Common K3s Commands

Here's a guide on how to manage your K3s cluster, including starting services, checking the status of nodes and pods, stopping services, and adding nodes. Additionally, we'll cover the usage of kubectl apply to manage deployments.

Start K3s Service

To start the K3s service if it's not already running, use:

sudo systemctl start k3s

Check K3s Service Status

To check the status of the K3s service, use:

sudo systemctl status k3s

Check Cluster Status

You can check the status of your nodes, pods, and services using the following kubectl commands:

View Nodes:

This command shows the list and status of all nodes in your cluster.
```
  kubectl get nodes -o wide
```
View Pods:

To list all pods in the default namespace or specify another namespace with -n <namespace>:
```
  kubectl get pods -o wide
```
View Services:

Lists all services running in the default namespace, or specify another namespace.
```
  kubectl get svc -o wide
```

Deploy Applications

To deploy an application using a YAML configuration file such as nginx-deployment.yml:

Apply Deployment: This command will create or update resources defined in the YAML file, handling the deployment of pods and services.

kubectl apply -f nginx-deployment.yml

Note: kubectl apply will ensure that services and pods are restarted and updated automatically as defined in the YAML file.

Delete Deployment: To delete a deployment, use the following command:

kubectl delete -f nginx-deployment.yml

Note: This command will delete the resources defined in the YAML file.

Check Deployment Status

To check the status of a deployment, use the following command:

kubectl get deployments -o wide

This command will show the status of all deployments in the default namespace.

Scale Deployments

To scale a deployment, use the following command:

kubectl scale deployment <deployment-name> --replicas=<number-of-replicas>

This command will scale the deployment to the specified number of replicas.

Update Deployments

To update a deployment with a new image or configuration, use:

kubectl set image deployment/<deployment-name> <container-name>=<new-image>

This command will update the deployment with the new image.

Delete Deployments

To delete a deployment, use the following command:

kubectl delete deployment <deployment-name>

This command will delete the specified deployment.

Stop K3s Service

To stop the K3s service, if needed:

sudo systemctl stop k3s

Add a Node to the K3s Cluster

To add a new node to your existing K3s cluster, perform the following:

Get the Token:

Retrieve the node token from the server, which is required for joining nodes:
```
 sudo cat /var/lib/rancher/k3s/server/node-token
```

Install K3s on the New Node:

Run the K3s installation script with the server's IP address and token to join the cluster:

 curl -sfL https://get.k3s.io | K3S_URL=https://<server-ip>:6443 K3S_TOKEN=<node-token> K3S_NODE_NAME=worker-1 sh -

Verify Node Joining:

Check the status of the new node to ensure it has joined the cluster:
```
 kubectl get nodes -o wide
```

Label the Node (Optional):

If needed, you can label the new node for specific workloads:

 kubectl label node <node-name> <label-key>=<label-value>

For example, to label a node as a worker:

 kubectl label node <node-name> node-role.kubernetes.io/worker=worker

Remove the label with:

 kubectl label node <node-name> <label-key>-

For example, to remove the worker label:

 kubectl label node <node-name> node-role.kubernetes.io/worker-

By following these commands and procedures, you can effectively manage your K3s cluster, ensuring smooth deployment and scaling of your applications. For further details on each command, consult the Kubernetes kubectl Documentation.

K3s Command List