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.
Which two statements are true about systemd socket activation? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The service unit must include 'Sockets=<socket unit>' to bind the service to the socket.
Option C is correct because the service unit must include a 'Sockets=' directive (e.g., 'Sockets=myapp.socket') to explicitly bind the service to the corresponding socket unit. This tells systemd which socket(s) the service should accept connections from when activated. Without this directive, the service will not receive the file descriptors for the socket, and activation will fail.
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 socket unit file must have an [Install] section.
Why it's wrong here
The socket unit can be enabled but it's not strictly required for activation.
✗
Socket activation requires the service to be of type 'socket'.
Why it's wrong here
The service type is separate; the socket unit handles the socket.
✓
The service unit must include 'Sockets=<socket unit>' to bind the service to the socket.
Why this is correct
This directive links the service to the socket unit.
Related concept
Read the scenario before looking for a memorised answer.
✓
A service can be started on demand when a connection arrives on a socket.
Why this is correct
This is the core feature of socket activation.
Related concept
Read the scenario before looking for a memorised answer.
✗
Socket activation only works with TCP sockets.
Why it's wrong here
It also works with Unix sockets.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the 'Type=' directive in the service unit (e.g., 'Type=socket') with the socket unit's role, leading them to incorrectly select Option B, when in fact the service type is independent of socket activation.
Detailed technical explanation
How to think about this question
Under the hood, systemd socket activation uses the 'sd_listen_fds()' mechanism (part of the sd-daemon protocol) to pass open file descriptors from the socket unit to the service process. The service must be written to accept these file descriptors (e.g., via the LISTEN_FDS environment variable). A real-world scenario is a web server like Apache or Nginx configured with socket activation to start only when a request arrives, reducing resource usage on idle systems.
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: The service unit must include 'Sockets=<socket unit>' to bind the service to the socket. — Option C is correct because the service unit must include a 'Sockets=' directive (e.g., 'Sockets=myapp.socket') to explicitly bind the service to the corresponding socket unit. This tells systemd which socket(s) the service should accept connections from when activated. Without this directive, the service will not receive the file descriptors for the socket, and activation will fail.
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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