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

ps aux

Answer

pstree -d

Answer

procmon

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

It stops the service immediately and removes its config

Answer

It only prevents automatic startup but still allows manual start

Answer

It pauses the service without stopping it completely

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

The command runs with elevated root privileges

Answer

The command output is redirected to /dev/null automatically

Answer

The command runs in an isolated subshell environment

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

To schedule a recurring job using cron syntax

Answer

To measure the total execution time of a process

Answer

To attach an interactive terminal to a running background process

Question 5

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

Accepted Answer

SIGKILL (9)

Answer

SIGTERM (15)

Answer

SIGHUP (1)

Answer

SIGINT (2)

Question 6

What does the 'fuser' command identify when run against a specific file or device?

Accepted Answer

The PIDs of processes that currently have the file or device open

Answer

The user who owns the file or device

Answer

All files that a specific user has opened

Answer

The filesystem type of the specified device

Question 7

Which command lists all cron jobs configured for a specific user named 'webadmin'?

Accepted Answer

crontab -u webadmin -l

Answer

crontab -l webadmin

Answer

cat /etc/cron.d/webadmin

Answer

crontab --user webadmin --list