Kubernetes – Kubectl Commands

The Kubernetes command-line tool, kubectl, allows you to run commands against Kubernetes clusters. You can use kubectl to deploy applications, inspect and manage cluster resources, and view logs. Some basic Kubectl commands in a Kubernetes cluster are as follows:

kubectl Commands

The most popular kubectl commands and flags are listed below.

1. Common Commands

Name	Commands
Run a two-replica nginx deployment	kubectl run my-nginx --image=nginx --replicas=5 --port=80
Run and expose the Nginx pod	kubectl run my-nginx --restart=Never --image=nginx --port=80 --expose
Run nginx deployment and expose it	kubectl run my-nginx --image=nginx --port=80 --expose
List of nodes and pods	kubectl get pod -o wide
List all of them	kubectl get all --all-namespaces
Get every service	kubectl get service --all-namespaces
Show labeled nodes	kubectl get nodes --show-labels
Using a dry run, verify the yaml file	kubectl create --dry-run --validate -f pod-GFG.yaml

2. Check Performance

Name	Command
Learn about node resource use	kubectl top node
Obtain pod resource use	kubectl top pod
Get the resource utilization for the specified pod	kubectl top <podname> --containers
List each container’s resource usage	kubectl top pod --all-namespaces --containers=true

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3. Label & Annotation

Name	Commands
By label, sort the pods	kubectl get pods -l owner=gfg
Add a label by hand to a pod	kubectl label pods <podname> owner=gfg
Remove label	kubectl label pods <podname> owner-

4. Secrets

Name	Commands
List secrets	kubectl get secrets --all-namespaces
Obtain a certain hidden field of secret	kubectl get secret GFG-cluster-kubeconfig

5. Service

Name	Commands
List all services	kubectl get services
List service endpoints	kubectl get endpoints
Get service detail	kubectl get service <servicename> -o yaml

6. Volumes & Volume Claims

Name	Commands
List storage class	kubectl get storageclass
Check the mounted volumes	kubectl exec storage<nameofpv>
Check persistent volume	kubectl describe <nameofpv>

Kubectl apply

We can update or apply the configuration to a cluster with the aid of “kubectl apply”. With the help of the apply command, Kubernetes resources can be modified and created using a configuration file or a collection of configurations from a directory.

Creating objects: The basic syntax of “kubectl apply”

kubectl apply -f <filename.yaml> 

Viewing and Finding Resources

These commands are used to show all the resources. It works like a READ operation. It is used to view resources like nodes, deployments, services, config maps, etc.

kubectl get <resource>

Getting all Resources

The “kubectl get all” command enables us to view all the cluster’s resource

Getting Nodes

The number of available nodes in the cluster will be displayed by “Kubectl get nodes”.

Getting Pods

“Kubectl get pod” can be used to find out how many pods are scheduled in the cluster.

Getting Services

“Kubectl get service” can be used to list the services that have been created in the cluster.

Creating Resources

These commands are used to create resources like deployments, services, secrets, config maps, etc.

kubectl create <resource_type> <resource_name> OPTIONS

Creating Deployment

The command creates a deployment named nginx-depl using the image Nginx.

Creating service

The command in the creates a service of type node port named nginx, and it is exposed on port 80 of the local machine

Editing Resources

After running the command below you can update the resource configuration file and if there are any changes the resource will be updated according to it.

kubectl edit <resource_type> <resource_name>

Updating Deployment

The command in the below output opens a Vim-like editor in the terminal to edit the Nginx-deal deployment config file.

Updating Service

The command opens a vim-like editor in the terminal to edit the Nginx service config file.

Deleting Resources

These commands are used to delete resources like deployments, services, config maps, pods, secrets, etc. You can choose a particular resource name of a resource type or you can also delete all resources of a resource type by specifying –all flag

kubectl delete <resource_type> <resource_name> | --all

Deleting Deployment

The command deletes a deployment named nginx-depl.

Deleting Service

The command deletes a service named Nginx.

Using Configuration File for CRUD

These commands are used to use YAML configuration files for CRUD operations in a cluster.

Applying a Config file

The command creates the resource if it does not exist or updates it if it already exists according to the configuration in the YAML file mentioned after the -f flag.

kubectl apply -f [file-name]

Deleting using Config file

The command deletes the resource that was created using the YAML config file mentioned after the -f flag

Interacting with running Pods

Viewing Logs of a Pod

The command shows the logs of the pod mentioned once the pod started.

kubectl logs [pod-name]

Get an Interactive terminal for a pod

The command starts an interactive terminal of the Nginx pod so that we can control the pod directly through its terminal.

kubectl exec -it [pod-name] -- bin/bash

Get info about a Resource

The command gives details about the nginx deployment.

kubectl describe <resource_type> [resource-name]

Copying Files and Directories to and from Containers

With the help of the “kubectl cp” command, we can copy files from host to container and vice versa.

The basic syntax of “kubectl cp”

kubectl cp <host path pod name:container path>

This command will only function if the “tar” command in the container images is present or the command failed to run.

Updating Resources

The “kubectl get rs” command allows us to check the list of deployments, To update them, look up the revision history of prior deployments, and roll back to a specific revision if necessary. Using the following commands.

kubectl rollout <history> , <undo> , <status>, <restart>