Linux system daemon and Scheduled tasks

the relationship between procedures and processes

* Program

• Executable code and data stored on hard disks, discs, and other media

• Statically saved code

* Process

• Program code running in CPU and in memory

• Dynamically executed code

• Parent, child process

> Each process can be created in one or more Process

*pid No.

• Unique identification of each process, usually used as the end process

* Process Query

PS Pgrep

Top Pstree

* Process Management

CTRL + Z foreground process into the background

CTRL + C End Process

Jobs View Background Process

fg# The background # process is running in the foreground

bg# running the background # process in the background

& Run the process directly in the background

Kill, Killall End Process

Scheduled Task management

*at command

One-time Scheduled tasks

Service script:/ETC/INIT.D/ATD

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

At>ctrl+d End Edit

* Enquiry and deletion

Atq

Atrm

At–c # Viewing the contents of a specified scheduled task

*crontab command

Periodically schedule tasks to execute user-made commands in a pre-set time period

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

Primary profile global configuration file/etc/crontab

The system default configuration file is located in/etc/cron.*/

User-defined profiles are located in the/var/spool/cron/user name

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Linux system daemon and Scheduled tasks