View source for Cron

This page documents the working of [https://en.wikipedia.org/wiki/Cron Cron], a job scheduler on Unix-like operating systems. Cron is most suitable for scheduling repetitive tasks. Scheduling one-time tasks can be accomplished using the associated at utility. 
There are many cron implementations, but Alpine Linux comes inbuilt with the [[BusyBox]] version of cron. Some of the other packages available in Alpine Linux are {{Pkg|cronie}}, {{Pkg|fcron}}, {{Pkg|dcron}}.

== Cronie ==

The default cron is ideal for systems that run 24x7. For desktops, due to irregular nature of turning OFF and ON, it is easy to miss the jobs scheduled through regular cron. The {{Pkg|cronie}} package comes with <code>anacron</Code> tool, which does this kind of asynchronous job processing. 

=== Anacron ===

Here are the steps to use <code>anacron</Code> in Alpine Linux:

# Add the line {{Codeline|<code>@reboot /usr/sbin/anacron -s</code>}} to the crontab of the '''root''' user:
#: {{Cmd|# crontab -e}}
# Once edited, '''root''' crontab should appear as follows, when viewed using the command {{Codeline|<code># crontab -l </code>}} or viewed directly:
#:{{cat|/var/spool/cron/crontabs/root| 
# do daily/weekly/monthly maintenance
# min	hour	day	month	weekday	command
*/15	*	*	*	*	run-parts /etc/periodic/15min
0	*	*	*	*	run-parts /etc/periodic/hourly
0	2	*	*	*	run-parts /etc/periodic/daily
0	3	*	*	6	run-parts /etc/periodic/weekly
0	5	1	*	*	run-parts /etc/periodic/monthly
@reboot /usr/sbin/anacron -s
}}
# Anacron needs the folder {{Path|/var/spool/anacron}} to avoid the error {{Codeline|cron.err anacron[2893]: Can't chdir to /var/spool/anacron: No such file or directory}}. So create the folder using the command:
#: {{Cmd|# mkdir /var/spool/anacron}}
# Edit the configuration file {{Path|/etc/anacrontab}} and test the configuration validity by <Code>anacron -T</Code>.
# Reboot the computer to test the working of anacron. The syslog file {{Path|/var/log/messages}} captures messages from anacron and can be searched by <Code>cat /var/log/messages |grep anacron</Code>.

== See Also ==
* [https://wiki.archlinux.org/title/Cron Archwiki Cron page]
* [https://github.com/cronie-crond/cronie Official cronie website]
* [https://crontab.guru/ crontab Generator]

[[Category:System Administration‏‎ ]]
[[Category:Desktop]]