Process Management

Question 1

What is a process?

Answer 1

The active execution of code that would otherwise be a file on a disk.

Question 2

What are the types of processes?

Answer 2

User - has a controlling terminal (i.e. chronyc)

Daemon - no controlling terminal (i.e. chronyd)

Question 3

What are the 3 relationships between processes?

Answer 3

1- All processes descend from PID 1 (init or systemd)
2- All others have a PID and a PPID
3- Parent processes spawn and manage children

Question 4

What is PID?

Answer 4

Process ID

Question 5

What is PPID?

Answer 5

Parent process ID

Question 6

What is an orphan process?

Answer 6

Parent ends (orphans), init/systemd adopts orphan process

Question 7

What is a zombie process?

Answer 7

Process ends, but parent doesn’t update status (false positive)

Question 8

Where is process information located on a system?

Answer 8

/proc

Question 9

How are processes managed?

Answer 9

Using the kill or killall command with signals (SIGTERM, SIGKILL, SIGHUP, etc.)

Question 10

How are processes viewed?

Answer 10

ps, pstree, top commands

Question 11

How does the process priority scale work?

Answer 11

Lowest numerical value = highest priority (-99)

Highest numerical value = lowest priority (99)

Question 12

What command runs a program and assigns a process a specific nice value that affects the calculation of the process priority (which can be either increased or decreased)?

Answer 12

nice

Question 13

What command changes the nice value of a running process without restarting it?

Answer 13

renice

Question 14

How can a process be moved to the background?

Answer 14

Ctrl+z to pause the task, then bg to continue the task in the background

Question 15

What is the difference between the kill and killall commands?

Answer 15

kill - kills process(es) by PID

killall - kills all processes by name (string)

Question 16

What do pgrep and pkill do?

Answer 16

pgrep - verifies process by attributes other than PID

pkill - pgrep + kill, which happens in the background

Question 17

How can a job start in the background?

Answer 17

Suffix a command with the ampersand &

Question 18

How can jobs be viewed?

Answer 18

jobs

Question 19

How can a job be brought into the foreground?

Answer 19

fg

Question 20

What is a job?

Answer 20

The passive execution of code that would otherwise be a file on a disk (aka: processes running in the background).

Question 21

For whatever reason (zombies most likely) you’re restricted to a single terminal. How do you multitask?

Answer 21

screen

Question 22

Who is your friend in screen? H’why?

Answer 22

Ctrl+a - has all the snacks (basic prompt to do sub commands)

Question 23

Who is cron?

Answer 23

Daemon that allows jobs to be scheduled

Question 24

What is crontab?

Answer 24

File containing a list of jobs and their schedules

Question 25

Break down the crontab entry syntax

Answer 25

``` WHEN: Minute of hour Hour of day Day of month Month of year Day of week ``` WHO: User to run as WHAT: Command / path to script

Question 26

Who is at?

Answer 26

Daemon to schedule a "one-off" task

Question 27

With screen, what is one way to create a new window?

Answer 27

Type screen while inside screen, i.e. attached screen

Question 28

With screen, what is one way to create a new session?

Answer 28

Type screen while outside of screen, i.e. detached screen

Question 29

Break down the "layout" of screen

Answer 29

bash > screen > session > window > program | bash > screen > [session1 > [window1 > program1] [window2 > program2]] [session2 > [window1 > program3]]