Command for Those Who Don’t Want Use Kubectl Edit

Photo by Erik Mclean on Unsplash

Introduction

For those of us who don’t want to edit resources with an editor that launches with a kubectl edit command, there is command kubectl patch, so let’s take advantage of it. The nice thing about the patch command is that you don’t have to handwrite it in the editor. Since resources can be changed with one liner, it is also suitable for embedding in shell scripts.

Let’s test this !

Run example deployment

root@vagrant:/home/vagrant# kubectl create deployment nginx --image=spy86/nginx:latest
deployment.apps/nginx created
root@vagrant:/home/vagrant# kubectl get po
NAME                     READY   STATUS    RESTARTS   AGE
nginx-6465f7cb5d-phgmr   1/1     Running   0          8s
root@vagrant:/home/vagrant# kubectl get deploy
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   1/1     1            1           10s
root@vagrant:/home/vagrant#

Modify the container image

It can be used when you want to change the image version temporarily.

root@vagrant:/home/vagrant# kubectl patch deployment nginx -p '{"spec":{"template":{"spec":{"containers":[{"name":"nginx","image":"spy86/nginx:147"}]}}}}'
deployment.apps/nginx patched
root@vagrant:/home/vagrant#
root@vagrant:/home/vagrant# kubectl describe deploy nginx | grep Image:
    Image:        spy86/nginx:147

Change the number of replicas

One-liner to change the number of replicas. It can be used when you want to change the number of replicas temporarily. By the way, 0 can also be specified, and it will be in a simple undeployed state.

root@vagrant:/home/vagrant# kubectl patch deployment nginx -p '{"spec":{"replicas":10}}'
deployment.apps/nginx patched
root@vagrant:/home/vagrant# kubectl get po
NAME                    READY   STATUS    RESTARTS   AGE
nginx-9ddb798cf-mrjds   1/1     Running   0          3m22s
nginx-9ddb798cf-rrhvv   1/1     Running   0          101s
nginx-9ddb798cf-fpzcw   1/1     Running   0          101s
nginx-9ddb798cf-dcg8d   1/1     Running   0          101s
nginx-9ddb798cf-rb5nc   1/1     Running   0          101s
nginx-9ddb798cf-fn5s4   1/1     Running   0          101s
nginx-9ddb798cf-69k48   1/1     Running   0          101s
nginx-9ddb798cf-hhd74   1/1     Running   0          101s
nginx-9ddb798cf-n4ww9   1/1     Running   0          101s
nginx-9ddb798cf-fzrk9   1/1     Running   0          101s

Change the Service Type

First we need to create Service for deployment

root@vagrant:/home/vagrant# kubectl expose deployment nginx --type=ClusterIP --name=nginx --port=80
service/nginx exposed
root@vagrant:/home/vagrant# kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.152.183.1     <none>        443/TCP   13m
nginx        ClusterIP   10.152.183.209   <none>        80/TCP    6s

One-liner to change service Type to NodePort

root@vagrant:/home/vagrant# kubectl get svc nginx -o jsonpath='{.spec.type}'
ClusterIP
root@vagrant:/home/vagrant# kubectl patch service nginx -p '{"spec":{"type":"NodePort"}}'
service/nginx patched
root@vagrant:/home/vagrant# kubectl get svc nginx -o jsonpath='{.spec.type}'
NodePort
root@vagrant:/home/vagrant# kubectl get svc nginx -o jsonpath='{.spec.ports[0].nodePort}'
30222
root@vagrant:/home/vagrant#

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