Kubernetes: Unable to connect to the server: Service Unavailable

After reboot of kubernetes master node, "kubectl" command throwing this error:

Unable to connect to the server: Service Unavailable

Kindly suggest how to start the service or fix this issue.

# kubectl get nodes
Unable to connect to the server: Service Unavailable
#
# kubectl cluster-info

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
Unable to connect to the server: Service Unavailable
#
# echo $KUBECONFIG
/root/.kube/config
#

# kubectl config view
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://192.168.1.1:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-admin
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED
#

Solution

You did not specify which container driver your cluster is using, so I'm going to assume it is docker, also assuming you are using linux.

Most probably you don't have kube-apiserver running. You have to start/restart it to solve your issue.

Check if docker daemon is running. If not, start/restart it.

$ systemctl status docker

# systemctl start docker

# systemctl restart docker

Once docker daemon is running, check if kube-apiserver container is running
```
# docker ps -a
```
look for a container with COMMAND kube-apiserver. If it's running you are done, if not, restart it
```
# docker restart <container ID>
```

To ensure you won't have the same problem in the future, configure Docker to start on boot

# systemctl enable docker.service
# systemctl enable containerd.service

If your distribution does not user systemd use service instead of systemctl

# service <service name> status/stop/start/restart

In above commands $ means run as normal user, # means run as root.