temp-note-k8s-v2

 https://iceburn.medium.com/kubectl-useful-commands-f5f47c0773f

Kubectl Useful Commands

Kubernetes Shortcuts

• po : Pods
• rs : ReplicaSets
• deploy : Deployments
• svc : Services
• ns : Namespaces
• netpol : Network policies
• pv : Persistent Volumes
• pvc : PersistentVolumeClaims
• in : Service Accounts

Backup

root@vagrant:/home/vagrant# kubectl get all -A -o yaml > backup.yaml

Explain

root@vagrant:/home/vagrant# kubectl explain sc --recursive | less

Pods

#List Pod
root@vagrant:/home/vagrant# kubectl get pods
root@vagrant:/home/vagrant# kubectl get pods -o wide
root@vagrant:/home/vagrant# kubectl get pods -n kube-system
root@vagrant:/home/vagrant# kubectl get pods --selector app=test-application,env=develop
root@vagrant:/home/vagrant# kubectl get pods -l app=test-application,env=develop
root@vagrant:/home/vagrant# kubectl get pods --all-namespaces
root@vagrant:/home/vagrant# kubectl get pods --show-labels#Pod Status
root@vagrant:/home/vagrant# kubectl describe pod mypod#Create Pod
root@vagrant:/home/vagrant# kubectl run mypod --image nginx#Edit Pod
root@vagrant:/home/vagrant# kubectl edit pod mypod
root@vagrant:/home/vagrant# kubectl get pod mypod -o yaml > mypod.yaml#Create Pod from YML file
root@vagrant:/home/vagrant# kubectl create -f mypod.yml
root@vagrant:/home/vagrant# kubectl apply -f mypod.yml#Delete Pod
root@vagrant:/home/vagrant# kubectl delete pod mypod

ReplicaSet

#Create ReplicaSetroot@vagrant:/home/vagrant# wget https://kubernetes.io/examples/controllers/frontend.yaml
root@vagrant:/home/vagrant# cat frontend.yaml
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: frontend
  labels:
    app: guestbook
    tier: frontend
spec:
  # modify replicas according to your case
  replicas: 3
  selector:
    matchLabels:
      tier: frontend
  template:
    metadata:
      labels:
        tier: frontend
    spec:
      containers:
      - name: php-redis
        image: gcr.io/google_samples/gb-frontend:v3root@vagrant:/home/vagrant# kubectl apply -f https://kubernetes.io/examples/controllers/frontend.yaml#Get ReplicaSet
root@vagrant:/home/vagrant# kubectl get rs#Delete ReplicaSet
root@vagrant:/home/vagrant# kubectl delete rs frontend

Deployment

#Scale Deployment
root@vagrant:/home/vagrant# kubectl replace -f application.yml
root@vagrant:/home/vagrant# kubectl scale --replicas=10 -f application.yml
root@vagrant:/home/vagrant# kubectl scale --replicas=10 replicaset application#Generate YML File From Deployment
root@vagrant:/home/vagrant# kubectl create deployment --image=nginx nginx --replicas=2 --dry-run=client -o yaml > nginx.yaml
root@vagrant:/home/vagrant# kubectl create deployment httpd-name --image=httpd
root@vagrant:/home/vagrant# kubectl scale deployment httpd-name --replicas=10#Rollout
root@vagrant:/home/vagrant# rollout status deployment/httpd-name
root@vagrant:/home/vagrant# kubectl rollout history  deployment/httpd-name --revision=1
root@vagrant:/home/vagrant# kubectl rollout undo deployment/httpd-name

Configuration Examples

• Pod Environment variable

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    env:
    - name: DB_NAME
      value: MyDB
    - name: DB_URL
      valueFrom:
        configMapKeyRef:
          name: config-url
          key: db_url
    - name: DB_PASSWORD
      valueFrom:
        secretKeyRef:
          name: config-passwd
          key: db_password

• ConfigMap

#Create ConfigMaproot@vagrant:/home/vagrant# kubectl create configmap testconfigmap --from-literal=TestKey1=TestValue1 --from-literal=TestKey2=TestValue2
root@vagrant:/home/vagrant# kubectl create configmap testconfigmap --from-file=/opt/test_file#Test
root@vagrant:/home/vagrant# kubectl get configmaps
root@vagrant:/home/vagrant# kubectl describe configmaps
root@vagrant:/home/vagrant# kubectl describe configmap testconfigmap

