#killer koda and bregman exercies

1. creating a pod
`kubectl run nginx --image=nginx`

2. list pods
`kubectl get pods`

3. deleting pods
`kubectl delete pods nginx`

3. creating a service
`kubectl run nginx --image nginx --port=80 --labels="app=dev-nginx`
```yaml
apiVersion: v1
kind: Service
metadata:
    name: nginx-service
spec:
    selector:
        app: dev-nginx
    ports:
        - protocol: TCP
          port: 80
          targetPort: 9372
```

4.  Creating a ReplicaSet
```
apiVersion: apps/v1
kind: ReplicaSet
metadata:
    name: web
    labels:
        app: somewebapp
        type: web
spec:
    replicas: 2
    selector:
        matchLabels:
            type: web
    template:
        metadata:
            labels:
                type: web
        spec:
            containers:
                - name: httpd
                  image: registry.redhat.io/rhscl/httpd-24-rhel7
```
`kubectl apply -f rs.yaml`
`kubectl get rs`

```

## Operating ReplicaSet

1.  Create ReplicaSet with 2 Replicas 
```
cat >> rs.yaml <<EOL
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: web
  labels:
    app: somewebapp
    type: web
spec:
  replicas: 2
  selector:
    matchLabels:
      type: web
  template:
    metadata:
      labels:
        type: web
    spec:
      containers:
      - name: httpd
        image: registry.redhat.io/rhscl/httpd-24-rhel7
EOL

kubectl apply -f rs.yaml
```

2. verify
`kubectl get rs`

3. remove ReplicaSet but NOT the pods it created
`kubectl delete -f rs.yaml --cascade=orphan`

4. verify
`kubectl get rs`
`kubectl get po`

5. create again the same replicaSet without any change
`kubectl apply -f rs.yaml`

6. Verify that the ReplicaSet used the existing Pods and didn't create new Pods
`kubectl describe rs web  # You should see there are no new events and if you list the pods with 'kubectl get po -f rs.yaml` you'll see they have the same names`

## ReplicaSets Selectors

1. create replicaset with 2 replicas

```
apiVersion: apps/v1
kind: ReplicaSet
metadata:
    name: web
    labels:
        app: somewebapp
        type: web
spec: 
    replicas: 2
    selector:
        matchLabels:
            type: web
    template:
        metadata:
            labels:
                type: web
        spec:
            containers:
            - name: httpd
              image: registry.redhat.io/rhscl/httpd-24-rhel7
```

`kubectl apply -f rs.yaml`

2. verify
`kubectl get rs`

3. List the pods and save output somewhere
`kubectl get po > running_pods.txt`

4. Remove the label (type=web) from one of the Pods created by the ReplicaSet
`kubectl label pod <POD_NAME> type-`

5. List the pods running? are there more pods? why?
`Yes, there is an additional Pod running because once the label (used as a matching selector) was removed, the Pod became independent meaning, it's not controlled by the ReplicaSet anymore and the ReplicaSet was missing replicas based on its definition so, it created a new Pod.`

6. verify
`kubectl describe rs web`


## labels and selectors 101



How to list all the Pods with the label "app=web"?
How to list all objects labeled as "env=staging"?
How to list all deployments from "env=prod" and "type=web"?

Solution
k get po -l app=web 
k get all -l env=staging
k get deploy -l env=prod,type=web