kubeadm 生成的token过期后，集群增加节点

通过kubeadm初始化后，都会提供node加入的token。

[root@walker-1 kubernetes]# kubeadm init --config ./kubeadm-init.yaml --skip-preflight-checks
[kubeadm] WARNING: kubeadm is in beta, please do not use it for production clusters.
[init] Using Kubernetes version: v1.8.1
[init] Using Authorization modes: [Node RBAC]
[preflight] Skipping pre-flight checks
[kubeadm] WARNING: starting in 1.8, tokens expire after 24 hours by default (if you require a non-expiring token use --token-ttl 0)
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [walker-1.novalocal kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local walker-1.novalocal walker-2.novalocal] and IPs [10.96.0.1 172.16.6.47 172.16.6.47 172.16.6.249 172.16.6.79]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
...

You can now join any number of machines by running the following on each node
as root:

   kubeadm join --token 19f284.da47998c9abb01d3 172.16.6.47:6443 --discovery-token-ca-cert-hash sha256:0fd95a9bc67a7bf0ef42da968a0d55d92e52898ec37c971bd77ee501d845b538

默认token的有效期为24小时，当过期之后，该token就不可用了。解决方法如下：

1. 重新生成新的token

[root@walker-1 kubernetes]# kubeadm token create
[kubeadm] WARNING: starting in 1.8, tokens expire after 24 hours by default (if you require a non-expiring token use --ttl 0)
aa78f6.8b4cafc8ed26c34f
[root@walker-1 kubernetes]# kubeadm token list
TOKEN                     TTL       EXPIRES                     USAGES                   DESCRIPTION   EXTRA GROUPS
aa78f6.8b4cafc8ed26c34f   23h       2017-12-26T16:36:29+08:00   authentication,signing   <none>        system:bootstrappers:kubeadm:default-node-token

1. 获取ca证书sha256编码hash值

[root@walker-1 kubernetes]# openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'
0fd95a9bc67a7bf0ef42da968a0d55d92e52898ec37c971bd77ee501d845b538

1. 节点加入集群

[root@walker-4 kubernetes]# kubeadm join --token aa78f6.8b4cafc8ed26c34f --discovery-token-ca-cert-hash sha256:0fd95a9bc67a7bf0ef42da968a0d55d92e52898ec37c971bd77ee501d845b538  172.16.6.79:6443 --skip-preflight-checks