Kubectl

 What is kubectl ?

Kubectl is a command line tool that allows us to interact with kubernetes. Kubectl uses the kubernetes API to communicate with the cluster and carry out our command 

We can use kubectl to deploy applications, insepct and manage cluster resources, and view logs. 

Kubectl get 

use kubectl get to list objects in the Kubernetes cluster

kubectl get <object type> <object name> -o <output> --sort-by <JSONPATH> -- selector <selector> 

-o = Set output format

--sort-by = Sort output using a JSONPath expression.

--selector - Filter results by label. 

kubectl get pods // its to give to you the list of pods 

kubectl describe 

We can get detailed information about kubernetes objects using kubectl describe. 

Kubectl describe <object type> <object name> 

kubectl describe pods my-pod // to detail information of my-pod

kubectl create

kubectl create to create objects. 

Supply a yaml file with -f to create an object form a yaml descriptor stored in the file 

if we attempt to create an object that already exists, an error will occur. 

kubectl create -f <file name> 

kubectl apply

kubectl apply is similar to kubectl create. 

However, if you use kubectl apply on an object that already exists, it will modify the existing object, if possible. 

kubectl apply -f <file name> 

kubectl delete 

Use kubectl delete to delete objects from the cluster. 

kubectl delete <object type >  <object name> 

kubectl exec

kubectl exec can be used to run commands inside containers. Keep in mind that, in order for a command to succeed, the necessary software must exist within the container to run it. 

For pods with multiple containers, specify the container name with -c. 

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

kubectl api-resources  // list all shortcuts name of resources 

Kubectl Tips

Declarative 

Define objects using data structures such as YAML or JSON

Imperative

Define objects using kubectl commands and flags. Some people find imperative commands faster. 

Experimnet and see what works for you!

kubectl create deployment my-deployment --image=nginx

Quick Sample YAML 

use the --dry-run flag to run an imperative command without creating an object. Combine it with -o yaml to quickly obtain a sample yaml file we can manipulate !

kubectl create deployment my-deploymnet --image=nginx --dry-run -o yaml 

Record a Command 

Use the --record flag to record the command that was used to make a change.