Chapter 9 - Managing Linux Processes

Process are started with what nice value by default?

0

What number indicates the lowest kernel priority (PRI) of a process possible?​

127

How many different kill signals can be sent by the kill command to give a process?

64

What kill level signal cannot be trapped?

9

The killall command uses the PID to kill a process. True or False

False

To kill a process running in the background, you must place a % characters before its process ID. True or False?

False

cron table

a file specifying tasks to be run by the cron daemon; there are user cron tables and system cron tables

parent process

a process that has started other processes (child processes)

child process

a process that was started by another process (parent process)

daemon process

a system process that is not associated with a terminal

process ID (PID)

a unique identifier assigned to every process as it begins

The killall command terminates ____________________________.

all instances of a process with the same name

The command used to schedule commands and tasks to run at a present time in the future.

at command

What command is used to view and modify user jobs scheduled to run with cron?

crontab

What is the name given to a process not associated with a terminal?

daemon process

Which of the following is not one of the three main types of Linux commands?

device calls

After a background process has been started, what command below can be used to move it to the foreground?

fg

A process spawning or initiating another process is referred to as _____________________.

forking

In a process referred to as _________________, when executing compiled programs or shell scripts, the BASH shell that interprets the command you typed creates a new BASH shell.

forking

Which of the following statements is true? (choose all that apply)

if /etc/at.allow exists, only users listed in it can use the at command if /etc/cron.allow exists, only users listed in it can use the cron command if /etc/cron.deny exists and /etc/cron.allow does no exist, any user not listed in /etc/cron.deny can use the cron command

Which process will all have PID of 1 and a PID of 0?

init

When there are multiple background process executing in the shell, the jobs command indicates the most recent one with which symbol?

+

Nice values are used to affect process priorities using a range between ______________________.

-20 and 19

What option can be used with the ps command to display an entire list of processes across all terminals and including daemons?

-e

What option, when added to the crontab command, opens the vi editor with a user's cron table?

-e

What two ps options can be used to display a full list of information about each process, and a long list of information about each process?

-f -l

In order to display a list of at jobs IDs, what option can be specified to the at command?

-l

On a Fedora based system, where are the shell environment and scheduled commands for at stored?

/var/spool/at

Where are individual user tasks scheduled to run with the cron daemon stored on a Fedora system?

/var/spool/cron/(the user's login name)

What two processes below will show up as PID 1, depending on whether a system uses UNIX SysV or Systemd init processes?

int systemd

A runaway process that is faulty and consuming mass amounts of system resources ________________________.

is a rogue process

Which command can be used to see processes running in the background?

jobs

What two commands below can be used to stop a process, either by PID number or process name?

kill killall

The ______________ can be used to affect the process priority indirectly.

nice value

Every process has a process ID and a __________________.

parent process ID

A(n) ____________refers to a program that is running in memory and on the CPU.

process

In the output of the ps -l command, what column is the most valuable to systems administrators because it indicates what the process is currently doing?

process state

Which command when entered without argument is used to display a list of processes running in the current shell?

ps

What command below is used to display the lineage of a process by tracing its PPIDs until the init daemon?

pstree

Which of the following commands will most likely increase the chance of a process receiving more time slices?

renice -12

Processes that have encountered an error during execution and continuously uses up system resources are referred to as ________________ processes.

rogue

The at command is used to ________________.

schedule processes to run at a single instance in the future

What character, when appended to a command, causes the command to be run in the background?

& (and command) &

When killing a background job with the kill command, the background job ID must be prefixed by what character below?

%

Describe how forking works, and how it affects the parent process.

Forking is the creation of a new subshell; it is carried out by the fork function in the BASH shell. It is used to create processes. It takes no arguments and returns a process ID. The purpose of fork is to create a new process which becomes the child process of the caller, after a new child process is created both processes will execute the next instruction following the fork system call.

What can be used on a Linux system to trace the lineage of each child process?

PPID - Parent Process ID

What kill signal stops a process, then restarts it with the same PID?

SIGH UP

What kill signal and number can be used to send an interrupt signal to a process, and is the same as using the Ctrl+c combination to kill a running process?

SIGINT 2

What signal name and number function as the absolute kill signal, and when issued, forces the Linux kernel to stop executing the process by sending the process's resources to /dev/null?

SIGKILL 9

Which kill signal terminates a process by taking the process information in memory and saving it to a file called core on the hard disk in the current working directory?

SIGQUIT

Explain why scheduling commands can be beneficial, and detail some of the methods available for scheduling commands.

Scheduling system maintenance commands to run during nonworking hours is good practice, as it does not disrupt normal business activities. There are two different methods to schedule commands: At daemon (atd) - which can be used to schedule a command to execute once in the future cron daemon (crond) - which is used to schedule a command to execute repeatedly in the future

In a cron table entry, what field specifies the absolute pathname to a command that is to be executed?

Sixth

How does the NICE value affect process priority? How and why can nice values by altered?

The NICE value (NI) can be used to affect the process priority indirectly, it is measured between -20 (a greater chance of a high priority) and 19 (a greater chance of a lower priority). The lower the number the more priority that task gets, if the nice value is high number like 19 the task will be set to its lowest priority and the CPU will process whenever it gets a chance. You can use the -n command line option to change the or adjust the nice value which adds a set of integer value to the niceness.

After a process has been started, you can change its priority by using the renice command. True or False.

True

As daemon process are not associated with terminals, you must use the -e switch with ps command to view them. True or False?

True

Each process can start an unlimited number of other processes. True or FAlse

True

If the /etc/at.allow and /etc/at.deny files do not exist, only the root user is allowed to schedule tasks using the at daemon. True or False

True

Zombie processes are also known as defunct process. True or FAlse

True

Describe the purpose the process state column displayed by the ps -l command. What values may appear in this column, and what do these values indicate?

the -l option to the ps command lists even more information about each process than the -f option. The process state (S) column is the most valuable to systems administrators because it indicates what the process is currently doing. The values that may appear are the (S) value for sleeping, the (R) value is for running, the (T) value is for a process that has stopped or is being traced by another process and the (Z) value indicates a zombie process

forking

the act of creating a new BASH shell child process from a parent BASH shell process

time slice

the amount of time a process is given on a CPU in a multiprocessing operating system

background (bg) command

the command used to run a foreground process in the background

at command

the command used to schedule commands and tasks to run at a preset time in the future

Describe the system cron table. How is it organized, and what information may be contained within it?

the cron table includes six fields separated by space or tab characters the first 5 fields specify the times to run the command and the sixth field is the absolute pathname to the command to be executed.

In the process state column, what does an "R" indicate?

the process is currently running on the processor

When viewing the output of the ps ax command, what does a < symbol in the STAT column indicate for a process?

the process is high priority

Trapping

the process of ignoring a kill signal

When you run the ps command, how are daemon process recognized?

there is a question mark in the TTY column

The amount of time a process has to use the CPU is called a(n) __________________________.

time slice

Which command is used to gain real-time information about processes running on the system, with the most processor-intensive processes appearing at the beginning of the list?

top

How can you bypass the wait function and send a user process to the background?

you can use the Ctrl+z key combination and the bg command