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85 lines
3.0 KiB
Markdown
85 lines
3.0 KiB
Markdown
<!-- BEGIN MUNGE: UNVERSIONED_WARNING -->
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<!-- BEGIN STRIP_FOR_RELEASE -->
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>
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If you are using a released version of Kubernetes, you should
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refer to the docs that go with that version.
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<!-- TAG RELEASE_LINK, added by the munger automatically -->
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<strong>
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The latest release of this document can be found
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[here](http://releases.k8s.io/release-1.1/docs/admin/etcd.md).
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Documentation for other releases can be found at
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[releases.k8s.io](http://releases.k8s.io).
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</strong>
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--
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<!-- END STRIP_FOR_RELEASE -->
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<!-- END MUNGE: UNVERSIONED_WARNING -->
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# etcd
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[etcd](https://coreos.com/etcd/docs/2.2.1/) is a highly-available key value
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store which Kubernetes uses for persistent storage of all of its REST API
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objects.
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## Configuration: high-level goals
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Access Control: give *only* kube-apiserver read/write access to etcd. You do not
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want apiserver's etcd exposed to every node in your cluster (or worse, to the
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internet at large), because access to etcd is equivalent to root in your
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cluster.
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Data Reliability: for reasonable safety, either etcd needs to be run as a
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[cluster](high-availability.md#clustering-etcd) (multiple machines each running
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etcd) or etcd's data directory should be located on durable storage (e.g., GCE's
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persistent disk). In either case, if high availability is required--as it might
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be in a production cluster--the data directory ought to be [backed up
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periodically](https://coreos.com/etcd/docs/2.2.1/admin_guide.html#disaster-recovery),
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to reduce downtime in case of corruption.
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## Default configuration
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The default setup scripts use kubelet's file-based static pods feature to run etcd in a
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[pod](http://releases.k8s.io/HEAD/cluster/saltbase/salt/etcd/etcd.manifest). This manifest should only
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be run on master VMs. The default location that kubelet scans for manifests is
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`/etc/kubernetes/manifests/`.
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## Kubernetes's usage of etcd
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By default, Kubernetes objects are stored under the `/registry` key in etcd.
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This path can be prefixed by using the [kube-apiserver](kube-apiserver.md) flag
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`--etcd-prefix="/foo"`.
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`etcd` is the only place that Kubernetes keeps state.
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## Troubleshooting
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To test whether `etcd` is running correctly, you can try writing a value to a
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test key. On your master VM (or somewhere with firewalls configured such that
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you can talk to your cluster's etcd), try:
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```sh
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curl -fs -X PUT "http://${host}:${port}/v2/keys/_test"
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```
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<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
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[]()
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<!-- END MUNGE: GENERATED_ANALYTICS -->
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