Kubernates Operational and Verification Command

Check node, version, name

kubectl get node

kubectl get node -o wide

kubectl version

Verify node detail

kubectl describe node <NODE NAME>

Verify resources available

kubectl api-resources

Use for api/resource detail check

kubectl explain <RESOURCE>

Get namespaces

kubectl get namespace

Get all pods on all namespace

kubectl get pods –all-namespaces

Running a single pod

kubectl run pingpong –image alpine ping 1.1.1.1

kubectl run webapp –image nginx

Remove Pods

kubectl delete pods webapp

Running a deployment

kubectl create deployment deployment-1 –image=alpine — ping 1.1.1.1

Create a deployment

kubectl create -f app.yml
kubectl apply -f app.yml

Scale deployment to 3

kubectl scale deployment deployment-1 –replicas 3

Check pod logs

Check Service on Cluster

kubectl get service

Get Service Detail

kubectl describe service [SERVICE,DEPLOYMENT]

psi-admin@mickrok8s-1:~$ kubectl describe service httpenv
Name: httpenv
Namespace: default
Labels: app=httpenv
Annotations:
Selector: app=httpenv
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: 10.152.183.234
IPs: 10.152.183.234
Port: 8888/TCP
TargetPort: 8888/TCP
Endpoints: 10.1.156.10:8888,10.1.156.11:8888,10.1.156.12:8888 + 7 more…
Session Affinity: None
Events:

Endpoint list that shows above are actually the POD

Headless Service

kubectl expose deploy my-little-deploy --cluster-ip=None --port=80 

Run a pod every 3 minutes

kubectl run --schedule=*/3 * * * * pingpong --image alpine ping 1.1.1.1

#it is cron time, which each * is minutes[0-59] hour[0-23] dayofmonth[1-31] monthofyear[1-12] dayofweek[0-6,0=sunday]

Exposing Port to Deployment/Pod, ie expose port 8888 to deployment=httpenv

kubectl expose deployment httpenv --port 8888

#when exposing, the service is created for it. To un-expose or remove expose
kubectl delete service httpenv

SHPOD install, for testing pod from internal IF we are using non-linux Controller

kubectl apply -f https://bret.run/shpod.yml

Run a console to SHPOD

kubectl attach --namespace=shpod -ti shpod

Sample yaml file for creating pods

Create yml from external deployment

kubectl get deploy/rng -o yaml >rng.yml

Selector and Label, using describe we can see a label for a service and what filter it is used to choose back end pods.

psi-admin@microk8s-2:~$ kubectl describe service rng
Name:              rng
Namespace:         default
Labels:            app=rng
Annotations:       <none>
Selector:          app=rng
Type:              ClusterIP
IP Family Policy:  SingleStack
IP Families:       IPv4
IP:                10.152.183.174
IPs:               10.152.183.174
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         10.1.100.139:80,10.1.100.153:80
Session Affinity:  None
Events:            <none>

Verify/list pods based on selector(filter based on selector) can be done using -l

psi-admin@microk8s-2:~$ kubectl get pods -l app=rng
NAME                   READY   STATUS    RESTARTS   AGE
rng-7c7c6c8d74-vt55b   1/1     Running   0          5h18m
rng-vljzk              1/1     Running   0          5m21s

Label and Selector

Check current label

kubectl desribe pod deployment

kubectl desribe pod daemonset

Both has the same label, but we can check the pod-template are different below:

The pod-template-hash ==> replicaset or deployment

The pod-template-generation ==> daemonset

To add new label

kubectl label pods -l app=rng enabled=yes

Editing the service to filter the correct/new label

kubectl edit service rng

Look for label in the spec section

Edited to:

Remove label enabled from only the deployment pod (has attribute pod-template-hash), keep the pod running and set only daemon sets pod active in service

kubectl label pod -l app=rng,pod-template-hash enabled-

enable- = remove label enable

Create a sample kubernates YAML file without disrupting the system

Create Deployment WEB with NGINX to output as yaml file

kubectl create deployment WEB --image nginx -o yaml --dry-run

Create Deployment WEB with NGINX to output as yaml file but SHORT yaml

kubectl create namespace SAMPLE -o yaml --dry-run