Crontab Basics

• crontab -e → edit crontab
• crontab -l → list crontab entries
• crontab -r → remove crontab entries
• systemctl status crond → check crond service status

AT: One-time Scheduled Tasks

• Used to schedule jobs only once.

Scheduling Examples:

• at HH:MM PM → schedule a job interactively

• at 11:23AM 12/24/25

  • Enter job (e.g., echo "test") and press Ctrl + D to finish
• at 2:45PM 01/30/25
• at 4PM + 4 days
• at now + 5 hours
• at 8:00AM Sun
• at 10:00AM next month

Managing AT Jobs

• atq → list the scheduled at jobs
• atrm # → remove a specific at job (use number from atq)
• systemctl status atd → check atd daemon status