Renew expiring Kubernetes cluster certificates - Container Service for Kubernetes

This topic describes how to renew Kubernetes cluster certificates that are about to expire. You can renew all certificates for a Container Service for Kubernetes (ACK) cluster by clicking one button in the ACK console or by running a single command in a command-line interface (CLI). You can also renew the certificates for master and worker nodes separately.

Prerequisites

An ACK cluster is created. For more information, see Create an ACK dedicated cluster.
Note In managed Kubernetes clusters, ACK automatically renews the certificates for master nodes.
A kubectl client is connected to the cluster. For more information, see Connect to Kubernetes clusters by using kubectl.

Renew the certificates for all nodes in the ACK console

Log on to the ACK console.
In the left-side navigation pane of the ACK console, click Clusters.
Select the cluster for which you want to renew the certificates and click Update Certificate. The Update Certificate message appears.
Note The Update Certificate button appears if the cluster certificate is about to expire in around two months.
In the Update Certificate message, click Update Certificate.
In the Note message, click Confirm.
The following message appears after the cluster certificates are renewed.
- In the Update Certificate message, The certificate has been updated appears.
- On the Clusters page, the Update Certificate button disappears.

Renew the certificates for all nodes in a CLI

Log on to a master node of the cluster and run the following command to renew the certificates for all nodes:

curl http://aliacs-k8s-cn-hangzhou.oss-cn-hangzhou.aliyuncs.com/public/cert-update/renew.sh | bash

Verify the result:

Run the following command to query the master nodes and worker nodes in the cluster:
```
kubectl get nodes
```
Run the following command and verify that the value in the COMPLETIONS column of each master node is 1 and the value in the COMPLETIONS column of each worker node equals the number of worker nodes in the cluster. This indicates that all certificates are renewed.
```
kubectl -n kube-system get job
```

Manually renew the certificates for master nodes

Create a file named job-master.yml in a random path and copy the following code to the file:

apiVersion: batch/v1
kind: Job
metadata:
  name: ${jobname}
  namespace: kube-system
spec:
  backoffLimit: 0
  completions: 1
  parallelism: 1
  template:
    spec:
      activeDeadlineSeconds: 3600
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: kubernetes.io/hostname
                operator: In
                values:
                - ${hostname}
      containers:
      - command:
        - /renew/upgrade-k8s.sh
        - --role
        - master
        image: registry.cn-hangzhou.aliyuncs.com/acs/cert-rotate:v1.0.0
        imagePullPolicy: Always
        name: ${jobname}
        securityContext:
          privileged: true
        volumeMounts:
        - mountPath: /alicoud-k8s-host
          name: ${jobname}       
      hostNetwork: true
      hostPID: true
      restartPolicy: Never
      schedulerName: default-scheduler
      securityContext: null
      tolerations:
      - effect: NoSchedule
        key: node-role.kubernetes.io/master
      volumes:
      - hostPath:
          path: /
          type: Directory
        name: ${jobname}

Obtain the number of master nodes in the cluster and the hostname of each master node.
- Method 1: Use the CLI
  Run the following command:
```
kubectl get nodes
```
- Method 2: Use the console
  1. Log on to the ACK console.
  2. In the left-side navigation pane of the ACK console, click Clusters.
  3. On the Clusters page, find the cluster that you want to manage. Then, click the name of the cluster or click Details in the Actions column.
  4. In the left-side navigation pane of the cluster details page, choose Nodes > Nodes to obtain the number of master nodes, and the name, IP address, and instance ID of each master node.
Run the following command to set the ${jobname} and ${hostname} variables in the job-master.yml file:
```
sed 's/${jobname}/cert-job-2/g; s/${hostname}/hostname/g' job-master.yml > job-master2.yml
```
Where:
- ${jobname} is the name of the Job. In this example, cert-job-2 is used.
- ${hostname} is the name of the master node. In this example, hostname is set to a master node name that is obtained in Step 2.
Run the following command to create the Job:
```
kubectl create -f job-master2.yml
```
Run the following command to query the Job. If the value in the COMPLETIONS column is 1, it indicates that the certificate of the master node is renewed.
```
kubectl get job -nkube-system
```
Repeat Steps 3 to 5 to renew the certificates for the other master nodes in the cluster.

Manually renew the certificates for worker nodes

Create a file named job-node.yml in a random path and copy the following code to the file:

apiVersion: batch/v1
kind: Job
metadata:
  name: ${jobname}
  namespace: kube-system
spec:
  backoffLimit: 0
  completions: ${nodesize}
  parallelism: ${nodesize}
  template:
    spec:
      activeDeadlineSeconds: 3600
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: job-name
                operator: In
                values:
                - ${jobname}
            topologyKey: kubernetes.io/hostname
      containers:
      - command:
        - /renew/upgrade-k8s.sh
        - --role
        - node
        - --rootkey
        - ${key}
        image: registry.cn-hangzhou.aliyuncs.com/acs/cert-rotate:v1.0.0
        imagePullPolicy: Always
        name: ${jobname}
        securityContext:
          privileged: true
        volumeMounts:
        - mountPath: /alicoud-k8s-host
          name: ${jobname}
      hostNetwork: true
      hostPID: true
      restartPolicy: Never
      schedulerName: default-scheduler
      securityContext: null
      volumes:
      - hostPath:
          path: /
          type: Directory
        name: ${jobname}

Note If a worker node has a taint, you must add tolerations that match the taint in the job-node.yml file. To do this, add the following code between the securityContext: {} and volumes: section. If you have n worker nodes that have taints, add the following code n times.

      tolerations:
      - effect: NoSchedule
        key: ${key}
        operator: Equal
        value: ${value}

To obtain the values of ${name} and ${value}, perform the following steps:

Create a file named taint.yml in a random path and copy the following code to the file:

{{printf "%-50s %-12s\n" "Node" "Taint"}}
{{- range .items}}
    {{- if $taint := (index .spec "taints") }}
        {{- .metadata.name }}{{ "\t" }}
        {{- range $taint }}
            {{- .key }}={{ .value }}:{{ .effect }}{{ "\t" }}
        {{- end }}
        {{- "\n" }}
    {{- end}}
{{- end}}

Run the following command to query the values of ${name} and ${value} for worker nodes that have taints:
```
kubectl get nodes -o go-template-file="taint.tml"
```

Run the following command to obtain the cluster Certificate Authority (CA) key:
```
sed '1d' /etc/kubernetes/pki/ca.key | base64 -w 0
```
Run the following command to set the ${jobname}, ${nodesize}, and ${key} variables in the job-node.yml file:
```
sed 's/${jobname}/cert-node-2/g; s/${nodesize}/nodesize/g; s/${key}/key/g' job-node.yml > job-node2.yml
```
Where:
- ${jobname} is the name of the Job. In this example, cert-node-2 is used.
- ${nodesize} is the number of worker nodes. For more information about how to obtain this value, see Step 1 in Manually renew the certificates for worker nodes. Replace nodesize with the actual value.
- ${key} is the cluster CA key. In this example, key is set to the CA key that is obtained in Step 2 of Manually renew the certificates for worker nodes.
Run the following command to create the Job:
```
kubectl create –f job-node2.yml
```
Run the following command to query the Job. If the value in the COMPLETIONS column equals the number of worker nodes in the cluster, it indicates that the certificates of all worker nodes are renewed.
```
kubectl get job –nkube-system
```