helm 安装prometheus过程中无法下载国外镜像的解决办法

helm install prometheus  prometheus-community/kube-prometheus-stack  -n monitoring

安装失败，通过kubectl describe pod 得知是镜像下载失败：

kubectl describe pod -n monitoring prometheus-kube-prometheus-admission-create-cf9st 

Events:
  Type     Reason     Age                From               Message
  ----     ------     ----               ----               -------
  Normal   Scheduled  39s                default-scheduler  Successfully assigned monitoring/prometheus-kube-prometheus-admission-create-cf9st to node03
  Warning  Failed     24s                kubelet            Failed to pull image "k8s.gcr.io/ingress-nginx/kube-webhook-certgen:v1.0@sha256:f3b6b39a6062328c095337b4cadcefd1612348fdd5190b1dcbcb9b9e90bd8068": rpc error: code = Unknown desc = Error response from daemon: Get "https://k8s.gcr.io/v2/": context deadline exceeded
  Warning  Failed     24s                kubelet            Error: ErrImagePull
  Normal   BackOff    23s                kubelet            Back-off pulling image "k8s.gcr.io/ingress-nginx/kube-webhook-certgen:v1.0@sha256:f3b6b39a6062328c095337b4cadcefd1612348fdd5190b1dcbcb9b9e90bd8068"
  Warning  Failed     23s                kubelet            Error: ImagePullBackOff
  Normal   Pulling    12s (x2 over 39s)  kubelet            Pulling image "k8s.gcr.io/ingress-nginx/kube-webhook-certgen:v1.0@sha256:f3b6b39a6062328c095337b4cadcefd1612348fdd5190b1dcbcb9b9e90bd8068"

解决办法如下：

第一步：先通过阿里云镜像看是否可以下载

docker pull registry.cn-hangzhou.aliyuncs.com/google_containers/kube-webhook-certgen:v1.0

确认可以下载后
第二步：通过helm pull