LFCS Operation of Running Systems Practice Question
A system administrator needs to schedule a one-time task that will run at 2:30 AM on July 15. Which command should be used to create this job?
⚠ Common exam trap
Many exam-takers confuse one-time scheduling with recurring jobs; cron is for recurring tasks, while at handles single executions.
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
✓
at 2:30 AM July 15
The at command is specifically designed for scheduling one-time tasks at a precise date and time. Using at 2:30 AM July 15 allows the administrator to queue a command that will execute once at that moment, fulfilling the requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
at 2:30 AM July 15
Why this is correct
The at command schedules a one-time task at a specified time and date. Running at 2:30 AM July 15 enters an interactive prompt where the command can be typed, and it will execute once at that time. This is the correct tool for one-time scheduling.
- ✗
crontab -e
Why it's wrong here
crontab -e opens the user's crontab file for editing, which is used for recurring jobs. While it can schedule a job to run on July 15 at 2:30 AM, it would repeat annually unless removed. It is not designed for one-time execution, so it is not the best choice.
- ✗
systemd-run --on-calendar="*-07-15 02:30:00"
Why it's wrong here
systemd-run with --on-calendar creates a transient timer unit that can schedule tasks, but it is more complex and typically used for recurring events. While it can be configured for a one-time run, it is not the standard or simplest method for a single future execution as described.
- ✗
batch
Why it's wrong here
batch schedules commands to run when system load averages drop below a certain threshold, typically 0.8. It does not accept a specific time or date, so it cannot be used to run a job at 2:30 AM on July 15. It is intended for deferrable, low-priority tasks.
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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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