錯誤：
[root@k8s-master ~]# kubeadm init \
> --apiserver-advertise-address=10.31.4.1 \
> --image-repository registry.aliyuncs.com/google_containers \
> --kubernetes-version v1.15.0 \
> --service-cidr=10.1.0.0/16 \
> --pod-network-cidr=10.244.0.0/16
[init] Using Kubernetes version: v1.15.0
[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/
error execution phase preflight: [preflight] Some fatal errors occurred:
[ERROR Port-10251]: Port 10251 is in use
[ERROR Port-10252]: Port 10252 is in use
[ERROR FileAvailable--etc-kubernetes-manifests-kube-apiserver.yaml]: /etc/kubernetes/manifests/kube-apiserver.yaml already exists
[ERROR FileAvailable--etc-kubernetes-manifests-kube-controller-manager.yaml]: /etc/kubernetes/manifests/kube-controller-manager.yaml already exists
[ERROR FileAvailable--etc-kubernetes-manifests-kube-scheduler.yaml]: /etc/kubernetes/manifests/kube-scheduler.yaml already exists
[ERROR FileAvailable--etc-kubernetes-manifests-etcd.yaml]: /etc/kubernetes/manifests/etcd.yaml already exists
[ERROR Port-10250]: Port 10250 is in use
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
解決辦法：
重啟一下kubeadm：
[root@k8s-master ~]# kubeadm reset