This LFCS practice question tests your understanding of service configuration. 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 custom systemd service unit file has been created but the service fails to start with 'Exec format error'. What 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
✓
The ExecStart command path is incorrect or missing shebang
The 'Exec format error' in systemd indicates that the binary or script specified in the ExecStart directive cannot be executed, typically because the path is incorrect, the file is not executable, or (most commonly) the script lacks a valid shebang line (e.g., #!/bin/bash). Without a shebang, the kernel does not know which interpreter to use, causing an execve() failure.
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 unit file has incorrect permissions
Why it's wrong here
Permissions on the unit file do not affect execution format.
✗
The user does not have permission to start the service
Why it's wrong here
Permission errors show 'permission denied', not exec format.
✗
The service is disabled
Why it's wrong here
Disabling affects boot start, not execution.
✓
The ExecStart command path is incorrect or missing shebang
Why this is correct
An invalid executable or missing interpreter causes exec format error.
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
Common exam trap: answer the scenario, not the keyword
Linux Foundation often tests the distinction between 'Exec format error' and other startup failures, trapping candidates who confuse permission issues (chmod +x) with the missing shebang requirement for interpreted scripts.
Trap categories for this question
Command / output trap
Permission errors show 'permission denied', not exec format.
Detailed technical explanation
How to think about this question
Under the hood, systemd uses execve() to launch the ExecStart command; if the file lacks a valid shebang or is not a recognized ELF binary, the kernel returns ENOEXEC (Exec format error). This is distinct from a missing file (ENOENT) or permission issues (EACCES). A common real-world scenario is writing a shell script without #!/bin/bash and forgetting to set the executable bit, but the shebang is the primary culprit for this specific error.
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.
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.
Service Configuration — This question tests Service Configuration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ExecStart command path is incorrect or missing shebang — The 'Exec format error' in systemd indicates that the binary or script specified in the ExecStart directive cannot be executed, typically because the path is incorrect, the file is not executable, or (most commonly) the script lacks a valid shebang line (e.g., #!/bin/bash). Without a shebang, the kernel does not know which interpreter to use, causing an execve() failure.
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: "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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This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
Question Discussion
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