k8s下线node节点
有时候我们想更新一些服务器，或者维护/更新一些镜像的时候，需要暂停一部分node节点，正确操作步骤如下：
1.获取节点列表
root@k8s-master1:~# kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
k8s-master1 Ready control-plane,master 103d v1.22.0 192.168.255.100 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-master2 Ready control-plane,master 103d v1.22.0 192.168.255.102 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-node1 Ready <none> 103d v1.22.0 192.168.255.103 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-node2 Ready <none> 103d v1.22.0 192.168.255.104 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
2.设置不可调度
root@k8s-master1:~# kubectl cordon k8s-node2
node/k8s-node2 cordoned
root@k8s-master1:~# kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
k8s-master1 Ready control-plane,master 103d v1.22.0 192.168.255.100 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-master2 Ready control-plane,master 103d v1.22.0 192.168.255.102 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-node1 Ready <none> 103d v1.22.0 192.168.255.103 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-node2 Ready,SchedulingDisabled <none> 103d v1.22.0 192.168.255.104 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
root@k8s-master1:~#
可以看到k8s-node2节点已经被暂停调度（SchedulingDisabled）
3.驱逐节点上运行的Pod
如果需要驱逐节点上的pod 可执行
root@k8s-master1:~# kubectl drain k8s-node2
node/k8s-node2 already cordoned
DEPRECATED WARNING: Aborting the drain command in a list of nodes will be deprecated in v1.23.
The new behavior will make the drain command go through all nodes even if one or more nodes failed during the drain.
For now, users can try such experience via: --ignore-errors
error: unable to drain node "k8s-node2", aborting command...
There are pending nodes to be drained:
k8s-node2
error: cannot delete DaemonSet-managed Pods (use --ignore-daemonsets to ignore): kube-system/kube-flannel-ds-wdwzs, kube-system/kube-proxy-dk4vn
root@k8s-master1:~#
注意：若node节点上存在daemonsets控制器创建的pod,则需要使用--ignore-daemonsets忽略错误错误警告
root@k8s-master1:~# kubectl drain k8s-node2 --ignore-daemonsets
node/k8s-node2 already cordoned
WARNING: ignoring DaemonSet-managed Pods: kube-system/kube-flannel-ds-wdwzs, kube-system/kube-proxy-dk4vn
node/k8s-node2 drained
root@k8s-master1:~#
查看pod，可以看到已经没有pod运行在k8s-node2节点
root@k8s-master1:~# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
php-fpm-nginx-5d8b7fd989-59ljf 2/2 Running 0 91m 10.10.3.243 k8s-node1 <none> <none>
php-fpm-nginx-5d8b7fd989-kfmln 2/2 Running 22 (22h ago) 24d 10.10.3.238 k8s-node1 <none> <none>
redis-svc-866fb777f8-4ps2s 1/1 Running 11 (22h ago) 24d 10.10.3.240 k8s-node1 <none> <none>
redis-svc-866fb777f8-lflkv 1/1 Running 11 (22h ago) 24d 10.10.3.239 k8s-node1 <none> <none>
test-www-7fcc4d5595-4mg5j 2/2 Running 0 91m 10.10.3.242 k8s-node1 <none> <none>
test-www-7fcc4d5595-kcllj 2/2 Running 0 91m 10.10.3.241 k8s-node1 <none> <none>
4、恢复可调度
当需要重新调度node节点的时候，执行
root@k8s-master1:~# kubectl uncordon k8s-node2
node/k8s-node2 uncordoned
查看node状态
root@k8s-master1:~# kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
k8s-master1 Ready control-plane,master 103d v1.22.0 192.168.255.100 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-master2 Ready control-plane,master 103d v1.22.0 192.168.255.102 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-node1 Ready <none> 103d v1.22.0 192.168.255.103 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
k8s-node2 Ready <none> 103d v1.22.0 192.168.255.104 <none> Ubuntu 18.04.5 LTS 4.15.0-154-generic docker://20.10.8
root@k8s-master1:~#
5、删除节点
如果需要直接删除节点（此方式比较暴力，一般情况不推荐使用）
kubectl delete nodes k8s-node2
如果删除的node想重新加入到k8s集群中 则需要master重新生成加入token即可
