Error in kubeadm join: [error port-10250]: port 10250 is in use [error fileavailable--etc kubernetes PKI

First use kubeadm structure k8s colony , Therefore, there is insufficient understanding of the process of adding child nodes to management nodes , As a result, I made a kubeadm init after , Just ready for kubeadm join operation . The result is the following error ：

[[email protected] ostrich5yw]# kubeadm join 192.168.139.129:6443 --token abcdef.0123456789abcdef \
>     --discovery-token-ca-cert-hash sha256:3ac4ae8b5b3b08f2b8cd8a85be7b37bc5855e749ec9126e3d87bebfb2235af9b 
[preflight] Running pre-flight checks
	[WARNING SystemVerification]: this Docker version is not on the list of validated versions: 20.10.6. Latest validated version: 18.09
error execution phase preflight: [preflight] Some fatal errors occurred:
	[ERROR DirAvailable--etc-kubernetes-manifests]: /etc/kubernetes/manifests is not empty
	[ERROR FileAvailable--etc-kubernetes-kubelet.conf]: /etc/kubernetes/kubelet.conf already exists
	[ERROR Port-10250]: Port 10250 is in use
	[ERROR FileAvailable--etc-kubernetes-pki-ca.crt]: /etc/kubernetes/pki/ca.crt already exists
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`

Question why ： Only the parent node needs to run kubeadm init --config=kubeadm-config.yaml --upload-certs | tee kubeadm-init.log To initialize ; For child nodes , No need to kubeadm init To initialize , Direct operation kubeadm join Just join the parent node .

resolvent ： function kubeadm reset Reset child nodes , Then directly use for child nodes kubeadm join 192.168.139.129:6443 --token abcdef.0123456789abcdef --discovery-token-ca-cert-hash sha256:3ac4ae8b5b3b08f2b8cd8a85be7b37bc5855e749ec9126e3d87bebfb2235af9b Add it to the corresponding parent node .