Task Scheduler for Linux Systems

Crontab Recurring Task Settings

# yum Install cronie-y# systemctl status crond.service# systemctl start crond.service# systemctl enable Crond.service

[[email protected] etc]# cat /etc/crontab shell=/bin/bashpath=/sbin:/bin:/usr/sbin:/ usr/binmailto=root# for details see man 4 crontabs# example of  job definition:# .---------------- minute  (0 - 59) # |  .--------- ---- hour  (0 - 23) # |  |  .---------- day of month   (1 - 31) # |  |  |  .------- month  (1 -  ( OR JAN,FEB,MAR,APR ...# |  |  |  | &NBSP):----  day of week  (0 - 6)   (sunday=0 or 7)  or sun,mon,tue,wed , thu,fri,sat# |  |  |  |  |# *  *  *   *  * user-name  command to be executed

To manage a user's scheduled tasks by using the crontab command

-E//Edit scheduled Task List-u//Specify which user the managed scheduled task belongs to, default to the current user, typically only the root user uses this option-l//list to display scheduled Tasks-r//Delete scheduled Task List

User Cron task Configuration Storage directory

[Email protected] etc]# ls/var/spool/cron/

Crontab-e

7 * * */USR/BIN/SYSTEMCTL Start SSHD50 * * */usr/bin/systemctl Stop sshd0 * */5 * */usr/bin/rm-rf/var/ftp/pub/ *30 7 * * 6/USR/BIN/SYTEMCTL Restart HTTPD30 * * 1,3,5/usr/bin/tar JCVF HTTPDCONF.TAR.BZ2/ETC/HTTPD

Note: When setting a task that is not performed every minute, the Minutes field should also fill in a specific time value instead of the default "*", otherwise the scheduled task will be executed every minute.

Confirm the contents of the root user's scheduled task list

[[email protected] etc]# CRONTAB-L50 7 * * */USR/BIN/SYSTEMCTL Start SSHD50 * * */usr/bin/systemctl stop sshd0 * */5 * */USR/BIN/RM-RF/VAR/FTP/PUB/*30 7 * * 6/USR/BIN/SYTEMCTL Restart HTTPD30 * * 1,3,5/usr/bin/tar JCVF httpdconf. Tar.bz2/etc/httpd

Confirm the contents of the Jerry user's scheduled Tasks list

[[email protected] ~]# crontab-l-u jerry55 * * 0/bin/cp/etc/passwd/home/jerry/pwd.txt[[email protected] ~]# ls-l /VAR/SPOOL/CRON/JERRY-RW-------. 1 Jerry Jerry 52 February 13:38/var/spool/cron/jerry

View and delete your own scheduled Tasks list after you log in with a Jerry user

[[email protected] ~]$ CRONTAB-L55 * * 0/bin/cp/etc/passwd/home/jerry/pwd.txt[[email protected] ~]$ Crontab-r[[ema Il protected] ~]$ crontab-lno crontab for Jerry

When you need to run multiple tasks in the same cycle, you typically write the related command action as a script file and then load the script in a scheduled task configuration and execute

Task Scheduler for Linux Systems