Help Needed with Kubernetes CronJob Question

Certified Kubernetes Application Developer
, ,
#1

Hey everyone,

I recently encountered a question related to Kubernetes CronJobs and would appreciate some insights from the community.

Question:

For this question, please set the context to cluster1 by running:

kubectl config use-context cluster1

In the ckad-job namespace, create a cronjob named simple-python-job to run every 30 minutes to list all the running processes inside a container that used python image (the command needs to be run in a shell).

In Unix-based operating systems, ps -eaf can be use to list all the running processes.

My Answer:
apiVersion: v1
items:

  • apiVersion: batch/v1
    kind: CronJob
    metadata:
    annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
    {“apiVersion”:“batch/v1”,“kind”:“CronJob”,“metadata”:{“annotations”:{},“creationTimestamp”:“2024-05-06T02:39:40Z”,“generation”:2,“name”:“simple-python-job”,“namespace”:“ckad-job”,“resourceVersion”:“2011”,“uid”:“df42fdca-65bb-4d6b-85df-35ecb1d69ef7”},“spec”:{“concurrencyPolicy”:“Allow”,“failedJobsHistoryLimit”:1,“jobTemplate”:{“metadata”:{“creationTimestamp”:null,“name”:“simple-python-job”},“spec”:{“template”:{“metadata”:{“creationTimestamp”:null},“spec”:{“containers”:[{“args”:[“-c”,“ps -eaf”],“command”:[“/bin/sh”],“image”:“python”,“imagePullPolicy”:“Always”,“name”:“simple-python-job”,“resources”:{},“terminationMessagePath”:“/dev/termination-log”,“terminationMessagePolicy”:“File”}],“dnsPolicy”:“ClusterFirst”,“restartPolicy”:“OnFailure”,“schedulerName”:“default-scheduler”,“securityContext”:{},“terminationGracePeriodSeconds”:30}}}},“schedule”:"*/30 * * * ",“successfulJobsHistoryLimit”:3,“suspend”:false},“status”:{“active”:[{“apiVersion”:“batch/v1”,“kind”:“Job”,“name”:“simple-python-job-28582720”,“namespace”:“ckad-job”,“resourceVersion”:“1609”,“uid”:“04c8389b-f080-47d9-b833-ba5391ee6dfd”},{“apiVersion”:“batch/v1”,“kind”:“Job”,“name”:“simple-python-job-28582721”,“namespace”:“ckad-job”,“resourceVersion”:“1669”,“uid”:“a039e141-2bf7-4f9a-a7eb-10656c22f77d”},{“apiVersion”:“batch/v1”,“kind”:“Job”,“name”:“simple-python-job-28582724”,“namespace”:“ckad-job”,“resourceVersion”:“2009”,“uid”:“0242d4d8-21e1-4bd3-9aba-c250a1f89188”}],“lastScheduleTime”:“2024-05-06T02:44:00Z”,“lastSuccessfulTime”:“2024-05-06T02:43:05Z”}}
    creationTimestamp: “2024-05-06T02:44:46Z”
    generation: 1
    name: simple-python-job
    namespace: ckad-job
    resourceVersion: “5423”
    uid: 3dccc20c-ff3f-4df4-8b20-8fb753b88844
    spec:
    concurrencyPolicy: Allow
    failedJobsHistoryLimit: 1
    jobTemplate:
    metadata:
    creationTimestamp: null
    name: simple-python-job
    spec:
    template:
    metadata:
    creationTimestamp: null
    spec:
    containers:
    - args:
    - -c
    - ps -eaf
    command:
    - /bin/sh
    image: python
    imagePullPolicy: Always
    name: simple-python-job
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    dnsPolicy: ClusterFirst
    restartPolicy: OnFailure
    schedulerName: default-scheduler
    securityContext: {}
    terminationGracePeriodSeconds: 30
    schedule: '    /30 * * * *’
    successfulJobsHistoryLimit: 3
    suspend: false
    status:
    lastScheduleTime: “2024-05-06T04:00:00Z”
    lastSuccessfulTime: “2024-05-06T04:00:35Z”
    kind: List
    metadata:
    resourceVersion: “”
    selfLink: “”

I crossed checked

student-node ~ ➜ k get pods -n ckad-job
NAME READY STATUS RESTARTS AGE
simple-python-job-28582740-4h22z 0/1 Completed 0 84m
simple-python-job-28582770-8qb5x 0/1 Completed 0 54m
simple-python-job-28582800-p4p6b 0/1 Completed 0 24m

student-node ~ ➜ k logs -f simple-python-job-28582800-p4p6b -n ckad-job
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 04:00 ? 00:00:00 /bin/sh -c ps -eaf
root 57 1 0 04:00 ? 00:00:00 ps -eaf

but this is wrong in while check
this solution by kodekloud
Create a YAML file with the content as below:

apiVersion: batch/v1
kind: CronJob
metadata:
  name: simple-python-job
  namespace: ckad-job
spec:
  schedule: "*/30 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: simple-python-job
            image: python
            imagePullPolicy: IfNotPresent
            command:
            - /bin/sh
            - -c
            - ps -eaf
          restartPolicy: OnFailure

Then use kubectl apply -f file_name.yaml to create the required object.

failed with this

Screenshot 2024-05-06 at 10.03.08 AM
Screenshot 2024-05-06 at 10.03.08 AM1340×672 55.5 KB

I’m not sure what’s missing or if there’s something wrong with my approach.
or the checker is not checking properly

#2

Your code is kind of a mess –

use code blocks:
  - so we
  - can read things

but I think the problem is that you are using both args and command. You don’t need to do this, and I think that this is why the grader is getting confused. Just do

            command:
            - /bin/sh
            - -c
            - ps -eaf

instead.

#3

but this is same thing
also endgoal is same

#4

Still, you don’t need to use both. I’m guessing that the grader makes a choice and is testing the content of the command block.

#5

but if we use both or not
at the end command is executed
/bin/sh -c "ps -eaf"

@mmumshad can you please take a look to this
Thanks

#6

I found your question in the CKAD Ultimate Mock Exams (Design #11/22). The key thing here is how the question is worded.

In the ckad-job namespace, create a cronjob named simple-python-job to run every 30 minutes to list all the running processes inside a container that used python image (the command needs to be run in a shell).

When you are working a problem like this one, you need to look for clues like this. Here they say you need to run a command – so this typically means that you need to use a command block.

The easiest way to get a valid cronjob is to use the imperative command k create cronjob. I tried this version of it, looking up the syntax with k create cj --help:

k -n ckad-job create cj simple-python-job --image python --schedule '*/30 * * * *'  --dry-run=client -o yaml -- sh -c "ps -eaf" > cj.yaml

This gives me something that looks pretty plausible:

student-node ~ ➜  cat cj.yaml 
apiVersion: batch/v1
kind: CronJob
metadata:
  creationTimestamp: null
  name: simple-python-job
  namespace: ckad-job
spec:
  jobTemplate:
    metadata:
      creationTimestamp: null
      name: simple-python-job
    spec:
      template:
        metadata:
          creationTimestamp: null
        spec:
          containers:
          - command:
            - sh
            - -c
            - ps -eaf
            image: python
            name: simple-python-job
            resources: {}
          restartPolicy: OnFailure
  schedule: '*/30 * * * *'
status: {}

When I press End Exam, this passes. It’s a little different than the version posted in the exam – I have sh, the standard solution has /bin/sh – but the grader still likes my answer. Notice that the imperative command automatically used a command block as well. This is standard; if you tried using both command and args in a real exam, the odds are good that you would not get full score.

Issues with CKAD Mock Exam Grading on KodeKloud