# 安装 network pod: flannel
网络组件用以在 pod 间进行通信，再此之前，我们会发现 coredns 组件处于 Pending 状态。我们使用网络组件 flannel 来确保 coredns 的正常运行。
$ kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-5644d7b6d9-8l2gv 0/1 Pending 0 56m
kube-system coredns-5644d7b6d9-l8zv5 0/1 Pending 0 56m
kube-system etcd-shanyue 1/1 Running 0 55m
kube-system kube-apiserver-shanyue 1/1 Running 0 55m
kube-system kube-controller-manager-shanyue 1/1 Running 0 55m
kube-system kube-proxy-5drlg 1/1 Running 0 56m
kube-system kube-scheduler-shanyue 1/1 Running 0 55m
在安装网络组件要确保路是通的，使用 sysctl 设置内核变量 net.bridge.bridge-nf-call-iptables 为1
$ sysctl net.bridge.bridge-nf-call-iptables=1
$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/2140ac876ef134e0ed5af15c65e414cf26827915/Documentation/kube-flannel.yml
podsecuritypolicy.policy/psp.flannel.unprivileged created
clusterrole.rbac.authorization.k8s.io/flannel created
clusterrolebinding.rbac.authorization.k8s.io/flannel created
serviceaccount/flannel created
configmap/kube-flannel-cfg created
daemonset.apps/kube-flannel-ds-amd64 created
daemonset.apps/kube-flannel-ds-arm64 created
daemonset.apps/kube-flannel-ds-arm created
daemonset.apps/kube-flannel-ds-ppc64le created
daemonset.apps/kube-flannel-ds-s390x created
此时，再次查看集群中所有的 pod 状态，此时 coredn 变为正常状态，且多了 kube-flannel-ds-amd64 这个 pod。
$ kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-5644d7b6d9-8l2gv 1/1 Running 0 136m
kube-system coredns-5644d7b6d9-l8zv5 1/1 Running 0 136m
kube-system etcd-shanyue 1/1 Running 0 136m
kube-system kube-apiserver-shanyue 1/1 Running 0 135m
kube-system kube-controller-manager-shanyue 1/1 Running 0 136m
kube-system kube-flannel-ds-amd64-pmlnw 1/1 Running 0 9m23s
kube-system kube-proxy-5drlg 1/1 Running 0 136m
kube-system kube-scheduler-shanyue 1/1 Running 0 136m
# 添加 worker node
在添加 worker node 时，需要在子节点也进行 docker 以及 kubeadm 的安装，按照以上章节步骤进行安装。
安装之后根据以上关于搭建主节点章节的输出指示，使用 kubeadm join 加入集群之中:
$ kubeadm join 172.17.68.39:6443 --token qq8hbl.4utma949mu0p47v4 \
--discovery-token-ca-cert-hash sha256:cce6cd7ec86cf4cd65215bea554f98c786783720b19262533cd98656ac6eb15e
[preflight] Running pre-flight checks
[WARNING Service-Docker]: docker service is not enabled, please run 'systemctl enable docker.service'
[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.16" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Activating the kubelet service
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...
This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.
Run 'kubectl get nodes' on the control-plane to see this node join the cluster.
kubeadm join 有两个关键的参数: token 与 hash。如果你已经丢失了新建 master node 时的输出 kubeadm join 信息怎么办？此时可以通过以下命令来获取
# 以下操作在 master node
# kubeadm join <control-plane-host>:<control-plane-port> --token <token> --discovery-token-ca-cert-hash sha256:<hash>
# 获取 token
$ kubectl token list
# 获取 hash
$ openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'
安装完之后，再次打印节点信息
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
shanyue Ready master 17m v1.16.0
shuifeng Ready <none> 15m v1.16.0
$ kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-5644d7b6d9-845lr 1/1 Running 0 24m
kube-system coredns-5644d7b6d9-k6dqm 1/1 Running 0 24m
kube-system etcd-shanyue 1/1 Running 0 23m
kube-system kube-apiserver-shanyue 1/1 Running 0 23m
kube-system kube-controller-manager-shanyue 1/1 Running 0 23m
kube-system kube-flannel-ds-amd64-tdvbs 1/1 Running 0 21m
kube-system kube-flannel-ds-amd64-vtrnh 1/1 Running 0 21m
kube-system kube-proxy-k46l2 1/1 Running 0 24m
kube-system kube-proxy-rhrrg 1/1 Running 0 22m
kube-system kube-scheduler-shanyue 1/1 Running 0 23m
至此，一个拥有 master node 与 worker node 的 kubernetes 集群就搭建完成了。