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Jason Heylon Blog

01 Mar 2019

Common Kubernetes Commands

Installation

# install docker
$ brew cask install docker
# instlal kube control commandline
$ brew install kubectl
# install minikube for our laptop
$ brew cask install minikube
# start minikube
$ minikube start
# maybe with other virtual machine driver
$ minikube start --vm-driver xxxx

Image from Dockerfile

FROM nginx
COPY www/* /usr/share/nginx/html

$ docker build -t my-demo:0.1 .

Create a Pod in k8s

# we need connect kubenetes docker environment
$ eval $(minikube docker-env)
# to revert previous command
$ eval $(minikube docker-env -u)

$ vi pod.yml

# pod.yml

apiVersion: v1
kind: Pod
metadata:
  name: my-demo
  labels:
    app: my-demo
spec:
  containers:
    - name: my-demo
      image: my-demo:0.1
      ports:
        - containerPort: 80

$ kubectl create -f pod.yml
pod "my-demo" created

$ kubectl get pods
NAME       READY     STATUS    RESTARTS   AGE
my-demo   1/1       Running   0          4s

Create service in k8s

  • We need service to talk with the pod in k8s.
$ vi service.yml

# service.yml
apiVersion: v1
kind: Service
metadata:
  name: my-demo-service
  labels:
    app: my-demo
spec:
  type: NodePort
  ports:
    - port: 80
      nodePort: 30050
  selector:
    app: my-demo

$ kubectl apply -f pod.yml

$ kubectl create -f service.yml
service "my-demo-svc" created

deployment in k8s

$ vi deployment.yml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: my-demo-deployment
spec:
  replicas: 10
  minReadySeconds: 10
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
      maxSurge: 1
  template:
    metadata:
      labels:
        app: my-demo
    spec:
      containers:
        - name: my-demo-pod
          image: my-demo:0.2
          ports:
            - containerPort: 80


$ kubectl create -f deployment.yml

commands about Pod

$ kubectl get pods
$ kubectl get pods -all-namespaces
$ kubectl get pods --show-labels
$ kubectl describe pod my-pod

# get pods with label
$ kubectl get pods -l app=first-demo
# add a label to pod
$ kubectl label pods my-pod app=first-demo-version1
# remove a label from pod
$ kubectl label pods my-pod app-

commands about Deployment

# Scale out
$ kubectl scale --replicas=3 deployment/nginx-app
# Update deployment and record command in history meanwile
$ kubectl apply -f deployment.yml --record=true
# online rolling upgrade
$ kubectl rollout app-v1 app-v2 --image=img:v2
# Roll backup
$ kubectl rollout app-v1 app-v2 --rollback
# List rollout
$ kubectl get rs
# Check update status
$ kubectl rollout status deployment nginx-app
# Check update history
$ kubectl rollout history deployment nginx-app
# Pause/Resume
$ kubectl rollout pause deployment nginx-deployment, resume
# Rollback to previous version
$ kubectl rollout undo deployment nginx-deployment
# Rollback to specfic version, we can find version in rollout history command
$ kubectl rollout undo deployment nginx-deployment --to-revision=1

commands about Service

# List all services
$ kubectl get services
# List service endpoints
$ kubectl get endpoints
# Get service detail
kubectl get service nginx-service -o yaml

commands about Secrets

# List secrets
$ kubectl get secrets --all-namespaces
# Create secret from cfg file
$ kubectl create secret generic db-user-pass --from-file./username.txt=
# Generate secret
echo -n 'mypasswd'=, then redirect to =base64 -decode

commands about Volumes

# List storage class
$ kubectl get storageclass
# Check the mounted volumes
$ kubectl exec storage ls /data
# Check persist volume
$ kubectl describe pv/pv0001
# Copy local file to pod
$ kubectl cp /tmp/my <some-namespace>/<some-pod>:/tmp/server
# Copy pod file to local
$ kubectl cp <some-namespace>/<some-pod>:/tmp/server /tmp/my

commands about Node

# Mark node as unschedulable
$ kubectl cordon $NDOE_NAME
# Mark node as schedulable
$ kubectl uncordon $NDOE_NAME
# Drain node in preparation for maintenance
$ kubectl drain $NODE_NAME

commands about namespace

# List authenticated contexts
$ kubectl config get-contexts, ~/.kube/config
# Load context from config file
$ kubectl get cs --kubeconfig kube_config.yml
# Switch context
$ kubectl config use-context <cluster-name>
# Delete the specified context
$ kubectl config delete-context <cluster-name>
# List all namespaces defined
$ kubectl get namespaces
# Set namespace preference
$ kubectl config set-context $(kubectl config current-context) --namespace=<ns1>
# List certificates
$ kubectl get csr

commands about Network

# Temporarily add a port-forwarding
$ kubectl port-forward redis-izl09 6379
# Add port-forwaring for deployment
$ kubectl port-forward deployment/redis-master 6379:6379
# Add port-forwaring for replicaset
$ kubectl port-forward rs/redis-master 6379:6379
# Add port-forwaring for service
$ kubectl port-forward svc/redis-master 6379:6379
# Get network policy
$ kubectl get NetworkPolicy

Til next time,
Jason Heylon at 00:00

Jason Heylon
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