解决k8s集群kubeadm init初始化镜像pull不下来的问题

新版本的Kubernetes在安装部署中，需要从k8s.grc.io仓库中拉取所需镜像文件，但由于国内网络防火墙问题导致无法正常拉取。

kubeadm init 所出现的问题：

[preflight] Some fatal errors occurred:
    [ERROR ImagePull]: failed to pull image [k8s.gcr.io/kube-apiserver-amd64:v1.11.2]: exit status 1
    [ERROR ImagePull]: failed to pull image [k8s.gcr.io/kube-controller-manager-amd64:v1.11.2]: exit status 1
    [ERROR ImagePull]: failed to pull image [k8s.gcr.io/kube-scheduler-amd64:v1.11.2]: exit status 1
    [ERROR ImagePull]: failed to pull image [k8s.gcr.io/kube-proxy-amd64:v1.11.2]: exit status 1
    [ERROR ImagePull]: failed to pull image [k8s.gcr.io/pause:3.1]: exit status 1
    [ERROR ImagePull]: failed to pull image [k8s.gcr.io/etcd-amd64:3.2.18]: exit status 1
    [ERROR ImagePull]: failed to pull image [k8s.gcr.io/coredns:1.1.3]: exit status 1

解决方法：

#!/bin/bash
K8S_VERSION=v1.13.1
ETCD_VERSION=3.2.24
DA