升级说明
- 可用的K8S集群，使用kubeadm搭建
- 可以小版本升级，也可以跨一个大版本升级，不建议跨两个大版本升级
- 对集群资源做好备份
升级目标
将kubernetes 1.17.9版本升级到1.18.9版本
现有集群版本已经节点如下：
# kubectl get nodes
NAME STATUS ROLES AGE VERSION
ecs-968f-0005 Ready node 102d v1.17.9
k8s-master Ready master 102d v1.17.9
备份集群
kubeadm upgrade 不会影响你的工作负载，只会涉及 Kubernetes 内部的组件，但备份终究是好的。这里主要是对集群的所有资源进行备份，我使用的是一个开源的脚本，项目地址是：https://github.com/solomonxu/k8s-backup-restore
（1）下载脚本
$ mkdir -p /data
cd /data
git clone https://github.com/solomonxu/k8s-backup-restore.git
（2）执行备份
cd /data/k8s-backup-restore
./bin/k8s_backup.sh
如果要恢复怎么办？只需要执行如下步骤。
（1）创建恢复目录
$ mkdir -p /data/k8s-backup-restore/data/restore
（2）将需要恢复的YAML清单复制到该目录下
$ cp devops_deployments_gitlab.yaml ../../restore/
（3）执行恢复命令
cd /data/k8s-backup-restore
./bin/k8s_restore.sh
会输出如下信息。
2021-01-06 15:09:43.954083 [11623] - INFO Kubernetes Restore start now. All yaml files which located in path [/data/k8s-backup-restore/data/restore] will be applied.
2021-01-06 15:09:43.957265 [11623] - INFO If you want to read the log record of restore, please input command ' tail -100f '
2021-01-06 15:09:43.986869 [11623] - WARN WARNING!!! This will create 1 resources from yaml files into kubernetes cluster. While same name of resources will be deleted. Please consider it carefully!
Do you want to continue? [yes/no/show] y
2021-01-06 15:10:00.062598 [11623] - INFO Restore No.1 resources from yaml file: /data/k8s-backup-restore/data/restore/devops_deployments_gitlab.yaml...
2021-01-06 15:10:00.066011 [11623] - INFO Run shell: kubectl delete -f /data/k8s-backup-restore/data/restore/devops_deployments_gitlab.yaml.
deployment.apps "gitlab" deleted
2021-01-06 15:10:00.423109 [11623] - INFO Delete resource from /data/k8s-backup-restore/data/restore/devops_deployments_gitlab.yaml: ok.
2021-01-06 15:10:00.426383 [11623] - INFO Run shell: kubectl create -f /data/k8s-backup-restore/data/restore/devops_deployments_gitlab.yaml.
deployment.apps/gitlab created
2021-01-06 15:10:00.614960 [11623] - INFO Create resource from /data/k8s-backup-restore/data/restore/devops_deployments_gitlab.yaml: ok.
2021-01-06 15:10:00.618572 [11623] - INFO Restore 1 resources from yaml files in all: count_delete_ok=1, count_delete_failed=0, count_create_ok=1, count_create_failed=0.
2021-01-06 15:10:00.622002 [11623] - INFO Kubernetes Restore completed, all done.
