alpha in Kubernetes v1.9, moved to beta in
|
|
Kubernetes v1.10, and is GA in Kubernetes v1.13.
|
|
|
|
{{< note >}}
|
|
Support for CSI spec versions 0.2 and 0.3 are deprecated in Kubernetes
|
|
v1.13 and will be removed in a future release.
|
|
{{< /note >}}
|
|
|
|
{{< note >}}
|
|
CSI drivers may not be compatible across all Kubernetes releases.
|
|
Please check the specific CSI driver's documentation for supported
|
|
deployments steps for each Kubernetes release and a compatibility matrix.
|
|
{{< /note >}}
|
|
|
|
Once a CSI compatible volume driver is deployed on a Kubernetes cluster, users
|
|
may use the `csi` volume type to attach, mount, etc. the volumes exposed by the
|
|
CSI driver.
|
|
|
|
The `csi` volume type does not support direct reference from Pod and may only be
|
|
referenced in a Pod via a `PersistentVolumeClaim` object.
|
|
|
|
The following fields are available to storage administrators to configure a CSI
|
|
persistent volume:
|
|
|
|
- `driver`: A string value that specifies the name of the volume driver to use.
|
|
This value must correspond to the value returned in the `GetPluginInfoResponse`
|
|
by the CSI driver as defined in the [CSI spec](https://github.com/container-storage-interface/spec/blob/master/spec.md#getplugininfo).
|
|
It is used by Kubernetes to identify which CSI driver to call out to, and by
|
|
CSI driver components to identify which PV objects belong to the CSI driver.
|
|
- `volumeHandle`: A string value that uniquely identifies the volume. This value
|
|
must correspond to the value returned in the `volume.id` field of the
|
|
`CreateVolumeResponse` by the CSI driver as defined in the [CSI spec](https://github.com/container-storage-interface/spec/blob/master/spec.md#createvolume).
|
|
The value is passed as `volume_id` on all calls to the CSI volume driver when
|
|
referencing the volume.
|
|
- `readOnly`: An optional boolean value indicating whether the volume is to be
|
|
"ControllerPublished" (attached) as read only. Default is false. This value is
|
|
passed to the CSI driver via the `readonly` field in the
|
|
`ControllerPublishVolumeRequest`.
|
|
- `fsType`: If the PV's `VolumeMode` is `Filesystem` then this field may be used
|
|
to specify the filesystem that should be used to mount the volume. If the
|
|
volume has not been formatted and formatting is supported, this value will be
|
|
used to format the volume.
|
|
This value is passed to the CSI driver via the `VolumeCapability` field of
|
|
`ControllerPublishVolumeRequest`, `NodeStageVolumeRequest`, and
|
|
`NodePublishVolumeRequest`.
|
|
- `volumeAttributes`: A map of string to string that specifies static properties
|
|
of a volume. This map must correspond to the map returned in the
|
|
`volume.attributes` field of the `CreateVolumeResponse` by the CSI driver as
|
|
defined in the [CSI spec](https://github.com/container-storage-interface/spec/blob/master/spec.md#createvolume).
|
|
The map is passed to the CSI driver via the `volume_attributes` field in the
|
|
`ControllerPublishVolumeRequest`, `NodeStageVolumeRequest`, and
|
|
`NodePublishVolumeRequest`.
|
|
- `controllerPublishSecretRef`: A reference to the secret object containing
|
|
sensitive information to pass to the CSI driver to complete the CSI
|
|
`ControllerPublishVolume` and `ControllerUnpublishVolume` calls. This field is
|
|
optional, and may be empty if no secret is required. If the secret object
|
|
contains more than one secret, all secrets are passed.
|
|
- `nodeStageSecretRef`: A reference to the secret object containing
|
|
sensitive information to pass to the CSI driver to complete the CSI
|
|
`NodeStageVolume` call. This field is optional, and may be empty if no secret
|
|
is required. If the secret object contains more than one secret, all secrets
|
|
are passed.
|
|
- `nodePublishSecretRef`: A reference to the secret object containing
|
|
sensitive information to pass to the CSI driver to complete the CSI
|
|
`NodePublishVolume` call. This field is optional, and may be empty if no
|
|
secret is required. If the secret object contains more than one secret, all
|
|
secrets are passed.
|
|
|
|
#### CSI raw block volume support
|
|
|
|
{{< feature-state for_k8s_version="v1.18" state="stable" >}}
|
|
|
|
Vendors with external CSI drivers can implement raw block volumes support
|
|
in Kubernetes workloads.
|
|
|
|
You can [setup your PV/PVC with raw block volume support](/docs/concepts/storage/persistent-volumes/#raw-block-volume-support)
|
|
as usual, without any CSI specific changes.
|
|
|
|
#### CSI ephemeral volumes
|
|
|
|
{{< feature-state for_k8s_version="v1.16" state="beta" >}}
|
|
|
|
This feature allows CSI volumes to be directly embedded in the Pod specification instead of a PersistentVolume. Volumes specified in this way are ephemeral and do not persist across Pod restarts.
