Upgrading kubeadm clusters from v1.10 to v1.11

This page explains how to upgrade a Kubernetes cluster created with kubeadm from version 1.10.x to version 1.11.x, and from version 1.11.x to 1.11.y, where y > x.

Before you begin
Upgrade the control plane
Upgrade master and node packages
Upgrade kubelet on each node
Recovering from a failure state
How it works

Before you begin

You need to have a kubeadm Kubernetes cluster running version 1.10.0 or later. Swap must be disabled. The cluster should use a static control plane and etcd pods.
Make sure you read the release notes carefully.
Make sure to back up any important components, such as app-level state stored in a database. kubeadm upgrade does not touch your workloads, only components internal to Kubernetes, but backups are always a best practice.

Additional information

All containers are restarted after upgrade, because the container spec hash value is changed.
You can upgrade only from one minor version to the next minor version. That is, you cannot skip versions when you upgrade. For example, you can upgrade only from 1.10 to 1.11, not from 1.9 to 1.11.
The default DNS provider in version 1.11 is CoreDNS rather than kube-dns. To keep kube-dns, pass --feature-gates=CoreDNS=false to kubeadm upgrade apply.

Upgrade the control plane

On your master node, run the following (as root):
```
export VERSION=$(curl -sSL https://dl.k8s.io/release/stable.txt) # or manually specify a released Kubernetes version
export ARCH=amd64 # or: arm, arm64, ppc64le, s390x
curl -sSL https://dl.k8s.io/release/${VERSION}/bin/linux/${ARCH}/kubeadm > /usr/bin/kubeadm
chmod a+rx /usr/bin/kubeadm
```
Note that upgrading the kubeadm package on your system prior to upgrading the control plane causes a failed upgrade. Even though kubeadm ships in the Kubernetes repositories, it’s important to install it manually. The kubeadm team is working on fixing this limitation.
Verify that the download works and has the expected version:
```
kubeadm version
```

On the master node, run:

kubeadm upgrade plan

You should see output similar to this:

[preflight] Running pre-flight checks.
[upgrade] Making sure the cluster is healthy:
[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'
I0618 20:32:32.950358   15307 feature_gate.go:230] feature gates: &{map[]}
[upgrade] Fetching available versions to upgrade to
[upgrade/versions] Cluster version: v1.10.4
[upgrade/versions] kubeadm version: v1.11.0-beta.2.78+e0b33dbc2bde88

Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT   CURRENT       AVAILABLE
Kubelet     1 x v1.10.4   v1.11.0

Upgrade to the latest version in the v1.10 series:

COMPONENT            CURRENT   AVAILABLE
API Server           v1.10.4   v1.11.0
Controller Manager   v1.10.4   v1.11.0
Scheduler            v1.10.4   v1.11.0
Kube Proxy           v1.10.4   v1.11.0
CoreDNS                        1.1.3
Kube DNS             1.14.8
Etcd                 3.1.12    3.2.18

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

    kubeadm upgrade apply v1.11.0

Note: Before you can perform this upgrade, you have to update kubeadm to v1.11.0.

_____________________________________________________________________

This command checks that your cluster can be upgraded, and fetches the versions you can upgrade to.

Choose a version to upgrade to, and run the appropriate command. For example:

kubeadm upgrade apply v1.11.0

If you currently use kube-dns and wish to continue doing so, add --feature-gates=CoreDNS=false.

You should see output similar to this:

