Check before Upgrade

Before upgrading, we need to confirm the version of each component

# check kubeadm
baiyutang@vb-n1:~$ kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.8", GitCommit:"9f2892aab98fe339f3bd70e3c470144299398ace", GitTreeState:"clean", BuildDate:"2020-08-13T16:10:16Z", GoVersion:"go1.13.15", Compiler:"gc", Platform:"linux/amd64"}

# check kubectl
baiyutang@vb-n1:~$ kubectl version
Client Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.8", GitCommit:"9f2892aab98fe339f3bd70e3c470144299398ace", GitTreeState:"clean", BuildDate:"2020-08-13T16:12:48Z", GoVersion:"go1.13.15", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.9", GitCommit:"94f372e501c973a7fa9eb40ec9ebd2fe7ca69848", GitTreeState:"clean", BuildDate:"2020-09-16T13:47:43Z", GoVersion:"go1.13.15", Compiler:"gc", Platform:"linux/amd64"}

# check kubeletbaiyutang@vb-n1:~$kubelet --version Kubernetes v1.18.8# check kube - apiserver
baiyutang@vb-n1:~$ kubectl exec -it kube-apiserver-vb-n1 -n kube-system -- kube-apiserver --version
Kubernetes v1.18.9

# check kube controller -- the manager
baiyutang@vb-n1:~$ kubectl exec -it kube-controller-manager-vb-n1  -n kube-system -- kube-controller-manager  --version
Kubernetes v1.18.9

baiyutang@vb-n1:~$ kubectl exec- Scheduler --version I0925 13:32:59.717135 56 Registry. Go :150] Registering EvenPodsSpread predicate and priorityfunctionI0925 13:32:59.718611 56 Registry. Go :150] Registering EvenPodsSpread predicate and priorityfunction
Kubernetes v1.18.9

Check kube-proxy. It is more appropriate to check the mirrored version of Daemonset
baiyutang@vb-n1:~$ kubectl exec-it kube-proxy-b488d-n kube-system -- kube-proxy --version Kubernetes v1.18.9# Check etCD service
baiyutang@vb-n1:~$ kubectl execGit SHA: 3cf2f69b5 Git SHA: 3cf2f69b5 Go version: Go1.12.12 Go OS/Arch: Linux /amd64 baiyutang@vb-n1:~$kubectlexec -it etcd-vb-n1  -n kube-system -- etcdctl  version
etcdctl version: 3.4.3
API version: 3.4

# Check DNS service
baiyutang@vb-n1:~$ kubectl describe deployments.apps  -l k8s-app=kube-dns -n kube-system  | grep image
baiyutang@vb-n1:~$ kubectl get deployments.apps  -l k8s-app=kube-dns -n kube-system -o yaml | grep image
                  f:image: {}
                  f:imagePullPolicy: {}
          image: registry.aliyuncs.com/google_containers/coredns:1.6.7
          imagePullPolicy: IfNotPresent
          
# Examine the CNI Flannel
baiyutang@vb-n1:~$ kubectl get ds kube-flannel-ds-amd64 -n kube-system -o yaml | grep image
      {"apiVersion":"apps/v1"."kind":"DaemonSet"."metadata": {"annotations": {},"labels": {"app":"flannel"."tier":"node"},"name":"kube-flannel-ds-amd64"."namespace":"kube-system"},"spec": {"selector": {"matchLabels": {"app":"flannel"}},"template": {"metadata": {"labels": {"app":"flannel"."tier":"node"}},"spec": {"affinity": {"nodeAffinity": {"requiredDuringSchedulingIgnoredDuringExecution": {"nodeSelectorTerms": [{"matchExpressions": [{"key":"beta.kubernetes.io/os"."operator":"In"."values": ["linux"] {},"key":"beta.kubernetes.io/arch"."operator":"In"."values": ["amd64"]}]}]}}},"containers": [{"args": ["--ip-masq"."--kube-subnet-mgr"]."command": ["/opt/bin/flanneld"]."env": [{"name":"POD_NAME"."valueFrom": {"fieldRef": {"fieldPath":"metadata.name"}}}, {"name":"POD_NAMESPACE"."valueFrom": {"fieldRef": {"fieldPath":"metadata.namespace"}}}]."image":"Quay. IO/coreos/flannel: v0.12.0 - amd64"."name":"kube-flannel"."resources": {"limits": {"cpu":"100m"."memory":"50Mi"},"requests": {"cpu":"100m"."memory":"50Mi"}},"securityContext": {"capabilities": {"add": ["NET_ADMIN"]},"privileged":false},"volumeMounts": [{"mountPath":"/run/flannel"."name":"run"}, {"mountPath":"/etc/kube-flannel/"."name":"flannel-cfg"}}]]."hostNetwork":true."initContainers": [{"args": ["-f"."/etc/kube-flannel/cni-conf.json"."/etc/cni/net.d/10-flannel.conflist"]."command": ["cp"]."image":"Quay. IO/coreos/flannel: v0.12.0 - amd64"."name":"install-cni"."volumeMounts": [{"mountPath":"/etc/cni/net.d"."name":"cni"}, {"mountPath":"/etc/kube-flannel/"."name":"flannel-cfg"}}]]."serviceAccountName":"flannel"."tolerations": [{"effect":"NoSchedule"."operator":"Exists"}]."volumes": [{"hostPath": {"path":"/run/flannel"},"name":"run"}, {"hostPath": {"path":"/etc/cni/net.d"},"name":"cni"}, {"configMap": {"name":"kube-flannel-cfg"},"name":"flannel-cfg"}]}}}} f:image: {} f:imagePullPolicy: {} f:image: {} f:imagePullPolicy: {} image: Quay. IO/coreos/flannel: v0.12.0 - amd64 imagePullPolicy: IfNotPresent image: Quay. IO/coreos/flannel: v0.12.0 - amd64 imagePullPolicy: IfNotPresentCopy the code