|
|
|
|
Example:
|
|
|
|
```yaml
|
|
kind: Pod
|
|
apiVersion: v1
|
|
metadata:
|
|
name: my-csi-app
|
|
spec:
|
|
containers:
|
|
- name: my-frontend
|
|
image: busybox
|
|
volumeMounts:
|
|
- mountPath: "/data"
|
|
name: my-csi-inline-vol
|
|
command: [ "sleep", "1000000" ]
|
|
volumes:
|
|
- name: my-csi-inline-vol
|
|
csi:
|
|
driver: inline.storage.kubernetes.io
|
|
volumeAttributes:
|
|
foo: bar
|
|
```
|
|
|
|
This feature requires CSIInlineVolume feature gate to be enabled. It
|
|
is enabled by default starting with Kubernetes 1.16.
|
|
|
|
CSI ephemeral volumes are only supported by a subset of CSI drivers. Please see the list of CSI drivers [here](https://kubernetes-csi.github.io/docs/drivers.html).
|
|
|
|
# Developer resources
|
|
For more information on how to develop a CSI driver, refer to the [kubernetes-csi
|
|
documentation](https://kubernetes-csi.github.io/docs/)
|
|
|
|
#### Migrating to CSI drivers from in-tree plugins
|
|
|
|
{{< feature-state for_k8s_version="v1.14" state="alpha" >}}
|
|
|
|
The CSI Migration feature, when enabled, directs operations against existing in-tree
|
|
plugins to corresponding CSI plugins (which are expected to be installed and configured).
|
|
The feature implements the necessary translation logic and shims to re-route the
|
|
operations in a seamless fashion. As a result, operators do not have to make any
|
|
configuration changes to existing Storage Classes, PVs or PVCs (referring to
|
|
in-tree plugins) when transitioning to a CSI driver that supersedes an in-tree plugin.
|
|
|
|
In the alpha state, the operations and features that are supported include
|
|
provisioning/delete, attach/detach, mount/unmount and resizing of volumes.
|
|
|
|
In-tree plugins that support CSI Migration and have a corresponding CSI driver implemented
|
|
are listed in the "Types of Volumes" section above.
|
|
|
|
### FlexVolume {#flexVolume}
|
|
|
|
FlexVolume is an out-of-tree plugin interface that has existed in Kubernetes
|
|
since version 1.2 (before CSI). It uses an exec-based model to interface with
|
|
drivers. FlexVolume driver binaries must be installed in a pre-defined volume
|
|
plugin path on each node (and in some cases master).
|
|
|
|
Pods interact with FlexVolume drivers through the `flexvolume` in-tree plugin.
|
|
More details can be found [here](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-storage/flexvolume.md).
|
|
|
|
## Mount propagation
|
|
|
|
Mount propagation allows for sharing volumes mounted by a Container to
|
|
other Containers in the same Pod, or even to other Pods on the same node.
|
|
|
|
Mount propagation of a volume is controlled by `mountPropagation` field in Container.volumeMounts.
|
|
Its values are:
|
|
|
|
* `None` - This volume mount will not receive any subsequent mounts
|
|
that are mounted to this volume or any of its subdirectories by the host.
|
|
In similar fashion, no mounts created by the Container will be visible on
|
|
the host. This is the default mode.
|
|
|
|
This mode is equal to `private` mount propagation as described in the
|
|
[Linux kernel documentation](https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt)
|
|
|
|
* `HostToContainer` - This volume mount will receive all subsequent mounts
|
|
that are mounted to this volume or any of its subdirectories.
|
|
|
|
In other words, if the host mounts anything inside the volume mount, the
|
|
Container will see it mounted there.
|
|
|
|
Similarly, if any Pod with `Bidirectional` mount propagation to the same
|
|
volume mounts anything there, the Container with `HostToContainer` mount
|
|
propagation will see it.
|
|
|
|
This mode is equal to `rslave` mount propagation as described in the
|
|
[Linux kernel documentation](https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt)
|
|
|
|
* `Bidirectional` - This volume mount behaves the same the `HostToContainer` mount.
|
|
In addition, all volume mounts created by the Container will be propagated
|
|
back to the host and to all Containers of all Pods that use the same volume.
|
|
|
|
A typical use case for this mode is a Pod with a FlexVolume or CSI driver or
|
|
a Pod that needs to mount something on the host using a `hostPath` volume.
|
|
|
|
This mode is equal to `rshared` mount propagation as described in the
|
|
[Linux kernel documentation](https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt)
|
|
|
|
{{< caution >}}
|
|
`Bidirectional` mount propagation can be dangerous. It can damage
|
|
the host operating system and therefore it is allowed only in privileged
|
|
Containers. Familiarity with Linux kernel behavior is strongly recommended.
|
|
In addition, any volume mounts created by Containers in Pods must be destroyed
|
|
(unmounted) by the Containers on termination.
|
|
{{< /caution >}}
|
|
|
|
### Configuration
|
|
Before mount propagation can work properly on some deployments (CoreOS,
|
|
RedHat/Centos, Ubuntu) mount share must be configured correctly in
|
|
Docker as shown below.
|
|
|
|
Edit your Docker's `systemd` service file. Set `MountFlags` as follows:
|
|
```shell
|
|
MountFlags=shared
|
|
```
|
|
Or, remove `MountFlags=slave` if present. Then restart the Docker daemon:
|
|
```shell
|
|
sudo systemctl daemon-reload
|
|
sudo systemctl restart docker
|
|
```
|
|
|
|
|
|
|
|
{{% capture whatsnext %}}
|
|
* Follow an example of [deploying WordPress and MySQL with Persistent Volumes](/docs/tutorials/stateful-application/mysql-wordpress-persistent-volume/).
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