---
approvers:
- pipejakob
- luxas
- roberthbailey
- jbeda
title: Upgrading kubeadm clusters from 1.7 to 1.8
---

{% capture overview %}

This guide is for upgrading `kubeadm` clusters from version 1.7.x to 1.8.x, as well as 1.7.x to 1.7.y and 1.8.x to 1.8.y where `y > x`.
See also [upgrading kubeadm clusters from 1.6 to 1.7](/docs/tasks/administer-cluster/kubeadm-upgrade-1-7/) if you're on a 1.6 cluster currently.

{% endcapture %}

{% capture prerequisites %}

Before proceeding:

- You need to have a functional `kubeadm` Kubernetes cluster running version 1.7.0 or higher in order to use the process described here.
- Make sure you read the [release notes](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG.md#v180-beta1) carefully.
- As `kubeadm upgrade` does not upgrade etcd make sure to back it up. You can, for example, use `etcdctl backup` to take care of this.
- Note that `kubeadm upgrade` will not touch any of your workloads, only Kubernetes-internal components. As a best-practice you should back up what's important to you. For example, any app-level state, such as a database an app might depend on (like MySQL or MongoDB) must be backed up beforehand.

Also, note that only one minor version upgrade is supported. That is, you can only upgrade from, say 1.7 to 1.8, not from 1.7 to 1.9.

{% endcapture %}

{% capture steps %}

## Upgrading your control plane

You have to carry out the following steps by executing these commands on your master node:

1. Install the most recent version of `kubeadm` using `curl` like so:

```shell
$ export VERSION=v1.8.0 # or any given released Kubernetes version
$ export ARCH=amd64 # or: arm, arm64, ppc64le, s390x
$ curl -sSL https://dl.k8s.io/release/${VERSION}/bin/linux/${ARCH}/kubeadm > /usr/bin/kubeadm
```

2. If this the first time you use `kubeadm upgrade`, in order to preserve the configuration for future upgrades, do:

Note that for below you will need to recall what CLI args you passed to `kubeadm init` the first time.

If you used flags, do:

```shell
$ kubeadm config upload from-flags [flags]
```

Where `flags` can be empty.

If you used a config file, do:

```shell
$ kubeadm config upload from-file --config [config]
```

Where the `config` is mandatory.

3. On the master node, run the following:

```shell
$ kubeadm upgrade plan
[preflight] Running pre-flight checks
[upgrade] Making sure the cluster is healthy:
[upgrade/health] Checking API Server health: Healthy
[upgrade/health] Checking Node health: All Nodes are healthy
[upgrade/health] Checking Static Pod manifests exists on disk: All manifests exist on disk
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[upgrade] Fetching available versions to upgrade to:
[upgrade/versions] Cluster version: v1.7.1
[upgrade/versions] kubeadm version: v1.8.0
[upgrade/versions] Latest stable version: v1.8.0
[upgrade/versions] Latest version in the v1.7 series: v1.7.6

Components that must be upgraded manually after you've upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT   CURRENT      AVAILABLE
Kubelet     1 x v1.7.1   v1.7.6

Upgrade to the latest version in the v1.7 series:

COMPONENT            CURRENT   AVAILABLE
API Server           v1.7.1    v1.7.6
Controller Manager   v1.7.1    v1.7.6
Scheduler            v1.7.1    v1.7.6
Kube Proxy           v1.7.1    v1.7.6
Kube DNS             1.14.4    1.14.4

You can now apply the upgrade by executing the following command:

	kubeadm upgrade apply v1.7.6

_____________________________________________________________________

Components that must be upgraded manually after you've upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT   CURRENT      AVAILABLE
Kubelet     1 x v1.7.1   v1.8.0

Upgrade to the latest experimental version:

COMPONENT            CURRENT   AVAILABLE
API Server           v1.7.1    v1.8.0
Controller Manager   v1.7.1    v1.8.0
Scheduler            v1.7.1    v1.8.0
Kube Proxy           v1.7.1    v1.8.0
Kube DNS             1.14.4    1.14.4

You can now apply the upgrade by executing the following command:

	kubeadm upgrade apply v1.8.0

Note: Before you do can perform this upgrade, you have to update kubeadm to v1.8.0

_____________________________________________________________________
```

The `kubeadm upgrade plan` checks that your cluster is in an upgradeable state and fetches the versions available to upgrade to in an user-friendly way.

