Editing Create and configure a basic Pod

== 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>[[devOps/Kubernetes/kubectl|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>
DevOps/Kubernetes/Certified Kubernetes Administrator/Create and configure basic Pods|Create and configure basic Pods]]

==Set up a [[DevOps/Kubernetes/Volumes|Volume]] for a [[DevOps/Kubernetes/Pods|Pod]]==
The file system of a [[DevOps/Container|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.

This feature is especially important for applications that must maintain a status, such as key-value storage engines (for example Redis) and databases.

Create a Pod that runs a single Container. This Pod has a Volume of type <code>emptyDir</code> (empty directory) (see [[DevOps/Kubernetes/Volumes|Volume]] for volume types) that exists throughout the Pod's life cycle, even when the Container is destroyed and restarted. Here is the Pod configuration file:

<code>pods/storage/redis.yaml</code>

<pre>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>


'''1.Create the Pod'''
<code>kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml</code>

'''2. Verify the Pod Container is running'''
<code>kubectl get pod redis --watch</code>

output:

<pre>NAME      READY     STATUS    RESTARTS   AGE
redis     1/1       Running   0          13s</pre>

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

'''4.In the terminal, go to <code>/data/redis</code> and create a file:'''
<pre>root@redis:/data# cd /data/redis/
root@redis:/data/redis# echo Hello > test-file</pre>

'''5.In the terminal, list the 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:

[[kubectl exec]] -it redis -- /bin/bash

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:

kubectl delete pod redis


== See also ==
* {{K8s}}

[[Category:Kubernetes]]

{{CC license}}
Source: wikiversity