下載鏡像提示 output: Error response from daemon: Get https://k8s.gcr.io/v2/: x509: certificate has expired or is not yet valid , error: exit status 1

出現這問題可能是兩種原因：
1、k8s 所有節點的時間不統一。
2、k8s 配置文件鏡像倉庫有問題

問題：

[root@master1 ~]# kubeadm config images pull --config kubeadm-config.yaml
W0920 01:12:10.794030    2723 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
failed to pull image "k8s.gcr.io/kube-apiserver:v1.18.2": output: Error response from daemon: Get https://k8s.gcr.io/v2/: x509: certificate has expired or is not yet valid
, error: exit status 1
To see the stack trace of this error execute with --v=5 or higher

解決
編輯 kubeadm-config.yaml 文件改鏡像倉庫

dns:
  type: CoreDNS
etcd:
  local:
    dataDir: /var/lib/etcd
imageRepository: registry.aliyuncs.com/google_containers      # 改完之后的鏡像倉庫地址
kind: ClusterConfiguration
kubernetesVersion: v1.18.2
networking:
  dnsDomain: cluster.local
  podSubnet: "10.244.0.0/16"
  serviceSubnet: 10.96.0.0/12
scheduler: {}

或者

同步 k8s 所有節點時間

timedatectl set-timezone Asia/Shanghai
chronyc -a makestep