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 service requires read-write access to a specific directory that is mounted from an NFS share. The directory is mounted via fstab with the option 'noauto'. The service starts before the mount is available. Which configuration change should be made in the service unit file to ensure the service only starts after the mount is mounted?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add After=mnt-nfs.mount and Requires=mnt-nfs.mount
Option A is correct because the service requires the NFS mount to be available before it starts. The `After=mnt-nfs.mount` directive ensures the service unit is ordered after the mount unit, and `Requires=mnt-nfs.mount` makes the mount a hard dependency: if the mount fails or is not active, the service will not start. This combination is necessary because the mount is defined with `noauto` in fstab, meaning it is not automatically mounted at boot; the mount unit must be explicitly started (e.g., by a dependency or another unit) before the service.
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.
✓
Add After=mnt-nfs.mount and Requires=mnt-nfs.mount
Why this is correct
This ensures the service starts after the mount and fails if the mount fails.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add Before=mnt-nfs.mount and Requires=mnt-nfs.mount
Why it's wrong here
Before would cause the service to start before the mount, which is the opposite of what is needed.
✗
Add Wants=mnt-nfs.mount and After=mnt-nfs.mount
Why it's wrong here
Wants is a soft dependency; the service can still start even if the mount fails.
✗
Add After=mnt-nfs.mount and BindsTo=mnt-nfs.mount
Why it's wrong here
BindsTo makes the service tightly bound; if the mount stops, the service stops, which may be undesirable.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse `Wants` with `Requires` or forget that `After` alone does not activate the mount unit, leading them to choose option C or D, which either provide weak dependencies or incorrect ordering.
Detailed technical explanation
How to think about this question
In systemd, mount units are automatically generated from fstab entries, but `noauto` prevents automatic activation at boot. The `Requires=` directive creates a hard dependency that activates the mount unit if it is not already active, while `After=` ensures proper ordering. Without `Requires`, the service could start before the mount unit is triggered, leading to a failure when the service tries to access the directory. This is a common pattern for services that depend on network filesystems like NFS, where the mount may not be available at boot time.
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: Add After=mnt-nfs.mount and Requires=mnt-nfs.mount — Option A is correct because the service requires the NFS mount to be available before it starts. The `After=mnt-nfs.mount` directive ensures the service unit is ordered after the mount unit, and `Requires=mnt-nfs.mount` makes the mount a hard dependency: if the mount fails or is not active, the service will not start. This combination is necessary because the mount is defined with `noauto` in fstab, meaning it is not automatically mounted at boot; the mount unit must be explicitly started (e.g., by a dependency or another unit) before the service.
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.
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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