You want a systemd timer to run a backup service every day at 3:30 AM but only if the system was off at that time. Which timer configuration achieves this?

hard📝 Application Q15 of 15

Linux CLI - Cron and Scheduling

A[Timer] OnActiveSec=03:30:00 Persistent=true

B[Timer] OnCalendar=*-*-* 03:30:00 AccuracySec=1min

C[Timer] OnCalendar=*-*-* 03:30:00 Persistent=true

D[Timer] OnBootSec=03:30:00 Persistent=false

Step-by-Step Solution

Solution:

Step 1: Identify daily schedule at 3:30 AM
The OnCalendar=*-*-* 03:30:00 sets the timer to run daily at 3:30 AM.
Step 2: Ensure missed runs execute after downtime
Persistent=true makes systemd run missed jobs after system was off at scheduled time.
Step 3: Evaluate other options
AccuracySec adjusts timing precision but doesn't affect missed runs; OnBootSec and OnActiveSec run relative to boot or activation, not fixed time.
Final Answer:
[Timer] OnCalendar=*-*-* 03:30:00 Persistent=true -> Option C
Quick Check:
Daily 3:30 AM with catch-up = OnCalendar + Persistent [OK]

Quick Trick: Use OnCalendar with Persistent=true for daily missed runs [OK]

Common Mistakes:

Using OnBootSec instead of OnCalendar for fixed time
Forgetting Persistent=true to run missed jobs
Confusing AccuracySec with scheduling behavior

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You want a systemd timer to run a backup service every day at 3:30 AM but only if the system was off at that time. Which timer configuration achieves this?

Step 1: Identify daily schedule at 3:30 AM

Step 2: Ensure missed runs execute after downtime

Step 3: Evaluate other options

Final Answer:

Quick Check:

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