[preflight] Running pre-flight checks.
[upgrade] Making sure the cluster is healthy:
[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'
I0614 20:56:08.320369   30918 feature_gate.go:230] feature gates: &{map[]}
[upgrade/apply] Respecting the --cri-socket flag that is set with higher priority than the config file.
[upgrade/version] You have chosen to change the cluster version to "v1.11.0-beta.2.78+e0b33dbc2bde88"
[upgrade/versions] Cluster version: v1.10.4
[upgrade/versions] kubeadm version: v1.11.0-beta.2.78+e0b33dbc2bde88
[upgrade/confirm] Are you sure you want to proceed with the upgrade? [y/N]: y
[upgrade/prepull] Will prepull images for components [kube-apiserver kube-controller-manager kube-scheduler etcd]
[upgrade/apply] Upgrading your Static Pod-hosted control plane to version "v1.11.0-beta.2.78+e0b33dbc2bde88"...
Static pod: kube-apiserver-ip-172-31-85-18 hash: 7a329408b21bc0c44d7b3b78ff8187bf
Static pod: kube-controller-manager-ip-172-31-85-18 hash: 24fd3157627c7567b687968967c6a5e8
Static pod: kube-scheduler-ip-172-31-85-18 hash: 5179266fb24d4c1834814c4f69486371
Static pod: etcd-ip-172-31-85-18 hash: 9dfc197f444be11fcc70ab1467b030b8
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests089436939/etcd.yaml"
[certificates] Using the existing etcd/ca certificate and key.
[certificates] Using the existing etcd/server certificate and key.
[certificates] Using the existing etcd/peer certificate and key.
[certificates] Using the existing etcd/healthcheck-client certificate and key.
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/etcd.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2018-06-14-20-56-11/etcd.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
Static pod: etcd-ip-172-31-85-18 hash: 9dfc197f444be11fcc70ab1467b030b8
< snip >
[apiclient] Found 1 Pods for label selector component=etcd
[upgrade/staticpods] Component "etcd" upgraded successfully!
[upgrade/etcd] Waiting for etcd to become available
[util/etcd] Waiting 0s for initial delay
[util/etcd] Attempting to see if all cluster endpoints are available 1/10
[upgrade/staticpods] Writing new Static Pod manifests to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests089436939"
[controlplane] wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests089436939/kube-apiserver.yaml"
[controlplane] wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests089436939/kube-controller-manager.yaml"
[controlplane] wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests089436939/kube-scheduler.yaml"
[certificates] Using the existing etcd/ca certificate and key.
[certificates] Using the existing apiserver-etcd-client certificate and key.
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-apiserver.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2018-06-14-20-56-11/kube-apiserver.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
Static pod: kube-apiserver-ip-172-31-85-18 hash: 7a329408b21bc0c44d7b3b78ff8187bf
< snip >
[apiclient] Found 1 Pods for label selector component=kube-apiserver
[upgrade/staticpods] Component "kube-apiserver" upgraded successfully!
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-controller-manager.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2018-06-14-20-56-11/kube-controller-manager.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
Static pod: kube-controller-manager-ip-172-31-85-18 hash: 24fd3157627c7567b687968967c6a5e8
Static pod: kube-controller-manager-ip-172-31-85-18 hash: 63992ff14733dcb9dcfa6ac0a3b8031a
[apiclient] Found 1 Pods for label selector component=kube-controller-manager
[upgrade/staticpods] Component "kube-controller-manager" upgraded successfully!
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-scheduler.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2018-06-14-20-56-11/kube-scheduler.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
Static pod: kube-scheduler-ip-172-31-85-18 hash: 5179266fb24d4c1834814c4f69486371
Static pod: kube-scheduler-ip-172-31-85-18 hash: 831e4b9425f758e572392976311e56d9
[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
[kubelet] Creating a ConfigMap "kubelet-config-1.11" in namespace kube-system with the configuration for the kubelets in the cluster
[kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.11" ConfigMap in the kube-system namespace
[kubelet] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "ip-172-31-85-18" as an annotation
[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
[bootstraptoken] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.11.0-beta.2.78+e0b33dbc2bde88". Enjoy!

[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets if you haven't already done so.

Manually upgrade your Software Defined Network (SDN).

Your Container Network Interface (CNI) provider may have its own upgrade instructions to follow. Check the addons page to find your CNI provider and see whether additional upgrade steps are required.

Upgrade master and node packages

Prepare each host for maintenance, marking it unschedulable and evicting the workload:

kubectl drain $HOST --ignore-daemonsets

On the master host, you must add --ignore-daemonsets:

kubectl drain ip-172-31-85-18
node "ip-172-31-85-18" cordoned
error: unable to drain node "ip-172-31-85-18", aborting command...

There are pending nodes to be drained:
ip-172-31-85-18
error: DaemonSet-managed pods (use --ignore-daemonsets to ignore): calico-node-5798d, kube-proxy-thjp9

kubectl drain ip-172-31-85-18 --ignore-daemonsets
node "ip-172-31-85-18" already cordoned
WARNING: Ignoring DaemonSet-managed pods: calico-node-5798d, kube-proxy-thjp9
node "ip-172-31-85-18" drained

Upgrade the Kubernetes package version on each $HOST node by running the Linux package manager for your distribution:

Ubuntu, Debian or HypriotOS
CentOS, RHEL or Fedora

apt-get update
apt-get upgrade -y kubelet kubeadm

yum upgrade -y kubelet kubeadm --disableexcludes=kubernetes

Upgrade kubelet on each node

On each node except the master node, upgrade the kubelet config:

sudo kubeadm upgrade node config --kubelet-version $(kubelet --version | cut -d ' ' -f 2)

Restart the kubectl process:
```
sudo systemctl restart kubelet
```
Verify that the new version of the kubelet is running on the host:
```
systemctl status kubelet
```
Bring the host back online by marking it schedulable:
```
kubectl uncordon $HOST
```
After the kubelet is upgraded on all hosts, verify that all nodes are available again by running the following command from anywhere – for example, from outside the cluster:
```
kubectl get nodes
```
The STATUS column should show Ready for all your hosts, and the version number should be updated.

Recovering from a failure state

If kubeadm upgrade fails and does not roll back, for example because of an unexpected shutdown during execution, you can run kubeadm upgrade again. This command is idempotent and eventually makes sure that the actual state is the desired state you declare.

To recover from a bad state, you can also run kubeadm upgrade --force without changing the version that your cluster is running.

How it works

kubeadm upgrade apply does the following:

Checks that your cluster is in an upgradeable state:
- The API server is reachable,
- All nodes are in the Ready state
- The control plane is healthy
Enforces the version skew policies.
Makes sure the control plane images are available or available to pull to the machine.
Upgrades the control plane components or rollbacks if any of them fails to come up.
Applies the new kube-dns and kube-proxy manifests and enforces that all necessary RBAC rules are created.
Creates new certificate and key files of the API server and backs up old files if they’re about to expire in 180 days.

Tasks