How to Run Cron Jobs every Minute, Hour, Day on Ubuntu Linux
You can schedule cron jobs to run every minute, hour, or day on Ubuntu Linux by editing the crontab file.
A cron job automates tasks on your Linux system, much like setting an alarm to remind your computer to perform an action. These automated tasks are invaluable for routine maintenance, such as clearing temporary files or executing backup scripts.
The crontab file uses a specific syntax to define schedules. For instance, entering `*/5 * * * *` tells cron to run a command every 5 minutes.
Mastering this syntax allows you to precisely control the frequency of your automated tasks on Ubuntu, ensuring they execute exactly when you need them.
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
As mentioned above, cron jobs in Linux are commonly used for operational and mundane functions such as cleaning up logs, backing up system files, and others.
Below is how one can use cron jobs to perform tasks at intervals.
Crontab (cron table) is a text file holding your scheduled tasks. Each line in your user crontab file has six parts: the time schedule followed by the command to run.
An example of a cron file will look similar to the one below:
* * * * * system command(s) to run | | | | | | | | | | schedules | | | | | ------- | | | | ----- Day of week (0 - 7) (Sunday=0 or 7) | | | ------- Month (1 - 12) (January - December) | | --------- Day of month (1 - 31) (1st day to 31st) | ----------- Hour (0 - 23) ------------- Minute (0 - 59)
Think of the asterisk (*) as a wildcard. It tells cron to run the task ‘every’ time slot it represents. So, if you see an asterisk in the Minute field, your task will run every minute. This applies to hours, days, and months too.
The hyphen (-) lets you set a range. For instance, if you’re setting the ‘Day of Week’ field, ‘1-5’ means Monday through Friday.
The comma (,) creates a list, so ‘1,2,3’ in the ‘Hour’ field means 1 AM, 2 AM, and 3 AM. If no day is specified, the task runs daily at 1 AM, 2 AM, and 3 AM. You can also combine these, like ‘1, 2, 5-8’, which means 1 AM, 2 AM, and 5 AM to 8 AM.
The syntax for the system-wide crontab file includes an extra user field. This field tells cron which user should run the job.
* * * * * <username> command(s) to run
There’s more to learn about cron and scheduling jobs, but this should give you a solid start.
How to schedule a cron job to run every 5 minutes
If you want the cron job to 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
To schedule a cron job to run every 15 minutes, enter the line below in the crontab file:
*/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
An example cron entry for Let’s Encrypt certbot to renew certificates automatically looks like the one below:
# 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 should do it!
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.
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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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