3. Kubectl Commands

Minikube

Minikube is a single node k8s cluster which can be run on virtual box in local machine (used for testing purposes).

minikube start -> will create a single node cluster
minikube stop
minikube remove
minikube status
minikube dashboard -> opens the dashboard in localhost
minikube docker-env -> prints the environment variable for docker
minikube ssh -> open minikube in secure shell

Kubectl

Kubectl allows the user to interact with k8s cluster, it is command line tool, which talks to the API server.

kubectl version -> prints version details
kubctl version --output=yaml ->prints yaml output of version details
kubctl get pods -> prints details of running nodes
kubectl get nodes
kubectl get
kubectl config
kubectl config current-context
kubectl get all
kubectl delete pod <name>

Basic Commands

Starting Cluster

minikube start will start Minikube(single node k8s cluster).

Getting Nodes

kubectl get nodes will display all the pods

Getting Services

kubectl get services will display all the services

Creating Deployment

kubectl create deployment <name> --image=<image> will create a deployment pod.
- deployment is the blueprint for creating pods (most basic configuration) ![][./images/kubectlcreatedeploymentname--image=image.png]

Getting Deployment

kubectl get deployment will display all the deployments ![][./images/kubectlgetdeployment.png]

Getting Pod

kubectl get pods will display all the pods
Layers of Abstraction: Deployment -> ReplicaSet -> Pod -> Container

Editing Deployment

kubectl edit deployment nginx-deploy to make changes in the deployment

# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: apps/v1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "1"
  creationTimestamp: "2024-07-31T18:41:34Z"
  generation: 1
  labels:
    app: nginx-deploy
  name: nginx-deploy
  namespace: default
  resourceVersion: "16345"
  uid: 1d944b5a-85c8-4ddc-bb3d-a27d2141d620
spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: nginx-deploy
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: nginx-deploy
    spec:
      containers:
        - image: nginx
          imagePullPolicy: Always
          name: nginx
          resources: {}
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      terminationGracePeriodSeconds: 30
status:
  availableReplicas: 1
  conditions:
    - lastTransitionTime: "2024-07-31T18:41:49Z"
      lastUpdateTime: "2024-07-31T18:41:49Z"
      message: Deployment has minimum availability.
      reason: MinimumReplicasAvailable
      status: "True"
      type: Available
    - lastTransitionTime: "2024-07-31T18:41:34Z"
      lastUpdateTime: "2024-07-31T18:41:49Z"
      message: ReplicaSet "nginx-deploy-854b9d5bdb" has successfully progressed.
      reason: NewReplicaSetAvailable
      status: "True"
      type: Progressing
  observedGeneration: 1
  readyReplicas: 1
  replicas: 1
  updatedReplicas: 1

Debugging Containers

Changing image version

kubectl edit deployment nginx-deploy and adding version to image

spec:
  containers:
    - image: nginx:1.16
      imagePullPolicy: Always
      name: nginx
      resources: {}
      terminationMessagePath: /dev/termination-log
      terminationMessagePolicy: File

$ kubectl get pods
 
NAME                            READY   STATUS              RESTARTS   AGE
nginx-deploy-7cfbfdcbcb-5dhw6   0/1     ContainerCreating   0          17s
nginx-deploy-854b9d5bdb-zv6fw   1/1     Running             0          21m

$ kubectl get pods
 
NAME                            READY   STATUS    RESTARTS   AGE
nginx-deploy-7cfbfdcbcb-5dhw6   1/1     Running   0          113s

$ kubectl get replicasets
 
NAME                      DESIRED   CURRENT   READY   AGE
nginx-deploy-7cfbfdcbcb   1         1         1       2m55s
nginx-deploy-854b9d5bdb   0         0         0       24m

kubectl describe pod nginx-deploy-7cfbfdcbcb used to get information about the pod

$ kubectl describe pod nginx-deploy-7cfbfdcbcb
 
Name:             nginx-deploy-7cfbfdcbcb-5dhw6
Namespace:        default
Priority:         0
Service Account:  default
Node:             minikube/192.168.50.1
Start Time:       Thu, 01 Aug 2024 00:32:41 +0530
Labels:           app=nginx-deploy
                  pod-template-hash=7cfbfdcbcb
Annotations:      <none>
Status:           Running
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  64m   default-scheduler  Successfully assigned default/nginx-deploy-7cfbfdcbcb-5dhw6 to minikube
  Normal  Pulling    64m   kubelet            Pulling image "nginx:1.16"
  Normal  Pulled     64m   kubelet            Successfully pulled image "nginx:1.16" in 14.989s (14.989s including waiting). Image size: 126681697 bytes.
  Normal  Created    64m   kubelet            Created container nginx
  Normal  Started    64m   kubelet            Started container nginx

Execute Pod in terminal

kubectl exec -it nginx-deploy-7cfbfdcbcb-5dhw6 -- sh

# ls
bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
#

Get All Components

kubectl get all shows all components inside cluster

$ kubectl get all
 
NAME                                    READY   STATUS    RESTARTS      AGE
pod/nginx-deployment-77d8468669-5s86g   1/1     Running   1 (36s ago)   17h
pod/nginx-deployment-77d8468669-p94hk   1/1     Running   1 (36s ago)   17h
 
NAME                    TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)     AGE
service/kubernetes      ClusterIP   10.96.0.1        <none>        443/TCP     5d12h
service/nginx-service   ClusterIP   10.105.137.204   <none>        27017/TCP   17h
 
NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx-deployment   2/2     2            2           17h
 
NAME                                          DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-deployment-77d8468669   2         2         2       17h

Deleting Pod

kubectl delete deployment <pod_name> will delete pod

$ kubectl get pods
 
NAME                            READY   STATUS    RESTARTS   AGE
nginx-deploy-7cfbfdcbcb-5dhw6   1/1     Running   0          93m

$ kubectl delete deployment nginx-deploy
 
deployment.apps "nginx-deploy" deleted

2. Architecture 4. K8s Config File