4 Hello minikube

This is a very short introduction to Kubernetes and a glossary is provided at the end of the chapter.

Consider that you already have minikube running on your local machine.

minikube status

minikube
type: Control Plane
host: Running
kubelet: Running
apiserver: Running
kubeconfig: Configured

Note

When you start minikube, it should configure kubectl to use minikube cluster and default namespace. If the configuration fail, you can always use

minikube kubectl --

instead of

kubectl

Note

You can visualise the changes in the minikube cluster using the dashboard. From a new terminal:

minikube dashboard --url

* Enabling dashboard ...
  - Using image docker.io/kubernetesui/metrics-scraper:v1.0.8
  - Using image docker.io/kubernetesui/dashboard:v2.7.0
* Some dashboard features require the metrics-server addon. To enable all features please run:

    minikube addons enable metrics-server   


* Verifying dashboard health ...
* Launching proxy ...
* Verifying proxy health ...
http://127.0.0.1:34183/api/v1/namespaces/kubernetes-dashboard/services/http:kubernetes-dashboard:/proxy/

Open the dashboard by pointing your web browser to http://127.0.0.1:34183/api/v1/namespaces/kubernetes-dashboard/services/http:kubernetes-dashboard:/proxy/.

Create a new Deployment (Pod and ReplicaSet):

kubectl create deployment hello-node \
    --image=registry.k8s.io/e2e-test-images/agnhost:2.39 \
    -- /agnhost netexec \
    --http-port=8080

deployment.apps/hello-node created

Screenshot of Kubernetes dashboard showing new Deployment.

4.1 Accessing Services

There are four types of services in Kubernetes: ClusterIP, NodePort, LoadBalancer, and ExternalName. In addition to access the service based on it’s type, a service can be accessed using Ingress.

4.1.1 `ClusterIP`

Diagram of `ClusterIP` service from https://medium.com/devops-mojo/kubernetes-service-types-overview-introduction-to-k8s-service-types-what-are-types-of-kubernetes-services-ea6db72c3f8c.

The service is accessible exclusively from inside the cluster or with the use of Ingress.

Create a new ClusterIP Service:

kubectl expose deployment hello-node --type=ClusterIP --port=8080

service/hello-node exposed

4.1.2 `NodePort`

Diagram of `NodePort` service from https://medium.com/devops-mojo/kubernetes-service-types-overview-introduction-to-k8s-service-types-what-are-types-of-kubernetes-services-ea6db72c3f8c.

The service is accessible using a port allocated by Kubernetes.

Create a NodePort new Service:

kubectl expose deployment hello-node --type=NodePort --port=8080

service/hello-node exposed

Note

8080 is the port number inside the cluster.

minikube service list

|-------------|------------|--------------|---------------------------|
|  NAMESPACE  |    NAME    | TARGET PORT  |            URL            |
|-------------|------------|--------------|---------------------------|
| default     | hello-node |         8080 | http://192.168.49.2:31039 |
|-------------|------------|--------------|---------------------------|

Open the Service by pointing your web browser to http://192.168.49.2:31039.

Important

minikube IP address is not reachable directly when using the Docker driver on macOS, Windows, or Windows Subsystem for Linux (WSL). A tunnel from localhost to minikube IP must be created using a separate terminal window to access the services:

minikube service hello-node --url

http://127.0.0.1:41023

Open the Service by pointing your web browser to http://127.0.0.1:41023.

4.1.3 `LoadBalancer`

Diagram of `LoadBalancer` service from https://medium.com/devops-mojo/kubernetes-service-types-overview-introduction-to-k8s-service-types-what-are-types-of-kubernetes-services-ea6db72c3f8c.

This is typically used with cloud providers and the creation of the load balancer is done by the cloud provider. The load balancer will provide external IP address to the service. When using minikube, a load balancer mock is created with

minikube tunnel

minikube tunnel must be run in a separate terminal window to keep the tunnel running.

Create a new LoadBalancer Service:

kubectl expose deployment hello-node --type=LoadBalancer --port=8080

service/hello-node exposed

Open the Service by pointing your web browser to http://localhost:8080.

4.1.4 `ExternalName`

Diagram of `ExternalName` service from https://medium.com/devops-mojo/kubernetes-service-types-overview-introduction-to-k8s-service-types-what-are-types-of-kubernetes-services-ea6db72c3f8c.

The service is accessed based on it’s DNS name and requires the configuration of the cluster DNS. More details at https://kubernetes.io/docs/concepts/services-networking/service/#externalname.

4.1.5 Ingress

Ingress only provide external access to HTTP and HTTPS services. Read more at https://kubernetes.io/docs/concepts/services-networking/ingress/.

