< VI > process management in Linux 2021-10-10

1, Process definition

Definition of process:
The program is a static code file
Process refers to the form of program running time
A process is a copy of a program
The process has a life cycle (preparation period, operation period, termination period)

Process & thread:
A process is the smallest unit of resource invocation

A thread is the smallest unit of a process
When the process is multitasking and the cpu is multi-core, multitasking should be processed by each core at the same time. The task processed by each core is called thread
Thread resources are shared

Process status
#R(TAKS_RUNNING) executable status (running, ready)
#S (task_intruptable) wakes up sleep
#D (task_unitrruptable) cannot wake up sleep
#T(TASK_STOP) pause status
#Z(EXIT_ZOMBIE) dead state

2, Process view command

1. Graphics process view

gnome-system-monitor ##Graphics process viewing tool

2,ps

ps 	  #Process view
	  #Three execution styles of ps command unix bsd GNU
ps a  #Terminal related processes with character terminals (processes generated after users log in to the system are all with terminals)
ps x  #Terminal independent, terminal free processes (all except those with dependencies?)
ps u  #Viewing method of user information classification
ps f  #Process hierarchy
ps o  #Display the specified parameters,
	   as pid comm nice pri pcpu ppid stat,user,group

ps -e #Show all processes

ps -f #Displays the full format of the information
ps -H #Displays the hierarchy of processes
ps -o #Displays the specified parameters
ps --sort= (as ps pid %CPU sort) #-sort = in reverse order (from small to large)
							   #If -- sort=-%CPU, the order is from large to small

ps ax The display information is as follows:
				#PID process id
				#Terminal used by TTY process
				#STAT process status
				#TIME cpu TIME consumed by the process
				#COMMAND process name

ps aux The display information is as follows:
				#USER process owner
				#PID process id
				#%The amount of cpu used by the cpu process
				#%The amount of memory used by the MEM process
				#The size of virtual memory used by the VSZ process
				#The size of the data resident in memory of the RSS process
				#Terminal used by TTY process
				#STAT process status
				#START process run time
				#TIME cpu TIME consumed by the process
				#COMMAND process name

3,pgrep

pgrep		#Process filtering
pgrep -u 	##uid displays the specified user process
pgrep -U 	##User displays the specified user process
pgrep -t 	##tty displays the specified terminal process
pgrep -l 	##Display process name
pgrep -a 	##Displays the full name of the process
pgrep -P 	##Displays the child processes of the process

pidof

View the of the command id	for example
pidof vim 	##View the pid of vim

top

Parameters of the top command

Open top first

top       #Open top

Then enter the parameters

Command parameterseffect
-dSpecify refresh rate
-bDisplay as batch
-nSpecifies the number of batches to display

top internal instruction

Instruction parameterseffect
PCPU sorting
MMemory sorting
TCumulative cpu time sorting
lTurn uptime information off / on
tTurn off / on CPU & task
sSpecify refresh rate
kOperation process
uView specified user processes

3, Process priority

Multi task and multi-user operation mode in system
The importance of tasks is differentiated
How to determine the importance of the task
"Priority"
Range: 0 – 139
Kernel automation priority range: 0-99
User controllable priority: 100-139

nice

nice scope:
(-20)-19

renice -n -5 43331 		##Change priority

nice -n -5 cat 			##Open process with specified priority
 Then you can see it in the process cat Priority of
ps ax -o pid,nice,comm | grep cat

Parameter description of stat

parameterexplain
Ssleeping
<High priority
sTop level process
Tstop
NPriority bottom
Rrunning
+Run in the foreground

4, Process background call

<ctrl>+<z>		 ##Put the process occupying the shell into the background and hang
bg				 ##Run the process suspended in the background
fg 				 ##Bring the background process back to the foreground
& 				 ##The running process is in the background
jobs 			 ##View all work in the background in the current shell

5, Process information number

Process signal

Process signalmeaning
1Re home in the system configuration file (source)
2Clear process data in memory
3Clear the mouse in memory (ctrl +)
9Forcibly end the process (cannot be blocked)
15Shut down the process normally (it will be blocked)
18Running a paused process
19Pause process (not blocked)
20Pause the process (it will be blocked)

Process signal control tool

kill Process signal pid
killall Process signal process name
pkill Process signal process condition

Open first vim,adopt ps View to pid 5925
kill -9 5925	##Delete a single process
pkill -9 westos	##Delete all processes for the westos user
killall -9 vim	##If multiple VIMS are opened at the same time, close all VIMS

6, systemd daemon

to configure ip address nm-connection-editor
 choice ens3   ipv4 Place selection mannual  Subnet mask 24   ip Old rules

1. Experimental environment

#linux.westos.com -------- > 172.25.254.10
#node1.westos.com ----------> 172.25.254.20

2. Remote operation host

ssh root -l 172.25.254.112

3. Daemon

1) A program that shares program control for the kernel, usually with a pid of 1
        systemd -----> systemctl
          systemctl management system service
2) Service refers to the program opened in the system to share system resources to the network
        cs client ------ server

4. Usage of systemctl command

start       ##open
stop       ##close
status      ##View status
reload      ##Reload
restart      ##Restart the service
enable      ##Set service startup
enable --now    ##Set the service startup and current service startup
disable      ##Set the service to be turned on
list-units      ##View the current status of all system services
list-unit-files     ##View service startup status
list-dependencies    ##List service dependencies
mask       ##Freeze service
unmask      ##Unlock
set-default     ##Set system operation mode
#multi-user.target     no graphics network mode
#graphical.target   network mode with graphics
get-default     ##View system operation mode
##System operation mode 0-6
			#0 POWEROFF
			#1 single
			#2 noG+NETWORK
			#3
			#4
			#5 G+NETWORK
			#6 REBOOT

7, Login audit in the system

w 		##Display the account number logging in to the system
w  -i   ##Show login source
		#/var/run/utmp

last 	##Successfully logged in and now has exited
		##/var/log/wtmp

lastb 	##Attempted to log in but failed
		##/var/log/btmp

Tags: Linux Unix server

Posted on Wed, 20 Oct 2021 13:35:03 -0400 by sanch