Pod using yaml

Creating a Pod using a Yaml based file.

Kubernetes uses yaml files as input to create object such as Pods, replicas, deployments, services 

pod-definition.yml

apiVersion: 
kind:
metadata:
  name: myapp-app
  labels: 
     app: myapp
     type: front-end

spec:
  containers: 
     -name: nginx-container
      image: nginx

---

kubectl create -f pod-definition.yml

kubectl apply -f pod-definition.yml

Both these commands work the same way when you are creating a new object

----

kubectl get pods

kubectl describe pod myapp-app

--

create a new pod using nginx image

kubectl run nginx --image=nginx

kubectl get pods -o wide

--

deleting a pod

kubectl delete pod webapp

-- 

dry run creating a pod yaml file , this will create a yaml file output. in this case the image is a wrong image > redis123

kubectl run redis --image redis123 --dry-run -o yaml

--dry-run=client   (this is the new one --dry-run is deprecated)

kubectl run redis --image redis123 --dry-run=client -o yaml

we can direct this to another file

kubectl run redis --image redis123 --dry-run=client -o yaml > redis.yaml

create the pod now

kubectl create -f redis.yaml

verify that is created 

kubectl get pods

-- Correcting the wrong image file to redis image

you can do this using kubectl edit command or open up the yaml file using a text editor and change it 

-- Now appy the changes

kubectl apply -f redis.yaml 

-- Replication Sets

Replication controller spans across multiple nodes in a cluster

---

Upscaling the ReplicaSet

edit the replica-set-definitions.yaml

edit the replicas and 

kubectl replace -f replica-set-definitions.yaml

second method to do this

kubectl scale --replicas=6 -f replica-set-definitions.yaml

or you can use the replicaset name

kubectl scale --replicas=6 replicaset myapp-replicaset

kubectl get replicasets

kubectl delete replicaset myapp-replicaset

kubectl explain replicaset

kubectl edit rs new-replicaset

kubectl scale rs new-replicaset --replicas=5

kubectl edit rs new-replicasets