Process and scheduled task management

Process and scheduled task management

Process and Scheduled Tasks list

1. View the process

1.1 Relationship of procedures and processes

Program: Save the hard disk, CD and other media executable code and data, is a static saved code

Process: Program code running in CPU and memory is code that executes dynamically

Parent, child process: each process can create one or more processes

1.2 Viewing process statistics at rest

Ps

PS aux: Show process information as a simple list

A: Displays all process information under the current terminal, including the processes of other users

U: Output process information in a user-oriented format

X: Displays process information for the current user under all terminals

Ps-elf: Displays process information in a long format and contains richer content

-E: Displays all process information in the system

-L: Display process information in long format

-F: Displaying process information using the full format

When you directly execute a PS command without any options, only the processes that are open in the current user session are displayed

The number of processes running in the system can be combined with a "| grep option uses the

Pgrep

Query process PID information based on specific criteria

-L: Show process name

-U: Specify a specific user

-T: Specify terminal

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Pstree

List process information in a tree-shaped structure

-A: Show full information

-U: List the corresponding user name

- P: list the corresponding PID      

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1.3 Viewing process statistics dynamically

Top: The current terminal in a full-screen interactive interface to display the process ranking, and tracking including CPU, memory and other system resource consumption, by default, every three seconds to refresh

Sort

P: Sort the list of processes based on CPU usage

M: Sort based on memory usage

N: Sort by start time

H: or Top program's online Help information

Q: Exit Top program

K, and then enter the PID number to kill a process

1.4 Control Process

Process start Mode

Manual start

Foreground start: User input command, execute program directly

Background start: Add the "&" symbol at the end of the command line

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Scheduled start

Use the AT command to set up a one-time scheduled task

Script Name:/ETC/INIT.D/ATD

Formatting: at [hh:mm] [YYYY-MM-DD]

Submit Task: Ctrl+d

View the list of non-performing tasks: ATQ

Delete Second task: ATRM 2

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Set up recurring scheduled tasks using the crontab command

Follow the pre-set time period (minutes, hours, days ...)

Service Script Name:/etc/init.d/crond

Global configuration file:/etc/crontab

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system default settings, located in directory:/etc/cron.*

User-defined settings:/var/spool/cron/user name

Manage Cron Scheduled Tasks

Edit Scheduled Task: Crontab-e [-u user Name]

View Scheduled Tasks: Crontab-l [-u user Name]

Delete Scheduled Task: Crontab-r [-u user Name]

Crontab the format of the task configuration

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A special method of representing time values

* Indicates any time within the range

, which represents multiple discontinuous points of time for the interval

-Represents a continuous range of time

/Specify the time frequency of the interval

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Front and back scheduling of processes

CTRL + Z: suspends the current process and moves into the background and stops execution

Jobs: View a list of tasks in the background (+ indicates the most recent task that was put in the background-the task that the second person put to the background)

FG: Restore the background process to the foreground to run, you can specify the task sequence number

BG: Background paused task resumes running, specifying task sequence number

To terminate the running of a process

CTRL + C: Interrupt the command being executed

Kill: The process used to terminate the specified PID number

Killall: Used to terminate all processes of the specified name

-9: Forced termination, kernel Force shutdown process (default to 15 for this parameter, normal exit)

Pkill: Terminates the corresponding process according to certain conditions

-U: Terminates the process based on the user name the process belongs to

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Process and scheduled task management