553f9f822b
hack/run-gendocs.sh puts ga-beacon analytics link into all md files, hack/verify-gendocs.sh verifies presence of link.
116 lines
4.2 KiB
Markdown
116 lines
4.2 KiB
Markdown
# How To Use Persistent Volumes
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The purpose of this guide is to help you become familiar with Kubernetes Persistent Volumes. By the end of the guide, we'll have
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nginx serving content from your persistent volume.
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This guide assumes knowledge of Kubernetes fundamentals and that you have a cluster up and running.
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## Provisioning
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A PersistentVolume in Kubernetes represents a real piece of underlying storage capacity in the infrastructure. Cluster administrators
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must first create storage (create their GCE disks, export their NFS shares, etc.) in order for Kubernetes to mount it.
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PVs are intended for "network volumes" like GCE Persistent Disks, NFS shares, and AWS ElasticBlockStore volumes. ```HostPath``` was included
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for ease of development and testing. You'll create a local ```HostPath``` for this example.
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> IMPORTANT! For ```HostPath``` to work, you will need to run a single node cluster. Kubernetes does not
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support local storage on the host at this time. There is no guarantee your pod ends up on the correct node where the ```HostPath``` resides.
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```
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// this will be nginx's webroot
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mkdir /tmp/data01
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echo 'I love Kubernetes storage!' > /tmp/data01/index.html
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```
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PVs are created by posting them to the API server.
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```
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cluster/kubectl.sh create -f examples/persistent-volumes/volumes/local-01.yaml
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cluster/kubectl.sh get pv
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NAME LABELS CAPACITY ACCESSMODES STATUS CLAIM
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pv0001 map[] 10737418240 RWO Available
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```
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## Requesting storage
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Users of Kubernetes request persistent storage for their pods. They don't know how the underlying cluster is provisioned.
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They just know they can rely on their claim to storage and can manage its lifecycle independently from the many pods that may use it.
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Claims must be created in the same namespace as the pods that use them.
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```
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cluster/kubectl.sh create -f examples/persistent-volumes/claims/claim-01.yaml
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cluster/kubectl.sh get pvc
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NAME LABELS STATUS VOLUME
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myclaim-1 map[]
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# A background process will attempt to match this claim to a volume.
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# The eventual state of your claim will look something like this:
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cluster/kubectl.sh get pvc
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NAME LABELS STATUS VOLUME
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myclaim-1 map[] Bound f5c3a89a-e50a-11e4-972f-80e6500a981e
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cluster/kubectl.sh get pv
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NAME LABELS CAPACITY ACCESSMODES STATUS CLAIM
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pv0001 map[] 10737418240 RWO Bound myclaim-1 / 6bef4c40-e50b-11e4-972f-80e6500a981e
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```
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## Using your claim as a volume
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Claims are used as volumes in pods. Kubernetes uses the claim to look up its bound PV. The PV is then exposed to the pod.
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```
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cluster/kubectl.sh create -f examples/persistent-volumes/simpletest/pod.yaml
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cluster/kubectl.sh get pods
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POD IP CONTAINER(S) IMAGE(S) HOST LABELS STATUS CREATED
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mypod 172.17.0.2 myfrontend nginx 127.0.0.1/127.0.0.1 <none> Running 12 minutes
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cluster/kubectl.sh create -f examples/persistent-volumes/simpletest/service.json
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cluster/kubectl.sh get services
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NAME LABELS SELECTOR IP PORT(S)
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frontendservice <none> name=frontendhttp 10.0.0.241 3000/TCP
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kubernetes component=apiserver,provider=kubernetes <none> 10.0.0.2 443/TCP
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kubernetes-ro component=apiserver,provider=kubernetes <none> 10.0.0.1 80/TCP
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```
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## Next steps
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You should be able to query your service endpoint and see what content nginx is serving. A "forbidden" error might mean you
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need to disable SELinux (setenforce 0).
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```
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curl 10.0.0.241:3000
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I love Kubernetes storage!
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```
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Hopefully this simple guide is enough to get you started with PersistentVolumes. If you have any questions, join
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```#google-containers``` on IRC and ask!
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Enjoy!
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[]()
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