Process management

Question 1

List all processes running on the system
List tree view of all processes running on the system
List processes showing status of processes

Answer 1

ps -aux
ps -efH
ps -el

Question 2

Find process by name, also show its pid

Answer 2

pgrep -l httpd

Question 3

Kill process matching specified name

Answer 3

pkill httpd

killall httpd

Question 4

Show all process names running by specific user

Answer 4

pgrep -u user -l

Question 5

Kill process with exact specified name

Answer 5

pkill -x vi

Question 6

Find all processes not own by specified user

Answer 6

pgrep -v -u user -l

Question 7

List all kill signals

Answer 7

kill -l

Question 8

Most useful signals

Answer 8

1. kill -1 or kill SIGHUP- hangup of controlling terminal
   Same as to closing terminal window on the right upper corner
2. kill -2 or kill SIGINT -interruption from keyboard. Same as pressing Ctrl+C
3. kill -15/kill -SIGTERM
   Default signal when killing a processes
4. kill -9/ kill -SIGKILL - kill process immediately
5. kill -18/ kill -SIGCONT
   kill -19/ kill -SIGSTOP
   SIGSTOP is the same as Ctrl-Z
   stop the process
   When SIGSTOP is sent to a process, the usual behaviour is to pause that process in its current state. The process will only resume execution if it is sent the SIGCONT signal. SIGSTOP and SIGCONT are used for job control in the Unix shell

Question 9

Kill a terminal running by specified user

Answer 9

1. w
   find terminal using by specified user
2. pkill -t pts/1

Question 10

Set priority of the process

Answer 10

nice [from -20 to 19]
nice -n 10 ping google.com
nice -n 1 httpd
(The higher the number the lower the priority)

Question 11

Change priority of the process

Answer 11

renice -n 5 -p 1234

renice -n 10 $(pgrep httpd)

Question 12

CPU info in pseudo fs

Answer 12

cat /proc/cpuinfo