Lesson 3.4: Identify CPU/memory intensive processes and kill processes

Process Monitoring tools

PS Command

Command: ps -ef

It displays the detail of both foreground and background processes.

[sanjeeb@assignmentserver class]$ ps -ef
UID          PID    PPID  C STIME TTY          TIME CMD
root           1       0  0 Sep19 ?        00:00:02 /usr/lib/systemd/systemd rhgb --switched-root --system
root           2       0  0 Sep19 ?        00:00:00 [kthreadd]
root           3       2  0 Sep19 ?        00:00:00 [rcu_gp]
root           4       2  0 Sep19 ?        00:00:00 [rcu_par_gp]
root           5       2  0 Sep19 ?        00:00:00 [slub_flushwq]
root           6       2  0 Sep19 ?        00:00:00 [netns]
sanjeeb     2988    2970  0 Sep19 pts/0    00:00:00 bash

If TTY column has ?, then it is a background process.
If pts/1 , pts/2 , tty/1 ,tty/2 etc, then is a foreground process.
UID is the owner name of the process.
PID is the process ID, and PPID is the parent's ID. If no PPID then it shows 0.
SystemD PID is always 1.
TIME is the time consumed.

TOP Command

Command: top

It shows info of resource intensive processes.

top - 07:49:49 up 11:50,  2 users,  load average: 0.19, 0.08, 0.03
Tasks: 317 total,   1 running, 316 sleeping,   0 stopped,   0 zombie
%Cpu(s):  4.0 us,  1.0 sy,  0.0 ni, 94.5 id,  0.0 wa,  0.0 hi,  0.5 si,  0.0 st
MiB Mem :   3584.9 total,    610.0 free,   1154.9 used,   2003.9 buff/cache
MiB Swap:   2048.0 total,   2044.7 free,      3.2 used.   2430.0 avail Mem 
 
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                            
   2308 sanjeeb   20   0 4084432 353312 122308 S   8.9   9.6  14:55.15 gnome-shell                        
   2970 sanjeeb   20   0  781936  57628  40140 S   1.0   1.6   1:34.78 gnome-terminal-                    
   2614 sanjeeb   20   0  394044  38988  31948 S   0.3   1.1   1:43.31 vmtoolsd                           
   2615 sanjeeb   20   0  924432  45364  32004 S   0.3   1.2   0:00.33 evolution-alarm                    
   7783 root      20   0       0      0      0 I   0.3   0.0   0:01.00 kworker/u4:3-events_unbound        
   8232 root      20   0       0      0      0 I   0.3   0.0   0:00.74 kworker/0:2-events                 
   8276 sanjeeb   20   0  226180   3968   3072 R   0.3   0.1   0:03.93 top                                
      1 root      20   0  173804  15544   9472 S   0.0   0.4   0:02.06 systemd                            
      2 root      20   0       0      0      0 S   0.0   0.0   0:00.04 kthreadd

Commands of top

S : To change snapshot delay time.
M : Sort processes based on memory usage.
P : Sort processes based on processor usage.
T : Sort based on total run time.
k : To kill (terminate) a process.
r : To change priority of a process.
q : To quit (exit).

Terminate/Kill a process

kill [signal] < pid > : To Kill a particular process.
killall [signal] < process > : To Kill all the instance of the given process.

Signal

-15 or -TERM : Soft Signal (Default)
-9 or -KILL : Strong signal

Example 1: Using the soft Signal to kill a file that's lagged.

# Creating a file and editing it in terminal 2. 
[sanjeeb@assignmentserver class]$ vim lagged_file
 
# Viewing the process in terminal 1. 
[sanjeeb@assignmentserver class]$ ps -ef
...         ....     ...    ...            ...
root        8385       2  0 10:40 ?        00:00:00 [kworker/0:1-events]
sanjeeb     8431    8337  0 10:41 pts/1    00:00:00 vim lagged_file
sanjeeb     8460    7691  0 10:42 pts/0    00:00:00 ps -ef
 
# Kill the process with PID 8431
[sanjeeb@assignmentserver class]$ kill -15 8431
# OR
[sanjeeb@assignmentserver class]$ kill -TERM 8431
 
# Check the terminal 2
Vim: Caught deadly signal TERM
Vim: preserving files...
Vim: Finished.
 
 
Terminated

Example 2: Using the strong Signal to kill a file that's lagged.

# View the process and PID
[sanjeeb@assignmentserver class]$ ps -ef | grep vim 
sanjeeb     8544    8337  0 10:47 pts/1    00:00:00 vim lagged_file
sanjeeb     8547    7691  0 10:48 pts/0    00:00:00 grep --color=auto vim
 
# Kill with strong signal -KILL or -9
[sanjeeb@assignmentserver class]$ kill -KILL 8544
# OR
[sanjeeb@assignmentserver class]$ kill -9 8544
 
# Check terminal 2, you can see killed at the cursor point (strong)
This is a lagged file strong. Killed
[sanjeeb@assignmentserver class]$

Example 3: Kill multiple instances using different PID

# Creating three file f1, f2, f3 in different terminal with vim 
 
# View the processes 
[sanjeeb@assignmentserver class]$ ps -ef | grep vim 
sanjeeb     8575    8337  0 10:52 pts/1    00:00:00 vim f1
sanjeeb     8603    8576  0 10:52 pts/2    00:00:00 vim f2
sanjeeb     8630    8604  0 10:53 pts/3    00:00:00 vim f3
sanjeeb     8633    7691  0 10:53 pts/0    00:00:00 grep --color=auto vim
 
# Kill using strong signal or soft signal.
[sanjeeb@assignmentserver class]$ killall -15 vim 
 
# Check if process exists 
[sanjeeb@assignmentserver class]$ ps -ef | grep vim 
sanjeeb     8650    7691  0 10:54 pts/0    00:00:00 grep --color=auto vim