By The Sacred Schedule of Cron We Automate, And Then We Nap

Hey there,

Welcome back to another edition of our bi-weekly newsletter! 

As always, we love to bring you insights and tips that make your life in the Cloud-Native and DevOps world smoother and a lot more productive.

Last time, we covered the art of managing Linux processes, getting those long-running tasks into the background so they don't hold your terminal hostage. But what if you have tasks that need to run regularly? Every hour? Every night? Every Sunday at 3 AM?

In today’s edition, we're taking that concept of background execution a notch higher by exploring cron, your Linux system's built-in time-traveling robot for automation. That’s right! 

Let’s get into it👇🏾.

If you don’t know what cron is, that’s gonna be a problem, but hey…that’s also why we’re here for you.

So, what is it? 

Cron is a time-based job scheduler on Linux operating systems with the sole purpose of automating repetitive tasks by scheduling them to run at specific dates and times. Think of it as an alarm clock for your server that also performs a task when it goes off.

Here’s why cron is essential: 

• Automated Updates: Automatically check for security patches and install software updates. 

• Regular Backups: Schedule regular backups of critical data to reduce the risk of losing data.

• Log Rotation: Archive, compress, and clean up old log files on a schedule to prevent them from occupying excessive storage space and hindering system performance.

• System Maintenance: Automate tasks like cleaning up temporary files, removing unused packages, or periodically restarting services to ensure optimal system stability and security.

• Report Generation: Run monitoring scripts to observe system performance and provide up-to-date health status and usage information.

Bonus: Broadly Compatible
Cron is a standard Unix and Linux command-line utility tool that is well-documented and supported across nearly all distributions, making it reliable for automation.

So, we know cron is like an alarm clock for your server, but how do you set the time on this thing? 

The magic of cron lies in its syntax, known as a cron expression. Each cron job entry in a crontab (the cron table configuration file) starts with five fields that define when the command should run, followed by the command itself.

From left to right, these fields represent:

1. Minute: (0-59)

2. Hour: (0-23)

3. Day of Month: (1-31)

4. Month: (1-12 or Jan-Dec)

5. Day of Week: (0-6, where 0 and 7 are Sunday, or Sun-Sat)

An asterisk (*) wildcard in any field means "every" possible value for that field.

Example: To run a command at 1:30 AM every day: 30 1 * * * (minute 30, hour 1, every day of the month, every month, every day of the week).

To run a command every Monday at 9:00 AM: 0 9 * * 1 (minute 0, hour 9, every day of the month, every month, Monday only).

Now that you understand how to speak Cron's time language, you'll need these essential commands to manage your scheduled jobs

By setting up cron jobs, you're essentially transforming repetitive manual work into reliable, automated processes. Here are some commands for managing your cron jobs:

• Edit your crontab: crontab -e - Opens your personal cron file for editing

• View your jobs: crontab -l - Lists all your current cron jobs

• Remove all jobs: crontab -r - Clears your entire crontab (RIP to all your automation - hope you had backups) 

• Install crontab from file: crontab filename - Loads cron jobs from a saved file 

• Check cron service status: systemctl status cron - Verify the cron daemon is actually running (because sometimes it just... stops caring)

•  Backup your crontab: crontab -l > my_cron_backup.txt - Save your cron jobs before making changes (future you will thank present you)

That's the essence of cron management - simple commands, complete control over your automation."

When it comes to mastering Cron, there's so much more to explore. Access the tutorial: ‘How to schedule a periodic task with cron’ alongside helpful recommendations here.

That’s it for today!

If you found this helpful, share this link with a colleague or fellow DevOps engineer.

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See you Friday for the week's news, upcoming events, and opportunities.

Divine Odazie
Founder of EverythingDevOps