I was trying to setup a Kubernetes cluster in centos 7 and i am facing issue while running the below kubeadm init command.

kubeadm init --apiserver-advertise-address=10.70.6.18 --pod-network-cidr=192.168.0.0/16



I1224 18:20:55.388552   11136 version.go:94] could not fetch a Kubernetes version from the internet: unable to get URL "https://dl.k8s.io/release/stable-1.txt": Get https://dl.k8s.io/release/stable-1.txt: dial tcp: lookup dl.k8s.io on 10.171.221.11:53: no such host
I1224 18:20:55.388679   11136 version.go:95] falling back to the local client version: v1.13.1
[init] Using Kubernetes version: v1.13.1
[preflight] Running pre-flight checks
        [WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly
        [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 18.09.0. Latest validated version: 18.06
[preflight] Pulling images required for setting up a Kubernetes cluster
[preflight] This might take a minute or two, depending on the speed of your internet connection
[preflight] You can also perform this action in beforehand using 'kubeadm config images pull'
error execution phase preflight: [preflight] Some fatal errors occurred:
        [ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-apiserver:v1.13.1: output: v1.13.1: Pulling from kube-apiserver
73e3e9d78c61: Pulling fs layer
e08dba503a39: Pulling fs layer
error pulling image configuration: Get https://storage.googleapis.com/asia.artifacts.google-containers.appspot.com/containers/images/sha256:40a63db91ef844887af73e723e40e595e4aa651ac2c5637332d719e42abc4dd2: x509: certificate signed by unknown authority
, error: exit status 1
        [ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-controller-manager:v1.13.1: output: v1.13.1: Pulling from kube-controller-manager