Process management

Question 1

List processes

Answer 1

ps -aux/ ps -ef[H] hierarchy
ps -u- list user processes
first process will get id=1

Question 2

List processes with their state

Answer 2

ps -el 
states:
S -sleep
T- terminated (ctrl+z)
X- dead (should not be seen)
Z- zombie
I -idle
R -running

Question 3

Set priority of processes

Answer 3

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

Question 4

Alter priority of running process

Answer 4

renice -n -15 2345 [PID]

Question 5

Display processes in real time

Answer 5

top
keys:
k-kill process
r-renice process
Sorting:
M- %MEM
N- PID
P- %CPU
T- TIME+

Question 6

Look for process based on name

Answer 6

pgrep -a ssh- lists pids and service paths
pgrep httpd only lists pids related to httpd
pgrep -u- list pids of current user

Question 7

Check how long takes a process to run

Answer 7

time ping -n 10 google.com

Question 8

Kill a process based on name

Answer 8

pkill ping

pkill -x httpd -to kill processes match exactly to httpd

Question 9

List open files

Answer 9

lsof

Question 10

Location in pseudo FS related to cpu and memory

Answer 10

cat /proc/cpuinfo

cat /proc/meminfo

Question 11

Tell how long the system has been running

Answer 11

uptime (1m, 5m, 15 m)

Question 12

Report system activity info

Answer 12

sar -u for CPU utilization
sar -A -report for all devices
sar -b -IO stat
sar -d -for each block device

Question 13

Configure kernel params in runtime

Answer 13

sysctl -a (display all values available)

Question 14

Kill process

Answer 14

kill -9 1234 [pid]
kill 1234
kill -l- get the list of signal to be passed to kill command

Question 15

Amount of RAM available+swap

Answer 15

free -m

Question 16

Kill all processes based on name

Answer 16

killall httpd

killall -s 9 httpd

Question 17

Run a command at specified intervals

Answer 17

watch date

watch -n 10 date

Question 18

Terminal window managers that allows to run commands in an isolated session

Answer 18

1. screen
   1.1. screen
   1.2. watch date
   1.3. ctlr+a d -detach from the session
   1.4. screen -r 2 [session screen id] -to re-attach
   screen -ls -to show screen session
2. tmux
   2.1. ssh kenny@1.2.3.4 …
   run commands
   2.2. ctrl+b d-detach from tmux session
   2.3. tmux ls - list sessions
   2.4 tmux attach-session -t 0-
   attach back to the session 0

Question 19

nohup

Answer 19

1. nohup ping google.com &
2. jobs -to see processes running on the background
3. tail -f nohup.out
4. fg 1 (job id) - back the job to fg
5. ctrl+z - to stop the job
6. bg % 1 (job id)-force to send the job to the background again
7. jobs -l => the nohup ping google.com is running again