Day 13/ 30 Days of Linux Mastery: Task Automation with Cron

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Introduction
What is Task Scheduling in Linux?
Core Cron Commands
Common Cron Expressions and Their Use Cases
Real-World Scenario: Automating Cron Job
Conclusion
Let's Connect

Introduction

Welcome back to Day 13 of the Linux Challenge.

We have now explored user management, permissions, and process management. Today, we move into something every serious sysadmin, DevOps engineer, and cloud platform team uses: automation.

Let’s be real, nobody wants to manually run a cleanup script at 1 AM. Now that’s where scheduling comes in.

What is Task Scheduling in Linux?

Task scheduling in Linux is how we automate repetitive or time-based operations. Whether it is:

Backing up logs every night
Clearing a temp folder every week
Triggering a script after deployment

This is done using cron for recurring tasks and at for one-time jobs.

Core Cron Commands

Command	Description
`cron`	For running repeating tasks
`crontab`	Where you list those scheduled tasks
`at`	For one-time scheduled tasks
`crontab -e`	Edit your scheduled tasks
`crontab -l`	View current cron jobs
`crontab -r`	Remove all scheduled cron jobs
`at TIME`	Schedule a one-time job
`echo "command"	at TIME`
`atq`	View all `at` jobs
`atrm <job number>`	Delete an `at` job
`systemctl status crond`	See if cron service is running
`systemctl restart crond`	To restart cron service
`MAILTO="email"`	Get cron output via email
`grep CRON /var/log/cron`	View cron logs (for debugging)
`/2 * * *`	Every 2 minutes cron syntax example

Common Cron Expressions and Their Use Cases

Cron Expression	Meaning	Example Use Case
`* * * * *`	Every minute	Run a health check script every minute
`/10 * * *`	Every 10 minutes	Auto-sync logs every 10 mins
`0 * * * *`	Every hour	Check and rotate logs hourly
`0 2 * * *`	At 2:00 AM daily	Perform system backup
`0 9 * * 1-5`	At 9:00 AM, Monday to Friday	Send out daily team reports
`0 0 1 * *`	At midnight on the 1st of the month	Generate monthly invoice or cleanup temp
`30 21 * * 5`	At 9:30 PM every Friday	Weekly audit or summary email
`15 14 1 * *`	At 2:15 PM on the 1st of the month	Send performance metrics report

Real-World Scenario: Automating Cron Job

Let's schedule a simple cron job by appending the text "2 minutes of job done" every 2 minutes.

Check if cron is running:

sudo systemctl status crond

Create a script file and a txt file for this cron job

bash
touch /democronjobs.txt   
vim /demojob.sh >> /democronjob.txt 

# Add '2 minutes of cron demo job done' inside the script.

Add Execution permission

We will change the permission mode of the script and assign it an execution mode to run.

Schedule a Repeating Job Using crontab

bash
crontab -e

*/2 * * * * /demojob.sh   - # add this inside 

crontab -l   - #to check it

Note
*/2 * * * * /demojob.sh
This expression means: run the /demojob.sh script every 2 minutes of every hour, every day

Let's check if this is running

The script is meant to add one line every 2 minutes.

bash

cat /democronjobs.txt

Stopping a Cron Job

We will simply open the crontab -e and delete the line.

bash 
crontab -e 

# delete the line or comment it using #


crontab -l - to verify

Alternatively: You can disable the cron job temporarily 

systemctl stop crond   - to temporarily stop

systemctl start crond -  to start it again

Conclusion

Whether you are scheduling backups, cleaning up logs, or monitoring server health, cron jobs save you time and keep your systems efficient. Practice writing a few simple cron jobs on your system and monitor the output just like we did in this article.

If this is helpful to you, feel free to bookmark, comment, like and follow me for Day 14!

Let's Connect!

If you want to connect or share your journey, feel free to reach out on LinkedIn.
I am always happy to learn and build with others in the tech space.

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