The correct approach is to use the CRON_TZ variable in the crontab file to specify EST and schedule the job at 3:00 AM. This works because the CRON_TZ variable overrides the system’s default time zone for that specific crontab, allowing the cron daemon to interpret the schedule entries in the specified time zone rather than the system’s UTC setting. On the LFCS exam, this tests your understanding of how cron handles time zone awareness, often appearing as a trap where candidates mistakenly adjust the system time zone or use TZ in the script itself, which would not persist across system time zone changes. The key is that CRON_TZ is set at the top of the crontab file and applies to all subsequent entries, ensuring the job runs at 3:00 AM EST regardless of system shifts. Memory tip: Think of CRON_TZ as the “local override” for cron—set it once, and your schedule stays anchored to your time zone.
LFCS Operation of Running Systems Practice Question
This LFCS practice question tests your understanding of operation of running systems. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator needs to schedule a cron job that runs a script every day at 3:00 AM, but the system is in a different time zone (UTC) than the administrator's local time (EST). The administrator wants the job to run at 3:00 AM local time regardless of system time zone changes. What is the best approach?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the CRON_TZ variable in the crontab file to specify EST and schedule at 3:00 AM
Option B is correct because the CRON_TZ variable, when set in a crontab file, allows you to specify a time zone for the cron daemon to interpret the schedule entries. This ensures the job runs at 3:00 AM EST regardless of the system's default time zone (UTC), and it persists even if the system time zone changes, as cron uses the variable for scheduling.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Change the system time zone to EST and set the cron job to run at 3:00 AM
Why it's wrong here
Changing the system time zone affects all applications and may not be desirable.
✓
Use the CRON_TZ variable in the crontab file to specify EST and schedule at 3:00 AM
Why this is correct
CRON_TZ sets the time zone for subsequent cron jobs in the file.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Set the TZ environment variable in the crontab file before the job definition
Why it's wrong here
cron daemon does not evaluate TZ in the crontab file; it uses system time zone.
✗
Calculate the UTC equivalent (8:00 AM UTC) and schedule the job at that time
Why it's wrong here
If the system time zone changes, the job will run at the wrong local time.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the TZ environment variable (which affects the job's runtime environment) with the CRON_TZ variable (which affects cron's scheduling logic), leading them to incorrectly select option C.
Detailed technical explanation
How to think about this question
The cron daemon (typically cronie or vixie-cron) reads the CRON_TZ variable from the crontab file to determine the time zone for interpreting the schedule fields. This is implemented by converting the specified times to UTC internally before storing them, making the schedule independent of the system's /etc/localtime. In real-world scenarios, this is critical for servers that span multiple time zones or for administrators who need to maintain consistent local-time schedules across systems with different or changing time zones.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use the CRON_TZ variable in the crontab file to specify EST and schedule at 3:00 AM — Option B is correct because the CRON_TZ variable, when set in a crontab file, allows you to specify a time zone for the cron daemon to interpret the schedule entries. This ensures the job runs at 3:00 AM EST regardless of the system's default time zone (UTC), and it persists even if the system time zone changes, as cron uses the variable for scheduling.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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