Knowledgebase

Introduction

Kubectl also known as Kube Control is a command-line tool used for interacting with Kubernetes clusters. It allows system administrators and developers to deploy, manage and monitor applications within a Kubernetes cluster. Kubectl tool uses the Kubernetes API to communicate with a Kubernetes cluster's control plane and perform a variety of management actions.

Using Kubectl, you can create, update, and delete resources such as pods, services, and deployments through a command-line interface. Additionally, you can scale your application, troubleshoot issues, and inspect the cluster state in real-time. This makes it easy for DevOps engineers, administrators, and developers to manage resources without the need for in-depth knowledge on the Kubernetes internal structure.

Kubectl offers a wide range of features that empower users to effectively manage and interact with Kubernetes clusters. Below are the tool's commonly used features:

• Real-time Insights

• Resource Discovery

• Resource Management

• Namespace Control

• Deployment and Scaling

• Configuration Editing

• Rolling Updates

• API Access

• Pod Interaction

• Automation Integration

This article explains how to install and use Kubectl to manage a RCS Kubernetes Engine (VKE) cluster. In addition, you are to use the tool's basic functionalities to view and manage Kubernetes cluster resources.

Prerequisites

Before you begin:

• Deploy a RCS Kubernetes Engine (VKE) cluster with at least three nodes

Install Kubectl

Kubectl tool is available on major operating systems such as Windows, Linux, and macOS. In this section, Install Kubectl depending on your management machine's operating system to connect and manage your Kubernetes clusters.

Install Kubectl on Linux

Kubectl is not available in the default apt or dnf package repositories for Debian/Ubuntu based, and CentOS/RHEL based distributions. Instead, you can install Kubectl using the Snap package manager, or manually add the latest binary to your system as described in the steps below.

Depending on your Linux distribution, you can install Kubectl using the Snap package manager or

1. Using the snap package manager, install the Kubectl on your Linux machine

   $ sudo snap install kubectl --classic
   

2. To manually install Kubectl, download the latest Kubectl binary using the following command

   $ curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
   

3. Grant execute permissions on the binary

   $ chmod +x kubectl
   

4. To activate kubectl as a system-wide command, move the downloaded binary to the /usr/local/bin directory

   $ sudo cp kubectl /usr/local/bin/
   

Install Kubectl on Windows

To install Kubectl on your Windows machine, either install Chocolatey or the Windows Package Manager to download the Kubectl files to your computer. Depending on your installed package manager, install Kubectl as described in the steps below.

• Open the Windows Start Menu, search and open a new Windows PowerShell session

• Using Chocolatey, install Kubectl

  > choco install kubernetes-cli
  

• To install Kubectl using the Windows Package Manager, run the following command

  > winget install -e --id CNCF.kubectl
  

• To manually install the application, download the latest Kubectl binary

  > Invoke-WebRequest -Uri "http://dl.k8s.io/release/$(Invoke-WebRequest -Uri http://dl.k8s.io/release/stable.txt).txt/bin/windows/amd64/kubectl.exe" -OutFile kubectl.exe
  

• Copy the downloaded file to a directory in your system's PATH.

  > copy "C:\path\to\kubectl.exe" "C:\bin"
  

Install Kubectl on macOS

On macOS, install the Homebrew package manager and use it to install Kubectl as described in the following steps.

• Using brew, install Kubectl

  $ brew install kubectl
  

• To manually install Kubectl, download the latest binary using curl

  $ curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/darwin/amd64/kubectl"
  

• Grant execute permissions on the file

  $ chmod +x kubectl
  

• To activate the system wide kubectl command, move the file to the /usr/local/bin directory

  $ sudo cp kubectl /usr/local/bin/
  

Verify the Kubectl Installation

When Kubectl is available as a system wide command on your management machine, verify the installed version to confirm that it works correctly

$ kubectl version --output=yaml

If Kubectl is available and installed correctly, your output should appear like the one below:

clientVersion:

  buildDate: "2023-04-14T13:21:19Z"

  compiler: gc

  gitCommit: 4c9411232e10168d7b050c49a1b59f6df9d7ea4b

  gitTreeState: clean

  gitVersion: v1.27.1

  goVersion: go1.20.3

  major: "1"

  minor: "27"

  platform: linux/amd64

kustomizeVersion: v5.0.1

Connect to a VKE Cluster using Kubectl

To connect to a VKE cluster using Kubectl, download your cluster configuration file, and configure Kubectl to connect to the cluster using the downloaded YAML file as described in the steps below.

