一、环境说明
本文升级的环境，为kubeadm部署的测试环境，一台master，一台node，可作为升级参考
二、升级详细记录，以及一些说明
执行以下脚本前，需要先下载k8s更新镜像，可用我的上篇博客在国内环境下下载镜像的脚本
1、升级kubeadm版本
不然升级时会报错。只升级Master就能完成下面的操作了，但是我还是连同Node的一起升级了。
yum update -y kubeadm查看kubeadm版本
kubeadm version查看kubeadm升级计划
root@node-1 ~]# kubeadm upgrade plan
[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] Fetching available versions to upgrade to
[upgrade/versions] Cluster version: v1.18.5
[upgrade/versions] kubeadm version: v1.18.5
W0721 11:02:38.021509 2388 version.go:102] could not fetch a Kubernetes version from the internet: unable to get URL "https://dl.k8s.io/release/stable.txt": Get https://storage.googleapis.com/kubernetes-release/release/stable.txt: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
W0721 11:02:38.021544 2388 version.go:103] falling back to the local client version: v1.18.5
[upgrade/versions] Latest stable version: v1.18.5
[upgrade/versions] Latest stable version: v1.18.5
[upgrade/versions] Latest version in the v1.18 series: v1.18.6
[upgrade/versions] Latest version in the v1.18 series: v1.18.6
Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT CURRENT AVAILABLE
Kubelet 2 x v1.18.5 v1.18.6
Upgrade to the latest version in the v1.18 series:
COMPONENT CURRENT AVAILABLE
API Server v1.18.5 v1.18.6
Controller Manager v1.18.5 v1.18.6
Scheduler v1.18.5 v1.18.6
Kube Proxy v1.18.5 v1.18.6
CoreDNS 1.6.7 1.6.7
Etcd 3.4.3 3.4.3-0
You can now apply the upgrade by executing the following command:
kubeadm upgrade apply v1.18.6
Note: Before you can perform this upgrade, you have to update kubeadm to v1.18.6.
_____________________________________________________________________按照任务指引进行升级
[root@node-1 ~]# kubeadm upgrade apply v1.18.6
[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 "v1.18.6"
[upgrade/versions] Cluster version: v1.18.5
[upgrade/versions] kubeadm version: v1.18.6
[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/prepull] Prepulling image for component etcd.
[upgrade/prepull] Prepulling image for component kube-apiserver.
[upgrade/prepull] Prepulling image for component kube-controller-manager.
[upgrade/prepull] Prepulling image for component kube-scheduler.
[apiclient] Found 0 Pods for label selector k8s-app=upgrade-prepull-kube-apiserver
[apiclient] Found 0 Pods for label selector k8s-app=upgrade-prepull-etcd
[apiclient] Found 0 Pods for label selector k8s-app=upgrade-prepull-kube-scheduler
[apiclient] Found 0 Pods for label selector k8s-app=upgrade-prepull-kube-controller-manager
[apiclient] Found 1 Pods for label selector k8s-app=upgrade-prepull-kube-apiserver
[apiclient] Found 1 Pods for label selector k8s-app=upgrade-prepull-etcd
[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-controller-manager
[upgrade/prepull] Prepulled image for component kube-apiserver.
[upgrade/prepull] Prepulled image for component etcd.
[upgrade/prepull] Prepulled image for component kube-scheduler.
[upgrade/prepull] Prepulled image for component kube-controller-manager.
[upgrade/prepull] Successfully prepulled the images for all the control plane components
[upgrade/apply] Upgrading your Static Pod-hosted control plane to version "v1.18.6"...
Static pod: kube-apiserver-node-1 hash: 885fee7a9fbfdeee96639f51278b09b1
Static pod: kube-controller-manager-node-1 hash: 84607590e836f839dcbf22068a9b216c
Static pod: kube-scheduler-node-1 hash: 3415bde3e2a04810cc416f7719a3f6aa
[upgrade/etcd] Upgrading to TLS for etcd
[upgrade/etcd] Non fatal issue encountered during upgrade: the desired etcd version for this Kubernetes version "v1.18.6" is "3.4.3-0", but the current etcd version is "3.4.3". Won't downgrade etcd, instead just continue
[upgrade/staticpods] Writing new Static Pod manifests to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests249686084"
W0721 11:10:32.301810 10692 manifests.go:225] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[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-2020-07-21-11-10-29/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-node-1 hash: 885fee7a9fbfdeee96639f51278b09b1
Static pod: kube-apiserver-node-1 hash: 885fee7a9fbfdeee96639f51278b09b1
Static pod: kube-apiserver-node-1 hash: ce5c99a18293147c422f8b70a4772a08
[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-2020-07-21-11-10-29/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-node-1 hash: 84607590e836f839dcbf22068a9b216c
Static pod: kube-controller-manager-node-1 hash: a498455ef3ba2eb7d5fd01ed8271dea6
[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-2020-07-21-11-10-29/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-node-1 hash: 3415bde3e2a04810cc416f7719a3f6aa
Static pod: kube-scheduler-node-1 hash: 3dd66788a2c7782d910d05ea37b91678
[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-1.18" in namespace kube-system with the configuration for the kubelets in the cluster
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.18" ConfigMap in the kube-system namespace
[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 in the cluster
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy
[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.18.6". Enjoy!
