The answer is ss -tlnp and netstat -tlnp, as both commands with the flags -t (TCP), -l (listening), -n (numeric), and -p (process) will list all listening TCP ports and their associated processes. This works because netstat reads /proc/net/tcp and /proc/*/fd to map sockets to PIDs, while ss uses kernel netlink interfaces for faster, more reliable output, making ss the modern replacement on many distributions. On the LPIC-2 exam, this tests your ability to troubleshoot network services and identify which daemon is bound to a specific port, a common scenario in system administration. A frequent trap is forgetting the -p flag, which omits process info, or using -a instead of -l, which shows all connections rather than just listeners. For a memory tip, think “TCP Listening Numeric Processes” to recall the -tlnp flags, and remember that ss is the newer, preferred tool, but netstat still appears on legacy systems.
LPIC-2 System Security Practice Question
This LPIC-2 practice question tests your understanding of system security. 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 commands can be used to list all currently listening TCP ports and the associated processes?
Why wrong: This also works but is not as standard as ss/netstat on minimal systems; however, the question asks for TWO, and ss/netstat are the most common.
B
ss -tlnp
ss -tlnp shows listening TCP ports with process info.
C
netstat -tlnp
netstat -tlnp also shows listening TCP ports with process info.
D
fuser -v 80/tcp
Why wrong: fuser shows processes using a specific port, not all ports.
E
nmap -sT localhost
Why wrong: nmap scans ports but does not show local process info.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ss -tlnp
Option B (ss -tlnp) is correct because the ss command with -t (TCP), -l (listening), -n (numeric), and -p (process) shows all listening TCP ports and their associated processes. Option C (netstat -tlnp) is correct because netstat with the same flags provides equivalent output, though ss is the modern replacement on many distributions.
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.
✗
lsof -i TCP -s TCP:LISTEN
Why it's wrong here
This also works but is not as standard as ss/netstat on minimal systems; however, the question asks for TWO, and ss/netstat are the most common.
✓
ss -tlnp
Why this is correct
ss -tlnp shows listening TCP ports with process info.
Related concept
Read the scenario before looking for a memorised answer.
✓
netstat -tlnp
Why this is correct
netstat -tlnp also shows listening TCP ports with process info.
Related concept
Read the scenario before looking for a memorised answer.
✗
fuser -v 80/tcp
Why it's wrong here
fuser shows processes using a specific port, not all ports.
✗
nmap -sT localhost
Why it's wrong here
nmap scans ports but does not show local process info.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think lsof or nmap are valid for listing all listening ports with processes, but lsof requires specific syntax and does not natively filter by listening state without extra flags, while nmap is an active scanner, not a passive listener display tool.
Trap categories for this question
Command / output trap
fuser shows processes using a specific port, not all ports.
Detailed technical explanation
How to think about this question
Under the hood, both ss and netstat read kernel data structures (e.g., /proc/net/tcp and /proc/net/tcp6) to display socket information; ss uses the netlink interface for faster and more detailed output, while netstat is legacy but still widely available. In real-world scenarios, ss is preferred on modern systems for performance and accuracy, especially when dealing with many connections, as it avoids parsing /proc files. The -p flag requires root privileges to show process names, which is a common oversight in exam scenarios.
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 LPIC-2 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.
System Security — This question tests System Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ss -tlnp — Option B (ss -tlnp) is correct because the ss command with -t (TCP), -l (listening), -n (numeric), and -p (process) shows all listening TCP ports and their associated processes. Option C (netstat -tlnp) is correct because netstat with the same flags provides equivalent output, though ss is the modern replacement on many distributions.
What should I do if I get this LPIC-2 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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