Editing CKA: Create and configure basic Pods

 Only available in first CKA versions

== Create a [[Pod]] ==
* To create a pod based on a yaml definition file:  <code>[[kubectl apply]] -f https://k8s.io/examples/pods/storage/redis.yaml</code><ref>https://kubernetes.io/docs/tasks/configure-pod-container/assign-memory-resource/</ref>
* To create a pod in a [[namespace]]:
:<code>[[kubectl create]] namespace MY_TEST_NAMESPACE</code>
:<code>[[kubectl apply]] -f https://k8s.io/examples/pods/storage/redis.yaml --namespace=MY_TEST_NAMESPACE</code><ref>https://kubernetes.io/docs/tasks/configure-pod-container/assign-memory-resource/</ref>
:To verify container is running: 
::<code>[[kubectl get pod]] NAME_POD --namespace=MY_TEST_NAMESPACE</code>

==Set up a [[Volume]] for a [[Pod]]==
The file system of a [[Container]] exists as long as the Container exists. Therefore, when a Container is destroyed or restarted, changes made to the file system are lost. For more consistent storage that is independent of the Container life cycle, you can use a Volume, review different Volume types in https://kubernetes.io/docs/concepts/storage/volumes/#types-of-volumes.

Create a Pod that runs a single Container. This Pod has a Volume of type <code>emptyDir</code> (empty directory) (see [[Volume]] for volume types) that exists throughout the Pod's life cycle, even when the Container is destroyed and restarted.
Example:
<code>pods/storage/redis.yaml</code>

 apiVersion: v1
 [[kind: Pod]]
 metadata:
   name: redis
 spec:
   containers:
   - [[name:]] redis
     [[image]]: redis
     [[volumeMounts]]:
     - name: redis-storage
       [[mountPath]]: /data/redis
   [[volumes:]]
   - name: redis-storage
     emptyDir: {}</pre>

=== Steps ===
==== Create Pod ====
:<code>kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml</code>
:<code>pod/redis created</code>

==== Verify [[Pod]] is running ====

 [[kubectl get pods]]
 NAME    READY   STATUS    RESTARTS   AGE
 redis   1/1     Running   0          3m29s

==== List all Kubernetes resources created ====
 [[kubectl get all]]
 NAME        READY   STATUS    RESTARTS   AGE
 pod/redis   1/1     Running   0          10m
 
 NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
 service/kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   3d21h

==== In another terminal, open an interactive session inside the Container that is running: ====
<code>[[kubectl exec]] -it redis -- /bin/bash</code>

'''5. Create a file in <code>/data/redis</code>'''
<pre>root@redis:/data# cd /data/redis/
root@redis:/data/redis# echo Hello > test-file</pre>

'''6. List running processes:'''
<pre>root@redis:/data/redis# apt-get update
root@redis:/data/redis# apt-get install procps
root@redis:/data/redis# ps aux</pre>

output:
<pre>USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
redis        1  0.1  0.1  33308  3828 ?        Ssl  00:46   0:00 redis-server *:6379
root        12  0.0  0.0  20228  3020 ?        Ss   00:47   0:00 /bin/bash
root        15  0.0  0.0  17500  2072 ?        R+   00:48   0:00 ps aux</pre>

'''6.In the terminal, kill the Redis process:'''

root@redis:/data/redis# kill <pid>

where <pid>is the process ID (PID) of Redis.

'''7.In the original terminal, observe the changes in the Redis Pod. You will eventually see something like the following:'''

NAME      READY     STATUS     RESTARTS   AGE
redis     1/1       Running    0          13s
redis     0/1       Completed  0         6m
redis     1/1       Running    1         6m

At this point, the Container has been destroyed and restarted. This is because the Redis Pod has a restartPolicy (restart policy) of Always(always).

1.Open a terminal in the restarted Container:
<code>[[kubectl exec]] -it redis -- /bin/bash</code>

2.In the terminal, go to /data/redisand verify that it test-filestill exists:

root@redis:/data/redis# cd /data/redis/
root@redis:/data/redis# ls
test-file

3.Remove the Pod you created for this exercise:
* <code>[[kubectl delete]] pod redis</code>

== Related terms ==
* [[Certified Kubernetes Administrator v1.21]]

== See also ==
* {{kubectl apply}}
* {{CKA versions}}
* {{CKA}}

{{CC license}}
Source: https://en.wikiversity.org/wiki/DevOps/Kubernetes/Certified_Kubernetes_Administrator/Create_and_configure_basic_Pods


[[Category:CKAD]]
[[Category:Kubernetes]]