Skip to main content

5.3.3. Kubelet Start

This section describes connecting a worker node to a Kubernetes cluster and starting Kubelet. For manual installation (Hard Way), you need to create a bootstrap kubeconfig with an authentication token, a base kubelet configuration file, and start the systemd service. When using kubeadm, simply run the kubeadm join command.

Start/Configure kubelet

● Required

This configuration file is required to start Kubelet.

Kubelet default config

Basic kubelet configuration file

cat <<EOF > /var/lib/kubelet/config.yaml
---
apiVersion: kubelet.config.k8s.io/v1beta1
authentication:
  anonymous:
    enabled: false
  webhook:
    cacheTTL: 0s
    enabled: true
  x509:
    clientCAFile: /etc/kubernetes/pki/ca.crt
authorization:
  mode: Webhook
  webhook:
    cacheAuthorizedTTL: 0s
    cacheUnauthorizedTTL: 0s
cgroupDriver: systemd
clusterDNS:
- 29.64.0.10
clusterDomain: cluster.local
containerRuntimeEndpoint: ""
cpuManagerReconcilePeriod: 0s
evictionPressureTransitionPeriod: 0s
fileCheckFrequency: 0s
healthzBindAddress: 127.0.0.1
healthzPort: 10248
httpCheckFrequency: 0s
imageMaximumGCAge: 0s
imageMinimumGCAge: 0s
kind: KubeletConfiguration
logging:
  flushFrequency: 0
  options:
    json:
      infoBufferSize: "0"
    text:
      infoBufferSize: "0"
  verbosity: 0
memorySwap: {}
nodeStatusReportFrequency: 0s
nodeStatusUpdateFrequency: 0s
resolvConf: /run/systemd/resolve/resolv.conf
rotateCertificates: true
runtimeRequestTimeout: 0s
shutdownGracePeriod: 0s
shutdownGracePeriodCriticalPods: 0s
staticPodPath: /etc/kubernetes/manifests
streamingConnectionIdleTimeout: 0s
syncFrequency: 0s
volumeStatsAggPeriod: 0s
EOF
Prerequisites

Before starting kubelet, complete the steps in 5.3.2. Authentication:

  • Fetch the CA certificate (ca.crt)
  • Create bootstrap-kubelet.conf (or generate certificates manually)

Environment variables

Note

This configuration block is applicable only when installing Kubernetes manually (using the "Kubernetes the Hard Way" method). When using the kubeadm utility, the configuration file will be created automatically based on the specification provided in the kubeadm-config file.

cat <<EOF > /var/lib/kubelet/kubeadm-flags.env
KUBELET_KUBEADM_ARGS="--container-runtime-endpoint=unix:///var/run/containerd/containerd.sock --pod-infra-container-image=registry.k8s.io/pause:3.9 --config=/var/lib/kubelet/config-custom.yaml --cluster-domain=cluster.local --cluster-dns=29.64.0.10
"
EOF

This command starts the Kubelet service, which is responsible for deploying all containers based on Static Pods manifests.

systemctl start kubelet

Systemd Unit Status

Systemd unit readiness check
Note

Note that when creating a cluster with Kubeadm without running kubeadm init or kubeadm join, the Systemd Unit will be added to autostart but will be disabled.

systemctl status kubelet
Command output
● kubelet.service - kubelet: The Kubernetes Node Agent
        Loaded: loaded (/usr/lib/systemd/system/kubelet.service; enabled; preset: enabled)
    Drop-In: /usr/lib/systemd/system/kubelet.service.d
                └─10-kubeadm.conf
        Active: active (running) since Sat 2025-02-22 10:33:54 UTC; 17min ago
        Docs: https://kubernetes.io/docs/
    Main PID: 13779 (kubelet)
        Tasks: 14 (limit: 7069)
        Memory: 34.0M (peak: 35.3M)
        CPU: 27.131s
        CGroup: /system.slice/kubelet.service
                └─13779 /usr/local/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml