A task planned via systemd does not run at the expected time.
Probable causes
- timer 1993.
- OnCalendar.
- service.
Verifications.
- Limit the impact. — Identify whether an endpoint, service, or whole site is affected.
- Collect evidence. — Keep the exact error message, timestamp, and associated logs.
- Test the simplest hypothesis first. — Compare the affected system with a known-good path.
- Correct the confirmed cause and validate the result. — Apply one controlled change at a time and retest.
Commands
systemctl list-timers --allSolutions.
- Correct the confirmed cause rather than the symptom.
- Document the change and its result.
- Establish monitoring if the fault can recur.
When to escalate?
Escalate if the impact expands, data are at risk, or remediation requires an irreversible change.
systemd timer focus
A timer can be enabled yet still fail to launch its service because the schedule, unit relationship or service execution fails. Troubleshoot the timer unit and the triggered service as two connected but separate components.
What to verify
- List timers and inspect the previous and next activation times for the affected unit.
- Check the timer definition, OnCalendar expression, Persistent behavior and the Unit value it triggers.
- Review the service status and journal at the expected execution time; a timer activation can succeed while the service immediately fails.
- Confirm system time, timezone and any user-versus-system unit context.
Resolution path
Correct the schedule or service dependency, reload systemd when unit files changed, then restart or re-enable the timer as appropriate. Avoid manually running only the command and assuming the timer path is fixed.
Validation
Trigger a controlled test and confirm both the timer activation and successful service completion in the journal.