The answer is a missing or unset MAILTO variable in the crontab. When a cron job produces output, cron normally sends that output via email to the job’s owner, but the MAILTO variable overrides this default by specifying an explicit recipient address. If MAILTO is not defined, cron falls back to mailing the crontab’s owner, which means an administrator expecting notifications at a different address will see no email at all. On the CompTIA Linux+ XK0-005 exam, this question tests your understanding of cron’s default behavior versus explicit configuration—a common trap is assuming cron always sends output to root or a system mailbox, when in fact it follows the crontab owner unless MAILTO redirects it. Remember the mnemonic: “No MAILTO? Mail goes to the owner, not the operator.”
XK0-005 Scripting, Containers and Automation Practice Question
This XK0-005 practice question tests your understanding of scripting, containers and automation. 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.
A cron job runs a script that produces output, but the administrator does not receive the expected email notification. Which is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MAILTO variable is not set in the crontab.
The MAILTO variable in a crontab specifies the email address to which cron sends the output (stdout/stderr) of a job. If MAILTO is not set, cron defaults to mailing output to the owner of the crontab (the user who created it). However, if the administrator expects notifications at a different address, the missing MAILTO variable would prevent that specific email from being sent. This is the most direct cause of not receiving the expected email notification.
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.
✗
The script uses absolute paths for all commands.
Why it's wrong here
Using absolute paths is good practice and does not prevent email delivery.
✓
MAILTO variable is not set in the crontab.
Why this is correct
Cron only sends output to the address specified in MAILTO; if not set, output is lost.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The PATH environment variable is not set.
Why it's wrong here
Missing PATH could cause commands within the script to fail, but any error output would still be e-mailed if MAILTO is set.
✗
The script is not executable.
Why it's wrong here
If the script were not executable, it would not run at all; the cron job would produce an error instead of output.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between variables that affect script execution (PATH) versus those that control cron's mail behavior (MAILTO), leading candidates to mistakenly choose PATH or executable permissions when the issue is specifically about email delivery.
Trap categories for this question
Command / output trap
Missing PATH could cause commands within the script to fail, but any error output would still be e-mailed if MAILTO is set.
Detailed technical explanation
How to think about this question
Cron uses the local MTA (e.g., sendmail, postfix) to deliver job output. The MAILTO variable overrides the default recipient; if unset, cron uses the crontab owner's local mailbox. A common subtlety is that if MAILTO is set to an empty string (MAILTO=""), cron suppresses all mail output entirely, which could also explain missing notifications. Additionally, cron only sends mail if the job produces output; redirecting output to /dev/null or a log file would also prevent mail.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: MAILTO variable is not set in the crontab. — The MAILTO variable in a crontab specifies the email address to which cron sends the output (stdout/stderr) of a job. If MAILTO is not set, cron defaults to mailing output to the owner of the crontab (the user who created it). However, if the administrator expects notifications at a different address, the missing MAILTO variable would prevent that specific email from being sent. This is the most direct cause of not receiving the expected email notification.
What should I do if I get this XK0-005 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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