Day 18 – Automating Tasks with Cron Jobs

🛠️ Day 18 of my DevOps journey introduced me to the power of cron jobs – the classic way to automate repetitive tasks in Linux. Today I scheduled log backups, tested simple echo jobs, and experimented with different cron timing formats.

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⏰ What is cron?

cron is a time-based job scheduler in Unix-like systems that allows you to run scripts or commands at scheduled times or intervals.

📁 Backup Jenkins Logs Every Day

🔄 Backup Script

#!/bin/bash
tar -czf /opt/jenkins_logs_$(date +\%F).tar.gz /var/log/jenkins/

Let’s say we save this as /opt/backup_jenkins.sh and make it executable:

chmod +x /opt/backup_jenkins.sh

🗓️ Set Up a Cron Job

Edit the crontab:

crontab -e

Add this line to run the script daily at 2:00 AM:

0 2 * * * /opt/backup_jenkins.sh

✅ This runs:

• Minute = 0

• Hour = 2

• Every Day, Every Month, Every Weekday

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📌 Sample Cron Timings

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👨‍🔬 Test Cron with Simple Commands

Echo a message to a file every minute:

* * * * * echo "Hello from Cron at $(date)" >> /tmp/cron_test.log

Verify it with:

tail -f /tmp/cron_test.log

🧠 What I Learned

✅ Automate tasks with crontab
✅ Time format: min hour day month weekday
✅ Use absolute paths in scripts
✅ Output redirection helps debug cron failures

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🛠️ Real-World Use Cases

• Log and config backups

• Auto-restarts of services

• Pull updates from Git

• Rotate or clean logs

• Monitoring scripts

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🔮 Next Steps

On Day 19, I’ll move on to exploring rsync for syncing files across servers and learning about SSH key-based authentication.