Now we can start the service. First enable and then start kubelet on your Kubernetes master machine:

$ sudo systemctl enable kubelet && sudo systemctl start kubelet

While checking the status of kubelet, you may be worried to see the status displaying activating (auto-restart); and you may get further frustrated to see the detail logs by the journalctl command, as follows:

error: unable to load client CA file /etc/kubernetes/pki/ca.crt: open /etc/kubernetes/pki/ca.crt: no such file or directory

Don't worry. kubeadm takes care of creating the certificate authorities file. It is defined in the service configuration file, /etc/systemd/system/kubelet.service.d/10-kubeadm.conf by argument KUBELET_AUTHZ_ARGS. The kubelet service won't be a healthy without this file, so keep trying to restart the daemon by itself.

Go ahead and start all the master daemons via kubeadm. It is worth noting that using kubeadm requires the root permission to achieve a service level privilege. For any sudoer, each kubeadm would go after the sudo command:

$ sudo kubeadm init

And you will see the sentence Your Kubernetes master has initialized successfully! showing on the screen. Congratulations! You are almost done! Just follow the information about the user environment setup below the greeting message:

$ mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown $(id -u):$(id -g) $HOME/.kube/config

The preceding commands ensure every Kubernetes instruction is fired by your account execute with the proper credentials and connects to the correct server portal:

// Your kubectl command works great now
$ kubectl version
Client Version: version.Info{Major:"1", Minor:"10", GitVersion:"v1.10.2", GitCommit:"81753b10df112992bf51bbc2c2f85208aad78335", GitTreeState:"clean", BuildDate:"2018-04-27T09:22:21Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"10", GitVersion:"v1.10.2", GitCommit:"81753b10df112992bf51bbc2c2f85208aad78335", GitTreeState:"clean", BuildDate:"2018-04-27T09:10:24Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}

More than that, kubelet goes into a healthy state now:

// check the status of kubelet
$ sudo systemctl status kubelet
...
Active: active (running) Mon 2018-04-30 18:46:58 EDT; 2min 43s ago
...