CKA Workloads and Scheduling Practice Question
Which CronJob schedule expression runs a job every day at midnight (00:00)?
⚠ Common exam trap
Watch out — candidates often confuse the minute and hour fields: candidates often pick Option A ('0 * * * *') thinking it means 'once per day' because they misread the first zero as 'daily', but it actually runs every hour at minute 0.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
0 0 * * *
The CronJob schedule expression '0 0 * * *' specifies minute 0, hour 0 (midnight), every day of the month, every month, and every day of the week. This matches the requirement to run a job daily at 00:00.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
0 * * * *
Why it's wrong here
This expression triggers the CronJob at the start of every hour (minute 0) of every day. Because the hour field is set to a wildcard asterisk, it executes 24 times a day rather than only once at midnight. To target midnight specifically, the hour field must be constrained to 0.
- ✗
0 0 1 * *
Why it's wrong here
This schedule restricts execution to midnight (00:00) but only on the first day of each month due to the third field being set to 1. It fails to meet the requirement of running daily because it skips all other days of the month. For a daily execution, the day-of-month field must be a wildcard.
- ✓
0 0 * * *
Why this is correct
This is the correct configuration because it explicitly targets minute 0 and hour 0 (midnight) while using wildcards for the day of the month, month, and day of the week. This ensures the job runs exactly once every single day of the year. It perfectly matches the standard crontab format used by Kubernetes CronJobs.
- ✗
* 0 * * *
Why it's wrong here
This expression uses a wildcard in the minute field, which causes the CronJob to trigger every single minute during the midnight hour (from 00:00 to 00:59). This results in 60 executions daily instead of a single run at midnight. To run only once, the minute field must be locked to a specific value like 0.
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Written by Johnson Ajibi, MSc IT Security
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