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XK0-006 Practice Question: A Linux system experiences high CPU usage from a…
A Linux system experiences high CPU usage from a process that appears to be a fork bomb. The administrator wants to prevent such attacks in the future by limiting the number of processes a user can create. Which configuration file should be modified, and what parameter should be set?
⚠ Common exam trap
CompTIA often tests the distinction between system-wide PID limits (kernel.pid_max) and per-user process limits (nproc), and candidates mistakenly choose A because they confuse maximum PID number with maximum number of processes.
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
✓
Add 'username hard nproc 100' in /etc/security/limits.conf
/etc/security/limits.conf is the PAM-based configuration file used to set per-user resource limits via the 'nproc' parameter. Adding 'username hard nproc 100' enforces a hard limit of 100 processes for that user, preventing a fork bomb from exhausting system resources.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set 'kernel.pid_max=100' in /etc/sysctl.conf
Why it's wrong here
Limits total PIDs system-wide, not per user.
- ✗
Set 'DefaultLimitNPROC=100' in /etc/systemd/system.conf
Why it's wrong here
This limits systemd services, not all user processes.
- ✓
Add 'username hard nproc 100' in /etc/security/limits.conf
Why this is correct
Correctly limits the number of processes for a user via PAM.
- ✗
Add 'ulimit -u 100' to /etc/profile
Why it's wrong here
ulimit in profile is not persistent for all sessions and can be bypassed.
Go deeper
Related to this question
Learn chapter
Linux Fundamentals and History
Key term
User
A user is any person, system, or device that interacts with an IT service, resource, or identity system, typically authenticated through credentials and authorized to perform specific actions.
Key term
Process
In IT service management, a process is a structured set of activities designed to accomplish a specific objective, such as managing incidents or changes, by transforming inputs into defined outputs.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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