whatis cron
Cron
Also known as: crontab, cron job
The classic Unix scheduler that runs commands at fixed times using five-field schedule expressions in a crontab file.
What Is Cron in Linux?
A crontab line has five time fields (minute, hour, day of month, month, day of week) followed by the command. 0 3 * * * means 03:00 every day. Edit your own with crontab -e; system jobs live in /etc/crontab and /etc/cron.d/.
Cron runs jobs with a minimal environment, so full paths and explicit PATH settings avoid most "works in my shell, fails in cron" problems. Many systems now use systemd timers instead, which add logging and missed-run catch-up.
Example
# m h dom mon dow command
0 3 * * 0 /usr/local/bin/backup.shLearn more about Cron
- Cron Jobs Explained Cron is the classic Unix job scheduler. This guide covers the crontab syntax, the five time fields, user and system crontabs, the cron.d and cron.daily directories, environment variables, logging, and common pitfalls.
- cron vs systemd Timers: Which to Use Why a cron job that fails silently is the default behaviour, what timers give you that cron cannot, and when cron is still the right answer.
- Writing Scheduled Scripts That Actually Work on Linux Scripts that run fine interactively often fail silently when triggered by cron or systemd timers. This guide covers the practical differences: environment variables, working directories, logging, locking, and failure notification for scripts meant to run unattended.
Related tools
- Crontab Generator Build cron schedule expressions visually, with plain-English previews of when your job will run.