（4）验证是否正常修复
$ kubectl get po -n devops
NAME READY STATUS RESTARTS AGE
gitlab-65896f7557-786hj 1/1 Running 0 66s
升级集群
Master升级
（1）确定要升级的版本
$ yum list --showduplicates kubeadm --disableexcludes=kubernetes
我这里选择的是1.18.9版本。
（2）升级kubeadm
$ yum install -y kubeadm-1.18.9-0 --disableexcludes=kubernetes
升级完成后验证版本是否正确。
$ kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.9", GitCommit:"94f372e501c973a7fa9eb40ec9ebd2fe7ca69848", GitTreeState:"clean", BuildDate:"2020-09-16T13:54:01Z", GoVersion:"go1.13.15", Compiler:"gc", Platform:"linux/amd64"}
（3）排空节点
$ kubectl cordon k8s-master
$ kubectl drain k8s-master
（4）运行升级计划，查看是否可以升级
$ 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: v1.17.9
[upgrade/versions] kubeadm version: v1.18.9
I0106 14:22:58.709642 10455 version.go:252] remote version is much newer: v1.20.1; falling back to: stable-1.18
[upgrade/versions] Latest stable version: v1.18.14
[upgrade/versions] Latest stable version: v1.18.14
[upgrade/versions] Latest version in the v1.17 series: v1.17.16
[upgrade/versions] Latest version in the v1.17 series: v1.17.16
Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT CURRENT AVAILABLE
Kubelet 2 x v1.17.9 v1.17.16
Upgrade to the latest version in the v1.17 series:
COMPONENT CURRENT AVAILABLE
API Server v1.17.9 v1.17.16
Controller Manager v1.17.9 v1.17.16
Scheduler v1.17.9 v1.17.16
Kube Proxy v1.17.9 v1.17.16
CoreDNS 1.6.5 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 v1.17.16
_____________________________________________________________________
Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT CURRENT AVAILABLE
Kubelet 2 x v1.17.9 v1.18.14
Upgrade to the latest stable version:
COMPONENT CURRENT AVAILABLE
API Server v1.17.9 v1.18.14
Controller Manager v1.17.9 v1.18.14
Scheduler v1.17.9 v1.18.14
Kube Proxy v1.17.9 v1.18.14
CoreDNS 1.6.5 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 v1.18.14
Note: Before you can perform this upgrade, you have to update kubeadm to v1.18.14.
_____________________________________________________________________
上面显示我可以升级到更高版本，不过我这里还是升级到1.18.9。
（5）升级集群
$ kubeadm upgrade apply v1.18.9 --config kubeadm.yaml
W0106 14:23:58.359112 11936 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
[upgrade/config] Making sure the configuration is correct:
W0106 14:23:58.367062 11936 common.go:94] WARNING: Usage of the --config flag for reconfiguring the cluster during upgrade is not recommended!
W0106 14:23:58.367816 11936 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
[preflight] Running pre-flight checks.
[upgrade] Running cluster health checks
[upgrade/version] You have chosen to change the cluster version to "v1.18.9"
[upgrade/versions] Cluster version: v1.17.9
[upgrade/versions] kubeadm version: v1.18.9
[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-controller-manager.
[upgrade/prepull] Prepulling image for component kube-scheduler.
[upgrade/prepull] Prepulling image for component kube-apiserver.
[apiclient] Found 1 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-kube-scheduler
[apiclient] Found 0 Pods for label selector k8s-app=upgrade-prepull-etcd
[apiclient] Found 1 Pods for label selector k8s-app=upgrade-prepull-etcd
[upgrade/prepull] Prepulled image for component etcd.
[upgrade/prepull] Prepulled image for component kube-controller-manager.
[upgrade/prepull] Prepulled image for component kube-apiserver.
[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 "v1.18.9"...
Static pod: kube-apiserver-k8s-master hash: d002f0455950f5b76f6097191f93db28
Static pod: kube-controller-manager-k8s-master hash: 54e96591b22cec4a1f5b76965fa90be7
Static pod: kube-scheduler-k8s-master hash: da215ebee0354225c20c7bdf28b467f8
[upgrade/etcd] Upgrading to TLS for etcd
[upgrade/etcd] Non fatal issue encountered during upgrade: the desired etcd version for this Kubernetes version "v1.18.9" 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-manifests328986264"
[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-2021-01-06-14-24-18/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-k8s-master hash: d002f0455950f5b76f6097191f93db28
Static pod: kube-apiserver-k8s-master hash: d002f0455950f5b76f6097191f93db28
Static pod: kube-apiserver-k8s-master hash: 6bc4f16364bf23910ec81c9e91593d95
[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-2021-01-06-14-24-18/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-k8s-master hash: 54e96591b22cec4a1f5b76965fa90be7
Static pod: kube-controller-manager-k8s-master hash: a96ac50aab8a064c2101f684d34ee058
[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-2021-01-06-14-24-18/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-k8s-master hash: da215ebee0354225c20c7bdf28b467f8
Static pod: kube-scheduler-k8s-master hash: 1a0670b7d3bff3fd96dbd08f176c1461
[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 "v1.18.9". Enjoy!
[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets if you haven't already done so.