• Use CofigMap in Pod

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    envFrom:
    - configMapRef:
        name: testconfigmap

• Secrets

#Create Secrets
root@vagrant:/home/vagrant# kubectl create secret generic testsecret --from-literal=Key1=Value1 --from-literal=Key2=Value2
root@vagrant:/home/vagrant# create secret generic testsecret --from-file=/opt/secret#Test
root@vagrant:/home/vagrant# kubectl get secrets
root@vagrant:/home/vagrant# kubectl describe secrets
root@vagrant:/home/vagrant# kubectl get secret testsecret
root@vagrant:/home/vagrant# kubectl describe secret testsecret
root@vagrant:/home/vagrant# kubectl get secret testsecret -o wide

• Use Secret in Pod

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    envFrom:
    - secretRef:
        name: testsecret

• Security Context

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  securityContext:
    runAsUser: 1000
    capabilities:
      add: ["ADMINISTRATOR"]
  containers:
  - name: nginx
    image: nginx
    command: ["printenv"]
    args: args: ["HOSTNAME"]
    securityContext:
      runAsUser: 2000
      capabilities:
        add: ["USER"]

• Service Account

#Create Service Account
root@vagrant:/home/vagrant# kubectl create serviceaccount testsa

• Use Service Account in Pod

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  serviceAccount: testsa
  containers:
  - name: nginx
    image: nginx
    envFrom:
    - secretRef:
        name: testsecret

• Resource requirements

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    resources:
      requests:
        memory: "1Mi"
        cpu: 0.2
      limits:
        memory: "1Gi"
        cpu: 1
    envFrom:
    - secretRef:
        name: testsecret

• Taints Node

Possible variants that we can set are: NoSchedule , PreferNoSchedule , NoExecute

#Create Taints
root@vagrant:/home/vagrant# kubectl taint nodes vagrant example-key=blue:NoSchedule

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    envFrom:
    - secretRef:
        name: testsecret
 tolerations:
  - key: "example-key"
    operator: "Equal"
    value: "blue"
    effect: "NoSchedule"

• Remove Taints

#Remove 
root@vagrant:/home/vagrant# kubectl taint nodes vagrant example-key=blue:NoSchedule-

• Node Selector

#Create Selector
root@vagrant:/home/vagrant# kubectl label nodes vagrant label-key=label-name

• Use in pod.yml

apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    envFrom:
    - secretRef:
        name: testsecret
  nodeSelector:
    label-key: label-name

Node Affinity

Assign Pods to Nodes using Node Affinity

This page shows how to assign a Kubernetes Pod to a particular node using Node Affinity in a Kubernetes cluster. Before…

kubernetes.io

Services

root@vagrant:/home/vagrant# kubectl expose deployment testdeployment --name=nginx-service --type=NodePort --target-port=8080 --port=80
root@vagrant:/home/vagrant# kubectl expose pod mypod --port=80 --name=nginx-service --type=NodePort
root@vagrant:/home/vagrant# kubectl create service nodeport mypod --tcp=80:80 --node-port=30080

Namespace

#Get Pods
root@vagrant:/home/vagrant# kubectl get pods --namespace=develop
root@vagrant:/home/vagrant# kubectl get pods -n develop 
root@vagrant:/home/vagrant# get pods --all-namespaces
root@vagrant:/home/vagrant# kubectl get ns#Change Default Namespace
root@vagrant:/home/vagrant# kubectl config set-context --current --namespace=develop

Readinesss Probe / Liveness Probe

#HTTP Test
apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    readinessProbe/livenessProbe:
     httpGet:
       path: /health
       port: 80
     initialDelaySeconds: 10
     periodSeconds: 5
     failureThreshold: 8
    envFrom:
    - secretRef:
        name: testsecret#TCP Test
apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    readinessProbe/livenessProbe:
      tcpSocket:
        port: 80
    envFrom:
    - secretRef:
        name: testsecret#Run Command
apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    role: myrole
spec:
  containers:
  - name: nginx
    image: nginx
    readinessProbe/livenessProbe:
      exec:
        command:
        - cat 
        - probe.htm
    envFrom:
    - secretRef:
        name: testsecret

Logs

root@vagrant:/home/vagrant# kubectl logs -f pod-name

Jobs

#Create Jobs
root@vagrant:/home/vagrant# kubectl create job test-job --image=nginx#Get Jobs
root@vagrant:/home/vagrant# kubectl get jobs test-job
root@vagrant:/home/vagrant# kubectl get jobs