The answer is the `After=` directive. This is correct because `After=` in a systemd unit file specifies ordering constraints without creating a hard dependency, meaning `myapp.service` will only begin its startup sequence after `network.target` and `postgresql.service` have both reached the active state. On the Linux Foundation Certified System Administrator LFCS exam, this tests your understanding of systemd’s dependency and ordering system—a common trap is confusing `After=` with `Requires=`, which would force those units to start but not guarantee order. Remember, `After=` controls the sequence, not the necessity. A useful memory tip: think of `After=` as the polite “you go first” hand gesture, while `Requires=` is the “I need you here” command.
LFCS Service Configuration Practice Question
This LFCS practice question tests your understanding of service configuration. 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 wants to ensure that a custom service (myapp.service) starts only after the network is available and the PostgreSQL database service is running. Which systemd unit file directive should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
After=network.target postgresql.service
Option D is correct because the `After=` directive in a systemd unit file specifies ordering constraints, ensuring that `myapp.service` starts only after `network.target` and `postgresql.service` have reached the 'started' state. This does not create a dependency that forces those units to start; it only orders the startup sequence, which is exactly what the administrator needs to guarantee the service starts after the network and PostgreSQL are available.
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.
✗
Requires=network.target postgresql.service
Why it's wrong here
Requires= creates a dependency but does not guarantee start order; After= is needed.
✗
Wants=network.target postgresql.service
Why it's wrong here
Wants= is a weaker dependency, but still no ordering.
✗
BindsTo=network.target postgresql.service
Why it's wrong here
BindsTo= binds the service lifecycle to the listed units, but does not specify ordering.
✓
After=network.target postgresql.service
Why this is correct
After= ensures myapp starts after the listed units are active, combined with Wants= or Requires= for dependency.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ordering directives (`After=`, `Before=`) with dependency directives (`Requires=`, `Wants=`, `BindsTo=`), and assume that `Requires=` or `Wants=` automatically imply ordering, which they do not without an explicit `After=` or `Before=`.
Detailed technical explanation
How to think about this question
Under the hood, systemd processes `After=` by recording the dependency in the unit's dependency graph and ensuring that the unit's activation job is not started until all listed units have completed their activation. A common real-world scenario is when a web application depends on a database; using `After=postgresql.service` combined with `Requires=postgresql.service` ensures both ordering and a hard dependency, but the question specifically asks only for ordering, making `After=` the precise choice. Note that `After=` does not pull in the listed units; if they are not already enabled or started, `myapp.service` will wait indefinitely, so in practice administrators often pair `After=` with `Wants=` or `Requires=`.
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.
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: After=network.target postgresql.service — Option D is correct because the `After=` directive in a systemd unit file specifies ordering constraints, ensuring that `myapp.service` starts only after `network.target` and `postgresql.service` have reached the 'started' state. This does not create a dependency that forces those units to start; it only orders the startup sequence, which is exactly what the administrator needs to guarantee the service starts after the network and PostgreSQL are available.
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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