由输出可以看出升级执行成功。
（6）取消调度保护
# kubectl uncordon k8s-master
（7）升级节点
$ 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 "v1.18.9"...
Static pod: kube-apiserver-k8s-master hash: 6bc4f16364bf23910ec81c9e91593d95
Static pod: kube-controller-manager-k8s-master hash: a96ac50aab8a064c2101f684d34ee058
Static pod: kube-scheduler-k8s-master hash: 1a0670b7d3bff3fd96dbd08f176c1461
[upgrade/etcd] Upgrading to TLS for etcd
[upgrade/etcd] Non fatal issue encountered during upgrade: the desired etcd version for this Kubernetes version "v1.18.9" 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-manifests315032619"
W0106 14:36:33.013476 30507 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.
（8）升级kubectl和kubelet
$ yum install -y kubelet-1.18.9-0 kubectl-1.18.9-0 --disableexcludes=kubernetes
重启kubelet
$ systemctl daemon-reload
$ systemctl restart kubelet
Node升级
（1）升级kubeadm
yum install -y kubeadm-1.18.9-0 --disableexcludes=kubernetes
（2）设置节点不可调度并排空节点
$ kubectl cordon ecs-968f-0005
$ kubectl drain ecs-968f-0005
（3）升级节点
$ 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] Skipping phase. Not a control plane node.
[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.
（4）升级kubelet
yum install -y kubelet-1.18.9-0 --disableexcludes=kubernetes
重启kubelet
$ systemctl daemon-reload
$ systemctl restart kubelet
（5）设置节点可调度
kubectl uncordon ecs-968f-0005
验证集群
（1）、验证集群状态是否正常
$ kubectl get no
NAME STATUS ROLES AGE VERSION
ecs-968f-0005 Ready node 102d v1.18.9
k8s-master Ready master 102d v1.18.9
（2）、验证集群证书是否正常
$ kubeadm alpha certs check-expiration
[check-expiration] Reading configuration from the cluster...
[check-expiration] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
CERTIFICATE EXPIRES RESIDUAL TIME CERTIFICATE AUTHORITY EXTERNALLY MANAGED
admin.conf Jan 06, 2022 06:36 UTC 364d no
apiserver Jan 06, 2022 06:24 UTC 364d ca no
apiserver-etcd-client Jan 06, 2022 06:24 UTC 364d etcd-ca no
apiserver-kubelet-client Jan 06, 2022 06:24 UTC 364d ca no
controller-manager.conf Jan 06, 2022 06:24 UTC 364d no
etcd-healthcheck-client Sep 25, 2021 06:55 UTC 262d etcd-ca no
etcd-peer Sep 25, 2021 06:55 UTC 262d etcd-ca no
etcd-server Sep 25, 2021 06:55 UTC 262d etcd-ca no
front-proxy-client Jan 06, 2022 06:24 UTC 364d front-proxy-ca no
scheduler.conf Jan 06, 2022 06:24 UTC 364d no
CERTIFICATE AUTHORITY EXPIRES RESIDUAL TIME EXTERNALLY MANAGED
ca Sep 23, 2030 06:55 UTC 9y no
etcd-ca Sep 23, 2030 06:55 UTC 9y no
front-proxy-ca Sep 23, 2030 06:55 UTC 9y no
注意：
kubeadm upgrade也会自动对它在此节点上管理的证书进行续约。 如果选择不对证书进行续约，可以使用--certificate-renewal=false。
故障恢复
在升级过程中如果升级失败并且没有回滚，可以继续执行kubeadm upgrade。如果要从故障状态恢复，可以执行kubeadm upgrade --force。
在升级期间，会在/etc/kubernetes/tmp目录下生成备份文件：
- kubeadm-backup-etcd-
- kubeadm-backup-manifests-
kubeadm-backup-etcd中包含本地etcd的数据备份，如果升级失败并且无法修复，可以将其数据复制到etcd数据目录进行手动修复。
kubeadm-backup-manifests中保存的是节点静态pod的YAML清单，如果升级失败并且无法修复，可以将其复制到/etc/kubernetes/manifests下进行手动修复。
参考：https://v1-18.docs.kubernetes.io/zh/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade/
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