The screenshot is shown below. Click to view the larger picture

Determines whether kubeadm is upgradable

sudo -i

apt update

apt-cache policy kubeadm
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Hover control plane node

kubectl drain vb-n1 --ignore-daemonsets
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Application Upgrade Version

Kubeadm upgrade apply v1.19.0 --etcd-upgrade=false # Do not upgrade etCD
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root@vb-n1:~V1.19.0 --etcd-upgrade=false
[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'
[preflight] Running pre-flight checks.
[upgrade] Running cluster health checks
[upgrade/version] You have chosen to change the cluster version to "v1.19.0"
[upgrade/versions] Cluster version: v1.18.9
[upgrade/versions] kubeadm version: v1.19.0
[upgrade/confirm] Are you sure you want to proceed with the upgrade? [y/N]: y
[upgrade/prepull] Pulling images required for setting up a Kubernetes cluster
[upgrade/prepull] This might take a minute or two, depending on the speed of your internet connection
[upgrade/prepull] You can also perform this action in beforehand using 'kubeadm config images pull'
[upgrade/apply] Upgrading your Static Pod-hosted control plane to version "v1.19.0". Static pod: kube-apiserver-vb-n1hash: 1c78c880abd4c7301a3e15e0b8ba0739
Static pod: kube-controller-manager-vb-n1 hash: a7092f0e72ccf0dde097448255396198
Static pod: kube-scheduler-vb-n1 hash: 1d49f6bea141a03c33715369a619d2a9
[upgrade/staticpods] Writing new Static Pod manifests to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests007582360"
[upgrade/staticpods] Preparing for "kube-apiserver" upgrade
[upgrade/staticpods] Renewing apiserver certificate
[upgrade/staticpods] Renewing apiserver-kubelet-client certificate
[upgrade/staticpods] Renewing front-proxy-client certificate
[upgrade/staticpods] Renewing apiserver-etcd-client certificate
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-apiserver.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2020-09-25-21-47-44/kube-apiserver.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[upgrade/staticpods] This might take a minute or longer depending on the component/version gap (timeout 5m0s)
Static pod: kube-apiserver-vb-n1 hash: 1c78c880abd4c7301a3e15e0b8ba0739
Static pod: kube-apiserver-vb-n1 hash: 1c78c880abd4c7301a3e15e0b8ba0739
Static pod: kube-apiserver-vb-n1 hash: 1c78c880abd4c7301a3e15e0b8ba0739
Static pod: kube-apiserver-vb-n1 hash: 79e1af63686084ebb219fefaaf989593
[apiclient] Found 1 Pods for label selector component=kube-apiserver
[upgrade/staticpods] Component "kube-apiserver" upgraded successfully!
[upgrade/staticpods] Preparing for "kube-controller-manager" upgrade
[upgrade/staticpods] Renewing controller-manager.conf certificate
[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-2020-09-25-21-47-44/kube-controller-manager.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[upgrade/staticpods] This might take a minute or longer depending on the component/version gap (timeout 5m0s)
Static pod: kube-controller-manager-vb-n1 hash: a7092f0e72ccf0dde097448255396198
Static pod: kube-controller-manager-vb-n1 hash: e300bc107fc98f68d284e0aa8a71380b
[apiclient] Found 1 Pods for label selector component=kube-controller-manager
[upgrade/staticpods] Component "kube-controller-manager" upgraded successfully!
[upgrade/staticpods] Preparing for "kube-scheduler" upgrade
[upgrade/staticpods] Renewing scheduler.conf certificate
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-scheduler.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2020-09-25-21-47-44/kube-scheduler.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[upgrade/staticpods] This might take a minute or longer depending on the component/version gap (timeout 5m0s)
Static pod: kube-scheduler-vb-n1 hash: 1d49f6bea141a03c33715369a619d2a9
Static pod: kube-scheduler-vb-n1 hash: 340ea85a0f34a4df64d62b1a784833ae
[apiclient] Found 1 Pods for label selector component=kube-scheduler
[upgrade/staticpods] Component "kube-scheduler" upgraded successfully!
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "Kubelet - config - 1.19" in namespace kube-system with the configuration for the kubelets in the cluster
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to get nodes
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates inGo :282] The Cluster W0925 21:48:01.019661 19731 DNS.go :282] The CoreDNS Configuration will not be migrated due to unsupported version of CoreDNS. The existing CoreDNS Corefile configuration and deployment has been retained. [addons] Applied essential addon: CoreDNS [addons] Applied essential addon: kube-proxy [upgrade/successful] SUCCESS! Your cluster was upgraded to"v1.19.0". Enjoy!

[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets if you haven't already done so.
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Screenshot below, click to see a larger picture



We take note of the last message

[upgrade/successful] SUCCESS! Your cluster was upgraded to “v1.19.0”. Enjoy!

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

Restoring the primary node can be scheduled

kubectl uncordon vb-n1
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conclusion

Kubeadm upgrade apply v1.19.0 –etcd-upgrade=false kubeadm upgrade apply v1.19.0 –etcd-upgrade=false

So let’s go back a little bit

reference

• Upgrade kubeadm cluster | Kubernetes