How to Run Cron Jobs every Minute, Hour, Day on Ubuntu Linux
Cron jobs on Ubuntu Linux act like automated alarm clocks that run tasks for you at set times, such as clearing temporary files every day or making backups every hour. A cron job uses a simple text file called a crontab to schedule commands.
You set a schedule using a line of five special code symbols, like writing */5 * * * * to run a task every five minutes. This built-in scheduling tool handles routine maintenance on your system automatically so you do not have to do it by hand.
Edit your crontab file by running `crontab -e`. Use asterisks for minute, hour, or day intervals, like `* * * * *` for every minute.
How to schedule cron tasks in Ubuntu Linux
Scheduling cron tasks in Ubuntu Linux relies on a dedicated configuration file called a crontab. This file functions as a to-do list for the computer, storing commands for automated execution and dictating exact run times to streamline system updates and backups.
Here is how to use cron jobs to perform tasks at specific intervals.
Crontab (cron table) is a text file holding scheduled tasks. Each line in a user crontab file contains six parts, starting with the time schedule and ending with the command to run.
An example cron file appears similar to the block below:
The asterisk (*) acts as a wildcard in cron. It tells cron to run a task during every available time slot it represents, like every minute if used in the Minute field. This wildcard behavior applies to the hour, day, and month fields too.
The hyphen (-) lets you set a range. For instance, writing 1-5 in the Day of Week field targets Monday through Friday.
Commas separate individual times within a schedule. Writing 1,2,3 in the Hour field triggers execution at 1 AM, 2 AM, and 3 AM. If no specific day gets set, execution happens daily at those specified hours. Combining operators works too, so 1,2,5-8 runs tasks at 1 AM, 2 AM, and hourly from 5 AM through 8 AM.
Cron scheduling jobs offer robust control over system tasks. Understanding how cron schedules jobs provides a solid foundation for automating routine operations on an Ubuntu Linux system.
How to schedule a cron job to run every 5 minutes
To make the cron job run every 5 minutes, enter the line below in the crontab file.
0,5,10,15,20,25,30,35,40,45,50,55 * * * * ~/script.sh
How to schedule a cron job to run every 10 minutes
To run a job every 10 minutes, enter the line below in the crontab file:
*/10 * * * * ~/scripts.sh
How to run a cron job every 10 minutes
Targeting ten-minute intervals requires adding a specific command line to the configuration. This line instructs the system to execute a chosen command every ten minutes without manual intervention, making it ideal for tasks requiring frequent checks or updates.
*/15 * * * * ~/script.sh
How to run a cron job every minute
To run a cron job every minute, enter the line below in the crontab file.
* * * * * ~/script.sh
# the cronjob.timer function takes precedence over this cronjob. For # more details, see the systemd.timer manpage, or use systemctl show # certbot.timer. SHELL=/bin/sh PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin 0 */12 * * * root test -x /usr/bin/certbot -a ! -d /run/systemd/system && perl -e 'sleep int(rand(43200))' && certbot -q renew
That completes the setup process.
Conclusion:
- Cron jobs in Ubuntu Linux are useful for automating operational and mundane tasks.
- The key to scheduling tasks with cron jobs lies in understanding the syntax and utilizing the crontab file effectively.
- By leveraging the asterisk, hyphen, and comma operators, users can create precise schedules for their cron jobs.
- Examples of scheduling cron jobs at various intervals, along with a Let's Encrypt certbot renewal cron entry, demonstrate the versatility of this feature.
- With this understanding, users can efficiently manage and automate tasks using cron jobs in Ubuntu Linux.
Where are cron jobs in Ubuntu?
System crontab files reside in /var/spool/cron/crontabs, where each filename matches the user account that owns the schedule. Direct file editing is discouraged; instead, view, update, and delete user crontab files using the crontab command.
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About the Author
Richard
Tech Writer, IT Professional
Richard, a writer for Geek Rewind, is a tech enthusiast who loves breaking down complex IT topics into simple, easy-to-understand ideas. With years of hands-on experience in system administration and enterprise IT operations, he’s developed a knack for offering practical tips and solutions. Richard aims to make technology more accessible and actionable. He's deeply committed to the Geek Rewind community, always ready to answer questions and engage in discussions.
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