This guide is for upgrading kubeadm
clusters from version 1.8.x to 1.9.x, as well as 1.8.x to 1.8.y and 1.9.x to 1.9.y where y > x
.
See also upgrading kubeadm clusters from 1.7 to 1.8 if you’re on a 1.7 cluster currently.
Before proceeding:
kubeadm
Kubernetes cluster running version 1.8.0 or higher in order to use the process described here. Swap also needs to be disabled.kubeadm upgrade
now allows you to upgrade etcd. kubeadm upgrade
will also upgrade of etcd to 3.1.10 as part of upgrading from v1.8 to v1.9 by default. This is due to the fact that etcd 3.1.10 is the officially validated etcd version for Kubernetes v1.9. The upgrade is handled automatically by kubeadm for you.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.Caution: All the containers will get restarted after the upgrade, due to container spec hash value gets changed.
Also, note that only one minor version upgrade is supported. For example, you can only upgrade from 1.8 to 1.9, not from 1.7 to 1.9.
Execute these commands on your master node:
kubeadm
using curl
like so: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
Caution: Upgrading thekubeadm
package on your system prior to upgrading the control plane causes a failed upgrade. Even thoughkubeadm
ships in the Kubernetes repositories, it’s important to installkubeadm
manually. The kubeadm team is working on fixing this limitation.
Verify that this download of kubeadm works and has the expected version:
kubeadm version
kubeadm upgrade plan
You should see output similar to this:
[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 -o yaml'
[upgrade] Fetching available versions to upgrade to:
[upgrade/versions] Cluster version: v1.8.1
[upgrade/versions] kubeadm version: v1.9.0
[upgrade/versions] Latest stable version: v1.9.0
[upgrade/versions] Latest version in the v1.8 series: v1.8.6
Components that must be upgraded manually after you've upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT CURRENT AVAILABLE
Kubelet 1 x v1.8.1 v1.8.6
Upgrade to the latest version in the v1.8 series:
COMPONENT CURRENT AVAILABLE
API Server v1.8.1 v1.8.6
Controller Manager v1.8.1 v1.8.6
Scheduler v1.8.1 v1.8.6
Kube Proxy v1.8.1 v1.8.6
Kube DNS 1.14.4 1.14.5
You can now apply the upgrade by executing the following command:
kubeadm upgrade apply v1.8.6
_____________________________________________________________________
Components that must be upgraded manually after you've upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT CURRENT AVAILABLE
Kubelet 1 x v1.8.1 v1.9.0
Upgrade to the latest stable version:
COMPONENT CURRENT AVAILABLE
API Server v1.8.1 v1.9.0
Controller Manager v1.8.1 v1.9.0
Scheduler v1.8.1 v1.9.0
Kube Proxy v1.8.1 v1.9.0
Kube DNS 1.14.5 1.14.7
You can now apply the upgrade by executing the following command:
kubeadm upgrade apply v1.9.0
Note: Before you do can perform this upgrade, you have to update kubeadm to v1.9.0
_____________________________________________________________________
The kubeadm upgrade plan
checks that your cluster is upgradeable and fetches the versions available to upgrade to in an user-friendly way.
To check CoreDNS version, include the --feature-gates=CoreDNS=true
flag to verify the CoreDNS version which will be installed in place of kube-dns.
kubeadm upgrade apply v1.9.0
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'
[upgrade/version] You have chosen to upgrade to version "v1.9.0"
[upgrade/versions] Cluster version: v1.8.1
[upgrade/versions] kubeadm version: v1.9.0
[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]
[upgrade/apply] Upgrading your Static Pod-hosted control plane to version "v1.9.0"...
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests802453804/etcd.yaml"
[upgrade/staticpods] Moved upgraded manifest to "/etc/kubernetes/manifests/etcd.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests502223003/etcd.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[apiclient] Found 1 Pods for label selector component=etcd
[upgrade/staticpods] Component "etcd" upgraded successfully!
[upgrade/staticpods] Writing upgraded Static Pod manifests to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests802453804"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests802453804/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests802453804/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests802453804/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-manifests502223003/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-manifests502223003/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-manifests502223003/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
[bootstraptoken] Configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[addons] Applied essential addon: kube-dns
[addons] Applied essential addon: kube-proxy
[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.9.0". Enjoy!
[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets in turn.
To upgrade the cluster with CoreDNS as the default internal DNS, invoke kubeadm upgrade apply
with the --feature-gates=CoreDNS=true
flag.
kubeadm upgrade apply
does the following:
Ready
statekube-dns
and kube-proxy
manifests and enforces that all necessary RBAC rules are created.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 if there are additional upgrade steps necessary.
For each host (referred to as $HOST
below) in your cluster, upgrade kubelet
by executing the following commands:
kubectl drain $HOST --ignore-daemonsets
When running this command against the master host, this error is expected and can be safely ignored (since there are static pods running on the master):
node "master" already cordoned
error: pods not managed by ReplicationController, ReplicaSet, Job, DaemonSet or StatefulSet (use --force to override): etcd-kubeadm, kube-apiserver-kubeadm, kube-controller-manager-kubeadm, kube-scheduler-kubeadm
$HOST
node by using a Linux distribution-specific package manager:If the host is running a Debian-based distro such as Ubuntu, run:
apt-get update
apt-get upgrade
If the host is running CentOS or the like, run:
yum update
Now the new version of the kubelet
should be running on the host. Verify this using the following command on $HOST
:
systemctl status kubelet
kubectl uncordon $HOST
kubelet
on each host in your cluster, verify that all nodes are available again by executing the following (from anywhere, for example, from outside the cluster):kubectl get nodes
If the STATUS
column of the above command shows Ready
for all of your hosts, you are done.
If kubeadm upgrade
somehow fails and fails to roll back, for example due to an unexpected shutdown during execution,
you can 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.