Linux Scheduled Tasks

One-time Scheduled tasks

At the specified time to execute a specific command

Usage: at [TIME]

Example:

At 9:00am #指定在当天早上9点执行计划任务

At > Cp/etc/passwd/tmp #计划任务内容

At > <EOT> #输入完成后, End by Ctrl+d

At-l List Current Scheduled tasks

Recurring Scheduled Tasks--crontab

Crontab-l List Scheduled Tasks

#service Crond Restart Restart

A) Use to open the service first

#service crond Status

#chkconfig--list List system service status

#chkconfig--list | grep crond View Crond service startup status

b) Specify the content of the scheduled task

Crontab content Format

First column	Second column	Third column	Fourth column	Fifth Column	Sixth column
Score of	When	Day	Month	Week	Command
00~59	00~23	1~31	1~12	0~7	Cmd

Week: 0~7, 0 and 7 all indicate Sunday

, if time is the time period, you can

Use a horizontal bar (-) to denote a continuous period of time

Use a comma (,) to indicate a number of discontinuous times

Use an asterisk (*) to indicate all times

Use Division sign (/) to indicate the time interval

b) Specify the content of the scheduled task

* * * * * cmd

Example: Every Wednesday 2 o'clock in the morning backup/etc/passwd

0 2 * * 3 cp/etc/passwd/tmp

Example: 10th No. 25th per month, 1:5 A.M. Clear/tmp

5 1 10,25 * * rm-rf/tmp/*

Example: Performing time synchronization every 10 minutes

*/10 * * * * * * ntpdate time server IP

Example: 1-6 hours a day.

0 1-6 * * * *

c) Restart Crond service

#service Crond Restart

View Files Dynamically

Tail-f/tmp/date.log

Linux Scheduled Tasks