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Cron vs anacron: which scheduler for laptops and servers that don't run 24/7?

Use cron for always-on servers that need precise scheduling. Use anacron for laptops, desktops, and any machine that might be powered off at the scheduled time. On a typical Linux desktop, both run side by side and the combination covers all scheduling needs.

Cron assumes your machine runs 24/7. If the server is off at the scheduled time, the job is skipped. Anacron is designed for machines that don't run continuously: it tracks when each job last ran and executes missed jobs after boot. If your workload includes laptops, development VMs, or spot instances, anacron is the right tool.

By TechCompare · Updated

Schedule pattern
Cron vs anacron
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Comparisons
Cron vs alternative schedulers
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How this is calculated

Anacron schedules are defined in days, not minutes. You can say 'run this job daily' or 'run this weekly' but not 'run at 2:15 AM.' Anacron runs jobs in sequence after a configurable delay from boot. On a server that runs 24/7, cron is better because it gives you precise wall-clock timing. On a laptop that sleeps overnight, anacron ensures the daily backup actually happens when you open the lid in the morning. Modern Linux distributions typically run both: cron handles minute-level precision for always-on jobs, and anacron catches up daily/weekly/monthly maintenance tasks.

Verdict

The dividing line is whether the machine stays on. Anacron works in day units only, no minute or hour fields, and runs queued jobs in sequence after a boot delay. A laptop that sleeps overnight misses the cron slot entirely, but anacron catches the daily backup when you lift the lid. Mainstream distros run both, so minute-level cron and day-level anacron maintenance cover the full range.

More Cron scenarios

Every 5 minutes
Running a cron job every 5 minutes uses the step operator in the minute field: */5 * * * *.
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Every hour
To run a job at the top of every hour, use 0 * * * *.
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Daily at midnight
0 0 * * * runs a job at exactly midnight (00:00) every day.
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Related guides

Unix epoch explained
The Unix time-zero that anacron catches up after offline.
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chmod 755: standard permissions
Executable permissions for anacron user scripts.
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Frequently asked questions

What's the difference between cron and anacron?
Cron assumes the machine is on and awake at the scheduled time, and a machine that was off simply misses the job. Anacron tracks when each job last ran and executes the overdue ones after boot. The trade: anacron schedules in day units only, so you can say 'daily' or 'weekly' but never '2:15 AM.'
Why did my cron job not run on my laptop overnight?
Because the laptop was asleep or powered off, and cron has no concept of catching up. A 0 2 * * * backup on a machine that's closed at 2 AM just never fires. On laptops, desktops, and spot instances that come and go, anacron is the right scheduler - it runs the missed daily job shortly after you open the lid.
Can cron and anacron run side by side on the same machine?
Yes, and most mainstream Linux distributions do exactly that. Cron handles minute-precision jobs that need exact wall-clock timing. Anacron covers the daily, weekly, and monthly maintenance (logrotate, man-db updates, package caches) so those still happen even if the machine was off at the nominal time. They complement each other rather than compete.

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