[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets if you haven't already done so.在Master上执行以下命令升级Node
[root@node-1 ~]# kubeadm upgrade node
[upgrade] Reading configuration from the cluster...
[upgrade] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[upgrade] Upgrading your Static Pod-hosted control plane instance to version "v1.18.6"...
Static pod: kube-apiserver-node-1 hash: ce5c99a18293147c422f8b70a4772a08
Static pod: kube-controller-manager-node-1 hash: a498455ef3ba2eb7d5fd01ed8271dea6
Static pod: kube-scheduler-node-1 hash: 3dd66788a2c7782d910d05ea37b91678
[upgrade/etcd] Upgrading to TLS for etcd
[upgrade/etcd] Non fatal issue encountered during upgrade: the desired etcd version for this Kubernetes version "v1.18.6" is "3.4.3-0", but the current etcd version is "3.4.3". Won't downgrade etcd, instead just continue
[upgrade/staticpods] Writing new Static Pod manifests to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests472349924"
W0721 11:35:50.284639 8362 manifests.go:225] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[upgrade/staticpods] Preparing for "kube-apiserver" upgrade
[upgrade/staticpods] Current and new manifests of kube-apiserver are equal, skipping upgrade
[upgrade/staticpods] Preparing for "kube-controller-manager" upgrade
[upgrade/staticpods] Current and new manifests of kube-controller-manager are equal, skipping upgrade
[upgrade/staticpods] Preparing for "kube-scheduler" upgrade
[upgrade/staticpods] Current and new manifests of kube-scheduler are equal, skipping upgrade
[upgrade] The control plane instance for this node was successfully updated!
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.18" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[upgrade] The configuration for this node was successfully updated!
[upgrade] Now you should go ahead and upgrade the kubelet package using your package manager.查看版本，发现Server已经升级了，Client还没有升级。这个是需要升级kubectl才会看到升级的。
[root@node-1 ~]# kubectl version
Client Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.5", GitCommit:"e6503f8d8f769ace2f338794c914a96fc335df0f", GitTreeState:"clean", BuildDate:"2020-06-26T03:47:41Z", GoVersion:"go1.13.9", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.6", GitCommit:"dff82dc0de47299ab66c83c626e08b245ab19037", GitTreeState:"clean", BuildDate:"2020-07-15T16:51:04Z", GoVersion:"go1.13.9", Compiler:"gc", Platform:"linux/amd64"}在各节点上执行
yum update kubectl此时查看Node，还是老版本。这个是需要升级kubelet并重启kubelet才看得到升级的。
[root@node-1 ~]# kubectl get nodes
NAME STATUS ROLES AGE VERSION
node-1 Ready master 5d14h v1.18.5
node-2 Ready <none> 5d12h v1.18.5在各个Node上升级kubelet
yum update -y kubelet
systemctl daemon-reload # 就算不执行，系统也会提示要执行这条命令的
systemctl restart kubelet再次查看，已经升级成功
[root@node-1 ~]# kubectl get nodes
NAME STATUS ROLES AGE VERSION
node-1 Ready master 5d14h v1.18.6
node-2 Ready <none> 5d12h v1.18.6注：升级还会更新集群的证书
升级前
[root@node-1 pki]# openssl x509 -in /etc/kubernetes/pki/apiserver.crt -noout -text |grep ' Not '
Not Before: Jul 15 13:35:12 2020 GMT
Not After : Jul 15 13:35:13 2021 GMT升级后
[root@node-1 ~]# openssl x509 -in /etc/kubernetes/pki/apiserver.crt -noout -text |grep ' Not '
Not Before: Jul 15 13:35:12 2020 GMT
Not After : Jul 21 03:10:32 2021 GMT