Kubernetes Deployment

Hello SRE or Platform Engineer  or DevOps Engineers, In this post I want to discuss, Understanding of Kubernetes deployment it's hierarchy of kube objects. Declaratives and imperative ways to make deployment on kube clusters. 

How to deploy an application on  Kubernetes pods, just follow these steps as shown in this post. 

Here I would like to share with you about Kubernetes deployment hierarchy, which internal call to replication controller to make desired number of replicas of pod temple specified.

Kubernetes Deployment hierarchy

Let's goto have a deep understanding about Kubernetes deployment hierarchy

Step 1: We need to create a YAML file to define the deployment of the Nginx Webserver. Here we are taking a file name as Nginx-deployment.

Command : 

k create deploy httpd-deploy --image=httpd:alpine --dry-run=client -o yaml
k create deploy httpd-deploy --image=httpd:alpine --dry-run=client -o yaml >httpd-deploy.yaml

vi httpd-deploy.yaml
# Insert the following manifestation for deployment using httpd:apline image

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: httpd-deploy
  name: httpd-deploy
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpd-deploy
  strategy: {}
  template:
    metadata:
      labels:
        app: httpd-deploy
    spec:
      containers:
      - image: httpd:alpine
        name: httpd

k create -f httpd-deploy.yaml #create
k get deploy,po #confirmation
    

1. List all the Deployments of default namespace 

kubectl get deployments
# or use alias name  
kubectl get deploy
# or use alternative name  
kubectl get deployment

2. Describe the Deployment details

kubectl describe deploy web-deployment  

Deployments contains Pods and its Replica information. 

3. To Show Rollout History of the given Deployment

kubectl rollout history deployment web-deployment 

4. Updates the existing deployment using update application new version. Do some R&D work here. Goto the Docker Hub find the Niginx tags consider the version tags to deploy. Currently I could see 1.22.0 and 1.23.1 versioned tags. So start with the new deployment with nginx:1.22.0 image after the pods up and application looks good we can update to the latest version that is nginx:1.23.1 versioned image.

k create deploy web-deploy --image=nginx:1.22 --replicas=2
k get deploy,po -o wide
# upgrade to new version 1.24
k set image deploy/web-deploy nginx=nginx:1.24 
k get deploy,po -o wide

5. Rolls back or roll Forward to a specific version

kubectl create –f app-deploy.yml 
kubectl get deploy app-deploy
kubectl apply –f app-deploy.yml --record 
kubectl rollout undo deployment app-deploy - -to-revision=1 
kubectl rollout undo deployment app-deploy - -to-revision=2