Glossary
Cron
The scheduler that runs commands at fixed times.
Cron runs commands on a schedule defined by five fields — minute, hour, day of month, month, day of week — followed by the command. It wakes every minute and runs whatever matches.
Cron jobs run in a minimal environment: a short PATH, no interactive shell config, and the user's home as working directory. Absolute paths and explicit output capture (>> log 2>&1) are what separate cron jobs that work from cron jobs that fail silently.
See it in practice
$ crontab -l && grep CRON /var/log/syslog | tail -5What is scheduled, and evidence of what actually ran. The second half is where silent failures surface.
Where you'll meet it
Run commands on a schedule — and read the five-field syntax fluently.
Environment variableA named value processes inherit when they start.
DaemonA background process providing a service, usually started at boot.