LFCS Networking Practice Question
A system administrator runs 'ss -tuln' and sees that port 80 is listening. What does the 'u' option represent?
⚠ Common exam trap
It's easy for candidates to confuse `-u` with 'Unix sockets' (which is `-x`) or 'User' (which is `-p`), because the letter 'u' is commonly associated with 'Unix' or 'user' in other commands, but in `ss` it specifically means UDP.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
UDP
In the `ss` command, the `-u` option filters output to show only UDP sockets. Since the question shows `ss -tuln`, which combines `-t` (TCP), `-u` (UDP), `-l` (listening), and `-n` (numeric), the `u` specifically represents UDP. This is confirmed by the `ss` man page and standard Linux networking tools.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
User
Why it's wrong here
There is no -u for user.
- ✗
Unix sockets
Why it's wrong here
Unix sockets are shown with -x.
- ✓
UDP
Why this is correct
The -u option filters for UDP sockets.
- ✗
Unicast
Why it's wrong here
Unicast is not a socket type; -u is for UDP.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.