Quick Answer
The answer is that the script requires environment variables not set in cron's shell. This is the most likely cause because cron executes jobs in a non-interactive, minimal shell environment—typically /bin/sh—with only a few default variables like LOGNAME and SHELL. Unlike a manual root shell, which inherits a full user profile with PATH, HOME, and any custom variables, cron’s stripped-down environment lacks these, so a script relying on specific paths or variable values will fail silently. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of how cron’s execution context differs from an interactive session; a common trap is assuming root’s cron inherits root’s full environment. Remember the mnemonic “Cron is a minimalist”—it only gives what it must, so always export needed variables or source a profile inside the script.
This XK0-005 practice question tests your understanding of scripting, containers and automation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 Linux engineer is troubleshooting a cron job that does not execute as expected. The crontab entry reads: '*/5 * * * * /usr/local/bin/backup.sh'. The script runs manually when executed as root. Which of the following 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.
The cron daemon is not running.
Why wrong: If daemon not running, no job runs.
The script file does not have execute permissions.
Why wrong: Would fail even manually if missing.
The system clock is incorrect.
Why wrong: Would affect timing but not execution.
The script requires environment variables that are not set in cron's shell.
Common issue: cron has limited PATH and env.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The script requires environment variables that are not set in cron's shell.
D is correct because cron jobs run in a minimal shell environment (typically /bin/sh) with a very limited set of environment variables. The script /usr/local/bin/backup.sh may rely on variables like PATH, HOME, or custom variables that are not set in cron's shell, causing it to fail even though it runs fine manually as root. This is a classic cron issue where the interactive shell's environment differs from cron's non-interactive environment.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The cron daemon is not running.
Why it's wrong here
If daemon not running, no job runs.
The script file does not have execute permissions.
Why it's wrong here
Would fail even manually if missing.
The system clock is incorrect.
Why it's wrong here
Would affect timing but not execution.
The script requires environment variables that are not set in cron's shell.
Why this is correct
Common issue: cron has limited PATH and env.
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.
Common exam traps
CompTIA often tests the misconception that a script failing in cron is due to permissions or the cron daemon status, when the real issue is the stripped-down environment that lacks variables the script depends on.
Detailed technical explanation
Cron executes jobs using /bin/sh with a minimal environment that typically only sets LOGNAME, HOME, and SHELL. The PATH variable in cron's shell is often just '/usr/bin:/bin', so if the script calls commands like 'rsync' or 'tar' without full paths, they may not be found. This is why best practices recommend using absolute paths in cron scripts or sourcing a profile file (e.g., .bash_profile) at the start of the script.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — Read the scenario before looking for a memorised answer..
The correct answer is: The script requires environment variables that are not set in cron's shell. — D is correct because cron jobs run in a minimal shell environment (typically /bin/sh) with a very limited set of environment variables. The script /usr/local/bin/backup.sh may rely on variables like PATH, HOME, or custom variables that are not set in cron's shell, causing it to fail even though it runs fine manually as root. This is a classic cron issue where the interactive shell's environment differs from cron's non-interactive environment.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This XK0-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the XK0-005 exam.
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