4.2 Debugging

Check that all pods are running:

kubectl get pods -A

NAMESPACE     NAME                               READY   STATUS    RESTARTS      AGE
default       hello-node-7b87cd5f68-7jcmv        1/1     Running   0             53s
kube-system   coredns-787d4945fb-ds2bn           1/1     Running   0             12m
kube-system   etcd-minikube                      1/1     Running   0             13m
kube-system   kube-apiserver-minikube            1/1     Running   0             13m
kube-system   kube-controller-manager-minikube   1/1     Running   0             13m
kube-system   kube-proxy-ngmvs                   1/1     Running   0             12m
kube-system   kube-scheduler-minikube            1/1     Running   0             13m
kube-system   storage-provisioner                1/1     Running   1 (12m ago)   13m

Check that all services are running:

kubectl get services -A

NAMESPACE     NAME         TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)                  AGE
default       hello-node   LoadBalancer   10.103.36.91   <pending>     8080:32161/TCP           9s
default       kubernetes   ClusterIP      10.96.0.1      <none>        443/TCP                  15m
kube-system   kube-dns     ClusterIP      10.96.0.10     <none>        53/UDP,53/TCP,9153/TCP   14m

Retrieve description of pod and service:

kubectl describe pod hello-node

Name:             hello-node-7b87cd5f68-7jcmv
Namespace:        default
Priority:         0
Service Account:  default
Node:             minikube/192.168.49.2
Start Time:       Wed, 08 Mar 2023 08:40:53 +0100
Labels:           app=hello-node
                  pod-template-hash=7b87cd5f68
Annotations:      <none>
Status:           Running
IP:               10.244.0.3
IPs:
  IP:           10.244.0.3
Controlled By:  ReplicaSet/hello-node-7b87cd5f68
Containers:
  agnhost:
    Container ID:  docker://00e9685398f108edc14b0cca98d0da7729726fee248893bfb61690dec6352aef
    Image:         registry.k8s.io/e2e-test-images/agnhost:2.39
    Image ID:      docker-pullable://registry.k8s.io/e2e-test-images/agnhost@sha256:7e8bdd271312fd25fc5ff5a8f04727be84044eb3d7d8d03611972a6752e2e11e
    Port:          <none>
    Host Port:     <none>
    Command:
      /agnhost
      netexec
      --http-port=8080
    State:          Running
      Started:      Wed, 08 Mar 2023 08:40:59 +0100
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-bs8bh (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kube-api-access-bs8bh:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age    From               Message
  ----    ------     ----   ----               -------
  Normal  Scheduled  4m53s  default-scheduler  Successfully assigned default/hello-node-7b87cd5f68-7jcmv to minikube
  Normal  Pulling    4m52s  kubelet            Pulling image "registry.k8s.io/e2e-test-images/agnhost:2.39"
  Normal  Pulled     4m47s  kubelet            Successfully pulled image "registry.k8s.io/e2e-test-images/agnhost:2.39" in 4.875796238s (4.875814953s including waiting)
  Normal  Created    4m47s  kubelet            Created container agnhost
  Normal  Started    4m47s  kubelet            Started container agnhost

kubectl describe service hello-node

Name:                     hello-node
Namespace:                default
Labels:                   app=hello-node
Annotations:              <none>
Selector:                 app=hello-node
Type:                     LoadBalancer
IP Family Policy:         SingleStack
IP Families:              IPv4
IP:                       10.103.36.91
IPs:                      10.103.36.91
Port:                     <unset>  8080/TCP
TargetPort:               8080/TCP
NodePort:                 <unset>  32161/TCP
Endpoints:                10.244.0.3:8080
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

Retrieve log from a pod:

Note

You must provide the unique name of the pod.

kubectl logs hello-node-7b87cd5f68-7jcmv

I0308 07:40:59.271836       1 log.go:195] Started HTTP server on port 8080
I0308 07:40:59.272048       1 log.go:195] Started UDP server on port  8081

Run a command from inside the pod:

Note

You must provide the unique name of the pod.

kubectl exec hello-node-7b87cd5f68-7jcmv -- uname -a

Linux hello-node-7b87cd5f68-7jcmv 5.15.90.1-microsoft-standard-WSL2 #1 SMP Fri Jan 27 02:56:13 UTC 2023 x86_64 Linux

4.3 Clean up

Now you can clean up the resources:

kubectl delete service hello-node

service "hello-node" deleted

kubectl delete deployment hello-node

deployment.apps "hello-node" deleted

minikube delete

* Deleting "minikube" in docker ...
* Deleting container "minikube" ...
* Removing /home/raniere/.minikube/machines/minikube ...
* Removed all traces of the "minikube" cluster.

4.4 Glossary

Container: virtual operating system
Pod: group of one or more Containers, tied together for the purposes of administration and networking.
Deployment: checks on the health of your Pod and restarts the Pod’s Container if it terminates
Service: exposition of Pod to IP address external to the Kubernetes cluster

4.1 Accessing Services

4.1.1 ClusterIP

4.1.2 NodePort

4.1.3 LoadBalancer

4.1.4 ExternalName

4.1.5 Ingress

4.2 Debugging

4.3 Clean up

4.4 Glossary

4.1.1 `ClusterIP`

4.1.2 `NodePort`

4.1.3 `LoadBalancer`

4.1.4 `ExternalName`