1. Log in to the RCS customer portal and navigate to the Kubernetes section

   

2. Find and select the Kubernetes cluster you intend to access

   

3. On the cluster dashboard, click Download Configuration to download a copy of the cluster YAML file to your computer

4. Open a new terminal session, and switch to the directory where you downloaded the VKE configuration file. For example /Downloads

   $ cd /home/user/Downloads
   

5. Create a .kube directory in your user home directory if it does not exist

   $ mkdir ~/.kube
   

6. Back up the original config file

7. Copy your downloaded VKE configuration file to the .kube directory and rename it to config

   $ cp /home/user/Downloads/vke.yaml /home/user/.kube/config
   

8. View your VKE cluster nodes to verify that Kubectl connects to the cluster correctly

   $ kubectl get nodes
   

   Output:

   NAME                   STATUS   ROLES    AGE     VERSION
   
   cluster-6da3897ae09b   Ready    <none>   4m36s   v1.27.2
   
   cluster-e4891719946c   Ready    <none>   4m37s   v1.27.2
   
   cluster-ea44561f3ee4   Ready    <none>   4m37s   v1.27.2
   

9. Use the cluster-info parameter to display the information about the Kubernetes cluster, including the endpoints of the control plane components.

   $ kubectl cluster-info
   

   The above command should print detailed information about your RCS Kubernetes Engine cluster

Use Kubectl to Manage a VKE Cluster

Using Kubectl ensures that your interactions with the VKE cluster are secure, authenticated, and aligned with the best practices for Kubernetes cluster management. In this section, apply basic Kubectl commands to manage your VKE cluster, and carry out essential tasks like retrieving information, managing resources, scaling applications, checking resource status, and viewing the cluster logs.

Manage Kubernetes Resources

Resources are various components used to run and manage containerized applications in the Kubernetes cluster. They are the building blocks of applications and workloads. Use Kubectl to carry out specific tasks on resources as described in the steps below.

Create Resources in Cluster

1. Create a new deployment using a specific Docker image

   $ kubectl create deployment <deployment-name> --image=<image-name>
   

2. Create resources defined in a YAML file

   $ kubectl create -f <filename.yaml>
   

3. Update the image of a deployment's container

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

   Replace <deployment-name> and <image-name> with the actual names in your environment.

List Cluster Resources

Common types of resources in a Kubernetes cluster include nodes, pods, services, deployments, configMaps, and secrets. Use the kubectl get command to list any resources within the VKE luster.

1. List all cluster nodes

   $ kubectl get nodes
   

2. View a list of all pods in the default namespace

   $ kubectl get pods
   

3. View all pods in a specific namespace

   $ kubectl get pods -n <namespace>
   

4. List pods from all cluster namespaces

   $ kubectl get pods --all-namespaces
   

5. Get a list of all deployments in the cluster

   $ kubectl get deployments
   

6. List all cluster services

   $ kubectl get services
   

Describe Resources in Cluster

To get more information about any Kubernetes cluster resources, use the kubectl describe command followed by resource name as described in the steps below.

1. Displays detailed information about a specific pod

   $ kubectl describe pod <pod-name>
   

2. Print detailed information about a specific node

   $ kubectl describe node <node-name>
   

3. Shows detailed information about a service

   $ kubectl describe service <service-name>
   

   Replace <pod-name>, <service-name> and <node-name> with the actual names in your environment.

Delete Resources in Cluster

To remove any resources from the Kubernetes clyster, use the kubectl delete command followed by the resource name as described in the steps below

1. Delete a specific pod in the cluster

   $ kubectl delete pod <pod-name>
   

2. Remove a specific cluster

   $ kubectl delete svc <service name>
   

3. Delete a specific deployment in the cluster:

   $ kubectl delete deployment <deployment-name>
   

4. Remove all resources in the default namespace:

   $ kubectl delete all --all
   

Replace <pod-name>, <deployment name> and <service name> with the actual resource names in your VKE cluster.

Create and Manage Namespace in Cluster

Namespace is a Kubernetes features used to organize clusters into virtual sub-clusters. It provides a way to apply access controls and permissions at the namespace level.

1. Create a new namespace in the cluster:

   $ kubectl create namespace <namespace-name>
   

2. List all namespaces in the cluster:

   $ kubectl get namespaces
   

3. Delete a specific namespace from the cluster:

   $ kubectl delete namespace <namespace-name>
   

   Replace <namespace-name> with the actual names in your environment.

ConfigMap and Secret Management

ConfigMap and Secret are types of objects in Kubernetes used to inject configuration data into a container during container start-up. A Secret is an API object used to store sensitive information such as passwords, SSH keys, and other confidential information. While a ConfigMap is specifically designed to store non-sensitive configuration data in configuration files.

