Kubectl Useful Commands

Kubectl Useful Commands

July 21, 2021 0 By Nam Vu
ntechdevelopersKubernetes Shortcuts
po : Pods
rs : ReplicaSets
deploy : Deployments
svc : Services
ns : Namespaces
netpol : Network policies
pv : Persistent Volumes
pvc : PersistentVolumeClaims
in : Service Accounts

Backup
kubectl get all -A -o yaml > backup.yaml

Explain
kubectl explain sc –recursive | less

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

ReplicaSet
#Create ReplicaSet
wget https://kubernetes.io/examples/controllers/frontend.yaml
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:v3
kubectl apply -f https://kubernetes.io/examples/controllers/frontend.yaml
#Get ReplicaSet
kubectl get rs
#Delete ReplicaSet
kubectl delete rs frontend

Deployment
#Scale Deployment
kubectl replace -f application.yml
kubectl scale –replicas=10 -f application.yml
kubectl scale –replicas=10 replicaset application
#Generate YML File From Deployment
kubectl create deployment –image=nginx nginx –replicas=2 –dry-run=client -o yaml > nginx.yaml
kubectl create deployment httpd-name –image=httpd
kubectl scale deployment httpd-name –replicas=10
#Rollout
kubectl rollout status deployment/httpd-name
kubectl rollout history  deployment/httpd-name –revision=1
kubectl rollout undo deployment/httpd-name
#Edit deployment on environment
kubectl edit deploy my-service-name dev

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 ConfigMap
kubectl create configmap testconfigmap –from-literal=TestKey1=TestValue1 –from-literal=TestKey2=TestValue2
kubectl create configmap testconfigmap –from-file=/opt/test_file
 
#Test
kubectl get configmaps
kubectl describe configmaps
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
kubectl create secret generic testsecret –from-literal=Key1=Value1 –from-literal=Key2=Value2
kubectl create secret generic testsecret –from-file=/opt/secret
#Test
kubectl get secrets
kubectl describe secrets
kubectl get secret testsecret
kubectl describe secret testsecret
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
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: NoSchedule , PreferNoSchedule , NoExecute
#Create Taints
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
kubectl taint nodes vagrant example-key=blue:NoSchedule-
– Node Selector
#Create Selector
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

Services
kubectl expose deployment testdeployment –name=nginx-service –type=NodePort –target-port=8080 –port=80
kubectl expose pod mypod –port=80 –name=nginx-service –type=NodePort
kubectl create service nodeport mypod –tcp=80:80 –node-port=30080

Namespace
#Get Pods
kubectl get pods –namespace=develop
kubectl get pods -n develop
kubectl get pods –all-namespaces
kubectl get ns
#Change Default Namespace
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
kubectl logs -f pod-name

Jobs
#Create Jobs
kubectl create job test-job –image=nginx
#Get Jobs
kubectl get jobs test-job
kubectl get jobs

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