Timed and delayed tasks in Linux

How to make the system scheduled to complete the task, how to let the system over a period of time to complete a task autonomously, the following will be detailed introduction of the system timing and delay.

# # # #一, at command # # #

1. Basic usage of AT command

   At-l # #列出延迟任务

   At-r Task ID # #删除此id任务

   AT-M # #让无输出的命令不产生邮件

   At-c task ID # #查看此id deferred task execution action

At-f File # #用文件内容记录的命令作为延迟任务的执行命令

At timed tasks, perform position monitoring with watch-n 1 tasks

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Execute touch/mnt/file{1..5} After one minute, press CTRL D to end

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View the task ID that will be executed

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Delete the task ID that will be executed, terminate task execution, ATQ task ID

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Emptying logs >/var/spool/mail/root MAILQ

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AT-M does not generate mail

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Editing files with student users

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Use the file content as a self-delay task

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View deferred task ID at-l

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View Action at-c task ID for deferred task execution

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Use Monitoring for 2.at commands

All users in the default system have the power to execute at command so how to set the black and white list at command

# #用户黑户单

By default, there is no black-and-white list in the system, and the path to this list

/etc/at.deny # #用户黑名单, this list is empty by default and will take effect when the whitelist does not exist

By default, student users can use the AT command

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Prohibit student user Login in blacklist

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Student user is forbidden to use the AT command

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White List of 3.at commands

By default, the system does not exist for the at whitelist user.

But when the whitelist appears, the AT command will be used by the user and the root user in the list

Other users cannot execute the AT command

Add student users to whitelist

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The root user can use the AT command

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Student users can use the AT command

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Class user cannot use the AT command

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# # # #二, cron####

Perform a specific task at an agreed time

1. This program is provided by the Crond.service service

2. The time to write the program is permanently saved

   # #设定方式

   CRONTAB-E-u user name (can not be written)

   Minute hour day month Week event

   7 * * * rm-fr/mnt/* # #每天7:30 Delete all contents of/mnt/

   7 3,16 * * rm-fr/mnt/* # #每月的3号和16号7:30 Delete all contents of/mnt/

   7 3-16 * * rm-fr/mnt/* # #每月的3号到16号7:30 Delete all contents of/mnt/

   7 3,16 2 3 rm-fr/mnt/* # #2月的3号和16号以及二月的每个周三的7:30 Delete all contents of/mnt/

   */30 * * * 1-5 rm-fr/mnt/* # #周一到周五每隔30分钟的7:30 Delete all contents of/mnt/

Start Service Systenctl start Crond.service

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Write Program Crontab-e

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Crontab-l # #列出当前用户的cron任务

crontab-r# #删除当前crontab任务

/var/spool/cron/* # #cront任务记录文件存放的位置

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can also be viewed according to the storage location

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Monitoring Watch-n 1 ' ls-l/mnt/'

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Black and white list of 2.cron

By default the system only has blacklist, when whitelist is established, blacklist expires

# #黑名单

/etc/cron.deny # #在此名单中的用户不能执行crontab

Class User Write Blacklist

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Class cannot execute crontab

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Student user can perform

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# #白名单

/etc/cron.allow # #用户白名单, when this list appears, other users except the root user and the list cannot use the crontab command

Write student in white list

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Student users can use crontab

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Class user cannot use the crontab command

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3. File Mode definition Crontab

vim/etc/spool/cron/User Name # #以某个用户身份执行cron, the file name must be the same as the user name

Time-of-day month-week action

vim/etc/cron.d/File # #设定多个用户身份执行cron

< > < > < day > < month > < week > < user > < action >

Perform an action on/mnt/, add executable permission to/mnt/

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Perform cron with student users

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Watch-n 1 ' ls-l/mnt/'

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Import in Append mode

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Execute cron vim cron.sh as a script

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Run the script

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Monitoring available, script command execution successful

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/etc/cron.d/files, there are some management to put our monthly, weekly, daily, hourly files to be executed in separate files to execute

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Timed and delayed tasks in Linux