Kubernetes 动态配置kubelet但不工作，kubelet陷阱处于自动重启循环中，节点未就绪

我根据上面的链接配置了我的k8s集群，但是kubelet服务无法正常启动

● 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 Mon 2021-04-19 10:18:42 CST; 5s ago
     Docs: https://kubernetes.io/docs/home/
  Process: 19453 ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS (code=exited, status=255)
 Main PID: 19453 (code=exited, status=255)

Apr 19 10:18:42 ndc-070 kubelet[19453]:         /workspace/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport/http2_client.go:300 +0xd31
Apr 19 10:18:42 ndc-070 kubelet[19453]: goroutine 491 [select]:
Apr 19 10:18:42 ndc-070 kubelet[19453]: k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport.(*controlBuffer).get(0xc0013131d0, 0x1, 0x0, 0x0, 0x0, 0x0)
Apr 19 10:18:42 ndc-070 kubelet[19453]:         /workspace/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport/controlbuf.go:395 +0x125
Apr 19 10:18:42 ndc-070 kubelet[19453]: k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport.(*loopyWriter).run(0xc0013279e0, 0x0, 0x0)
Apr 19 10:18:42 ndc-070 kubelet[19453]:         /workspace/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport/controlbuf.go:513 +0x1d3
Apr 19 10:18:42 ndc-070 kubelet[19453]: k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport.newHTTP2Client.func3(0xc001378000)
Apr 19 10:18:42 ndc-070 kubelet[19453]:         /workspace/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport/http2_client.go:346 +0x7b
Apr 19 10:18:42 ndc-070 kubelet[19453]: created by k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport.newHTTP2Client
Apr 19 10:18:42 ndc-070 kubelet[19453]:         /workspace/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/google.golang.org/grpc/internal/transport/http2_client.go:344 +0xefc

我使用了k8sv1.20，并通过编辑文件/etc/default/kubelet设置了kubelet--dynamic config dir标志：

KUBELET_EXTRA_ARGS=--dynamic-config-dir=/var/lib/kubelet-dynamic

正如/etc/systemd/system/kubelet.service.d/10 kubeadm.conf所建议的那样：

# Note: This dropin only works with kubeadm and kubelet v1.11+
[Service]
Environment="KUBELET_KUBECONFIG_ARGS=--bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf"
Environment="KUBELET_CONFIG_ARGS=--config=/var/lib/kubelet/config.yaml"
# This is a file that "kubeadm init" and "kubeadm join" generates at runtime, populating the KUBELET_KUBEADM_ARGS variable dynamically
EnvironmentFile=-/var/lib/kubelet/kubeadm-flags.env
# This is a file that the user can use for overrides of the kubelet args as a last resort. Preferably, the user should use
# the .NodeRegistration.KubeletExtraArgs object in the configuration files instead. KUBELET_EXTRA_ARGS should be sourced from this file.
EnvironmentFile=-/etc/default/kubelet
ExecStart=
ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS

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如果我删除了/etc/default/kubelet的内容，一切都会很好。

什么是/etc/default/kubelet文件的内容？