The kubelet that is deployed next to the kubeadm package will crashloop until you start kubeadm init. check the status of the kubelet after kubeadm init finishes.
scnzzh@zubt1:~/zzh$ service kubelet status ● kubelet.service - kubelet: The Kubernetes Node Agent Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled) Drop-In: /etc/systemd/system/kubelet.service.d └─10-kubeadm.conf Active: activating (auto-restart) (Result: exit-code) since Thu 2021-01-21 07:01:14 EST; 5s ago Docs: https://kubernetes.io/docs/home/ Process: 4688 ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS (code=exited, status=255/EXCEPT> Main PID: 4688 (code=exited, status=255/EXCEPTION) scnzzh@zubt1:~/zzh$ sudo kubeadm init --control-plane-endpoint zvip:8443 --upload-certs [sudo] password for scnzzh: [init] Using Kubernetes version: v1.20.2 [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/ [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 20.10.2. Latest validated version: 19.03 [preflight] Pulling images required for setting up a Kubernetes cluster [preflight] This might take a minute or two, depending on the speed of your internet connection [preflight] You can also perform this action in beforehand using 'kubeadm config images pull' [certs] Using certificateDir folder "/etc/kubernetes/pki" [certs] Generating "ca" certificate and key [certs] Generating "apiserver" certificate and key [certs] apiserver serving cert is signed for DNS names [kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local zubt1 zvip] and IPs [10.96.0.1 10.0.2.7] [certs] Generating "apiserver-kubelet-client" certificate and key [certs] Generating "front-proxy-ca" certificate and key [certs] Generating "front-proxy-client" certificate and key [certs] Generating "etcd/ca" certificate and key [certs] Generating "etcd/server" certificate and key [certs] etcd/server serving cert is signed for DNS names [localhost zubt1] and IPs [10.0.2.7 127.0.0.1 ::1] [certs] Generating "etcd/peer" certificate and key [certs] etcd/peer serving cert is signed for DNS names [localhost zubt1] and IPs [10.0.2.7 127.0.0.1 ::1] [certs] Generating "etcd/healthcheck-client" certificate and key [certs] Generating "apiserver-etcd-client" certificate and key [certs] Generating "sa" key and public key [kubeconfig] Using kubeconfig folder "/etc/kubernetes" [endpoint] WARNING: port specified in controlPlaneEndpoint overrides bindPort in the controlplane address [kubeconfig] Writing "admin.conf" kubeconfig file [endpoint] WARNING: port specified in controlPlaneEndpoint overrides bindPort in the controlplane address [kubeconfig] Writing "kubelet.conf" kubeconfig file [endpoint] WARNING: port specified in controlPlaneEndpoint overrides bindPort in the controlplane address [kubeconfig] Writing "controller-manager.conf" kubeconfig file [endpoint] WARNING: port specified in controlPlaneEndpoint overrides bindPort in the controlplane address [kubeconfig] Writing "scheduler.conf" kubeconfig file [kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env" [kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml" [kubelet-start] Starting the kubelet [control-plane] Using manifest folder "/etc/kubernetes/manifests" [control-plane] Creating static Pod manifest for "kube-apiserver" [control-plane] Creating static Pod manifest for "kube-controller-manager" [control-plane] Creating static Pod manifest for "kube-scheduler" [etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests" [wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s [apiclient] All control plane components are healthy after 28.165576 seconds [upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace [kubelet] Creating a ConfigMap "kubelet-config-1.20" in namespace kube-system with the configuration for the kubelets in the cluster [upload-certs] Storing the certificates in Secret "kubeadm-certs" in the "kube-system" Namespace [upload-certs] Using certificate key: 35c5f69136287ed3d2c9d49fb8a0572aad9e37c243e98c97d08e47a7dd806bb3 [mark-control-plane] Marking the node zubt1 as control-plane by adding the labels "node-role.kubernetes.io/master=''" and "node-role.kubernetes.io/control-plane='' (deprecated)" [mark-control-plane] Marking