Exercise 2: Create A Pod

This Exercise demonstrates the use of a YAML file to create a pod declaratively.

Task 1 - Create A Pod Declaratively

1. Create a pod definition using YAML:

   ​

   AZ CLI PowerShell AZ CLI Bash

   $simplePodYaml = @"
   apiVersion: v1
   kind: Pod
   metadata:
     name: nginx-pod  
     labels:
       kind: web
       target: dev
   spec:
     containers:
     - image: k8sonazureworkshoppublic.azurecr.io/nginx
       name: nginx
       ports:
       - containerPort: 80
         protocol: TCP
     nodeSelector:
       kubernetes.io/os: linux
   "@
   
   # Review the YAML
   $simplePodYaml

   cat << EOF > nginx-pod.yaml
   apiVersion: v1
   kind: Pod
   metadata:
     name: nginx-pod  
     labels:
       kind: web
       target: dev
   spec:
     containers:
     - image: k8sonazureworkshoppublic.azurecr.io/nginx
       name: nginx
       ports:
       - containerPort: 80
         protocol: TCP
     nodeSelector:
       kubernetes.io/os: linux
   EOF
   
   # Review the YAML
   cat nginx-pod.yaml

   The pod definition contains the nginx container that listens to port 80.

2. Create the pod using the YAML definition:

   ​

   AZ CLI PowerShell AZ CLI Bash

   $simplePodYaml | kubectl apply -f -

   kubectl apply -f nginx-pod.yaml

3. Now, make sure pod is up and running. You may need to re-run the command if it takes a while for the pod to start.

   ​

   AZ CLI PowerShell AZ CLI Bash

   kubectl get pods

   kubectl get pods

   You should see a pod named nginx-pod

   

   Tip

   If the pod has the STATUS ContainerCreating and shows READY 0/1, this means the pod is still starting up. Wait a few seconds and run the commend again.

4. Add a second pod, then check the list again.

   ​

   AZ CLI PowerShell AZ CLI Bash

   $simplePod2Yaml = @"
   apiVersion: v1
   kind: Pod
   metadata:
     name: nginx-pod2
     labels:
       kind: api
       target: dev
   spec:
     containers:
     - image: k8sonazureworkshoppublic.azurecr.io/nginx
       name: nginx
       ports:
       - containerPort: 80
         protocol: TCP
     - image: k8sonazureworkshoppublic.azurecr.io/mysql:5.7
       name: mysql
       ports:
       - containerPort: 3306
         protocol: TCP      
       env: 
       - name: MYSQL_ALLOW_EMPTY_PASSWORD
         value: "true"
     nodeSelector:
       kubernetes.io/os: linux
   "@
   
   $simplePod2Yaml | kubectl apply -f -
   kubectl get pods

   cat << EOF > nginx-pod2.yaml
   apiVersion: v1
   kind: Pod
   metadata:
     name: nginx-pod2
     labels:
       kind: api
       target: dev
   spec:
     containers:
     - image: k8sonazureworkshoppublic.azurecr.io/nginx
       name: nginx
       ports:
       - containerPort: 80
         protocol: TCP
     - image: k8sonazureworkshoppublic.azurecr.io/mysql:5.7
       name: mysql
       ports:
       - containerPort: 3306
         protocol: TCP      
       env: 
       - name: MYSQL_ALLOW_EMPTY_PASSWORD
         value: "true"
     nodeSelector:
       kubernetes.io/os: linux
   EOF
   
   kubectl apply -f nginx-pod2.yaml
   kubectl get pods

Task 2 - Filter Pods Based On A Label

1. Show all the labels in the pods

   ​

   AZ CLI PowerShell AZ CLI Bash

   kubectl get pods --show-labels

   kubectl get pods --show-labels

   

2. Let’s say you want to list pods that have a label named kind=web associated with them. You can use -l switch to apply filter based on labels.

   ​

   AZ CLI PowerShell AZ CLI Bash

   kubectl get pod -l kind=web

   kubectl get pod -l kind=web

3. To prove that this works as expected, run the command again but change the value of label kind to db. Notice, this time kubectl doesn’t return any pods because there are no pods that match the label kind and a value of db.

   ​

   AZ CLI PowerShell AZ CLI Bash

   kubectl get pod -l kind=db

   kubectl get pod -l kind=db

Task 3 - View complete definition of the pod

1. Query Kubernetes to return the complete definition of a pod from its internal database by exporting the output (-o) to YAML. Then pipe the result to a file.

   ​

   AZ CLI PowerShell AZ CLI Bash

   kubectl get pods nginx-pod -o yaml > mypod.yaml

   kubectl get pods nginx-pod -o yaml > mypod.yaml

   Tip

   To view the JSON version, use the -o json flag instead.

2. View the contents of the generated file in VS Code (or an editor of your choice).

   ​

   AZ CLI PowerShell AZ CLI Bash

   code mypod.yaml

   code mypod.yaml

   

   Tip

   Observe all the properties that Kubernetes populated with default values when it saved the pod definition to its database.