Kubernetes – Imperative commands – part 1 – simplifying concepts

Hi All,

Greetings for the day!!!

Lets continue discussing Kubernetes – Today Kubernetes Imperative CMDLETs

Take away from this article

• What are Kubernetes Imperative CMDLEts
• What prerequisites required to use Kubernetes imperative CMDLETs
• Imperative CMDLETs for Kubernetes cluster
• Imperative CMDLETs Kubernetes objects
• Imperative CMDLETs Kubernetes Nodes

What are Kubernetes Imperative commands

• Imperative commands are the CMDLETs used to create , update, delete Kubernetes objects on the Kubernetes cluster built into the KUBECTL command line tool
• To deploy application on the Kubernetes cluster

Prerequisites

• We need Kubernetes cluster
  • To practice or for development purpose we can use minikube utility for setting up Kubernetes cluster locally
  • Kubernetes – Setting up kubernetes cluster for development on Windows 10 box using minikube
  • Kubernetes simplifying: Setting up local environment – creating Kubernetes cluster locally (helps in Interview Preparation) – Kubernetes for beginners
• We need kubectl command line utility, which actually interacts with Kubernetes cluster
  • Kubernetes – kubectl command line utility
• Understanding of Yaml file – for creating Kubernetes object
  • Complete Guide To YAML

Local development cluster

• Here I have setup my local Kubernetes cluster using minikube
• Start the minikube

minikube start

• Know the details of Kubernetes commands – using -h option
  • Syntax : kubectl <command-name> -h
  • Example :

#get the help on kubectl get command / parameter
kubectl get -h

Imperative CMDLET for verifying KubeCtl installation

• We can verify if kubectl command line utility is successfully installed or not by using “version” attribute to kubectl CMDLET as

kubectl version

Imperative CMDLETs for Kubernetes cluster

• To get cluster information
  • Shows the address of control plane

kubectl cluster-info

• To get more detailed information about cluster using dump parameter
  • This option is used for debugging purpose and to analyse the cluster problems
  • By default it prints all information on console
  • We can specify directory path using –output parameter, in this case Kubernetes put all files in specified directory path

kubectl cluster-info dump

• To have dump details in files and in directory

kubectl cluster-info dump --output-directory "C:\\Prasham\\Articles\\Kubernetes\\Imperative CMDLETS\\dump"

• To know the Api Versions on the server

kubectl api-versions

General Kubernetes objects CMDLETs

• What are Kubernetes objects – for details please have a look our article – Kubernetes – Objects – simplifying concepts
• Creating Kubernetes object with specification in Yaml / JSON file
  • Syntax – kubectl create -f <kubernetes object yaml specification file path>
  • Examples:

kubectl create -f "C:\Prasham\Articles\Kubernetes\Imperative CMDLETS\YAML files\knoweldgejunction_pod.yaml"

• Delete kubernetes object – using delete object
  • Syntax – kubectl delete <Kubernetes object>
  • Examples:

kubectl delete deployment/nginx

• Get one or more object / resources using get parameter to kubectl CMDLET- print basic information about object
  • Syntax – kubectl get [(-o|--output=)json|yaml|object name | resource name
  • Examples:

#list all pods in cluster
kubectl get pods

#list all pods with details in cluster
kubectl get pods -o wide

# List deployments in JSON output format, in the "v1" version of the "apps" API group
kubectl get -f pod.yaml -o json

#To get the multiple objects at time - separated by ","
kubectl get rc,services

Get very detailed information about one or more object / resources using describe parameter to kubectl CMDLET

kubectl describe pod <pod-name>

To get the yaml specification of any Kubernetes object

kubectl get <object-name> <object-value> -o yaml

Here,
<object-name> like - pod , deployment, service, ingress 

Example - 
kubectl get pod nginx -o yaml

CMDLETs for Nodes

• To get all labels of node

kubectl get nodes <node name> --show-labels

Example:
kubectl get nodes node01 --show-labels

• Apply a label to nodes

kubectl label nodes <node name> <labelname>=<labelvalue>

Example:
kubectl label nodes KnowledgeJunction-Mode01 color=blue

Thanks for reading the article !!! Please feel free to discuss in case any issues / suggestions / thoughts / questions !!!

HAVE A GREAT TIME AHEAD !!!