CKA: Create and configure basic Pods
Contents
Create a Pod
- To create a pod based on a yaml definition file:
kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml[1] - To create a pod in a namespace:
kubectl create namespace MY_TEST_NAMESPACEkubectl 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
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.
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 emptyDir (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:
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
Create Pod
kubectl apply -f https://k8s.io/examples/pods/storage/redis.yamlpod/redis created
2. Verify the Pod Container is running
kubectl get pods NAME READY STATUS RESTARTS AGE redis 1/1 Running 0 3m29s
4. In another terminal, open an interactive session inside the Container that is running:
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:
kubectl delete pod redis
Related terms
See also
kubectl: [cp | config | create|delete|edit | explain |apply|exec|get|set|drain | uncordon | rolling-update|rollout|logs|run|auth|label | annotate|version|top|diff|debug|replace|describe|port-forward | proxy|scale|rollout|api-resources| expose deployment | expose | patch | attach | get endpoints | ~/.kube/config | kubectl logs --help | kubectl --help, kubectl-convert, kubectl autoscale, kubectl.kubernetes.io- CKA: v1.28: API, Namespace, Pods, secrets, Services, deployments, nodes, Volumes, Ingress, CKS
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