How do you schedule a recurring job, and how do you debug one that did not run?
What they are really testing: Whether you know cron and, more importantly, the classic reasons cron jobs fail silently (environment and PATH differ from your shell). That second half separates juniors from operators.
A real interview question
How do you schedule a recurring job, and how do you debug one that did not run?
What most people say
drag me
“I would add it to crontab; if it does not run I would check that the cron syntax is right.”
Syntax is rarely the real problem. The usual culprit, cron running with a stripped-down environment and PATH, is exactly what this question is probing, and the weak answer misses it entirely.
The follow-ups they ask next
The script runs fine when you run it manually but fails under cron. Why?
Almost always environment: cron has a minimal PATH and none of your shell env. Use absolute paths, export the vars it needs, and capture stderr (2>&1) to see the actual error.
How would you run a periodic task in a containerized/cloud setup instead of host cron?
A Kubernetes CronJob, or a cloud scheduler (EventBridge Scheduler/Cloud Scheduler) triggering a job/function, more observable and not tied to one host that might be down.
What the interviewer is listening for
- Knows the 5 cron fields
- Calls out the minimal cron env/PATH
- Redirects output to a log (2>&1)
- Checks cron actually fired
What sinks the answer
- Blames only syntax
- Unaware cron strips the environment
- Uses relative paths
- No output capture
If you genuinely do not know
Say this instead of freezing. Reasoning out loud from what you do know beats silence every single time, and a good interviewer is listening for exactly that.
“I schedule with [crontab -e: 5 time fields + command]. The classic failure is [the minimal cron env/PATH, it does not load your profile], so I [use absolute paths, set env explicitly, redirect output 2>&1 to a log]. To debug a no-run I [confirm cron fired in syslog, then read the job log].”
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