4. Pick a version to upgrade to and run, for example, `kubeadm upgrade apply` as follows:

```shell
$ kubeadm upgrade apply v1.8.0
[preflight] Running pre-flight checks
[upgrade] Making sure the cluster is healthy:
[upgrade/health] Checking API Server health: Healthy
[upgrade/health] Checking Node health: All Nodes are healthy
[upgrade/health] Checking Static Pod manifests exists on disk: All manifests exist on disk
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[upgrade/version] You have chosen to upgrade to version "v1.8.0"
[upgrade/versions] Cluster version: v1.7.1
[upgrade/versions] kubeadm version: v1.8.0
[upgrade/prepull] Will prepull images for components [kube-apiserver kube-controller-manager kube-scheduler]
[upgrade/prepull] Prepulling image for component kube-scheduler.
[upgrade/prepull] Prepulling image for component kube-apiserver.
[upgrade/prepull] Prepulling image for component kube-controller-manager.
[apiclient] Found 0 Pods for label selector k8s-app=upgrade-prepull-kube-scheduler
[apiclient] Found 1 Pods for label selector k8s-app=upgrade-prepull-kube-scheduler
[apiclient] Found 1 Pods for label selector k8s-app=upgrade-prepull-kube-apiserver
[apiclient] Found 1 Pods for label selector k8s-app=upgrade-prepull-kube-controller-manager
[upgrade/prepull] Prepulled image for component kube-apiserver.
[upgrade/prepull] Prepulled image for component kube-controller-manager.
[upgrade/prepull] Prepulled image for component kube-scheduler.
[upgrade/prepull] Successfully prepulled the images for all the control plane components
[upgrade/apply] Upgrading your Static Pod-hosted control plane to version "v1.8.0"...
[upgrade/staticpods] Writing upgraded Static Pod manifests to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests432902769"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests432902769/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests432902769/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests432902769/kube-scheduler.yaml"
[upgrade/staticpods] Moved upgraded manifest to "/etc/kubernetes/manifests/kube-apiserver.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests155856668/kube-apiserver.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[apiclient] Found 1 Pods for label selector component=kube-apiserver
[upgrade/staticpods] Component "kube-apiserver" upgraded successfully!
[upgrade/staticpods] Moved upgraded manifest to "/etc/kubernetes/manifests/kube-controller-manager.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests155856668/kube-controller-manager.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[apiclient] Found 1 Pods for label selector component=kube-controller-manager
[upgrade/staticpods] Component "kube-controller-manager" upgraded successfully!
[upgrade/staticpods] Moved upgraded manifest to "/etc/kubernetes/manifests/kube-scheduler.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests155856668/kube-scheduler.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[apiclient] Found 1 Pods for label selector component=kube-scheduler
[upgrade/staticpods] Component "kube-scheduler" upgraded successfully!
[uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[bootstraptoken] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstraptoken] Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[addons] Applied essential addon: kube-dns
[addons] Applied essential addon: kube-proxy

[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.8.0". Enjoy!

[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets in turn.
```

`kubeadm upgrade apply` does the following:

- It checks that your cluster is in an upgradeable state, that is:
  - The API Server is reachable,
  - All nodes are in the `Ready` state, and
  - The control plane is healthy
- It enforces the version skew policies.
- It makes sure the control plane images are available or available to pull to the machine.
- It upgrades the control plane components or rollbacks if any of them fails to come up.
- It applies the new `kube-dns` and `kube-proxy` manifests and enforces that all necessary RBAC rules are created.

5. Manually upgrade your Software Defined Network (SDN).

   Your Container Network Interface (CNI) provider might have its own upgrade instructions to follow now.
   Check the [addons](/docs/concepts/cluster-administration/addons/) page to
   find your CNI provider and see if there are additional upgrade steps
   necessary.

## Upgrading your worker nodes

For each worker node (referred to as `$WORKER` below) in your cluster, upgrade `kubelet` by executing the following commands:

1. Prepare the node for maintenance, marking it unschedulable and evicting the workload:

```shell
$ kubectl cordon $WORKER
$ kubectl drain $WORKER
```

2. Upgrade the `kubelet` version on the `$WORKER` node by using a Linux distribution-specific package manager:

If the node is running a Debian-based distro such as Ubuntu, run:

```shell
$ apt-get update
$ apt-get install -y kubelet
```

If the node is running CentOS or the like, run:

```shell
$ yum update
$ yum install -y kubelet
```

Now the new version of the `kubelet` should be running on the `$WORKER` node. Verify this using the following command:

```shell
$ systemctl status kubelet
```

3. Bring the `$WORKER` node back online by marking it schedulable:

```shell
$ kubectl uncordon $WORKER
```

4. After upgrading `kubelet` on each worker node in your cluster, verify that all nodes are available again by executing the following (from anywhere, for example, from outside the cluster):

```shell
$ kubectl get nodes
```

If the `STATUS` column of the above command shows `Ready` for all of your worker nodes, you are done.

## Recovering from a bad state

If `kubeadm upgrade` somehow fails and fails to roll back, due to an unexpected shutdown during execution for instance,
you may run `kubeadm upgrade` again as it is idempotent and should eventually make sure the actual state is the desired state you are declaring.

You can use `kubeadm upgrade` to change a running cluster with `x.x.x --> x.x.x` with `--force`, which can be used to recover from a bad state.

{% endcapture %}

{% include templates/task.md %}
