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Scheduling important jobs with CRONTAB
Originally published on LinuxTechLab.com
Hello Linux-addicts, in this tutorial we will learn to use an important Linux utility named ‘Crontab’. With the help of Crontab or cron, we can execute a command or a script to run at a particular time. For example , let’s say you created a script for taking backup & you need to run the script daily at 11:00 PM . For one or two systems, we can run the script manually, it might not be an issue but if we are having 10-20 systems or even more it will be a problem. So instead, we will use ‘crontab‘ to create an cron–job that will run the script automatically daily at 11:00PM. Now let’s see some commands & then we will discuss some examples of crontab
• Add a new cron-job To edit or create a cronjob , run $ crontab –e
• Display all cron-jobs $ crontab –l
• Removing a cron-job $ crontab –r Or we can also prompt a user before deleting an item by $ crontab –ir
Syntax for using Crontab (minute) (hour) (day of month) (month) (day of week) (command/script path)
Examples of crontab 1- Running a backup script named bkp.sh located at /etc/script everynight at 11:00PM, 00 23 * * * /etc/script/bkp.sh 2- Running a weekly backup script named week.sh on every Friday at 11:30, 30 23 * * 5 /etc/script/week.sh
3- Running a monthly backup script named monthly.sh on 1st day of every month at 11:45PM, 45 11 1 * * /etc/script/monthly.sh 4- Running backup script named weekday.sh on weekdays only at 11:59 PM 59 11 * * *1-5 /etc/script/weekday.sh 59 11 * * *1 2 3 4 5 /etc/script/weekday.sh 5- Running top command every 15 minutes to performance monitoring * /15 * * * top Crontab is pretty easy to use and will make life of sysadmin much easier once you learn to make full use of it.
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