Difference between revisions of "CKA: Create and configure basic Pods"

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== Create a Pod ==
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Only available in first CKA versions
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== 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 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]]:
 
* To create a pod in a [[namespace]]:
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:<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>
 
:<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:  
 
:To verify container is running:  
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::<code>[[kubectl get]] pod NAME_POD --namespace=MY_TEST_NAMESPACE</code>
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::<code>[[kubectl get pod]] NAME_POD --namespace=MY_TEST_NAMESPACE</code>
  
 
==Set up a [[Volume]] for a [[Pod]]==
 
==Set up a [[Volume]] for a [[Pod]]==
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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.
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Review different Volume types in https://kubernetes.io/docs/concepts/storage/volumes/#types-of-volumes.
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This feature is especially important for applications that must maintain a status, such as key-value storage engines (for example Redis) and databases.
 
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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. Here is the Pod configuration file:
 
  
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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.
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Example:
 
<code>pods/storage/redis.yaml</code>
 
<code>pods/storage/redis.yaml</code>
  
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<pre>apiVersion: v1
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apiVersion: v1
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kind: Pod
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[[kind: Pod]]
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metadata:
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metadata:
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  name: redis
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  name: redis
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spec:
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spec:
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  containers:
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  containers:
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  - name: redis
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  - [[name:]] redis
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    image: redis
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    [[image]]: redis
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    volumeMounts:
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    [[volumeMounts]]:
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    - name: redis-storage
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    - name: redis-storage
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      mountPath: /data/redis
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      [[mountPath]]: /data/redis
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  volumes:
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  [[volumes:]]
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  - name: redis-storage
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  - name: redis-storage
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    emptyDir: {}</pre>
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    emptyDir: {}</pre>
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'''1.Create the Pod'''
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=== Steps ===
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<code>kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml</code>
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==== Create Pod ====
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:<code>kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml</code>
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:<code>pod/redis created</code>
  
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'''2. Verify the Pod Container is running'''
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==== Verify [[Pod]] is running ====
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<code>kubectl get pod redis --watch</code>
 
  
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output:
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[[kubectl get pods]]
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NAME    READY  STATUS    RESTARTS  AGE
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redis  1/1    Running  0          3m29s
  
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<pre>NAME     READY     STATUS    RESTARTS  AGE
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==== List all Kubernetes resources created ====
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redis     1/1       Running  0          13s</pre>
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[[kubectl get all]]
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NAME       READY   STATUS    RESTARTS  AGE
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pod/redis   1/1     Running  0          10m
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NAME                TYPE        CLUSTER-IP  EXTERNAL-IP  PORT(S)  AGE
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service/kubernetes  ClusterIP  10.96.0.1    <none>        443/TCP  3d21h
  
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'''3.In another terminal, open an interactive session inside the Container that is running:'''
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==== In another terminal, open an interactive session inside the Container that is running: ====
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<code>kubectl exec -it redis -- /bin/bash</code>
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<code>[[kubectl exec]] -it redis -- /bin/bash</code>
  
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'''4.In the terminal, go to <code>/data/redis</code> and create a file:'''
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'''5. Create a file in <code>/data/redis</code>'''
 
<pre>root@redis:/data# cd /data/redis/
 
<pre>root@redis:/data# cd /data/redis/
 
root@redis:/data/redis# echo Hello > test-file</pre>
 
root@redis:/data/redis# echo Hello > test-file</pre>
  
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'''5.In the terminal, list the running processes:'''
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'''6. List running processes:'''
 
<pre>root@redis:/data/redis# apt-get update
 
<pre>root@redis:/data/redis# apt-get update
 
root@redis:/data/redis# apt-get install procps
 
root@redis:/data/redis# apt-get install procps
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root        15  0.0  0.0  17500  2072 ?        R+  00:48  0:00 ps aux</pre>
 
root        15  0.0  0.0  17500  2072 ?        R+  00:48  0:00 ps aux</pre>
  
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6.In the terminal, kill the Redis process:
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'''6.In the terminal, kill the Redis process:'''
  
 
root@redis:/data/redis# kill <pid>
 
root@redis:/data/redis# kill <pid>
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where <pid>is the process ID (PID) of Redis.
 
where <pid>is the process ID (PID) of Redis.
  
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7.In the original terminal, observe the changes in the Redis Pod. You will eventually see something like the following:
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'''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
 
NAME      READY    STATUS    RESTARTS  AGE
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1.Open a terminal in the restarted Container:
 
1.Open a terminal in the restarted Container:
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<code>[[kubectl exec]] -it redis -- /bin/bash</code>
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[[kubectl exec]] -it redis -- /bin/bash
 
  
 
2.In the terminal, go to /data/redisand verify that it test-filestill exists:
 
2.In the terminal, go to /data/redisand verify that it test-filestill exists:
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3.Remove the Pod you created for this exercise:
 
3.Remove the Pod you created for this exercise:
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* <code>[[kubectl delete]] pod redis</code>
  
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kubectl delete pod redis
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== Related terms ==
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* [[Certified Kubernetes Administrator v1.21]]
  
 
== See also ==
 
== See also ==
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* {{kubectl}}
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* {{kubectl apply}}
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* [[Certified Kubernetes Administrator]]
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* {{CKA versions}}
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* {{CKA}}
  
 
{{CC license}}
 
{{CC license}}

Latest revision as of 16:12, 29 February 2024

Only available in first CKA versions

Create a Pod[edit]

kubectl create namespace MY_TEST_NAMESPACE
kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml --namespace=MY_TEST_NAMESPACE[2]
To verify container is running:
kubectl get pod NAME_POD --namespace=MY_TEST_NAMESPACE

Set up a Volume for a Pod[edit]

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 emptyDir (empty directory) (see Volume for volume types) that exists throughout the Pod's life cycle, even when the Container is destroyed and restarted. Example: pods/storage/redis.yaml 

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: {}

Steps[edit]

Create Pod[edit]

kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml
pod/redis created

Verify Pod is running[edit]

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

List all Kubernetes resources created[edit]

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:[edit]

kubectl exec -it redis -- /bin/bash

5. Create a file in /data/redis 

root@redis:/data# cd /data/redis/
root@redis:/data/redis# echo Hello > test-file

6. List running processes: 

root@redis:/data/redis# apt-get update
root@redis:/data/redis# apt-get install procps
root@redis:/data/redis# ps aux

output: 

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

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:

Related terms[edit]

See also[edit]

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Source: https://en.wikiversity.org/wiki/DevOps/Kubernetes/Certified_Kubernetes_Administrator/Create_and_configure_basic_Pods

  1. ↑ https://kubernetes.io/docs/tasks/configure-pod-container/assign-memory-resource/
  2. ↑ https://kubernetes.io/docs/tasks/configure-pod-container/assign-memory-resource/
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