2020-10-07 18:16:47 +00:00
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---
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title: Upgrade A Cluster
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content_type: task
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---
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<!-- overview -->
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This page provides an overview of the steps you should follow to upgrade a
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Kubernetes cluster.
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The way that you upgrade a cluster depends on how you initially deployed it
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and on any subsequent changes.
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At a high level, the steps you perform are:
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- Upgrade the {{< glossary_tooltip text="control plane" term_id="control-plane" >}}
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- Upgrade the nodes in your cluster
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- Upgrade clients such as {{< glossary_tooltip text="kubectl" term_id="kubectl" >}}
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- Adjust manifests and other resources based on the API changes that accompany the
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new Kubernetes version
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## {{% heading "prerequisites" %}}
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You must have an existing cluster. This page is about upgrading from Kubernetes
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{{< skew prevMinorVersion >}} to Kubernetes {{< skew latestVersion >}}. If your cluster
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is not currently running Kubernetes {{< skew prevMinorVersion >}} then please check
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the documentation for the version of Kubernetes that you plan to upgrade to.
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## Upgrade approaches
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### kubeadm {#upgrade-kubeadm}
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If your cluster was deployed using the `kubeadm` tool, refer to
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[Upgrading kubeadm clusters](/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade/)
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for detailed information on how to upgrade the cluster.
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Once you have upgraded the cluster, remember to
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2021-03-14 23:22:29 +00:00
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[install the latest version of `kubectl`](/docs/tasks/tools/).
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2020-10-07 18:16:47 +00:00
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### Manual deployments
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{{< caution >}}
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These steps do not account for third-party extensions such as network and storage
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plugins.
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{{< /caution >}}
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You should manually update the control plane following this sequence:
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- etcd (all instances)
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- kube-apiserver (all control plane hosts)
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- kube-controller-manager
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- kube-scheduler
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- cloud controller manager, if you use one
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At this point you should
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2021-03-14 23:22:29 +00:00
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[install the latest version of `kubectl`](/docs/tasks/tools/).
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2020-10-07 18:16:47 +00:00
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For each node in your cluster, [drain](/docs/tasks/administer-cluster/safely-drain-node/)
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that node and then either replace it with a new node that uses the {{< skew latestVersion >}}
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kubelet, or upgrade the kubelet on that node and bring the node back into service.
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### Other deployments {#upgrade-other}
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Refer to the documentation for your cluster deployment tool to learn the recommended set
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up steps for maintenance.
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## Post-upgrade tasks
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### Switch your cluster's storage API version
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The objects that are serialized into etcd for a cluster's internal
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representation of the Kubernetes resources active in the cluster are
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written using a particular version of the API.
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When the supported API changes, these objects may need to be rewritten
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in the newer API. Failure to do this will eventually result in resources
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that are no longer decodable or usable by the Kubernetes API server.
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For each affected object, fetch it using the latest supported API and then
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write it back also using the latest supported API.
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### Update manifests
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Upgrading to a new Kubernetes version can provide new APIs.
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You can use `kubectl convert` command to convert manifests between different API versions.
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For example:
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```shell
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kubectl convert -f pod.yaml --output-version v1
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```
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The `kubectl` tool replaces the contents of `pod.yaml` with a manifest that sets `kind` to
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Pod (unchanged), but with a revised `apiVersion`.
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