Cron Job — What It Is & How to Create One

A cron job is a command or script that runs automatically at a scheduled time on a Unix/Linux system. The schedule is defined by a cron expression, and the jobs are managed through a crontab file. Together, the cron daemon, crontab, and your script form a cron job.

To create a cron job: (1) write the script or command you want to run, (2) build a cron expression for the schedule (use SimpleCronTab to build it visually), (3) run crontab -e to open your crontab, and (4) add a line with the expression and command, e.g., 0 0 * * * /path/to/backup.sh. This example runs backup.sh every day at midnight.

Cron jobs are used for backups, log rotation, sending scheduled emails, database maintenance, health checks, data syncing, cache clearing, and report generation. Cloud platforms offer managed cron jobs too — AWS EventBridge, GitHub Actions scheduled workflows, and Kubernetes CronJobs all use cron expressions to define schedules.