概述

将 slave 节点加入到集群中很简单，只需要在 slave 服务器上安装 kubeadm，kubectl，kubelet 三个工具，然后使用kubeadm join 命令加入即可。准备工作如下：

修改主机名
配置软件源
安装三个工具
由于之前章节已经说明了操作步骤，此处不再赘述。

将 slave 加入到集群

kubeadm join 192.168.141.130:6443 --token abcdef.0123456789abcdef --discovery-token-ca-cert-hash sha256:cab7c86212535adde6b8d1c7415e81847715cfc8629bb1d270b601744d662515

# 安装成功将看到如下信息
[preflight] Running pre-flight checks
        [WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
[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-1.14" 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.

说明：

token
- 可以通过安装 master 时的日志查看 token 信息
- 可以通过kubeadm token list 命令打印出 token 信息
- 如果 token 过期，可以使用 kubeadm token create 命令创建新的 token
discovery-token-ca-cert-hash
- 可以通过安装 master 时的日志查看 sha256 信息
- 可以通过 openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'命令查看 sha256 信息

验证是否成功

回到 master 服务器

kubectl get nodes

# 可以看到 slave 成功加入 master
NAME                STATUS     ROLES    AGE   VERSION
kubernetes-master   NotReady   master   9h    v1.14.1
kubernetes-slave1   NotReady   <none>   22s   v1.14.1

如果 slave 节点加入 master 时配置有问题可以在 slave 节点上使用 kubeadm reset 重置配置再使用 kubeadm join 命令重新加入即可。希望在 master 节点删除 node ，可以使用 kubeadm delete nodes <NAME> 删除。

查看 pod 状态

kubectl get pod -n kube-system -o wide

NAME                                        READY   STATUS    RESTARTS   AGE   IP                NODE                NOMINATED NODE   READINESS GATES
coredns-8686dcc4fd-gwrmb                    0/1     Pending   0          9h    <none>            <none>              <none>           <none>
coredns-8686dcc4fd-j6gfk                    0/1     Pending   0          9h    <none>            <none>              <none>           <none>
etcd-kubernetes-master                      1/1     Running   1          9h    192.168.141.130   kubernetes-master   <none>           <none>
kube-apiserver-kubernetes-master            1/1     Running   1          9h    192.168.141.130   kubernetes-master   <none>           <none>
kube-controller-manager-kubernetes-master   1/1     Running   1          9h    192.168.141.130   kubernetes-master   <none>           <none>
kube-proxy-496dr                            1/1     Running   0          17m   192.168.141.131   kubernetes-slave1   <none>           <none>
kube-proxy-rsnb6                            1/1     Running   1          9h    192.168.141.130   kubernetes-master   <none>           <none>
kube-scheduler-kubernetes-master            1/1     Running   1          9h    192.168.141.130   kubernetes-master   <none>           <none>

由此可以看出 coredns 尚未运行，此时我们还需要安装网络插件。