Scheduling

Cron jobs are the hidden backbone of most systems. They run backups, sync data, send reports, clean up old files. They also fail silently, leaving you wondering why that report hasn’t arrived in three weeks. Here’s how to build scheduled jobs that actually work. The Silent Failure Problem Classic cron: 1 0 2 * * * /usr/local/bin/backup.sh What happens when this fails? No notification No logging (unless you set it up) No way to know it didn’t run You find out when you need that backup and it’s not there Capture Output At minimum, capture stdout and stderr: ...

Cron has been scheduling Unix tasks since 1975. It’s simple, reliable, and will silently fail in ways that waste hours of debugging. Here’s how to use it properly. Cron Syntax │ │ │ │ │ └ ─ │ │ │ │ └ ─ ─ ─ │ │ │ └ ─ ─ ─ ─ ─ │ │ └ ─ ─ ─ ─ ─ ─ ─ │ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ c ─ ─ ─ ─ ─ o m D M D H M m a o a o i a y n y u n n t r u d o h o t f f ( e ( 0 w 1 m - ( e - o 2 0 e 1 n 3 - k 2 t ) 5 ) h 9 ( ) 0 ( - 1 7 - , 3 1 0 ) a n d 7 a r e S u n d a y ) Common Schedules 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 # Every minute * * * * * /script.sh # Every 5 minutes */5 * * * * /script.sh # Every hour at minute 0 0 * * * * /script.sh # Daily at 3 AM 0 3 * * * /script.sh # Weekly on Sunday at midnight 0 0 * * 0 /script.sh # Monthly on the 1st at 6 AM 0 6 1 * * /script.sh # Every weekday at 9 AM 0 9 * * 1-5 /script.sh # Every 15 minutes during business hours */15 9-17 * * 1-5 /script.sh The Silent Failure Problem Cron’s default behavior: run command, discard output, send errors to email (which you probably haven’t configured). ...

Cron works. It’s also from 1975. systemd timers offer logging integration, dependency handling, and more flexible scheduling. Here’s how to use them. Why Timers Over Cron? Logging: Output goes to journald automatically Dependencies: Wait for network, mounts, or other services Flexibility: Calendar events, monotonic timers, randomized delays Visibility: systemctl list-timers shows everything Consistency: Same management as other systemd units Basic Structure A timer needs two files: A .timer unit (the schedule) A .service unit (the job) Place them in /etc/systemd/system/ (system-wide) or ~/.config/systemd/user/ (user). ...

Cron has run scheduled tasks since 1975. It works, but systemd timers offer significant advantages: integrated logging, dependency management, randomized delays, and calendar-based scheduling that actually makes sense. Why Switch from Cron? Logging: Timer output goes to journald. No more digging through mail or custom log files. Dependencies: Wait for network, mounts, or other services before running. Accuracy: Monotonic timers don’t drift. Calendar timers handle DST correctly. Visibility: systemctl list-timers shows all scheduled jobs and when they’ll run next. ...