Server operations · Lesson 35 of 36 · 8 minutes

Scheduled service evidence

Relate a user schedule to cron service state and log entries.

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learner@clairos:~ $

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Your objectives

Hints are always available. Wrong turns never cost XP.

1
Read the learner schedule
Run crontab -l.
Hint & worked example
Inspect the simulated user schedule. No task is scheduled outside the browser.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
crontab -l
```
Remember: A scheduled entry is not proof that its last run succeeded.
2
Check the cron service
Run systemctl status cron.
Hint & worked example
Inspect or change a simulated systemd service. Status, active state, and unit configuration reveal different evidence.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
systemctl status cron
```
Remember: A service can be active while an application endpoint is unhealthy; verify both layers.
3
Find scheduled-run evidence
Run grep CRON /var/log/cron.log.
Hint & worked example
Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
grep CRON /var/log/cron.log
```
Remember: No matches is exit status 1, which is different from a malformed invocation.

Understand the pattern

Triangulating scheduled work from configuration and runtime evidence helps operators explain what they know before they change anything.

crontab: Inspect the simulated user schedule. No task is scheduled outside the browser.
A scheduled entry is not proof that its last run succeeded.
systemctl: Inspect or change a simulated systemd service. Status, active state, and unit configuration reveal different evidence.
A service can be active while an application endpoint is unhealthy; verify both layers.
grep: Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
No matches is exit status 1, which is different from a malformed invocation.

Worked example and expected result

$ crontab -l

# learner training crontab
*/15 * * * * /home/learner/scripts/health-check.sh

Exit status: 0. The command completed successfully in the training fixture.

$ systemctl status cron

cron.service - simulated cron
   Loaded: loaded
   Active: active
   Notes: running scheduled simulated maintenance

Exit status: 0. The command completed successfully in the training fixture.

$ grep CRON /var/log/cron.log

May 26 08:00:00 clairos-learn CRON[126]: health-check.sh completed
May 26 08:15:00 clairos-learn CRON[126]: health-check.sh completed

Exit status: 0. The command completed successfully in the training fixture.

Try a variation

Repeat this workflow in the sandbox with a different scratch filename. Keep the system fixtures unchanged and compare the observed output with your expectation before moving on.

Explain it

In “Scheduled service evidence”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.A service can be active while an application endpoint is unhealthy; verify both layers.

Apply it elsewhere

Before adapting the systemctl workflow from “Scheduled service evidence” to another server, what should you do?Skip output inspection whenever the command is familiar.Confirm the current directory, target identity, permissions, and the installed command behavior first.Paste the training paths unchanged into production.

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Server operations bridge Try an incident drill

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