Kubernetes¶

Reference¶

Terms¶

Configuration¶

Work with configuration:

export KUBECONFIG=~/openshift-installer/gcp/auth/kubeconfig

Namespace¶

Create namespace (resource management):

kubectl create namespace myspace

Setting namespace (in order to not specify in every single command):

kubectl config set-context --current --namespace=myspace

Or, with openshift (if running):

oc project myspace

Pods¶

Create pod:

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: pod
metadata:
  name: quarkus-demo
    containers:
    - name: quarkus-demo
      image: quay.io/rhdevelopers/quarkus-demo:v1
EOF

Get list of pods running (in namespace):

kubectl get pod

Enter pod:

kubectl exec quarkus-demo -it /bin/bash

Delete pod:

kubectl delete pod <pod>

ReplicaSet¶

Create a ReplicaSet:

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: ReplicaSet
metadata:
    name: rs-quarkus-demo
spec:
    replicas: 3
    selector:
        matchLabels:
           app: quarkus-demo
    template:
        metadata:
           labels:
              app: quarkus-demo
              env: dev
        spec:
             containers:
             - name: quarkus-demo
               image: quay.io/rhdevelopers/quarkus-demo:v1
EOF

Edit ReplicaSet:

kubectl edit rs rs-quarkus-demo

Describe ReplicaSet:

kubectl describe rs rs-quarkus-demo

Delete ReplicaSet:

kubectl delete rs rs-quarkus-demo

Deployments¶

Create a Deployment:

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
    name: quarkus-demo-deployment
spec:
    replicas: 3
    selector:
        matchLabels:
           app: quarkus-demo
    template:
        metadata:
           labels:
              app: quarkus-demo
              env: dev
        spec:
             containers:
             - name: quarkus-demo
               image: quay.io/rhdevelopers/quarkus-demo:v1
               imagePullPolicy: Always
               ports:
               - containerPort: 8080
EOF

NOTE: If in production use imagePullPolicy: IfNotPresent

Get Deployments:

kubectl get deployments

Describe Deployments:

kubectl describe deployment <deployment name>

Logs¶

Get pod logs:

kubectl logs <pod name>
stern <app name

Service¶

Create a Service:

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Service
metadata:
  name: the-service
spec:
  selector:
    app: quarkus-demo
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
  type: LoadBalancer
EOF

NOTE: Uses labels in order to random requests, via selector field.

Get Services:

kubectl get services
kubectl get service
kubectl get svc

Get Endpoints:

kubectl get endpoints

Ingress/Expose¶

Create Ingress:

cat <<EOF | kubectl apply -f -
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: myingress
spec:
  rules:
  - host: <cluster domain>
    http:
      paths:
      - path: /
        backend:
          serviceName: the-service
          servicePort: 80
EOF

Get Ingress:

kubectl get ingress

Delete Ingress:

kubectl delete ingress <ingress name>

Ingress has a router/revproxy based on haproxy.

Expose Service:

oc expose svc <service name>

Get exposed route:

kubectl get route
oc get route

Delete exposed route:

kubectl delete route <service name>

Blue/Green Deployments¶

Manage pods in service through labels:

kubectl label pod -l app=mypython inservice=mypods
kubectl label pod -l <label in use> inservice=<inservice name>

NOTE: Service must have a inservice selector.

Remove pods in service through labels:

kubectl label pod -l app=mypython inservice-

Operators¶

Create an helm operator with a blank chart:

operator-sdk new vis-helm --type=helm --api-version dobtech.io/v1 --kind Visitorsite

Create an helm operator with an existing helm archive/chart:

operator-sdk new vis-helm --type=helm --api-version dobtech.io/v1 --kind Visitors --helm-chart https://github.com/kubernetes-operators-book/chapters/releases/download/1.0.0/visitors-helm.tgz

Create an ansible operator with a blank chart:

operator-sdk new vis-ansible --type=ansible --api-version dobtech.io/v1 --kind Visitorsite