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oam/knowledge base/cron.md
2024-06-12 21:46:29 +02:00

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# Cron
1. [TL;DR](#tldr)
1. [Further readings](#further-readings)
1. [Sources](#sources)
## TL;DR
Files in `/etc/cron.hourly` and similar must:
- Be **scripts**.<br/>
Normal crontab files will error out.
- Be **executable**.<br/>
If not executable, execution will silently fail.
- Match the Debian cron script namespace (`^[a-zA-Z0-9_-]+$`).<br/>
Files **with** an extension **won't** work.
```sh
systemctl --enable --now 'crond.service'
journalctl -xefu 'crond.service'
# Validate crontab files.
crontab -T '/etc/cron.d/prometheus-backup'
# List files in given directories.
# Kinda… useless?
run-parts --list '/etc/cron.daily'
# Print the names of the scripts which would be invoked.
# '--report' is *not* available everywhere.
run-parts --report --test '/etc/cron.hourly'
# Manually run crontab files in given directories.
run-parts '/etc/cron.weekly'
```
## Further readings
- [Crontab]
### Sources
- [Function of /etc/cron.hourly]
- [Use anacron for a better crontab]
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[crontab]: crontab.md
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[function of /etc/cron.hourly]: https://askubuntu.com/questions/7676/function-of-etc-cron-hourly#607974
[use anacron for a better crontab]: https://opensource.com/article/21/2/linux-automation