Processes

Question 1

How do you list processes running on the system

Answer 1

ps

i.e ps -aux

Question 2

How do you search for a process?

Answer 2

pgrep >pname<
pgrep -l >name< *show name aswell as PID
ps aux | grep >name

Question 3

How do you search for processes belonging to a specific user?

Answer 3

pgrep -u

i.e pgrep -u cloud_user -l

Question 4

How do you do an inverse search for a process?

Answer 4

pgrep -v

i.e pgrep -v -u user *all processes not owned by user

Question 5

How do you kill a process using its name?

Answer 5

pkill >pname

Question 6

How do you list all possible kill signals?

Answer 6

kill -l

Question 7

What is the default kill signal of pkill and kill?

Answer 7

15 - SIGTERM

*instructs program to close

Question 8

How would you kill a program that is not responding to a standard kill signal?

Answer 8

9 - SIGKILL
kill -9 >PID<
*forces program to close

Question 9

What is kill -SIGHUP?

Answer 9

1 - SIGHUP
kill -1 >PID<
hang up connection to controlling processes within terminal, is issued when closing a terminal

Question 10

What is kill -SIGINT?

Answer 10

2 - SIGINT
kill -2 >PID<
keyboard interrupt

Question 11

What is kill -SIGQUIT?

Answer 11

3 - SIGQUIT

process sent by controlling terminal for it to quit

Question 12

What is kill -SIGSTOP?

Answer 12

19 - SIGSTOP
kill -19 >PID<
stop a running process (pause)

Question 13

What is kill -SIGTSTP

Answer 13

20 - SIGTSTP
kill -20 >PID<
request a process to stop (pause), can be ignored by process

Question 14

What is kill -SIGCONT?

Answer 14

18 - SIGCONTINUE
kill -18 >PID<
resume a stopped process

Question 15

How do you close a users terminal window?

Answer 15

pkill -t >tty<

*get tty (terminal) from w command

Question 16

How would you kill a process for another user only?

Answer 16

pkill -u >user< >pname<

i.e pkill -u cloud_user sshd

Question 17

How do you run a command and put it in the background as a job?

Answer 17

‘&’ command

i.e yes&raquo_space; /dev/null &

Question 18

How do you show running jobs?

Answer 18

jobs

Question 19

How do you stop (pause) a running job?

Answer 19

kill -19 %

*% targets job instead of process

Question 20

What is nice an renice?

Answer 20

Sets the priority for a process
-20 - highest priority
19 - lowest priority

Question 21

How do you start a process with a specific priority level?

Answer 21

nice -n >n< >pname<

i. e nice 0 httpd
* child processes will have the same priority

Question 22

How do you set the priority of an already running process?

Answer 22

renice -n >n< >pid<

i.e renice 5 2743

Question 23

How do you set the priority of all running processes with a specific name?

Answer 23

renice -n {n} $(pgrep {pname})

*$() subshell is evaluated as a command and passed as a parameter to renice

Question 24

How do you measure the time for a command to complete?

Answer 24

time

i.e time w

Question 25

How would you get the number of processors on a system?

Answer 25

cat /proc/cpuinfo | grep 'model name' | wc -l
*/proc/cpuinfo is pseudo filesystem

Question 26

Within the top command what are RES and SHR?

Answer 26

RES - no swap physical memory size

SHR - shared memory size

Question 27

How do you use top to refresh a specified number of times then quit?

Answer 27

top -n >n<

i.e top -n 5

Question 28

How do you use top with a specific frequency to update process information?

Answer 28

top -d >n<

i. e top -d 0.5
* twice a second

Question 29

What is the output of load average for instance with the uptime command?

Answer 29

load average 1m 5m 15m

*divide percentage by number of CPUs to get system as a whole, numbers are represented in decimal format