the node zubt1 as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule] [bootstrap-token] Using token: 7obk27.9rx2nfu1xzpht3p7 [bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles [bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to get nodes [bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials [bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token [bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster [bootstrap-token] Creating the "cluster-info" ConfigMap in the "kube-public" namespace [kubelet-finalize] Updating "/etc/kubernetes/kubelet.conf" to point to a rotatable kubelet client certificate and key [addons] Applied essential addon: CoreDNS [endpoint] WARNING: port specified in controlPlaneEndpoint overrides bindPort in the controlplane address [addons] Applied essential addon: kube-proxy Your Kubernetes control-plane has initialized successfully! To start using your cluster, you need to run the following as a regular user: mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config Alternatively, if you are the root user, you can run: export KUBECONFIG=/etc/kubernetes/admin.conf You should now deploy a pod network to the cluster. Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at: https://kubernetes.io/docs/concepts/cluster-administration/addons/ You can now join any number of the control-plane node running the following command on each as root: kubeadm join zvip:8443 --token 7obk27.9rx2nfu1xzpht3p7 \ --discovery-token-ca-cert-hash sha256:04d6797bce75890be6519915695c817bcb053441c1a7d5f215368d45821a63b3 \ --control-plane --certificate-key 35c5f69136287ed3d2c9d49fb8a0572aad9e37c243e98c97d08e47a7dd806bb3 Please note that the certificate-key gives access to cluster sensitive data, keep it secret! As a safeguard, uploaded-certs will be deleted in two hours; If necessary, you can use "kubeadm init phase upload-certs --upload-certs" to reload certs afterward. Then you can join any number of worker nodes by running the following on each as root: kubeadm join zvip:8443 --token 7obk27.9rx2nfu1xzpht3p7 \ --discovery-token-ca-cert-hash sha256:04d6797bce75890be6519915695c817bcb053441c1a7d5f215368d45821a63b3 scnzzh@zubt1:~/zzh$ service kubelet status ● kubelet.service - kubelet: The Kubernetes Node Agent Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled) Drop-In: /etc/systemd/system/kubelet.service.d └─10-kubeadm.conf Active: active (running) since Thu 2021-01-21 07:03:18 EST; 58s ago Docs: https://kubernetes.io/docs/home/ Main PID: 6750 (kubelet) Tasks: 14 (limit: 4654) Memory: 33.0M CGroup: /system.slice/kubelet.service └─6750 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubel> Jan 21 07:03:51 zubt1 kubelet[6750]: E0121 07:03:51.614187 6750 kubelet.go:2163] Container runtime network not ready: NetworkReady=false reason:NetworkPluginNotR> Jan 21 07:03:54 zubt1 kubelet[6750]: W0121 07:03:54.367653 6750 cni.go:239] Unable to update cni config: no networks found in /etc/cni/net.d Jan 21 07:03:56 zubt1 kubelet[6750]: E0121 07:03:56.892274 6750 kubelet.go:2163] Container runtime network not ready: NetworkReady=false reason:NetworkPluginNotR> Jan 21 07:03:59 zubt1 kubelet[6750]: W0121 07:03:59.369288 6750 cni.go:239] Unable to update cni config: no networks found in /etc/cni/net.d Jan 21 07:04:01 zubt1 kubelet[6750]: E0121 07:04:01.920368 6750 kubelet.go:2163] Container runtime network not ready: NetworkReady=false reason:NetworkPluginNotR> Jan 21 07:04:04 zubt1 kubelet[6750]: W0121 07:04:04.370517 6750 cni.go:239] Unable to update cni config: no networks found in /etc/cni/net.d Jan 21 07:04:06 zubt1 kubelet[6750]: E0121 07:04:06.963302 6750 kubelet.go:2163] Container runtime network not ready: NetworkReady=false reason:NetworkPluginNotR> Jan 21 07:04:09 zubt1 kubelet[6750]: W0121 07:04:09.372341 6750 cni.go:239] Unable to update cni config: no networks found in /etc/cni/net.d Jan 21 07:04:11 zubt1 kubelet[6750]: E0121 07:04:11.992464 6750 kubelet.go:2163] Container runtime network not ready: NetworkReady=false reason:NetworkPluginNotR> Jan 21 07:04:14 zubt1 kubelet[6750]: W0121 07:04:14.374020 6750 cni.go:239] Unable to update cni config: no networks found in /etc/cni/net.d