LCA Process Management & System Services 3

Question 1

Which command provides a dynamic, real-time, auto-refreshing view of system processes sorted by resource usage?

Accepted Answer

top

Answer

top displays an interactive and continuously updated view of processes, memory, and CPU usage, refreshing every few seconds by default.

Question 2

How does 'systemctl mask nginx' differ from 'systemctl disable nginx'?

Accepted Answer

It prevents the service from being started by any means, including manually or as a dependency

Answer

Masking creates a symlink from the unit file to /dev/null, completely blocking all start attempts whether manual, automatic, or as a dependency.

Question 3

What happens when you append an ampersand (&) to a shell command such as 'long-script.sh &'?

Accepted Answer

The command runs in the background, freeing the terminal for other commands

Answer

Appending & runs the command as a background job, returning control to the shell immediately while the process continues running.

Question 4

What is the primary purpose of the 'at' command in Linux?

Accepted Answer

To schedule a one-time command to execute at a specified future time

Answer

The at command schedules a command or script to run exactly once at a specified future time, which distinguishes it from cron's recurring scheduling.

Question 5

Which signal cannot be caught, blocked, or ignored by any process, including processes running as root?

Accepted Answer

SIGKILL (9)

Answer

SIGKILL is handled entirely by the kernel and bypasses any signal handlers registered by the process, guaranteeing termination.

(LCA) Certified Linux Administrator Practice Test