Module 11

Question 1

What is a process in an operating system?

Answer 1

A process is a running program with associated information such as Process Identifier (PID), scheduling priority, memory context, file descriptors, and security references.

Question 2

What are the different process statuses?

Answer 2

• R: Running or ready to run.
• S: Sleeping (waiting for an event).
• T: Traced or stopped.
• D: Non-interruptible sleeping (waiting for I/O).
• Z: Zombie (terminated but not cleaned up).

Question 3

Which command is used to display information about all running processes?

Answer 3

ps -A or ps -ef.

Question 4

What does the ps -f command display?

Answer 4

It shows processes in full-format, with detailed information like UID, PID, PPID, CPU usage, start time, and command name.

Question 5

What does the ps aux command provide?

Answer 5

It displays processes from all users, with user/owner information and processes not started from a terminal.

Question 6

What is a PID?

Answer 6

Process Identifier, a unique number assigned to each process.

Question 7

What is a PPID?

Answer 7

The Parent Process Identifier, indicating the parent process of a given process.

Question 8

What does the CMD column in the ps output represent?

Answer 8

The command that started the process, including its name, options, and arguments.

Question 9

What is the difference between foreground and background processes?

Answer 9

Foreground processes require user input and run visibly, while background processes do not require user interaction and run in the background.

Question 10

What command is used to terminate a process using its PID?

Answer 10

kill <PID>.</PID>

Question 11

What does the killall command do?

Answer 11

Terminates all processes with a specified name.

Question 12

What is the default signal sent by the kill command?

Answer 12

SIGTERM (signal number 15).

Question 13

What signal is used for forced termination?

Answer 13

SIGKILL (signal number 9).

Question 14

What is a Zombie process?

Answer 14

: A terminated process that has not been cleaned up by its parent process.

Question 15

How do you suspend a foreground job?

Answer 15

Press CTRL+Z.

Question 16

Which command resumes a suspended job in the background?

Answer 16

bg.

Question 17

Which command resumes a suspended job in the foreground?

Answer 17

fg.

Question 18

What does the jobs command display?

Answer 18

A list of all background and suspended jobs.

Question 19

How do you prioritize processes using niceness values?

Answer 19

By using the nice or renice commands.

Question 20

What is the syntax to start a process with a specific niceness value?

Answer 20

nice -n <nice_value> <command></command>.</nice_value>

Question 21

What is the range of niceness values?

Answer 21

From -20 (highest priority) to 19 (lowest priority).

Question 22

How do you change the niceness value of a running process?

Answer 22

renice <nice_value> -p <PID>.</PID></nice_value>

Question 23

What does the pgrep command do?

Answer 23

Searches for processes based on their name.

Question 24

How can you combine ps and grep to find a process?

Answer 24

ps -ef | grep <process_name>.</process_name>

Question 25

What does the top command do?

Answer 25

Continuously displays real-time information about all processes.

Question 26

What is the htop command?

Answer 26

An interactive version of top for managing processes.

Question 27

What does the pidof command do?

Answer 27

Returns the PID of a specified process.

Question 28

What is a signal in Unix?

Answer 28

A communication tool used to notify processes about events.

Question 29

Which signal is used to end a session?

Answer 29

SIGHUP (signal number 1).

Question 30

What does the SIGINT signal do?

Answer 30

Interrupts a process, typically triggered by CTRL+C.

Question 31

What is the default nice value assigned to processes in Linux?

Answer 31

The default nice value is 0.

Question 32

What happens when you run find / -name core -exec rm -f {} \; &?

Answer 32

It searches for files named “core” throughout the system and deletes them, running the command in the background.

Question 33

What does the TIME field in the ps output represent?

Answer 33

It shows the cumulative execution time of the process.

Question 34

What is a Teletype (TTY) as shown in ps output?

Answer 34

It refers to the controlling terminal of the process.

Question 35

How do you identify the owner of a process?

Answer 35

By looking at the UID field in the ps output.

Question 36

What is the purpose of pgrep -u ?

Answer 36

Searches for processes owned by a specific user and matches the given process name.

Question 37

How can you view the status of a specific process using its PID?

Answer 37

Use ps or ps -p .

Question 38

What are the characteristics of a non-interruptible sleep state (D) in process status?

Answer 38

The process is waiting for I/O operations, such as disk access, and cannot be interrupted.

Question 39

What does kill -9 specifically do?

Answer 39

It forcefully terminates a process by sending the SIGKILL signal, which cannot be ignored.

Question 40

What happens when a non-root user tries to kill a system process?

Answer 40

The operation is denied because system processes can only be terminated by the root user.

Question 41

What is the command to kill multiple processes at once using PIDs?

Answer 41

kill or kill -9 .

Question 42

What is the function of the renice command?

Answer 42

It modifies the priority (niceness value) of an already running process.

Question 43

What is the difference between ps aux and ps -ef?

Answer 43

* ps aux includes processes without a terminal and shows the user column. * ps -ef lists all processes in a full format with additional details like PPID.

Question 44

What is the fg command used for?

Answer 44

To bring a background or stopped process to the foreground.

Question 45

What is the bg command used for?

Answer 45

To resume a suspended process in the background.

Question 46

What does the jobs command show?

Answer 46

It lists background processes and suspended jobs.

Question 47

Why are Zombie processes problematic?

Answer 47

They consume resources since their termination is not properly handled by the parent process.

Question 48

What does the SIGFPE signal represent?

Answer 48

A floating-point exception error.