1. Create a ConfigMap from a file:

   $ kubectl create configmap <configmap-name> --from-file=<file-path>: 
   

2. List all ConfigMaps in the default namespace:

   $ kubectl get configmaps
   

3. Delete a specific ConfigMap.

   $ kubectl delete configmap <configmap-name>
   

4. Create a Secret from literal values:

   $ kubectl create secret generic <secret-name> --from-literal=key=value 
   

5. List all secrets in the default namespace.

   $ kubectl get secrets
   

6. Delete a specific secret.

   $ kubectl delete secret <secret-name>
   

Scale Applications

1. You can use the kubectl scale deployment command followed by deployment name and replica numbers to scale a deployment to a specified number of replicas:

   $ kubectl scale deployment <deployment-name> --replicas=<desired-replicas>
   

2. Edit an existing deployment to update an application:

   $ kubectl edit deployment <deployment-name>
   

View Cluster Logs

You can use the kubectl logs command to view cluster logs of individual pods.

1. View logs of a specific pod:

   $ kubectl logs <pod-name>
   

2. View logs of a container within a pod:

   $ kubectl logs <pod-name> -c <container-name>
   

3. Stream logs from a pod in real-time:

   $ kubectl logs -f <pod-name>
   

4. Use the --previous flag with the kubectl command to view the logs of previous instances.

   $ kubectl logs --previous <pod-name>
   

5. Use the --timestamps flag to view the logs of a pod including timestamps in the log output:

   $ kubectl logs --timestamps <pod-name>
   

   Replace <pod-name> and <container-name> with the actual names in your environment.

Advanced Kubectl Commands

In this section, explore the advanced Kubectl commands that offer greater control and flexibility when managing your Kubernetes cluster.

Run Commands Within Pods

The kubectl exec command allows you to check the status and contents of containers running in your Kubernetes clusters. It will help you to inspect and troubleshoot applications running inside the Kubernetes cluster.

1. Below is the basic syntax to execute a command within a pod:

   $ kubectl exec -it <pod-name> -c <container-name> -- <command>
   

   Below is what the command does.

   • -it: Start an interactive terminal shell.

   • <pod-name>: Name of the pod.

   • -c <container-name>: Specify the container name running within your pod.

   • -- <command>: Specify the command that you want to run inside the container.

For example, start an interactive shell within a specific container using the following command.

$ kubectl exec -it <pod-name> -c <container-name> -- /bin/sh

List files in a specific directory of the container.

$ kubectl exec -it <pod-name> -c <container-name> -- ls /app

Replace <pod-name> and <container-name> with the actual names in your environment.

Enable Port forwarding for Local Access to Kubernetes Cluster Resources

Port forwarding is a Kubernetes feature that lets you access an application running on your Kubernetes from your local machine. It's a handy feature to test applications during development.

Below is the The basic syntax to enable port forwarding from your cluster to your local machine's port

$ kubectl port-forward <service-name> <local-port>:<service-port>

The following command forwards traffic from port 8000 on the service named my-service to port 8080 on your local machine

$ kubectl port-forward my-service 8080:8000

After executing the above command, you can access the my-service service using the URL http://localhost:8080 in your local web browser.

Manage Resource Quotas

Resource Quotas in Kubernetes allow you to manage and assign resources within namespaces in your Kubernetes cluster.

1. View Resource Quotas in a namespace:

   $ kubectl get resourcequota -n <namespace>
   

2. View the used quotas within a namespace:

   $ kubectl describe resourcequota -n <namespace>
   

3. Edit your existing Resource Quatas:

   $ kubectl edit resourcequota <resource-quota-name> -n <namespace>
   

4. Deletes a Resource Quota within a namespace:

   $ kubectl delete resourcequota <resource-quota-name> -n <namespace>
   

Drain Nodes for Maintenance

Node maintenance is an essential process when you perform updates, patches, or any other tasks on a node. Kubectl helps you to drain nodes for maintenance via the command line.

1. Identify the node that you want to drain.

   $ kubectl get nodes
   

2. Pick your node from the above list and mark it as un-schedulable to prevent new workloads from getting placed on the node while you perform maintenance.

   $ kubectl cordon <node-name>
   

3. Drain the node for maintenance to remove pods that are running on the node.

   $ kubectl drain <node-name>
   

   The above command will reschedule pods to other nodes in the cluster before the maintenance begins.

   Here are some additional flags that you can use with kubectl drain command:

   • --force: Forcefully drains the node.

   • --timeout: Specify the timeout period for the drain operation.

   • --ignore-daemonsets: Evict DaemonSet pods during the draining process.

4. Mark the node as schedulable again after completing the maintenance process.

   $ kubectl uncordon <node-name>
   

Conclusion

In this tutorial, you have installed Kubectl on your local machine and configured it to interact with the RCS Kubernetes engine. Then, you learned how to use Kubectl to manage resources, scale applications, check status, and view logs in a Kubernetes cluster. Using Kubectl effectively is an essential skill for system administrators working with the Kubernetes cluster.