LFCS Service Configuration Practice Question
An administrator is creating a systemd timer unit called backup.timer that should trigger backup.service every day at 2:00 AM. The timer should also run the service immediately if the system was powered off at 2:00 AM. Which timer directives are required to achieve this?
⚠ Common exam trap
The trap here is using OnCalendar=daily thinking it means 2:00 AM, or forgetting that Persistent=true is needed for catch-up after downtime.
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
✓
OnCalendar=*-*-* 02:00:00 and Persistent=true
The correct directives are OnCalendar with a full calendar specification for 2:00 AM daily and Persistent=true to handle missed runs. OnCalendar=*-*-* 02:00:00 sets the exact time, and Persistent=true stores the last trigger time on disk, so if the system was off, the timer fires immediately on next boot. Other options either set wrong times or lack persistence.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
OnCalendar=*-*-* 02:00:00 and Persistent=true
Why this is correct
OnCalendar=*-*-* 02:00:00 schedules the timer to trigger daily at 2:00 AM. Persistent=true ensures that if the system was off at the scheduled time, the service runs immediately upon boot. Together, these directives satisfy both the daily schedule and the catch-up requirement. They are placed in the [Timer] section of the timer unit.
- ✗
OnBootSec=2h and OnUnitActiveSec=1d
Why it's wrong here
OnBootSec=2h triggers the service 2 hours after boot, not at 2:00 AM. OnUnitActiveSec=1d schedules subsequent runs 1 day after the service was last activated, which is not aligned with a specific clock time. This does not meet the daily 2:00 AM requirement, and there is no persistence for missed runs.
- ✗
OnCalendar=02:00 and Persistent=false
Why it's wrong here
OnCalendar=02:00 is an invalid calendar specification because it lacks date components; systemd requires a full calendar event. Even if corrected, Persistent=false would not run the service if the system was off at the scheduled time. Thus, it fails both the correct syntax and the catch-up requirement.
- ✗
OnCalendar=daily and AccuracySec=1h
Why it's wrong here
OnCalendar=daily triggers once a day at midnight, not at 2:00 AM. AccuracySec=1h allows the timer to fire within an hour of the scheduled time, which does not guarantee 2:00 AM. Also, neither directive provides catch-up behavior if the system was off. Thus, it fails the specific time and persistence requirements.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Linux Foundation exam blueprint
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