Getting Started with Cron Jobs on Linux

Cron is a time-based job scheduler in Unix-like operating systems that allows you to automate repetitive tasks by scheduling them to run at specific intervals. Whether you want to schedule a script, command, or program to run at specific times or intervals, Cron provides a simple and reliable solution. In this guide, we'll walk you through the process of setting up and managing Cron jobs on Linux.

Prerequisites

Before you begin, ensure that you have the following:

• A Linux-based operating system (such as Ubuntu, CentOS, or Debian) with Cron installed.
• Basic knowledge of the Linux command line.

Now, let's get started with Cron jobs.

Step 1 — Getting started with Cron

1. Open a terminal or SSH into your Linux system.
2. Type crontab -e to open the Cron table for editing.

Step 2 — Writing your first Cron job

1. In the Cron table, each line represents a separate job. The structure of a Cron job entry is as follows:

   * * * * * command
   

   The five asterisks represent the time and date when the job should run, and the command is the script or command you want to execute.

2. For example, to schedule a job to run every day at 8:00 AM, you would use the following entry:

   0 8 * * * /path/to/your/script.sh
   

   This entry specifies that the job should run at minute 0, hour 8, every day of the month, every month, and every day of the week. Adjust the path and filename (/path/to/your/script.sh) to match your script or command.

3. Save the Cron table and exit the editor.

Step 3 — Managing crontab files

Cron jobs are stored in crontab files. Each user can have their own crontab file, and the system also has a system-wide crontab file. To manage crontab files:

• To edit the current user's crontab file, use the command crontab -e.
• To edit the system-wide crontab file, use the command sudo crontab -e.

Step 4 — Executing script files with Cron

When writing Cron jobs, it's common to use shell scripts to execute multiple commands or complex tasks. To execute a script file with Cron:

1. Create a shell script using a text editor. For example, create a file named backup.sh.

2. Add your desired commands to the script, such as copying files or running programs.

3. Make the script executable by running the command chmod +x backup.sh.

4. In your crontab file, specify the path to the script. For example:

   0 2 * * * /path/to/backup.sh
   

   This example schedules the script backup.sh to run every day at 2:00 AM.

Step 5 — Monitoring Cron output

By default, Cron sends any output (stdout and stderr) to the email address associated with the user account. To monitor the output of Cron jobs:

1. Install and configure a mail transfer agent (MTA) if it is not already set up on your system. Popular MTAs include Postfix and Sendmail.

2. Configure an email forwarding rule to redirect Cron emails to your preferred email address. This ensures that you receive the output and any potential error messages.

3. Open the Cron table by running crontab -e.

4. At the end of your Cron job entry, append >> /path/to/logfile.log 2>&1. This redirects both stdout and stderr to a specified log file. Replace /path/to/logfile.log with the actual path and filename for your log file.

   For example:

   0 8 * * * /path/to/your/script.sh >> /path/to/logfile.log 2>&1
   

   This example captures the output of the Cron job and appends it to logfile.log.

5. Save the Cron table and exit the editor.

Final thoughts

Cron provides a powerful and flexible way to automate tasks on Linux systems. By following the steps outlined in this guide, you can get started with Cron and schedule your own jobs with ease.

Remember to test your Cron jobs thoroughly and ensure they run as expected. Regularly review and update your Cron jobs as your requirements change.

That's it! You now have a basic understanding of Cron jobs and how to set them up on Linux. Happy scheduling and monitoring!

We notify you when your website experiences downtime

Stay informed with a comprehensive infrastructure monitoring platform

• Check Uptime, Ping, Ports, SSL, and more.

• Receive incident alerts via Slack, SMS, and phone.

• Easily schedule on-call duties.

• Create a free status page on your own domain.

Explore monitoring →